EGU General Assembly 2024  

My presentation will cover the present and recent configurations of Mars’ water cycle. The Martian water is only visible in two forms: gas and ice. The existence of a water cycle on Mars was deduced from the first seasonal monitoring of water vapor performed by the Viking mission in 1982. It revealed that the same seasonal and spatial pattern repeated itself for nearly two consecutive Martian years. After Viking, other missions have confirmed this initial conclusion: seasonal water vapor variations appear to be controlled by exchanges between various reservoirs, achieving an annual stationary state with some inter-annual differences. These variations are primarily influenced by the seasonal evolution of the climate in the north polar region, as the latter hosts the most massive reservoir of water, consisting of an ice cap of more than 2 million km³. When exposed to sunlight in spring and summer, this cap releases a massive amount of water vapor that then spreads across the Martian globe, only to return to the North Pole the following winter in the form of frost. Decades of theoretical and observational exploration have delivered a nearly comprehensive view of Mars’ water cycle. From the water molecules that leave the cap in summer to the hydrogen atoms that escape Martian gravity and get lost in space; I will show how the Mars missions and the 3D models used to simulate Mars’ climate have laid the foundations for our understanding of the main processes that govern the evolution of water on Mars.

How to cite: Franck, M.: Deciphering Mars’ water cycle with missions and models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2888, https://doi.org/10.5194/egusphere-egu24-2888, 2024.

How to cite: Mandon, L., Ehlmann, B. L., Greenberger, R. N., Ellison, E. T., Mayhew, L. E., and Templeton, A. S. and the Oman Drilling Project Science Team: Hyperspectral mapping of a kilometer of mantle rock core: insight into active serpentinization systems , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4012, https://doi.org/10.5194/egusphere-egu24-4012, 2024.

I look at what astronomy from the Moon might be like in the visible over the next few decades.
The Moon offers the possibility of installing large telescopes or interferometers with instruments larger than those on orbiting telescopes. I first present examples of ambitious science cases, in particular ideas that cannot be implemented from Earth. I discuss also the issues which I telescope will encounter underlunar conditions. After a general review of observational approaches, from photometry to high contrast and high angular resolution imaging, I propose as a first step a 1-metre-class precursor and explore what science can be done with it.

How to cite: Schneider, J.: Astronomy from the Moon: From Exoplanets to Cosmology in Visible Light, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-142, https://doi.org/10.5194/egusphere-egu24-142, 2024.

Hyperspectral images, despite their rich spectral information, often suffer from low spatial resolution due to physical constraints in imaging sensors. However, when higher spatial resolution data of the same scene are available, we can perform data fusion to generate hyperspectral images with high spatial resolution. This fused data can be viewed as the output of a synthetic sensor that combines the high spatial and spectral resolution data acquired by different sensors. This fusion allows for new applications with increased accuracy, such as high-resolution mapping of minerals and surface materials. Imaging spectroscopy facilitates the identification and discrimination of materials and their constituents. Data fusion enhances both the spatial and spectral characteristics of the initial data. It is based on the synergistic exploitation of data from different sources, aiming to produce superior results. By integrating data from The Moon Mineralogy Mapper (M3) by NASA and the Imaging Infrared Spectrometer (IIRS) by ISRO, we can improve the spatial and spectral resolutions, enhance measurement accuracy, and reduce uncertainties. This will enable a more precise assessment of the mineral composition of the area of interest. The objective is to fuse high spatial resolution data, which has discontinuities in the spectral domain, with low spatial resolution data that has continuous spectra. The ultimate goal is to estimate an image with high spatial and spectral content, providing a more comprehensive and accurate understanding of the area of interest. We replaced the noisy bands in the M3 and IIRS data and used cubic convolution to resample the M3 bands to the IIRS band’s native spatial resolution. However, the M3 bandwidth is different from the IIRS bandwidths. Nevertheless, this gap-filling procedure will allow us to identify endmembers. As a followup study we are going to employ a spectral unmixing technique to obtain endmembers information and high-resolution abundance matrices from the initial images. Data fusion helps overcome the limitations of individual datasets, exploit the strengths of different sensors, and extract more valuable information.

How to cite: Ivanov, I. and Filchev, L.: Fusion of IIRS and M3 data for the purpouse of finer resolution mineral mapping, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-292, https://doi.org/10.5194/egusphere-egu24-292, 2024.

Impact craters have been identified on almost every type of celestial body, and are among the most destructive processes. The lunar surface is covered in craters ranging from 2500km in diameter, down to sub-millimetre scale, and >600 lunar impact flash (LIF) events have been observed by ground based telescopes, detecting the generated light. Despite this large volume of data, previously only three freshly formed craters had been both located within LROC imagery, and have the forming LIF documented.
Using PyNAPLE (Sheward et al., 2022) - software which locates fresh craters from the selenographic latitude, longitude, and epoch of a LIF - a search was performed upon the 22 most energetic LIFs within literature. For completeness, this included the three LIF events with already identified craters.

There were sufficient LROC images to locate six new freshly formed craters, in addition to the three already identified. For these nine events, the likely parent meteoroid stream for each event is identified to constrain the velocity, impact geometry, and impactor properties. From this, the pre-impact kinetic energy could be obtained from an estimation for the luminous efficiency, and the luminous energy released by the LIF.

Furthermore, using the crater scaling laws from Melosh (1989), both the predicted crater size from the kinetic energy, and the predicted energy from the observed crater size, could be calculated for each event.

From this, it was found that the predicted crater diameter was consistently larger than the observed crater. While there are several factors that could contribute to this, the single most likely factor is the poorly constrained luminous efficiency. Under this assumption, a more accurate value for the luminous efficiency can be calculated using the observed craters. Using a rearrangement of the crater scaling laws, with the kinetic energy equation, and luminous efficiency, η = E_lum/E_kwhere E_lum is the energy released by the LIF, and E_kis the kinetic energy. After outlier removal and meteoroid stream identification, this produces an average value of η=0.0171324. While this is slightly larger than the typically used values of between 10⁻²and 10⁻⁴, the difference is not drastic.

References

Melosh, H. J. (1989). Impact cratering : a geologic process.
Sheward, D. et al (2022). MNRAS, 514(3):4320–4328

How to cite: Sheward, D., Avdellidou, C., Cook, A., and Delbo, M.: Lunar Impact Flashes and their Resultant Craters , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1216, https://doi.org/10.5194/egusphere-egu24-1216, 2024.

Seismic observation is a powerful tool to investigate the Earth’s geological activities and internal structure and has also been applied to the Moon and Mars [e.g., Latham et al., 1969; Banerdt et al., 2020]. For the Moon, a seismic network was constructed on the nearside during the Apollo missions, and nearly eight years of observation provided us with more than 13,000 seismic events [Nakamura et al., 1981]. These events have contributed to understanding the seismicity rate on the Moon and its internal structure [e.g., Garcia et al., 2019; Nunn et al., 2020], both of which are important to know the current geological activity level and trace back to the thermal evolution in the past.

In the Apollo lunar seismic observation, two types of seismometers were installed: Long-Period (LP) and Short-Period (SP) seismometers. While the LP sensor has sensitivity at 0.2 – 1.5 Hz, the SP is sensitive at 1 – 10 Hz [e.g., Nunn et al., 2020]. In previous studies, the LP data were mainly used. In fact, all the cataloged events were detected solely using the LP data [Nakamura et al., 1981]. On the other hand, because of numerous unnatural signals and/or spikey noises, the majority of SP data remained unanalyzed after the initial description of high-frequency quakes by Duennebier and Sutton (1974a, 1974b) [e.g., Frohlich and Nakamura, 2006; Knapmeyer-Endrun and Hammer, 2015]. This fact implies that there are potential seismic events only identifiable in the SP data, and the lunar seismicity might be underestimated.

Lately, Onodera (2023) denoised all the SP data and performed an automatic event detection. As a result, he discovered about 22,000 new seismic events, including thermally driven quakes (thermal moonquakes), impact-induced events, and tectonic-related quakes (shallow moonquakes). While the former two types are useful to understand the surface evolution or degradation processes, the latter type is closely related to the seismic activity level of the Moon. Here, I focus on shallow moonquakes. In the past, since only 28 shallow moonquakes were identified, it was difficult to give a detailed description of their source mechanism, regionality, and correlation with tidal force. In this study, using the newly discovered 46 shallow moonquakes, I’m trying to give new insights into this type of event.

In the presentation, I will describe the general characteristics of newly discovered shallow moonquakes (e.g., waveforms and spectral features) and summarize the estimated source parameters (such as energy release, seismic moment, and body wave magnitude).

References

• Banerdt et al. (2020), Nat. Geosci., 13(3), 183-189.
• Duennebier and Sutton (1974a), JGR, 79(29), 4365-4374.
• Duennebier and Sutton (1974b), JGR, 79(29), 4351-4363.
• Frohlich and Nakamura (2006), Icarus, 185(1), 21-28.
• Garcia et al. (2019), Space Sci. Rev., 215(8), 50.
• Knapmeyer-Endrun and Hammer (2015), JGR Planets, 120 (10), 1620-1645.
• Latham et al. (1969), Science, 165(3890), 241-250.
• Nakamura et al. (1981), UTIG Technical Report, No. 118.
• Nunn et al. (2020), Space Sci. Rev., 216(5), 89.
• Onodera (2023), ESSOAr, DOI: 22541/essoar.169841663.38914436/v1

How to cite: Onodera, K.: Newly Discovered Shallow Moonquakes: General Characteristics and Source Parameters, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1694, https://doi.org/10.5194/egusphere-egu24-1694, 2024.

As an important physical property of the Moon, the lunar crustal density provides evidence for the early evolution process of the Moon, such as the asymmetry of its nearside and farside. The apparent density is the average value of the bulk density at a certain depth. The gravity inversion method is an effective tool of determining the apparent density distribution of the lunar crust. Benefiting from the lunar GRAIL mission's high-precision gravity field models, it is theoretically possible to establish a global high-resolution apparent density model through the gravity inversion. However, there are two major problems, namely, the accuracy and efficiency of the inversion. To solve these problems, different from the admittance methods, we develop a high-precision apparent density mapping method in the spherical coordinate. The improved 2D Gauss-Legende formula and adaptive subdivision algorithm are adopted to calculate the high-precision gravity anomalies of the Tesseroid cells. The parallel algorithm based on OpenMP is involved to improve the calculation efficiency of the global data. And the Cordell iterative algorithm is utilized to derive the apparent density model fitting the real gravity anomalies. The synthetic data tests verify the accuracy and efficiency of our method. Subsequently, we use LOLA topographic data to correct the gravity anomalies obtained from GRAIL and derive the global lunar Bouguer gravity anomalies. The lunar crust thickness model given by Wieczorek et al (2013) is chosen as the bottom interface of the density layer. As a result, we obtain a global high-resolution lunar crust apparent density model with a resolution of about 20 km by the presented mapping method. Our model shows that the apparent density of the lunar crust ranges from about 2200 - 2900 kg/m³ with a mean value of about 2600 kg/m³. The Procellarum KREEP Terrane (PKT) and the large impact basins present higher apparent density, while the Feldspathic Highlands Terrane (FHT) varies around the mean apparent density, and there is a significant variation within the South Pole-Aiken Basin Terrane (SPAT). Our apparent density distribution around the PKT and FHT is significantly relevant to the surface grain density model derived from the current FeO and TiO₂ abundance map. However, our apparent density distribution around the SPAT differs from the surface grain density, suggesting a more complex density structure in this region.

How to cite: Yang, J. and Guo, L.: The apparent density distribution of the lunar crust revealed by the spherical coordinate-based mapping method, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3166, https://doi.org/10.5194/egusphere-egu24-3166, 2024.

Water plays a crucial role in the Moon's evolution and holds significant implications for potential human activities on its surface. Previous studies, based on measurements of a limited number of lunar soil particles, have revealed evidence supporting various sources of lunar water, including its origin from the lunar interior, solar wind implantation, and impacts from comets or asteroids. Nevertheless, the limitation of these studies stems from the restricted number of particle samples, hindering the achievement of adequate statistical significance. As a result, the primary source of water on the Moon remains enigmatic. To address this critical question and advance our understanding of lunar water sources, we initiated new spectral measurements using lunar bulk soil collected by Chang'e-5 under controlled conditions. We observed variations in water content across different particle sizes. Our findings suggest that solar/ Earth wind implantation is likely the primary source of lunar surface water. The controlled experiments conducted on the lunar bulk soil samples provide valuable insights, offering statistical evidence for the origin of water in lunar soil. We also bridged the laboratory, in-situ, and orbital results, offering a cohesive understanding of lunar surface water characteristics as represented by Chang'e-5.

How to cite: Lin, H.: Primary Origin of Lunar Surface Water: Constraints from Observations of Chang'e-5, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3294, https://doi.org/10.5194/egusphere-egu24-3294, 2024.

Zircon is one of the most important U-bearing minerals in the lunar geochronological studies. Since the first lunar zircon grains were analyzed in the early 1980’s, the majority of lunar zircon U(Pb)-Pb ages obtained from the Apollo missions in the last decades were distributed between about 4.4 and 3.9 Ga. Although the crystallization age of Chang’e-5 (CE-5) basalts were obtained from baddeleyite, zirconolite and tranquillityite, we attempted to search for lunar zircon grains from the collected CE-5 lunar sample for comparison with the previous studies. We scanned almost all polished sections of the CE-5 powder sample to identify lunar zircon grains, most of which are isolated grains or mineral clast in agglutinates and impact melt breccias. In our study, only one zircon grain was preserved in the lithic clast of CE-5 basalts after the scanning of hundreds polished sections. This zircon records a precise Pb-Pb isochron age of 2036 ± 19 Ma, which is the youngest crystallization age ever reported for lunar zircon geochronology. Combined with the petrology, mineralogy and geochronology, we have demonstrated that this zircon grain is the extreme fractional product from a non-KREEP mantle source similar to CE-5 basalt. Compared to the zircon from Apollo mission, the sampling site of CE-5 provides a new case that lunar zircon can crystallize from a variety of magmatic compositions in addition to KREEP-related magma. In the future, we plan to perform the studies of zircon grains from CE-5 samples in different lithologies and try to find the origin of these zircons grains.

How to cite: Zhou, Q., Li, C., Liu, J., Wen, W., Liu, Y., Yang, S., Li, Q.-L., Zhang, G., Zhang, H., Liu, B., and Liu, D.: Lunar zircon from the Chang’e-5 landing site, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4876, https://doi.org/10.5194/egusphere-egu24-4876, 2024.

Comprehending the internal structure of the Moon is crucial for uncovering its formation and evolution. The existence of the lunar core can be proved by several pieces of evidence, including electromagnetic sounding analyses, mass and moment of inertia analyses, and seismic analyses. However, the precise size and composition of the lunar core are still unknown. In this study, the induced magnetic field generated by the lunar metallic core is illustrated through a three-dimensional MHD simulation. Several cases have been discussed in which the lunar core are set with different electrical conductivities and thicknesses. Compared to the hybrid model, our MHD model can calculate more accurate results with a more refined grid. Our simulation can capture the variations of parameters (plasma densities, temperature, and flow speed) in original and final conditions, while the hybrid model cannot.

How to cite: Yi, S., Xu, X., Xie, L., Wang, X., Xu, Q., Zhou, Z., Man, H., Luo, L., He, P., and Yang, P.: Three-dimensional MHD simulation of lunar induced magnetic field generated by lunar metallic core, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4978, https://doi.org/10.5194/egusphere-egu24-4978, 2024.

A large number of meteoroids and micrometeoroids enter the Earth–Moon system continuously, constituting a potential threat to our planet. Lunar meteoroid impacts have caused in the past a substantial change in the lunar surface and its properties. With no atmospheric shield, the Moon is subject to a large number of impacts from meteoroids, typically ranging from a few tens of grams to a few kilograms every day. The high impact rate on the lunar surface has important implications for future human and robotic assets that will inhabit the Moon for significant periods of time. Therefore, a better understanding of the meteoroid population in the cislunar environment is required for future exploration of the Moon. Moreover, refining current meteoroid models is of paramount importance for many applications, including planetary science investigations. For instance, since meteoroids may travel dispersed along the orbit of their parent body, understanding meteoroids and associated phenomena can be valuable for the study of asteroids and comets themselves, and their dynamical paths. Studying meteoroid impacts can help deepening the understanding of the spatial distribution of near-Earth objects in the Solar System. The study of dust particles is also relevant to the topic of space weather. The ability to predict impacts is therefore critical to many applications, both related to engineering aspects of space exploration, and to more scientific investigations regarding evolutional processes in the Solar System. Also, accurate impact flux models would be crucial to support planetary defense actions, as large meteoroids can cause severe damage to our communities.

In this context, the Lunar Meteoroid Impacts Observer (LUMIO) is a CubeSat mission to observe, quantify, and characterise lunar meteoroid impacts, by detecting their impact flashes on the far-side of the Moon. This complements the information available from Earth-based observatories, which are bounded to the lunar near-side, with the goal of synthesising a global recognition of the lunar meteoroid environment. LUMIO envisages a 12U CubeSat form-factor placed in a halo orbit at Earth-Moon L2. The detections are performed using the LUMIO-Cam, an optical instrument capable of detecting light flashes in the visible spectrum (450-950 nm). LUMIO has successfully passed Phases A and B and is currently moving towards Phase C.

We present the latest results on the modelling of the meteoroid environment in the Earth-Moon system, including an estimate of LUMIO’s potential impact on our existing knowledge of meteoroids, supported by high-fidelity simulation data. An overview of the present-day LUMIO CubeSat design is also given, with a focus on the latest developments involving both the ongoing/planned scientific activities and the development of the payload.

How to cite: Ferrari, F., Topputo, F., Buonagura, C., Giordano, C., Panicucci, P., Piccolo, F., Rizza, A., Cervone, A., Koschny, D., Ammannito, E., Moissl, R., and Walker, R.: LUMIO: a CubseSat to detect meteoroid impacts on the lunar farside, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6314, https://doi.org/10.5194/egusphere-egu24-6314, 2024.

The surface rock abundance map derived from the Lunar Reconnaissance Orbiter (LRO) Diviner Lunar Radiometer Experiment (Diviner) revealed variability in the rock abundance across the surface of the lunar maria [1]. Rocks on the lunar surface break down quickly relative to lunar geologic history [2, 3], so surface rock abundance is likely to be strongly tied to subsurface rock content which could include both coherent layers of mare basalts or large boulders mixed in with regolith. Most of the Moon’s surface is now covered in fine grained regolith, and historically various authors have argued that each surface unit started as a flat coherent layer of rock which gradually broke down into a layer of regolith whose thickness is a function of its bombardment history [e.g. 4, 5]. However, recently Head and Wilson (2020) [6] argued that modern understanding of lunar volcanism suggests substantial variability in post eruption surface conditions (e.g. void space, pyroclastic deposits, etc.) which could affect subsequent regolith development possibly leading to surfaces of the same age having regolith layers of different thicknesses and/or suspended rock populations. We compare the Diviner rock abundance [1] in different maria units defined and dated by Hiesinger et al. (2011) [7] to investigate both the change in surface rock abundance with time, and possible regional variability in rock properties [8]. We find that surface rock abundance does decrease with unit age as expected for a thickening layer of regolith. However, there is significant scatter in this relationship. We calculate the best-fit linear relationship between the median rock abundance and age of the units defined by Hiesinger et al. (2011) [7]. Investigation of the residuals of this fit reveals that they are not random. For example, Mare Australe is similar in age to Mare Tranquillitatis, but nearly all units in Mare Tranquillitatis are rockier than those in Mare Australe. Mare Humorum is notable for being one of the rockiest regions in the maria despite its relatively ancient surface (>3 Ga). These observations support the hypothesis of Head and Wilson (2020) [6], and suggest that further investigation into the properties of present-day surface rocks may provide insight into the initial mare basalts before billions of years of communition. Specifically, future in situ missions across diverse mare locations could offer insights into the variability of basaltic eruption styles that may have formed the lunar maria.

[1] Bandfield+ (2011), JGR, 116, E00H02.

[2] Basilevsky+ (2013), PSS, 89, 118.

[3] Ghent+ (2014) Geology, 42, 1059.

[4] McKay+ (1991) Lunar Sourcebook, Cambridge Press, 285.

[5] Hörz (1977), PCE, 10, 3.

[6] Head+ (2020) GRL, 47.

[7] Hiesinger+ (2011), GSA Special Papers, 477.

[8] Elder+ (2023) PSJ, 4:244.

How to cite: Elder, C., Ghent, R., Haber, J., Hayne, P., Morgan, G., Robinson, M., Siegler, M., and Williams, J.-P.: The Variability of Lunar Mare Basalt Properties Inferred from Present-Day Surface Rock Abundance, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6905, https://doi.org/10.5194/egusphere-egu24-6905, 2024.

NASA selected a new in-situ seismic experiment, Farside Seismic Suite (FSS), onboard CP-12 lander with the landing site at the farside of the Moon in Schrödinger Basin. This future mission should provide us with the data to further constrain lunar interior and the Moon seismicity. Due to the single-station nature of the mission, localisation of the newly detected events will be challenging. Therefore, in this study we develop a pipeline for the deep moonquake (DMQ) source region localisation on the legacy of the data acquired during the Apollo missions. We are interested into DMQs since their source regions, called nests, on the near side have been identified, and since their occurrence patterns follow specific spatial and temporal patterns. Spatial patterns are related to tsp=ts-tp travel time measurement. We can show that based on tsp measurements we can form group of nests, called sets, that share similar travel times within error bars and therefore we cannot distinguish between nests that belong to the same set just using the travel time information. Temporal patterns are related to the fact that occurrence of DMQs is closely related to the monthly motion of the Moon around the Earth. Different nests correspond differently to three lunar months: synodic, draconic, anomalistic. By combining the spatial and temporal patterns we try to characterise different nests and exploit this information for their prediction. For this purpose we develop a machine learning model for nets classification. An input data into model we use orbital parameters related to the monthly motion of the Moon around Earth, which we relate to different nests. The ML model is learned to classify between nests that belong to the sam set. We report that models are achieving an accuracy over 70% when those are trained to classify =< 4 nests within the set, and better than 90% when only two DMQ nests are in the same set. This approach opens up a new way to DMQ location estimate, on the near and farside of the Moon, when captured by the future FSS single-station seismometers or other seismic stations on the Moon. 

How to cite: Majstorović, J., Lognonné, P., Kawamura, T., and Panning, M.: Relating deep moonquake source regions from Apollo missions with their temporal and spatial patterns using machine learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8297, https://doi.org/10.5194/egusphere-egu24-8297, 2024.

The Andrade rheological law ε(t)=ε₀+βt^α has been introduced by Andrade in 1910 for the description of elongation in metal wires. Since then, this model has gained increasing popularity in geophysics and planetary sciences, being extremely effective in the description of numerous materials, including polycrystalline ices, amorphous solids and silicate rocks. Recently, many works in the field of planetology have adopted this model for the description of the response of solar system or extra-solar planets to tidal perturbations, especially for bodies whose properties are still poorly constrained. This is because the Andrade rheology can describe transient deformation using a low number of parameters, a highly valued characteristic for the study of planetary bodies for which few observational constraints are available, such as exoplanets. For the Moon, the Andrade rheology provides an accurate description of the viscoelastic tidal deformation, satisfying the observed frequency dependence of the quality factor.

While for uniform bodies described by a steady-state Maxwell rheology the analytical form of the time-dependent Love numbers (LNs) was established long ago, in the case of the transient Andrade model no closed-form solutions have been determined so far. This is mainly due to the fact that the planetary response is normally studied in the Fourier-transformed frequency domain or by numerical methods in the time domain. Closed-form expressions could be important since they have the potential of providing insight into the dependence of LNs upon the model parameters and the viscoelastic relaxation time-scales of the planet.

In this work, we focus on the Andrade rheological law in 1-D and we obtain a previously unknown explicit expression, in the time domain, for the relaxation modulus in terms of the Mittag-Leffler function E_α,β(z), a higher transcendental function that generalises the exponential function. Second, we consider the general response of a uniform, incompressible planetary model - the “Kelvin sphere” - studying the Laplace-transformed, the frequency domain and the time-domain LNs by analytical methods. By exploiting the results obtained in the 1-D case, we establish closed-form expressions of the time domain LNs and we discuss the frequency-domain response of the Kelvin sphere with Andrade rheology analytically.

Our findings exhibit a complex relation between the planet parameters and the resulting deformation. From the analysis of the frequency-dependent LNs we show that dissipation in Earth-like planets is strongly dependent upon the choice of the planet density, rigidity and viscosity, while the variation of the Andrade creep parameter α has an effect that is limited to short-period tidal forcing. Concurrently, the study of the time dependent LNs shows that α regulates the duration of the transient phase, while the remaining parameters set the value of elastic limit, and the rate at which  the fluid limit is reached. Finally, some examples concerning the tidal deformations of the Moon are presented to point out the relevance that the Andrade rheology assumes in this particular case.

How to cite: Consorzi, A., Melini, D., Gonzáles-Santander, J. L., and Spada, G.: Love numbers for an Andrade planet, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8305, https://doi.org/10.5194/egusphere-egu24-8305, 2024.

With NASA's emphasis on lunar exploration through the Artemis program, novel scientific objectives have been formulated to enhance our understanding of the Solar System's historical context, particularly the evolution of the Earth-Moon system. Simultaneously, the establishment of a permanent human presence on the Moon is proposed as a primary objective within the Artemis program, with the achievement of this goal hinging on in-situ resource utilization (ISRU) of lunar materials. Effective ISRU needs methodologies for chemical analysis and selecting appropriate lunar materials in-situ. To facilitate these tasks, the deployment of sensitive instrumentation capable of determining the element and isotope composition of lunar materials is imperative.

In this contribution, we present the current progress in developing a reflectron-type time-of-flight laser ablation ionisation mass spectrometer (RTOF-LIMS) to allow for direct sensitive chemical microanalysis of lunar regolith grains in-situ on the lunar surface. This LIMS system will operate in the lunar south pole region on a CLPS mission within NASA’s Artemis program.

The contribution will provide a general overview of the instrument and focus primarily on the design and operations of the sample handling system (SHS). Furthermore, we will discuss the results of experiments conducted on lunar regolith simulant. These experiments were performed using a prototype LIMS system to validate the feasibility of the SHS. This prototype system has capabilities representative of the flight instrument currently in development regarding the mass analyser and optical sub-system. The laboratory and flight optical sub-systems are based on a microchip Nd:YAG laser system (~ 1.5 ns pulse width, λ = 532 nm, 100 Hz laser pulse repetition rate, laser irradiance ~ 1 GW/cm²), and custom-made laser optics to achieve a focal spot on the sample surface of ~20 μm. Consequently, the conducted measurements can serve as a qualification baseline for the flight instrument during ground-based tests.

(1) P. Keresztes Schmidt et al., Sample handling concept for in-situ lunar regolith analysis by laser-based mass spectrometry, IEEE Aerospace Conference, 2024, submitted
(2) P. Wurz et al., In Situ Lunar Regolith Analysis by Laser-Based Mass Spectrometry, IEEE Aerospace Conference, 2023, 1-10
(3) P. Keresztes Schmidt, A. Riedo, P. Wurz, Chimia 2022, 76, 257
(4) A. Riedo, A. Bieler, M. Neuland, M. Tulej and P. Wurz, J. Mass Spectrom., 2013, 48, 1-15
(5) P. Wurz, M. Tulej, A. Riedo, V. Grimaudo, R. Lukmanov, and N. Thomas, IEEE Aerospace Conference, 2021, 50100, 1-15.

How to cite: Keresztes Schmidt, P., Boeren, N. J., Gruchola, S., Tulej, M., Riedo, A., and Wurz, P.: In-situ sample handling and chemical analysis of lunar regolith by laser ablation ionisation mass spectrometry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8916, https://doi.org/10.5194/egusphere-egu24-8916, 2024.

Ground motion observations on planetary objects are a prerequisite for a detailed understanding of their interior structure and evolution. The imaging of the near surface structure - in particular on the Moon - has strong practical implications. First, the race is on to detect ice-bearing rocks near the surface from which water could be extracted and used as a resource for crewed missions. Second, due to the substantial bombardment of the lunar surface with meteorites and the lack of an atmosphere, observatories or habitats may have to be built underground. It has been proposed that cavities from ancient lava flows below the lunar surface could be used to place infrastructure. Current mission plans for geophysical exploration focus on static seismic sensors/arrays that would be restricted to the area they can explore.      
With the NEPOS project we want to go beyond these restrictions and develop concepts for mobile seismic arrays that work in an autonomous way using robotic technology. The scientific challenges include the understanding of wavefield effects of icy rocks and caves in a strongly scattering environment, the provision of optimal source-receiver configurations to detect them, as well as an integrated data-processing workflow from observation to subsurface image including the quantification of uncertainties.   
In order to solve these challenges, we first developed a Digital Twin for wave propagation in the strongly heterogeneous lunar crust to generate synthetic seismic data using the spectral element code SALVUS. We compared the synthetic seismograms to data from the Apollo 17 Lunar Seismic Profiling Experiment (LPSE) and find that their main characteristics coincide. We further generated synthetic seismograms for a variety of network configurations and subsurface heterogeneities, which will be used to test appropriate imaging methods for the lunar subsurface structure. Due to the presence of strongly scattering media ambient noise tomography seems to be a promising method, as was already shown in previous studies. We apply seismic interferometry to LPSE data, as well as to our synthetic seismograms, to reconstruct Green’s functions, which give us information on the subsurface properties.

How to cite: Keil, S., Igel, H., Bernauer, F., Shutin, D., Shin, B.-S., Nierula, K., Reiss, P., Sesko, R., and Lindner, F.: The NEPOS Project: Near-Surface Seismic Exploration of Planetary Bodies with Adaptive Networks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9849, https://doi.org/10.5194/egusphere-egu24-9849, 2024.

Space stations on the lunar surface are exposed to cosmic rays, solar flares, micrometeorites and huge temperature variations. Therefore human outposts on the lunar surface have to be covered by huge layers of regolith. In 2009 the Japanese lunar orbiter SELENE (Selenological and Engineering Explorer) has detected three giant lunar holes: Mare Tranquilitatis Hole (MTH), Marius Hills Hole and Mare Ingenii Hole. The holes differ from normal impact craters and may be the entrances to underground lave tubes. The deepest one is MTH with 107 m and 98 x 84 m in diameter. According to Haruyama et al. the soil of lunar holes could contain water resources (protons from solar-wind hydrogen flux or even water molecules). Lunar holes reduce the effects of cosmic rays because of their limited field of view from the bottom. They provide also milder temperatures than the lunar surface. In the shadowed areas the temperature  ranges from -20°C to +30°C during the lunar day. These benefits make lunar holes become favourite locations to establish initial lunar stations. In a first step we propose to build an initial base on the lunar surface at the edge of MTH. It can be used for storage and as a "site hut" for astronauts to supervise the following work. In a second step the initial base is enlarged by a modular structure down to the bottom of MTH. Robotic and semi-robotic machinery is used to erect the modular structures. Lunar regolith is used for protection against cosmic rays and meteorites (ISRU In Situ Resource Utilization). Finally MTH could be  closed by a transparent dome and filled with air to create a "green" habitat for human settlers.

How to cite: Grandl, W.: Mare Tranquilitatis Hole - a habitable place for a first lunar settlement, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10730, https://doi.org/10.5194/egusphere-egu24-10730, 2024.

The surfaces of planetary bodies reflect their evolution through primary surface shaping via their continuous evolvement over time. Surface formation and degradation processes need to be understood in detail to infer the timescales over which these processes operate.

Planetary surfaces which are heavily cratered offer the opportunity to investigate various aspects of the cratering processes which are initiated when an impactor strikes their surface and ejects rock fragments from the impact point upon the newly-formed crater cavity and its surroundings (e.g. Hörz, F. and Cintala, M., 1997). Among the ejecta material from the impact are boulders covering a wide range of sizes (e.g. Nagori,R. et al., 2024). Dependent on the planet’s environment and the size of the impact fragments, these boulders can form either secondary craters or simply become subject to the various environmental forces which ultimately add through different degradation processes to the formation of planetary regolith. To understand many of the aspects of the above processes, size distributions of both the impact-generated boulders and secondary craters need to be understood (e.g. Cadogan, P., 2024).

As many of the techniques to identify boulders and small craters on albedo images are using shadow-based identification methods one has to be aware that ambiguities can arise through complex topographies and overlapping surface features. These factors can modify the shape of the shadow and make the identification of its borders difficult, thereby preventing a precise determination of both it’s location and it’s radius.

To obtaining high-quality statistics for boulders and craters over large and varied planetary surfaces, machine learning and deep learning methods have been applied to automate the tedious human based detection work (e.g. DeLatte, D. et al, 2019). However, little attention has been paid to investigate the influence of the training sets on the success rates of these efforts (Mall, U. et al., 2023). We are investigating in this study the influence of crater training sets, originating from specifically chosen lunar areas on the resulting confusion matrices produced by specific convolution neural networks and compare these with the results found from traditional imaging methods.

Cadogan, P., (2024), Automated precision counting of small lunar craters - A broader view, Icarus, Volume 408, 2024,115796.

DeLatte, D.M., Crites, S.T., Guttenberg, N., Yairi, T. (2019), Automated crater detection algorithms from a machine learning perspective in the convolutional neural network era, Advances in Space Research, Volume 64, Issue 8, Pages 1615-1628.

Hörz, F. and Cintala, M. (1997), The Barringer Award Address Presented 1996 July 25, Berlin, Germany: Impact experiments related to the evolution of planetary regoliths. Meteoritics & Planetary Science, 32: 179-209. https://doi.org/10.1111/j.1945-5100.1997.tb01259.x.

Mall, U., Kloskowski, D., Laserstein, P., (2023), Artificial intelligence in remote sensing geomorphology—a critical study, Front. Astron. Space Sci., 30 November 2023, Sec. Planetary Science , Volume 10 – 2. https://doi.org/10.3389/fspas.2023.1176325.

Nagori,R., Dagar, A. K., Rajasekhar, R.P., (2024),  Age estimation and boulder population analysis of the West crater at Apollo 11 landing site using Orbiter High Resolution Camera on board Chandrayaan-2 mission, Planetary and Space Science, Volume 240, 2024, 105828.

How to cite: Mall, U., Surkov, Y., and Cadogan, P.: How do training sets influence crater and boulder detection in machine learning?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12084, https://doi.org/10.5194/egusphere-egu24-12084, 2024.

            The DIMPLE (Dating an Irregular Mare Patch with a Lunar Explorer) experiment has been selected by NASA for flight to the Moon later this decade. The objective is to date volcanic rocks from Ina, the largest known (3×2 km) irregular mare patch. Ina is remarkable for its scarcity of impact craters; taken at face value, the crater density implies a surface model age of 33 ± 2 Ma [1]. If the Moon was volcanically active this recently, it would require a profound reassessment of our understanding thermal evolution of the lunar interior. An alternative explanation for the anomalously low crater density posits that Ina is a chilled magmatic foam [2], the vesicularity of which favors crumbling rather than cratering during meteoroid impacts. If vesicularity can make a ~3000 Ma old terrane appear to be 100× younger, it begs the question of what other surface age estimates based on crater density, from anywhere in the inner Solar System, can also be wildly inaccurate.  

            The DIMPLE payload includes (i) the CODEX (Chemistry, Organics, and Dating Experiment) instrument, (ii) a sample-handling system including an arm for gripping rocks off the lunar surface, and (iii) a rover-mounted rake for collecting rock samples from farther afield. CODEX works by analyzing hundreds of 35 μm spots over rock samples 1.9-3.8 cm across, using laser-ablation mass spectrometry to measure the abundances of major elements and some trace elements, and using laser-ablation resonance-ionization mass spectrometry to measure the isotopic abundances of Rb and Sr. In this lunar context, the organics capability of CODEX will not be exploited.  The mass spectrometer for CODEX is a re-flight of the mass spectrometer designed for the Luna-Resurs mission, with an optimized ion source to collect resonantly excited ions in addition to ions produced directly by laser ablation. CODEX data will enable dating by the ⁸⁷Rb-⁸⁷Sr isochron technique and, by mapping elemental composition, will permit lithologic classification and petrologic interpretation of the analyzed rock samples from Ina.

References:        [1] Braden S.E. et al. (2014) Nature Geoscience 7, 787.

                             [2] Qiao L. et al. (2021) Planet. Sci. J. 2 66.

How to cite: Anderson, F. S., Bierhaus, E. B., Braden, S. E., Fagan, A. L., Fausch, R. G., Head III, J. W., Joy, K. H., Levine, J., Osterman, S., Pernet-Fisher, J., Tartèse, R., Wurz, P., and Yant, M.: The DIMPLE Experiment to Date Ina, a Young-Looking Volcanic Structure on the Moon, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13507, https://doi.org/10.5194/egusphere-egu24-13507, 2024.

Sulfides are common minerals in lunar rocks and have great implications for lunar magma origin and subsequent evolution. Pentlandite as an important sulfide, usually coexisted with troilite, which could indicate the geological thermal history of lunar rocks. Previous researchers proposed three potential mechanisms to explain the origin of pentlandite in lunar soil: (i) the reaction between mobilized sulfur and metallic FeNi, ilmenite and an Fe-bearing silicate; (ii) it is formed by the reaction between migrating Ni and troilite; (iii) pentlandite may exsolve from the Ni-rich troilite during the cooling of rocks. Here, we used the scanning electron microscopy (SEM), X-Ray electron probe micro-analyzer (EPMA) and transmission electron microscopy (TEM) to decipher the formation mechanisms of pentlandite in Chang’e-5 (CE-5) lunar soils. Our results show that pentlandites occurred as lamella and veinlets in troilites from basalts and breccias, forming a troilite-pentlandite assemblage. Crystallographic data from TEM provide the first robust evidence that pentlandites from both basalts and breccias were exsolved from the host troilite during the magma cooling, rather than formed by the reaction between mobilized sulfur and metallic FeNi, or mobilized Ni with troilite. Furthermore, we found taenite was exsolved from pentlandite in lunar breccia, forming a troilite-pentlandite-taenite assemblage. Given exclusively exsolved taenite and higher Ni content in troilite in breccia than that in basalts, it suggests the origin of pentlandite in breccia may involve a geological process involving the addition of exotic meteorite materials. Finally, we established two atom shuffling models to describe the transformation mechanism from troilite to pentlandite, and pentlandite to taenite. This work provides new insights into the origin and geological evolution of lunar sulfides, and also provides new method for the study of mineral evolution in other extraterrestrial samples.

How to cite: Tang, X., Gu, L., Tian, H., Li, Q., and Li, J.: Origin of pentlandite in Chang’e-5 lunar soils revealed by transmission electron microscopy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14455, https://doi.org/10.5194/egusphere-egu24-14455, 2024.

How to cite: Nguyen, D. T., Jacquemoud, S., Lucas, A., Douté, S., Ferrari, C., Coustance, S., Marcq, S., and Meygret, A.: Unveiling the characteristics of the lunar surface by massive inversion of the Hapke model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17062, https://doi.org/10.5194/egusphere-egu24-17062, 2024.

High resolution gravity field measurements from GRAIL [1], in-situ heat flux [2] and seismic measurements from Apollo [3,4], surface composition from Clementine and Lunar Prospector [5,6], and the analysis of lunar samples have provided a wealth of information about the thermal evolution of the Moon [7].

Constraints on the present-day thermal state of the lunar interior come from the Apollo surface heat flux measurements: 21±3 mW m^-2 at the Apollo 15 and 14±2 mW m^-2 at the Apollo 17 landing sites [2]. A peak heat flux of ~180 mW m^-2 was recently inferred by [8] from the Chang’E 1 and 2 data at the Compton-Belkovich location, a Thorium anomaly feature on the lunar farside. A lower bound for the lunar heat flux of only ~6 mW m^-2 has been suggested, for the so-called Region 5, by measurements of the Diviner Lunar Radiometer Experiment onboard LRO [9]. Additionally, thermal expansion/contraction estimates [10] provide secondary constraints on the thermal state of the interior throughout lunar history.

Here, we model the interior dynamics of the Moon to infer plausible distributions of heat producing elements (HPEs) that, in turn, are directly linked to surface heat flux variations. To this end, we compare the present-day surface heat flux obtained in our models with the above constraints. Similar to [11], we combine global geodynamical models [12] with crustal thickness models derived from gravity and topography data [13]. We include higher HPEs abundances in the Procellarum KREEP Terrane (PKT) and crust compared to the mantle, and a mantle rheology similar to [14]. We test both constant and pressure/temperature dependent thermal conductivity scenarios. In addition to present-day heat flux, we compute the thermal expansion/contraction based on the interior thermal state obtained from our models at different times during lunar evolution and compare these values with available estimates to select best-fit models.

We find that variations in crustal thickness and the distribution of HPEs in the crust, mantle, and PKT region predominantly affect the convection pattern in the lunar interior and the surface heat flux. Models best compatible with the heat fluxes in the Apollo regions and Region 5 show an average Thorium abundance in the PKT region of ~2.4 ppm, smaller than the observed surface values [6], suggesting a strong Thorium enrichment close to the surface. These models have a crustal thermal conductivity of ~1.2 W/(mK), ~3 times lower than that of the mantle. None of our models matches the heat flux estimated at the Compton-Belkovich location, indicating either specific local processes [8] or large measurement uncertainties.

References:

[1] Zuber et al., 2013; [2] Langseth et al., 1976; [3] Garcia et al., 2019; [4] Nunn et al., 2020; [5] McEwen et al., 1997; [6] Lawrence at al., 2003; [7] Jaumann et al., 2012; [8] Siegler et al., 2023; [9] Paige & Siegler, 2016; [10] Andrews-Hanna et al. 2013; [11] Plesa et al., 2016; [12] Hüttig et al., 2013; [13] Broquet & Andrews-Hanna, 2023; [14] Laneuville et al., 2013.

How to cite: Santangelo, S., Plesa, A.-C., Broquet, A., Breuer, D., and Root, B. C.: Present-day surface heat flux variations on the Moon from global geodynamic and crustal thickness models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17449, https://doi.org/10.5194/egusphere-egu24-17449, 2024.

We know from spacecraft measurements that the crust of the Moon is heterogeneously magnetized. With the exception of a few magnetic anomalies related to craters and swirls, the origin of most of the lunar magnetic anomalies is not understood. Here we evaluate the performance of an inversion methodology, initially conceived to infer the direction of the underlying magnetization from magnetic field measurements, commonly referred to as Parker's method, to elucidate the origin of the magnetic sources by constraining the location and geometry of the underlying magnetization. We assess the performance of the method by conducting a variety of tests, using synthetic magnetized bodies of different geometries. These have been chosen such that they mimic  the main geological structures potentially magnetized within the lunar crust. Our test results show that the Parker method successfully localizes and delineates the two-dimensional surface projection of subsurface three-dimensional magnetized bodies, when certain conditions are fulfilled. In particular, the magnetization should be close to unidirectional, and the magnetic field data should have a higher spatial resolution than the smallest dimension of the magnetized body as well as a high signal-to-noise ratio. As an additional evaluation test, we applied this inversion methodology to two lunar magnetic anomalies that are associated with visible geological features, the Mendel-Rydberg impact basin and the Reiner Gamma swirl. For Mendel-Rydberg,  our analysis shows that the strongest magnetic sources are located within the basin's inner ring in agreement with previous studies showing that during an impact, the crust inside the newly formed crater undergoes demagnetization and potentially remagnetization (if an ambient magnetic field is present). For Reiner Gamma, we found the strongest magnetic sources form a narrow dike-like body that emanates from the center of the Marius Hills volcanic complex. The reason that only one such dike emanating from Marius Hills is magnetized could be linked to an atypical iron-metal composition or to the lunar ambient magnetic field being only intermittently present. Future applications of this method can focus on constraining the origin of the many lunar magnetic anomalies that are not associated with visible geological features.

How to cite: Oliveira, J. S., Vervelidou, F., Wieczorek, M. A., and Diaz Michelena, M.: Constraints on the spatial distribution of lunar crustal magnetic sources from orbital magnetic field data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20166, https://doi.org/10.5194/egusphere-egu24-20166, 2024.

The Chinese Lunar mission Chang'E-4 soft-landed on the far side of the Moon on January 2019 marking a significant milestone in space exploration. The mission's landing site is on the eastern floor of Von Kármán (VK) crater (45.4446°S, 177.5991°E), within the South Pole–Aitken (SPA) basin, one of the oldest and largest impact craters in the solar system.

Yutu-2 is the rover of the Chang;E-4 mission. Similar to its twin rover Yutu-1, amongst its scientific payloads Yutu-2 carries a set of ground-penetrating radar (GPR) systems. GPR is a well-established geophysical method and has been instrumental in the new era of planetary exploration. Chang’E-3 was the first mission incorporating in-situ planetary GPR, a trend continued by subsequent Lunar and Martian missions, including Chang'E-4, Perseverance, Chang'E-5 and Tianwen-1; with plans for future missions such as Chang'E-7 and ExoMars [1].

Existing Lunar GPR studies often assume that the dielectric properties of Lunar materials can be modelled via a constant electric permittivity and a conductive term. However, treating the electric permittivity as non-dispersive overlook the frequency-dependent complex electric permittivity of ilmenite. Ilmenite is a titanium mineral, particularly abundant in Lunar mare basalts and soils. Recent investigations [1] using a complex Cole-Cole function have shown that ilmenite-mixtures act as low-pass filters, causing a decrease in the pulse's central frequency as the wave propagates through an ilmenite formation. This frequency shift, proportional to the ilmenite content, serves as a basis for inferring the presence of basalts and approximating their ilmenite content.

In this study, we explore the frequency shift of signals received both from Channel-2B and Channel-1. Our analysis reveals a sequence of basaltic layers extending to approximately 300 m depth, displaying varying thickness and ilmenite content. Based on the estimated ilmenite content, the GPR data indicates three distinct phases of Lunar volcanism: an early phase with high-Ti basalts, followed by a low-Ti volcanic activity, and a final phase with high-Ti basalts. These findings align with generic models of Lunar lava emplacement [1]. According to these models, Lunar volcanic history includes an early "blue" titanium-rich volcanic event (~ 3.8-3.5 Ga), followed by low-Ti "red" basalts (~ 3.5-3 Ga), and a subsequent phase of "blue" high-Ti basalts (~3 Ga) [2].

References

[1]   Giannakis, I., Martin-Torres, J., Su, Y., Feng, J., Zhou, F., Zorzano, M-P., Warren, C., Giannopoulos, A., (2024). Evidence of Shallow Basaltic Lava Layers in Von Kármán Crater from Yutu-2 Lunar Penetrating Radar, Icarus, 2024.

[2] Cattermole, P. J., (1996). Planetary Volcanism: A Study of Volcanic Activity in the Solar System, Wiley, Chichester, 2^ndEdition, 1996.

How to cite: Giannakis, I., Warren, C., and Giannopoulos, A.: Lunar Penetrating Radar Reveals Three Phases of Volcanism at Von Kármán Crater, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20971, https://doi.org/10.5194/egusphere-egu24-20971, 2024.

Spacecraft magnetic field measurements and paleomagnetic studies on Apollo lunar samples indicate that the Moon once sustained a core dynamo. However, strength and  duration of the dynamo field are key unknowns that may constrain the mechanism that powered it. Shedding light on these questions can improve our understanding about the generation of dynamos on small planetary bodies. Here, I will present new paleointensity measurements of the lunar magnetic field, based on alternating field and controlled atmosphere thermal demagnetization. In particular, we measured mare basalts and regolith breccias from the Apollo 16 and Apollo 17 missions, with ages ranging from 1.7 to 3.75 Gy old. I will discuss the results in the context of two issues surrounding lunar paleomagnetism. Firstly, I will show, through the example of an Apollo 17 mare basalt specimen carrying magnetizations acquired at two different epochs, that the magnetic record of these rocks is of lunar origin, as opposed to spacecraft or terrestrial contamination. Secondly, I will show results from the Apollo 16 regolith breccias suggesting that the lunar dynamo was fluctuating in intensity at least since 3.4 Ga. A fluctuating dynamo has been proposed as a possible resolution to the energy conundrum of the early phase of the lunar dynamo. Over a period of several hundred million years, extending up to 3.5 Gy ago, various paleomagnetic studies have inferred paleointensities that require an energy budget in excess of what numerical simulations, assuming a dynamo powered by thermochemical convection, estimate to have been available, given the Moon’s small metallic core. While our results do not directly address the energy budget conundrum during that time period, the fact that magnetic field fluctuations have occurred at least since 3.4 Gy ago, hints at the possibility that they could have occurred also at earlier times. If these fluctuations were large enough, they could allow for a reconciliation between paleomagnetic studies and numerical simulations, without the need to evoke alternative dynamo mechanisms.

How to cite: Vervelidou, F., Weiss, B. P., Nichols, C. I. O., Murray, M., Shah, J., Lagroix, F., McDonald, H., and Carvallo, C.: New paleointensity measurements of Apollo samples and implications for the lunar dynamo, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21481, https://doi.org/10.5194/egusphere-egu24-21481, 2024.

We present LunarLeaper, a robotic explorer concept in response to the ESA 2023 Small Missions call. Pits, volcanic collapse features with near-vertical walls, have been identified across the lunar and Martian surface. These pits are high priority exploration destinations because some, referred to as skylights, might provide access to subsurface lava tube systems. Lava tubes are of particular interest for future human exploration as they offer protection from harmful radiation, micrometeorites and provide temperate and more stable thermal environments compared to the lunar surface. We propose to use a small legged robot (ETH SpaceHopper, <10 kg), to access and investigate the pit edge, using its ability to access complex and steep terrain more safely than a wheeled rover. LunarLeaper will land in Marius Hills within a few 100 m of the pit and traverse across the lateral extent of the hypothesized subsurface lava tube. On its traverse it will take measurements with a ground penetrating radar and a gravimeter, measurements that will allow us to survey the subsurface structure and detect and map lava tube geometry if present. The robot will approach the pit edges and acquire high resolution images of the pit walls containing uniquely exposed layers of the geophysically mapped lava flows and regolith layers. These images will allow not only scientific advances of lunar volcanism and regolith formation, but also enable assessment of the stability of the pit structure and its use as a possible lunar base. The mission is expected to last 1 lunar day. The robot could be delivered to the surface by a small lander, as they are currently developed and planned by various national and commercial agencies and hop off the landing platform without the need for a robotic arm. It is highly flexible in accommodation and can thus make full use of the new international lunar ecosystem.

How to cite: Mittelholz, A., Stähler, S. C., Kolvenbach, H., Bickel, V., Church, J., Hamran, S.-E., Karatekin, O., Ritter, B., Aaron, J., Anhorn, B., Coloma, S., de Palézieux dit Falconnet, L., Grott, M., Ogier, C., Robertsson, J., and Walas, K.: Lunarleaper – Unlocking a Subsurface World, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21578, https://doi.org/10.5194/egusphere-egu24-21578, 2024.

Lunar Vertex, selected as NASA’s first Payloads and Research Investigations on the Surface of the Moon (PRISM) delivery, will explore a portion of Reiner Gamma (7.585° N, 58.725° W) with instruments mounted on a lander and small rover. Reiner Gamma (RG) is home to a magnetic anomaly, a region of magnetized crustal rocks. The RG magnetic anomaly is co-located with the type example of a class of irregular high-reflectance markings known as lunar swirls. The Lunar Vertex payload was designed to address three science goals: (1) test hypotheses for the origin of the RG magnetic anomaly, (2) test hypotheses for the origin of the RG swirl, and (3) determine the structure of the RG mini-magnetosphere. The payload suite consists of three instruments on the lander, and two instruments on a small commercial rover.

The Lunar Vertex payload will be carried to the lunar surface on a commercial lander as part of NASA's Commercial Lunar Payload Services (CLPS) program. The lander and payload are designed for operation during one lunar daylight period (i.e., no night operations or survival). NASA selected Intuitive Machines as the CLPS provider for the Reiner Gamma delivery. At the time of this writing, the launch will be no earlier than June of 2024.

Lander Instruments: The three Lunar Vertex lander instruments were delivered to Intuitive Machines in June 2023. The Magnetic Anomaly Plasma Spectrometer (MAPS), built by the Southwest Research Institute, is capable of measuring the ion and electron velocity distribution over a 292.5° x 90° FOV from 8 eV/e to 17.5 keV/e. The Vector Magnetometer–Lander (VML) suite, built by APL, is comprised of a tetrahedral array of four commercial fluxgate magnetometers mounted on the bottom of a 0.5-meter mast, with a science-grade dual-ring core fluxgate magnetometer at the top of the mast. Together, MAPS and VML will characterize the magnetic field and surface plasma environment within RG. The Vertex Camera Array (VCA) suite, built by Redwire, is a set of three clusters of three RGB cameras. VCA images will be used to characterize the landing site geology and to understand the physical properties of the lunar regolith around the lander.

Rover and Rover Instruments: The rover vehicle is from vendor Lunar Outpost. The rover instruments were integrated with the vehicle at APL, and environmental testing was carried out on the integrated system. The Vector Magnetometer–Rover (VMR), built by APL, is also comprised of a tetrahedral array of commercial fluxgate sensors, mounted on a 0.2-meter mast. With VML, VMR will characterize local spatial structuring of the magnetic field at RG. The Rover Multispectral Microscope (RMM), mounted inside the rover body, is a close-up imager that can provide information on soil texture, as well as active LED illumination at a set of UV to NIR wavelengths chosen for their utility in determining the composition and maturity state of the regolith. The rover will be delivered to Intuitive Machines in early January 2024.

How to cite: Vines, S., Ho, G., and Blewett, D. and the The Lunar Vertex Science Team: The Lunar Vertex PRISM Payload: Ready for the Moon, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21717, https://doi.org/10.5194/egusphere-egu24-21717, 2024.

The Planet Mercury has been studied by the earlier MESSENGER mission which results show that Mercury’s history is expressed by: (i) volcanism, (ii) global contraction with consequent formation of tectonic-compressive features, and (iii) impact cratering with consequent formation of basins or minor craters [e.g., 1, 2]. However, it is still unclear how the interplay between tectonic induced by impact basins and compressional activity has influenced volcanism. Thus, we investigated the presence and the absence of a correlation between the various volcanic features and their geological context (e.g., inside craters and/or basins, relationship with tectonic structures) to understand which processes could have influenced the volcanic activity of the planet. The study was developed using the ESRI ArcGIS (Geographic Information System) software package. The data and base maps used in the main part of the project come from the MESSANGER mission. To carry out the correlation study on a global scale, a new GIS database was created in which all the volcanic structures identified so far on Mercury, their morphological characteristics and their associations with various other tectonic or volcanic have been specified. Specifically, we included 346 samples comprehensive of (i) volcanic vents and their morphological classification [3, 4], (ii) presumed volcanic cones [5], and (iii) irregular pitted terrains [6, 7]. Once this global database was created, the study was divided into two parts. The first qualitative part was based on the study of the global distribution of the volcanic features considered concerning the basin structures [8] and global compressional tectonic features [9]. This part allowed us to identify patterns and areas of interest for more detailed observations and analyses. A second quantitative part evaluated the presence of a correlation between the different parameters and geological features considered. Our study has highlighted how the majority of these volcanic centers are distributed on the margins of large basins whether they were formed inside or outside craters. The studied volcanic features are also often related to compressive tectonic structures at distances ranging from 10 to 200 km. Explosive volcanic activity on a global scale seems to have been triggered mainly in areas where minor impacts were formed near critically stressed tectonic basin structures (caused by the large impact) reactivated by the global compression. Dike propagation along those areas has likely caused the explosive eruptions in weaker areas often triggered by smaller impacts.

References: [1] Denevi, et al., (2018), Cambridge Planetary Science, 144-175. [2] Rothery et al., (2020), Space Science Reviews, 216, 66 (2020). [3] Pegg et al., (2021), Icarus, Volume 365, 114510. [4] Jozwiak et al., (2018), Icarus Volume 302, 191-212. [5] Wright et al., (2018), JGR Planets, 123, 952–971. [6] Ru Xu et al. (2022), Remote Sens., 14(17), 4164. [7] Goudge et al., (2014), J. Geophys. Res.Planets,119, 635–658. [8] Orgel et al., (2020), Journal of Geophysical Research: Planets,125, e2019JE006212. [9] Byrne et al., (2014), Nature Geoscience volume 7, 301–307 (2014).

How to cite: Mirino, M., Massironi, M., and Pozzobon, R.: A Correlation Study on Volcanic Features and their Geological Context on Mercury., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-228, https://doi.org/10.5194/egusphere-egu24-228, 2024.

Mercury’s exospheric atoms are mainly ejected from the surface through several processes such as thermal input, UV irradiation, solar wind particle sputtering, and micro-meteoroid impact. Observations by the MESSENGER spacecraft have shown that Mercury magnesium (Mg) exosphere is related to its surface abundance. Additionally, Mg is an interesting species as its surface abundance reflects the non-uniformity of magma compositions. However, spatial distribution (especially in the latitude direction) and seasonal variability of Mg exosphere is not well understood due to its dark brightness and the geometry of observations.

BepiColombo, the Mercury orbiting mission led by ESA and JAXA, is on its way to the planet. The 2nd and 3rd Mercury swing-bys were conducted on 22/06/2022 and 19/06/2023 (UTC), respectively, and many instruments observed the Mercury environments then. In this study, we analyzed Mg exosphere data from PHEBUS, the UV spectrometer onboard BepiColombo, to deduce temperature and production rate of Mg exosphere during each swing-by.

As a result, similar signals were obtained through both swing-bys. Season, local time, and longitude of Mercury during both observations were similar, but boresights of PHEBUS were different (2nd: northward, 3rd: southward). These results show that Mg production rates have little year-to-year variability, which is consistent with the fact that Mg is mainly ejected by micro-meteoroid impact. Besides, these results mean that dust impact flux has little north-south asymmetry.

In this presentation, we introduce the results obtained by observations of the spectrometer onboard BepiColombo, PHEBUS, during the 2nd and 3rd swing-bys. 

How to cite: Suzuki, Y., Quémerais, E., Robidel, R., Chaufray, J.-Y., Murakami, G., Leblanc, F., Yoshioka, K., and Yoshikawa, I.: Comparison of Exospheric Mg Distributions Observed by BepiColombo/PHEBUS During the 2nd and 3rd Mercury Swing-bys, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-798, https://doi.org/10.5194/egusphere-egu24-798, 2024.

Modeling the plasma and magnetic field state in Mercury's magnetosheath is one of the most urgent tasks in Mercury science in view of the upcoming BepiColombo mission. By considering the steady-state and constructing the Laplace equation for the scalar magnetic potential in the magnetosheath (eliminating the interplanetary magnetic field in the magnetosphere and vice versa), the plasma and magnetic field state is obtained as a function of the solar wind condition and the spatial coordinates of the magnetosphere. We make extensive use of the exact solution of the Laplace equation for the parabolically shaped magnetosheath, and map the solution onto the realistic shape of magnetosheath by assuming the magnetosheath thickness is scalable between the parabolic shape and the realistic shape along the magnetopause-normal direction. The quality of the constructed model can successfully be tested against the global hybrid simulation of Mercury's magnetosheath, promising that the model serves as a useful tool for BepiColombo's detailed magnetosheath studies at Mercury.

How to cite: Holzkamp, H., Schmid, D., Heyner, D., Pump, K., and Narita, Y.: Modeling Mercury's magnetosheath by the potential-mapping method , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2214, https://doi.org/10.5194/egusphere-egu24-2214, 2024.

This work aimed to study the dynamical response of the near-Mercury environment to different interplanetary conditions experienced along its orbit by means of 3D multi-species hybrid simulations.

Mercury features an eccentric and rapid orbit around the Sun, with its extreme aphelion (0.47 AU) and perihelion (0.31 AU) positions being embedded in significantly different interplanetary conditions.
Given the different environments and its weak magnetic field strength, the position, size and behavior of the bow-shock, magnetosheath and magnetopause can vary significantly as highly coupled with the interplanetary medium.

In this work, we consider an interplanetary magnetic field aligned along the Parker spiral direction at the Mercury's distance from the Sun, i.e., quasi-radial, and the case of an interaction with slow and fast solar winds. We show the response of the bow-shock due to such quasi-radial interplanetary field and the compression of the bow-shock / magnetosheath /  magnetopause system as the planet passes from the aphelion to perihelion orbital points, as well as the solar wind velocity increases.
 
In particular, certain portions of the planet no longer present a significant protection from the interplanetary environment, so that the surface is exposed to the precipitation of interplanetary ions. An analysis of their fluxes revealed that the high latitude polar cusps are still the main regions for the interplanetary particles to reach out the surface. However, when the interplanetary conditions are sharp enough to cause a strong bow-shock and magnetosheath compression, the interplanetary particles are able to directly penetrate these boundaries and can precipitate at much lower latitudes.

These results are particularly timely for the BepiColombo mission, and are compared with its first fly-bys observations.

How to cite: Cazzola, E., Fontaine, D., and Modolo, R.: On the Hermean near-planet boundaries response under different orbital interplanetary conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3429, https://doi.org/10.5194/egusphere-egu24-3429, 2024.

On June 19^th 2023, BepiColombo performed its third (MFB3) gravity assist maneuvers at Mercury. During this flyby, the spacecraft approaching the planet from dusk-nightside toward dawn-dayside and traveling down to close distances ~ 235 km altitudes above the planet’s surface. Even though BepiColombo is in a so-called “stacked configuration” during cruise (meaning that most of the instruments cannot be fully operated yet), a number of instruments can still make interesting observations. Particularly, despite their limited field-of-view, the particle sensors allow us to get a hint on the plasma composition and dynamics along a unique path across the magnetosphere and very close to the planet. In this presentation, we will show an overview of the plasma environment from the Mercury Ion Analyzer (MIA) and the Mercury Electron Analyzer (MEA); moreover we will present the first ion composition observations of the Mass Spectrum Analyzer (MSA). MIA, MSA and MEA are part of the Mercury Plasma Particle Experiment (MPPE, PI: Y. Saito) consortium that is a comprehensive instrumental suite for plasma, high-energy particle and energetic neutral atom measurements onboard Mio (Saito et al. 2021). During this flyby, MSA and MIA revealed the presence of energetic (> 10 keV) and cold (< 100 eV) heavy ions inside the magnetosphere around closest approach. Moreover, we will show major features of the Mercury magnetosphere highlighting different regions: 1) plasma sheet, 2) nightside bounday-layer and 3) magnetosheath [Hadid et al., Nature Communications, under review].

How to cite: Hadid, L. and the MSA, MIA and MEA / MPPE teams: Plasma environment of Mercury’s magnetosphere as seen by BepiColombo during its third flyby, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3528, https://doi.org/10.5194/egusphere-egu24-3528, 2024.

The study of the internal structure of Mercury is fundamental for understanding the formation and evolution of the planet and of the entire Solar System. The main purpose of this work was the analysis of the MESS160A gravity field model [1] to show the presence of crustal heterogeneities in density. According to the flexural isostatic response curve, we noted that the lithospheric flexure occurs in the spherical harmonic degree range 5-80, consistently with a flexural compensation model, while for degrees lower than 5 the flexural rigidity tends to 0 and a local compensation model can be assumed. Removing spherical harmonic components up to degree 4, as they are associated with the polar mass deficit and to the morphological contrasts, we assumed a flexural compensation model [2] to first estimate a mean elastic thickness of 30 ± 10 km. We, then, modeled the lithospheric flexure regardless of the gravity field and calculated the isostatic gravity anomalies by subtracting the gravity effect caused by the isostatic compensation to Bouguer anomalies. In this way, we proved that considerable lateral density variations occur within the Mercury's crust [3]. We also estimated the curst-mante interface depth, varying from 19 to 42 km. Isostatic anomalies are mainly related to density variations in the crust: gravity highs mostly correspond to large-impact basins, suggesting intra-crustal magmatic intrusions as the main origin of these anomalies. Isostatic gravity lows prevail, instead, above intercrater plains and may represent the signature of a heavily fractured crust.

Acknowledgements: We gratefully acknowledge funding from the Italian Space Agency (ASI) under ASI-INAF agreement 2017-47-H.0.

References:

[1] Konopliv, A. S. et al. (2020). Icarus, 335.

[2] Turcotte, D. L. et al. (1981). J. Geophys. Res., 86.

[3] Buoninfante, S. et al. (2023). Sci. Rep., 13.

How to cite: Buoninfante, S., Milano, M., Negri, B., Plainaki, C., Sindoni, G., and Fedi, M.: Mercury's crustal heterogeneity revealed by gravity data modelling , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4391, https://doi.org/10.5194/egusphere-egu24-4391, 2024.

Geological cartography and structural analysis are essential for understanding Mercury’s geological history and tectonic processes. This work focuses on the geological and structural analysis of the Michelangelo quadrangle (H12), located at latitudes 22.5°S-65°S and longitudes 180°E-270°E. We present the first geological map of H12 at 1:3,000,000 scale, based on the photointerpretation of the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) Mercury Dual Imaging System (MDIS) imagery. The present study is a contribution to the 1:3M geological map series, planned to identify targets to be observed at high resolution during the ESA-JAXA BepiColombo mission [1]. 

We mapped tectonic structures and geological contacts using the MDIS derived basemaps, characterized by an average resolution of 166 m/pixel. Linear features are subdivided into large craters (crater rim diameter > 20 km), small craters (5 km < crater rim diameter < 20 km), subdued or buried craters, certain or uncertain thrusts, certain or uncertain faults, wrinkle ridges and irregular pits. Geological contacts, mapped as certain or approximate, delimit the geological units grouped into three classes of crater materials (c1-c3) based on degradation degree, and plains (smooth, intermediate and intercrater plains).

Michelangelo appears as a densely cratered quadrangle dominated by degraded crater materials (c2) and intermediate plains. We identified two main regional thrust system trending NW-SE and NE-SW. We found that many lobate scarps developed at the edges of ancient, large impact basins. Clear examples of such tectonic structures in the Michelangelo quadrangle are provided by the Beethoven basin (20.8°S–236.1°E) or by the Vincente-Yakovlev basin (52.6°S–197.9°E). We propose a thick-skinned tectonic model according to which the lobate scarps were formed after positive reactivation of previous impact-related normal faults, due to the contractional tectonic regime deriving from the global contraction. Evidence of thick-skinned tectonics on Mercury are provided by the presence of fault systems exceeding the basin rim, and by the estimated rooting depth of thrusts bordering large basins (e.g., Discovery Rupes, Soya Rupes).

Following [2], we found that the NW-SE system largely borders the southwestern edge of the HMR. We also show that the volcanic vents on Mercury are often associated with impact craters and/or lobate scarps (e.g., [3,4]), which can be considered as possible preferential areas for magma uprising.

Acknowledgements: We gratefully acknowledge funding from the Italian Space Agency (ASI) under ASI-INAF agreement 2017-47-H.0.

References:

[1] Galluzzi, V. et al. (2021). LPI Contrib., 2610.

[2] Galluzzi, V. et al. (2019). J. Geophys. Res., 124(10), 2543-2562.

[3] Thomas, R. J. et al., (2014). J. Geophys. Res., 119, 2239-2254.

[4] Jozwiak, L. M. et al., (2018). Icarus, 302, 191-212.

How to cite: Buoninfante, S., Galluzzi, V., Ferranti, L., Milano, M., and Palumbo, P.: Geology and tectonic structures of the Michelangelo (H12) quadrangle, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4401, https://doi.org/10.5194/egusphere-egu24-4401, 2024.

Mercury possesses a dynamic magnetosphere driven primarily by magnetic reconnection occurring regularly at the magnetopause and in the magnetotail. Using the Magnetohydrodynamics with Adaptively Embedded Particle-in-Cell (MHD-AEPIC) model, we have performed a series of global simulations with different upstream conditions to study in detail the kinetic signatures, asymmetries, and flux transfer events (FTEs) associated with Mercury’s dayside magnetopause reconnection. By treating both ions and electrons kinetically, the embedded PIC model reveals crescent-shaped phase-space distributions near reconnection sites, counter-streaming ion populations in the cusp region, and strong temperature anisotropies within FTEs. A novel algorithm has been developed to automatically identify reconnection sites in our 3D simulations. The spatial distribution of reconnection sites as modeled by the PIC code exhibits notable dawn-dusk asymmetries, likely due to such kinetic effects as X-line spreading and Hall effects. Across all simulations, simulated FTEs occur quasi-periodically every few seconds with their key properties showing clear dependencies on the upstream solar wind Alfvénic Mach number and the IMF orientation, consistent with MESSENGER observations and previous Hall-MHD simulations. FTEs formed in our MHD-AEPIC model are found to contribute a significant amount (~ 3% - 36%) of the total open flux generated at the dayside magnetopause. Taken together, the results from our MHD-AEPIC simulations provide new insights into the kinetic processes associated with Mercury’s magnetopause reconnection that should prove useful for interpreting in situ observations from MESSENGER and BepiColombo.

How to cite: Jia, X., Li, C., Chen, Y., and Toth, G.: Kinetic signatures, asymmetries, and FTEs associated with Mercury’s dayside magnetopause reconnection as revealed by 3D MHD-AEPIC simulations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4716, https://doi.org/10.5194/egusphere-egu24-4716, 2024.

Tolstoj quadrangle is located in the equatorial area of Mercury, between 22.5°N and 22.5°S of latitude and 144° and 216°E of latitude. In this work we present the geological map (1:3M scale) performed on the quadrangle. The main basemap used for the mapping is the MDIS (Mercury Dual Imaging System) 166 m/pixel BDR (map-projected Basemap reduced Data Record) monochrome mosaic compiled using NAC (Narrow Angle Camera) and WAC (Wide Angle Camera) 750 nm-images. Moreover, to distinguish spectral characteristics and topography of the surface, MDIS global color mosaics [Denevi et al., 2016)] and the MDIS global DEM [Becker et al., 2009), have been taken into account. Then, the quadrangle has been mapped using ArcGIS at an average scale of 1:400k for a final out-put of 1:3M. The mapping highlights as Caloris basin related features dominate the geology of H08. Indeed, the southern half of the basin is located in the upper left corner of quadrangle. Inside and outside the basin extended smooth plains were emplaced and they represent the most extended volcanic deposits in the quadrangle. Also structural framework is mainly linked with the basin with radial and concentric grabens located in its floor and wrinkle ridges widespread both on the interior and exterior Caloris smooth plains. Further, lobate scarps have been detected in the quadrangle: they are located outside the Caloris basin but they are absent within its floor. These thrusts show a preferential orientation in the smooth plains located outside the basin whereas they are more randomly oriented in the intercrater plains. Besides smooth plains, products of effusive volcanism, features related to explosive volcanism have also been frequently detected. Interestingly, several volcanic vents have been identified in the inner Caloris smooth plains, aligned with the rim of Caloris basin, suggesting a correlation between these two features. However, vents are not clustered only inside Caloris basin, but other crater floors are affected by this type of features. The vents are surrounded by extended pyroclastic deposits appearing in bright yellow in MDIS enhanced global color mosaics. Finally, hollow fields have also been mapped, although they are not very frequent. Some of them are associated to the pyroclastic deposits located along Caloris rim, the others are detected within floors or peaks of a few craters in the intercrater plains.

The geological map will be integrated into the global 1:3M geological map of Mercury (Galluzzi et al., 2021), which is being prepared in support to ESA/JAXA (European Space Agency, Japan Aerospace Agency) BepiColombo mission.

Acknowledgements:  We gratefully acknowledge funding from the Italian Space Agency (ASI) under ASI-INAF agreement 2017-47-H.0 and from the GMAP, Europlanet RI 20-24 grant n.: 871149-GMAP

References:

Becker K. J., et al. AGU, Fall Meeting, ab-stract#P21A-1189, 2009

Denevi et al.:LPS XLVII. Abstract#1264, 2016

Galluzzi V. et al.:. Planetary Geologic Mappers 2021, LPI #2610, 2021

How to cite: Giacomini, L., Guzzetta, L., Galluzzi, V., Ferranti, L., and Palumbo, P.: Geological map of Tolstoj quadrangle (H08) of Mercury, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6003, https://doi.org/10.5194/egusphere-egu24-6003, 2024.

The results from planetary investigation in the last years strongly point out that the integration of compositional information with the morphology, stratigraphy and tectonics permits to produce a more comprehensive geological approach, obtaining geological maps instead of purely morpho-stratigraphic maps. In this view, firstly PLANMAP project, and then GMAP (within EUROPLANET-RI 20-24), have given indications on different approaches to follow for such integration.
Investigating the surface of Mercury is an important task of the Bepicolombo mission. To be prepared for this task we are investigating the data obtained by past MESSENGER mission in order to understand which geological features and/or region of Mercury should hide key information.
In this work we investigate the Kuiper crater (62 kilometer in diameter) which overlies the northern rim of the larger crater Murasaki. The Kuiper crater is one of the highest albedo features on the surface of Mercury with an important ray system, indicative of  its young age. From this point of view Kuiper can be considered an important feature on hermean surface history, such as to give the name at the last period of Mercury timeline (the Kuiperian age). However, on the other side,its relatively young age does not permit it to investigate the local geology by using the global basemaps, since the albedo is saturating within the crater, making difficult to understand the variegation on it and on the proximal and distal ejecta. Whereas considering the color variegation from the different filters of the WAC camera onboard MESSENGER, at relatively high spatial resolution (385 m/px), we clearly highlighted how several peculiar geological features arise. These regions have been later investigated by ad-hoc mosaics considering the highest resolution images available (~ 120 m/pixel) from the NAC camera onboard MESSENGER.
The extension of the ejecta could be improved and differentiated from reflectance properties of the crater floor, showing an asymmetry towards S-SE. Moreover, the crater wall seems to reveal the possible impact direction. Evidence of pyroclastic-like material, from spectral reflectance properties, are present on the N-E wall, whereas from north to west the terraced wall seems to show the presence of re-melted material. Interestingly, two different hollows-like terrain are present on both the inner peaks and on the southern wall, indicating that hollows could be emplaced on different bedrock terrains. In addition, the spectral indication shows a clear distinction from Kuiper material with respect to the Murasaki terrains.
We want to acknowledge the GMAP, Europlanet RI 20-24 grant n.: 871149-GMAP and the Bepicolombo (SIMBIO-SYS) project, ASI-INAF agreement n.: 2017-47-H.0

How to cite: Carli, C., Giacomini, L., Massironi, M., Zambon, F., Galiano, A., Capaccioni, F., and Palumbo, P.: Geological mapping of Kuiper Crater: a break within Mercury crust, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6397, https://doi.org/10.5194/egusphere-egu24-6397, 2024.

BepiColombo, the ESA/JAXA joint mission, has already performed three out of the six flybys of Mercury scheduled during its journey to the innermost planet of our solar system. The first two flybys were conducted at a similar True Anomaly Angle (TAA~265°), while the third one occurred closer to the perihelion (TAA=311°).

During these three flybys, several instruments observed the planet and its environment, including PHEBUS (Probing of Hermean Exosphere By Ultraviolet Spectroscopy), the UV spectrograph on board BepiColombo/MPO. The two visible channels of PHEBUS, centered at 404nm and 422nm, observed Mercury’s exosphere during each of the three flybys. The third flyby provided the first observations of the southern hemisphere of Mercury. Indeed, PHEBUS was pointing towards the south ecliptic direction during the third flyby while the instrument was pointing towards the north ecliptic direction during the first two flybys.

We report the detection of the calcium (Ca) emission line at 422.8nm during each of the three flybys. Our results reveal that Mercury Ca exosphere is very extended on the morning side (up to ~10,000 km of altitude) and is enhanced near the dawn region. We then discuss year-to-year variability and potential source processes.

We also report the detection of additional species with the visible channel centered at 404nm during the three flybys, potentially manganese (Mn) or potassium (K). The detection is confined to the predawn region. Mn was detected by MESSENGER at similar local times (2-5 A.M.) but at different TAA (0-70°). However, the K doublet near 404nm has never been detected by MESSENGER.

Finally, we briefly discuss the geometric configuration of the next flybys of Mercury that will take place in September 2024, December 2024 and January 2025.

How to cite: Robidel, R., Quemerais, E., Chaufray, J.-Y., Leblanc, F., and Koutroumpa, D.: PHEBUS observations of exospheric calcium and potential detection of exospheric manganese during BepiColombo first three flybys of Mercury., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6547, https://doi.org/10.5194/egusphere-egu24-6547, 2024.

Observations from the MESSENGER (MErcury Surface, Space Environment, GEochemistry, and Ranging) mission have demonstrated the presence of the region 1-like field-aligned currents (FACs) in Mercury’s northern hemisphere. Due to the limitations of the single-point measurement, the upstream solar wind condition is blind to MESSENGER when it’s inside the magnetosphere. Thus, the statistical analyses of FACs are hard to be carried out and the results could be obscured. Here, we used a hybrid model to investigate Mercury’s FACs. The two-layer model was concerned. We studied how Mercury’s conductivity profile controls the establishment and closure of the FACs, and how the IMF orientation regulated the intensity and the spatial distributions of the FACs. Previous statistical results of MESSENGER’s observations can be well explained by the simulations. And future observations from BepiColombo will help us gain a better understanding of Mercury’s FACs. 

How to cite: Shi, Z., Rong, Z., Fatemi, S., Dong, C., Gao, J., and Wei, Y.: Mercury’s Field-aligned Currents: Hybrid Simulation Results, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6904, https://doi.org/10.5194/egusphere-egu24-6904, 2024.

A planet’s orbital eccentricity can experience major changes over time as a result of planetary secular perturbations. Mercury's proximity to the Sun, its unique 3:2 spin-orbit resonance, and its high orbital eccentricity makes it an intriguing subject for investigating tidal forces and their resulting stresses. Throughout its history, Mercury may have experienced a state of further heightened eccentricity, potentially leading to tidal forces significant enough to modify the planet's surface. In the study presented here, we explore the tidal potential currently influencing Mercury and examine possible historical values of eccentricity to estimate past stress values. Employing a four-layer crustal model, we calculate Love numbers that reflect Mercury's internal physical properties and compute global tidal potential, surface stresses, and radial tidal displacement with respect to location and position in orbit. A suggested past orbital eccentricity of e = 0.41 could produce estimated maximum principal surface stresses of ~ +/-70 kPa which are comparable to current diurnal tidal principal stress values for Europa and Enceladus (~ +/-85 kPa). At present, Mercury experiences tidal stress values of up to ~ +/-15 kPa with a tidal bulge that can radially displace the surface by a mean of ~ 2.3 m. As tidal stresses could have been significantly higher in the past, we can hypothesize that Mercury might have experienced surface alterations induced by its orbital dynamics. On the other hand, the present-day surface of the planet has not retained evidence of any tidal stress modifications, suggesting that these characteristics, if present, would have been likely covered by the volcanic activity that persisted up to 3 billion years ago. Sophisticated instruments like the BepiColombo Laser Altimeter (BELA), to be inserted into orbit around Mercury in early 2026 onboard the European Space Agency’s BepiColombo mission, promise to provide unprecedented data and will be instrumental in precisely measuring Mercury's global topography, contributing to a more accurate understanding of the planet's surface variations. This, in turn, will aid in refining our calculations and representations of Mercury's internal structure and its evolution.

How to cite: Burkhard, L. and Thomas, N.: Insights into Mercury’s tidal stresses: Linking present and past potentials, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7623, https://doi.org/10.5194/egusphere-egu24-7623, 2024.

Understanding Mercury's magnetosphere is a primary goal of the BepiColombo mission. In addition to spacecraft observations, numerical modeling efforts have shown to add invaluable insight to the Hermean magnetic field topology, current systems and plasma distributions. However, existing comparisons between observed and modeled data are predominantly qualitative, lacking quantitative agreement due to diverse mathematical approaches. Notably, quantitative inconsistencies of observed and modeled ion densities and energies are particularly affected. Hence, this study addresses systematic and stochastic deviations, focusing on establishing confidence intervals for "ion counting" within the hybrid AIKEF (Adaptive Ion Kinetic Electron Fluid) model. The kinetic treatment of the ions enables to directly compare model results with observations of the Planetary Ion Camera (PICAM), which is a part of the SERENA suite onboard the BepiColombo mission. Multiple ion counting methods are introduced and evaluated, including a simple sphere method, an omnidirectional method, and a field-of-view method. Our findings demonstrate that applying the field-of-view method to the modeled data, within the derived confidence interval, yields ion velocity distributions consistent with PICAM observations of Mercury’s magnetosheath. The AIKEF model and the developed analysis tools serve as a powerful and convenient method of reproducing the ion and electro-magnetic field profile around Mercury for the BepiColombo mission, both in flyby and in-orbit measurements.

How to cite: Teubenbacher, D., Exner, W., Narita, Y., Varsani, A., and Laky, G.: Hybrid plasma simulation around Mercury: ion counting statistics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7659, https://doi.org/10.5194/egusphere-egu24-7659, 2024.

Whistler-mode chorus waves are natural electromagnetic emissions known to play a key role in electron acceleration and loss mechanisms via wave–particle interactions in planetary magnetospheres. Chorus waves have not yet been detected in Mercury’s magnetosphere due to the limited capabilities of the instruments onboard the spacecraft that already visited the planet. Here, we present the first detection of chorus waves in the localized dawn sector during the first and second Mercury flybys by the BepiColombo/Mio spacecraft. Mio’s search coil magnetometers measured chorus waves with tens of picotesla intensities in the dawn sector, while no clear wave activity was observed in the night sector. The simulation results suggest that this dawn-dusk asymmetry could be explained by the impact of background magnetic field inhomogeneities on the nonlinear wave generation process. Potential direct comparisons with electron data will be discussed. This observational evidence is crucial for understanding the dynamics of energetic electron in the localized dawn sector of Mercury’s magnetosphere.

How to cite: Sahraoui, F., Ozaki, M., Yagitani, S., Kasaba, Y., Kasahara, Y., Matsuda, S., Omura, Y., Hikishima, M., Mirioni, L., Chanteur, G., Kurita, S., Nakazawa, S., and Murakami, G.: First observations of whistler waves in Mercury’s magnetosphere by BepiColombo/Mio spacecraft, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8409, https://doi.org/10.5194/egusphere-egu24-8409, 2024.

In this study, we suggest a model for the origin and abundance of exospheric Helium at Mercury. It was derived ab initio, assuming He-saturated regolith at the surface and a “steady-state” Helium exosphere. A 1D Monte Carlo computer simulation [1] was used to calculate the exospheric He density profiles according to the model.

The Helium abundance in the Hermean exosphere was first constrained from UV Spectrometer measurements aboard Mariner 10 [2] and has been discussed extensively since, also in the light of probable analogies to the Lunar He environment. It is believed that there are two major sources for exospheric Helium: release of Solar Wind implanted He from the regolith of the Hermean surface and outgassing of radiogenic He from the interior [3]. However, there is no agreement on the quantitative contribution of the two possible origins. Through a larger volume and diversity of data, new insights concerning the origins and other aspects of the Hermean Helium system could be derived. Novel approaches are allowing the derivation of Helium density profiles from MESSENGER data [4], and soon the SERENA plasma/neutral particles package [5] on BepiColombo’s Mercury Planetary Orbiter (MPO) is expected to add the first ever in-situ density measurements to the picture.

The presented model shows that the Helium exosphere is dominated by exospheric recycling. This term describes the process in which particles that have been released into the exosphere at energies below E_esc return to the surface and bounce back into the exosphere immediately at the energy corresponding to the local surface temperature. The Helium accumulates in the exosphere, where its abundance is eventually limited by the exospheric loss processes of Jeans escape and ionization. This model can build the foundation for an evaluation of future data and can allow a quantification of the two exospheric Helium sources.

[1] Wurz, P. and Lammer, H. (2003). Icarus 164.1 (2003): 1-13.
[2] Broadfoot, A. L., et al. (1976). Geophys. Res. Lett., 3: 577-580.
[3] Hartle, R. E., et al. (1975),  J. Geophys. Res.,  80(25)
[4] Weichbold, F., et al. (2024), in preparation.
[5] Orsini, S., et al. (2021), Space Sci Rev 217, 11

How to cite: Hener, J., Vorburger, A., Wurz, P., Weichbold, F., and Lammer, H.: Ab-Initio Model for Mercury’s Helium Exosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9496, https://doi.org/10.5194/egusphere-egu24-9496, 2024.

Mercury, the smallest and innermost planet of our solar system, is exposed to a strong solar wind. The internal field is dipole-dominated, relatively weak, axisymmetric and significantly offset towards north. Through the interaction with the strong solar wind, this field leads to a comparatively small and dynamic magnetosphere.

To first order the magnetopause completely separates the magnetosphere from the magnetosheath and thus no magnetic field may penetrate this boundary. In reality, the magnetosheath magnetic field may diffuse across the very thin boundary within a finite time.  We first investigate how the magnetosheath magnetic field changes under different IMF conditions and directions. Second, we can investigate the penetration of the magnetic field from the magnetosheath through the magnetopause inside the magnetosphere and obtain the structure of the IMF influence on the Hermean magnetosphere. 

How to cite: Pump, K., Heyner, D., Plaschke, F., and Exner, W.: Influence of the IMF direction on Mercury's magnetosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9733, https://doi.org/10.5194/egusphere-egu24-9733, 2024.

Mariner 10 detected the existence of an exosphere around Mercury in 1974-1975 by remote spectrometric observations during flybys. More than four decades later the MErcury Surface, Space ENvironment, Geochemistry and Ranging (MESSENGER) spacecraft confirmed the existence of the exosphere. So far, the neutral helium (He) number density around Mercury’s exosphere was based on assumptions related to the spectroscopic observations, which are applied to exospheric models to derive an altitude-dependent density profile of the neutral helium around the planet. Here, we present the first on-site measured density profile of He, using in-situ magnetic field measurements from MESSENGER. These data were analyzed for the identification of Ion-Cyclotron Waves (ICWs) that originated from exospheric pick-up He⁺ ions. The results reveal an extended He-exosphere with a lower surface number density as expected by previous studies. To provide further context, the results are compared with measurements obtained by Mariner 10 and BepiColombo (first flyby), which shows that the measurements of the PHEBUS UV-instrument onboard of the MPO align very well with the determined density from this study.

How to cite: Weichbold, F., Lammer, H., Schmid, D., Volwerk, M., Hener, J., Vorburger, A., and Wurz, P.: Mercury's Helium Exosphere determined by Ion Cyclotron Waves, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10358, https://doi.org/10.5194/egusphere-egu24-10358, 2024.

Following its launch, BepiColombo has already performed three flybys at Mercury. The next three flybys at Mercury are time wise very close together and are planned with about four months starting in September 2024. About 10 months after these flybys the orbit insertion preparation will start. When in orbit, BepiColombo with its state of the art and very comprehensive payload will perform measurements to increase our knowledge on the fundamental questions about Mercury’s evolution, composition, interior, magnetosphere, and exosphere.
Although the two BepiColombo spacecraft are in a stacked configuration during the cruise and only some of the instruments can perform scientific observations, the mission produces already some very valuable results. As an example, Mercury’s southern inner magnetosphere, a so far unexplored region, has been observed by the BepiColombo ion and fields instruments during the pass.  Data taken during the Mercury's flybys revealed a magnetosphere populated by diverse populations and confirmed a really dynamic regime. 
BepiColombo is a joint mission between the European Space Agency (ESA) and the Japanese Aerospace Exploration Agency (JAXA) for comprehensive exploration of planet Mercury. BepiColombo, has been launched on 20 October 2018 from the European spaceport Kourou in French Guyana and it is currently on a seven-year-long cruise to Mercury. BepiColombo consists of two orbiters, the Mercury Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (Mio). In late 2025/early 2026 these orbiters will be put in orbit around the innermost planet of our Solar System. 
During the talk a status of the mission and results from science operations during cruise will be presented.

How to cite: Benkhoff, J. and Murakami, G.: BepiColombo Mission Update, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10851, https://doi.org/10.5194/egusphere-egu24-10851, 2024.

How to cite: Lennox, A., Rothery, D., Malliband, C., Balme, M., wright, J., and Conway, S.: Global occurrences of very smooth plains patches on Mercury: geologic settings and implications for effusive volcanism, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11148, https://doi.org/10.5194/egusphere-egu24-11148, 2024.

Mercury is the only telluric planet of the solar system, apart from Earth, possessing an intrinsic magnetic field. This magnetic field influences the dynamics of the solar wind plasma impinging on the planet, forming a magnetosphere. Mercury’s magnetosphere has been investigated by multiple space missions in the past, notably the NASA Mariner10 and MESSENGER missions, and is today the target of the joint ESA/JAXA BepiColombo mission, currently en route, with orbit insertion scheduled for December 2025. BepiColombo instruments will observe for the first time the electron kinetic physics at Mercury. In order to interpret and plan BepiColombo’s in-situ observations, an interplay is needed between numerical simulations of Mercury’s magnetosphere and instrumental modelling.

In this work, we present a study of the expected instrumental response of the PWI/AM2P and PWI/SORBET experiments onboard BepiColombo, based on a two-step, fully-kinetic numerical approach.

First, we run fully-kinetic, three-dimensional, global simulations of the interaction between Mercury’s magnetic field and the solar wind using the implicit particle-in-cell code iPIC3D. Non-maxwellian electron distribution functions are observed in the simulations.

Second, we use the electron distribution function derived from the previous step as input for a numerical model of the electric antennas used by both the AM2P and SORBET experiments onboard the JAXA Mio craft (part of BepiColombo). The influence of the spacecraft and antennas geometries is included self-consistently in this second step.

Our 3D full-PIC simulations show that magnetic reconnection in the tail accelerates and heats electrons up to energies of few keVs when the interplanetary magnetic field (IMF) is southward. Such high-energy electrons are ejected from the neutral line in the tail planetward in a substorm-like process, leading to strong particle precipitation in the nightside of Mercury, especially at local time 0-6 h. Double Maxwellian electron distribution functions are inferred from the simulations in the nightside of Mercury (with temperature and density ratio of order 10 and 0.1-1, respectively). We investigate the possibility of detecting these two Maxwellian populations using the AM2P and SORBET experiments, operating at Mercury after orbit insertion. We also explore regions where the AM2P experiment can be calibrated in-flight.

How to cite: Dazzi, P., Lavorenti, F., Henri, P., and Issautier, K.: Mutual impedance and quasi-thermal noise to measure electron properties at Mercury: merging simulations of the magnetosphere and of the instrumental apparatus, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13502, https://doi.org/10.5194/egusphere-egu24-13502, 2024.

The very low obliquity of Mercury causes important surface temperature variations between its polar and equatorial regions [1]. At the same time, its 3:2 spin orbit resonance leads to longitudinal temperature variations [2]. The combination of these two effects creates a peculiar surface temperature distribution with equatorial hot and warm poles, and cold poles at the geographic poles of the planet. Models that considered the insolation pattern were found compatible with the low-degree shape and geoid from MESSENGER [3]. The models of [3] showed that the insolation pattern imposes a long wavelength thermal perturbation throughout the mantle, whose temperature distribution is strongly correlated with the surface temperature variations. In addition to surface temperature variations, lateral variations of crustal thickness can also affect the temperature distribution of the lithosphere and mantle as it was suggested for Mars [4]. With the topography and gravity data from MESSENGER, a series of models of Mercury’s crustal thickness have been derived assuming constant or variable crustal density, based on the composition of the surface [5].

In this study we include crustal thickness and surface temperature variations of Mercury in the geodynamical code GAIA [6], similar to [4]. We tested several crustal thickness models from [5]. All the simulations are carried in a full 3D spherical geometry, use the extended Boussinesq Approximation, and consider core cooling and radioactive decay. We also use a pressure- and temperature-dependent viscosity in the mantle. The crust is  enriched in heat producing elements (HPEs) compared to the depleted mantle according to a fixed enrichment factor. We model the entire thermal evolution of Mercury to determine the variations of surface and core-mantle boundary heat fluxes in addition to the temporal evolution and distribution of the elastic lithosphere thickness.

Our models indicate that the surface temperature variations of Mercury induce a long-wavelength pattern on both the elastic lithosphere thickness and the heat fluxes, while the crustal thickness variations lead to smaller scale variations of the two quantities. Our models show that different geochemical terranes such as the North Volcanic Plains (NVP) or the High Mg-Region [7] could have experienced drastically different thermal histories throughout the evolution of Mercury.

Future data from the BepiColombo mission [8] will provide a better resolution for the gravity and topography of Mercury, as well as measurements of its surface composition. These data could be used to provide additional estimates of the elastic lithosphere thickness and to constrain the time of formation of the associated geological features. This will help to improve our geodynamical models and in turn constrain Mercury’s thermal evolution.

References:

[1] Margot et al., 2012. [2] Siegler et al., 2013. [3] Tosi et al., 2015. [4] Plesa et al., 2018. [5] Beuthe et al., 2020. [6] Hüttig et al., 2013. [7] Weider et al., 2015. [8] Benkhoff et al., 2021.

How to cite: Fleury, A., Plesa, A.-C., Tosi, N., Walterová, M., and Breuer, D.: Variations of Heat Flux and Elastic Thickness of Mercury derived from Thermal Evolution Modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15341, https://doi.org/10.5194/egusphere-egu24-15341, 2024.

The ESA-JAXA joint mission BepiColombo is now on the track to Mercury. After the successful launch of the two spacecraft for BepiColombo, Mio (Mercury Magnetospheric Orbiter: MMO) and Mercury Planetary Orbiter (MPO), commissioning operations of the spacecraft and their science payloads were completed. BepiColombo will arrive at Mercury in the end of 2025, and it has 7-years cruise with the heliocentric distance range of 0.3-1.2 AU. The long cruise phase also includes 9 planetary flybys: once at the Earth, twice at Venus, and 6 times at Mercury. Even before arrival, we already obtained fruitful science data from Mercury during three Mercury flybys completed on 1 October 2021, 23 June 2022, and 19 June 2023. We performed science observations with almost all the instruments onboard Mio and successfully obtained comprehensive data of Mercury’s magnetosphere such as magnetic fields, plasma particles, and waves. Here we present the updated status of BepiColombo/Mio, initial results of the science observations during the Mercury flybys, and the upcoming observation plans.

How to cite: Murakami, G. and Benkhoff, J.: Updated status of BepiColombo and initial reports on Mercury flyby observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15387, https://doi.org/10.5194/egusphere-egu24-15387, 2024.

Mercury has an extended exosphere that consists of various species. Based on theoretical considerations, the existence of Lithium (Li) in the exosphere around Mercury is predicted to be less than 5x10⁷ cm^-2. Because these density values are well below the detection limits of remote observation instruments on board past missions, Li has never been directly observed. Here we show the first on-site determined altitude-density profile of atomic Li₇, derived from in-situ magnetic field observations by the MESSENGER spacecraft. The results suggest that the source of Li at Mercury is most likely meteoritic ablation. The findings will help to interpret the remote observations of Mercury's exosphere that will be realized in the near future by the BepiColombo mission.

How to cite: Schmid, D., Lammer, H., Volwerk, M., Weichbold, F., Scherf, M., Varsani, A., Roberts, O. W., Simon-Wedlund, C., and Plaschke, F.: First detection of Lithium in Mercury's exosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16068, https://doi.org/10.5194/egusphere-egu24-16068, 2024.

The NASA/MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) mission provided measurements of Mercury’s Ca exosphere, allowing the study of its configuration and its seasonal variations. The observed Ca column densities exhibit a scale height consistent with a temperature > 50,000 K, and with a source located mainly on the dawn-side of the planet. It was suggested that the originating process is due to MMIV (Micro-Meteoroids Impact Vaporization), but previous estimations were not able to justify the observed intensity and energy. The most likely origin of this exospheric element is very probably a combination of different processes involving the release of atomic and molecular surface particles. We use an exospheric Monte Carlo model (Mura et al., 2007) to simulate the 3-D spatial distribution of the Ca-bearing molecule and atomic Ca in the exosphere of Mercury generated by the MMIV process. We investigate the possible pathways to produce the observed Ca exosphere and we discuss about the generating mechanism. Following previous studies, we consider that the atomic Ca in Mercury’s exosphere may be produced in a sequence of different processes: the exospheric energetic Ca component derives from the shock-induced non-equilibrium dissociative ionization and neutralization of Ca+ during the vapor cloud expansion, while a low energy Ca component is generated later by the photo-dissociation of the CaO molecules released by micro-meteoroid impact vaporization. Since the exact temperature, the photolysis lifetimes of the produced molecules and the excess energy during photolysis processes are still not well constrained by observations, we investigate different model assumptions. The theoretical calculations better agree with observations at shorter photolysis lifetimes and higher excess energy of Ca atoms obtained during photolysis of Ca-bearing species. In that case we show the presence of two Ca components: energetic Ca component more intense at high altitudes, and a low energy component in the post-dawn region at low altitudes. The total Ca content obtained through a best fit to the observations shows excess emission near TAA ∼ 25° and TAA ∼150°, which was attributed to the vaporization of surface material induced by the impact of a meteor stream. We investigate the possible contribution due to the comet 2P/Encke for explaining the excess Ca emission at specific orbit positions; the simulation results show some discrepancy when compared to the observations.

How to cite: Moroni, M., MIlillo, A., Mura, A., Plainaki, C., Mangano, V., Aronica, A., Berezhnoy, A., De Angelis, E., Del Moro, D., Di Bartolomeo, P. P., Kazakov, A., Massetti, S., Orsini, S., Rispoli, R., Sordini, R., and Stumpo, M.: Seasonal variation of Ca and Ca-bearing molecules in Mercury's exosphere as a product of micro-meteoroids and comet stream particles impact, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17612, https://doi.org/10.5194/egusphere-egu24-17612, 2024.

Planet Mercury, with its weak internal magnetic field, is continuously exposed to an intense solar wind. This interaction becomes particularly dynamic during coronal mass ejections, resulting in a strong compression of the magnetosphere. Such events drive electrical currents within the planet, which, depending on the planetary conductivity structure, lead to secondary magnetic fields detectable outside. Analysis of these induced fields provides insights into Mercury’s interior structure.
Here, we utilized data from the Helios-1 probe, recorded during a CME at 0.31 AU, to evaluate changes in solar wind conditions and their impact on Mercury's magnetosphere. We applied a semi-empirical model to estimate the external field variations and employed endmembers of radial symmetric conductivity models to calculate the range of induced magnetic fields. Our analysis highlights the influence of these variations on Mercury's upper mantle layers, taking into account both dipolar and quadrupolar components of the magnetic field. Eventually, we predict the potential induced magnetic fields at the future location of the BepiColombo spacecraft, currently en route to Mercury.

How to cite: Heyner, D., Langermann, L., Pump, K., and Zomerdijk-Russell, S.: Spectral Modelling the Induction Effect of a Strong CME Hitting Planet Mercury, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17752, https://doi.org/10.5194/egusphere-egu24-17752, 2024.

The BepiColombo spacecraft, designed by ESA/JAXA, is currently in its cruise phase towards Mercury. The Mercury Orbiter Radio-science Experiment (MORE), one of the scientific investigations of the mission, will exploit a multi-frequency microwave tracking system with an advanced Ka-band transponder to fulfill scientific goals in Mercury’s geodesy and fundamental physics. Thanks to the precise measurements enabled by the state-of-the-art radio tracking system, MORE is expected to provide new insights on the planet and its interior, expanding and improving the results of the MESSENGER mission. In this work, we assess the performance of the geodesy investigation conducted by MORE, focusing on the orbital phase, starting in early 2026. In particular, this study evaluates how BepiColombo's refined gravity data can reduce the uncertainty in the estimate of the Love Number k₂, rotational state and crustal thickness of Mercury.  We report the results of the numerical simulation based on the up-to-date mission scenario, which consists of a two-year orbital phase. We simulate synthetic radio observables and estimate the model parameters through a precise analysis of the spacecraft orbital motion. We include different sources of mismodelling to reproduce a perturbed dynamical state of the probe, such as errors in the thermo-optical coefficients of the spacecraft, wheel off-loading maneuvers with unbalanced ΔVs and random fluctuations of solar irradiance, which cannot be modelled or measured by the onboard accelerometer. We use the covariance matrix coming from this analysis to perform a Monte Carlo simulation to obtain a set of gravity fields statistically compatible with a reference field (HgM009, derived from a recent reanalysis of the MESSENGER dataset). By combining these gravity fields with available topographic data, we produce a distribution of Mercury’s crustal thickness maps, from which we infer the corresponding estimation uncertainty. We compare the expected accuracies of the BepiColombo gravity experiment with the current state of knowledge. We show that MORE shall fulfill its scientific goals by improving the estimate of the planet’s gravity field, tidal response and rotational state. Our findings demonstrate how the estimate of Mercury’s crustal thickness benefits from BepiColombo’s high precision gravity measurements. The uncertainties derived from our simulation show that MORE will provide a reliable and high resolution basis for associating gravity anomalies with geological surface features on Mercury, such as impact craters, rift zones, and lobate scarps.

How to cite: Zurria, A., di Stefano, I., Cappuccio, P., De Filippis, U., and Iess, L.: Expected performance of the MORE geodesy experiment during the orbital phase of BepiColombo, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18499, https://doi.org/10.5194/egusphere-egu24-18499, 2024.

The recent swingbys of Mercury by BepiColombo were the first ones ever to pass through the southern magnetosphere, revealing unseen signatures in observational data.

Our electron instrument SORBET/PWI can be used to identify signatures of boundary crossings, such as shock, magnetopause, but also trapped plasma population on closed magnetic field lines in the night side. To bring the observations along the swingbys into a global magnetospheric context, we employ the global 3D magnetohydrodynamic and hybrid models ARMVAC_PLANET (Lesia, l’Observatoire de Paris) and AIKEF (TU Braunschweig/ESA). A new step consists of injecting test particles (especially electrons) in the MHD simulations.

Exploring Mercury's magnetosphere is important both for modeling Mercury's intrinsic magnetic field and for recovering the properties of the upstream IMF once the probe is inside the magnetosphere. These latest results are a major asset for future coordinated observations planned for BepiColombo two spacecraft.

How to cite: Griton, L., Exner, W., Heyner, D., Houeibib, A., Issautier, K., Kasaba, Y., Kojima, H., Moncuquet, M., and Pantellini, F.: Multi-technique investigation of Mercury's southern magnetosphere based on BepiColombo first swingbys, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18888, https://doi.org/10.5194/egusphere-egu24-18888, 2024.

Mercury is known to possess a Magnetosphere that is highly responsive to the upstream Solar Wind conditions. Previous studies using MESSENGER data have contributed to understanding the dynamics of Mercury's respond to the upstream. However, the interactions between the Magnetospheric plasma and the Solar Wind is yet to be fully understood; and it is indeed one of the main focuses of the ESA/JAXA's current mission, BepiColombo. We report the observations of BepiColombo's flyby-3 at Mercury on 19th June 2023, using ion data from SERENA-PICAM and magnetic field data from MAG/MGF instruments. The preliminary analyses have given an insight into the rapidly changing plasma, at the inbound Magnetopause crossing. There is evidence that bursty reconnection could be the main contributor to such dynamic boundary.

How to cite: Varsani, A., Schmid, D., Lammer, H., Nakamura, R., Pump, K., Heyner, D., Laky, G., Jeszenszky, H., Giono, G., Volwerk, M., Milillo, A., Orsini, S., Fischer, D., Magnes, W., Baumjohann, W., and Matsuoka, A.: Bursty reconnection during BepiColombo's third Mercury flyby, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19987, https://doi.org/10.5194/egusphere-egu24-19987, 2024.

Here,  we use a state-of-art method to diagnose the Mercury’s dipolar field which is assumed to originate from a magnetic dipole. This method can effectively separate and solve the dipole parameters, and gives the error of how much the dataset of sampled magnetic field deviated from the dipole field . By employing this method and the MESSENGER field data, the derived optimum dipole parameters demonstrated that the dipole center is at [x=5.0;y=-16.0;z=480.5]km, the dipole moment is about M=2.5*10^19 nA.m^2 (or 172 nT*RM^-3), the dipole tilt angle is 3.7 degree. Our yielded dipole moment is weaker than that estimated in previous studies. We compared and discussed with previous studies.

How to cite: Rong, Z.: The non-axial dipolar magnetic field of Mercury, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20477, https://doi.org/10.5194/egusphere-egu24-20477, 2024.

We will present the design and establishment of a cutting-edge molecular beam facility at Southwest Research Institute (SwRI). The primary focus of this facility is to support the operations of Strofio, the neutral mass spectrometer and payload of the BepiColombo mission. Testing of this instrument requires a molecular beam with an average speed of 3 km/s. Beyond serving the immediate needs of Strofio, our vision extends to collaborative efforts with other organizations in the development of future instrumentation. We look forward to fostering partnerships that will collectively advance the capabilities of in-situ particle instruments and contribute to the broader scientific community.

How to cite: Schroeder, J., Livi, S., Patrick, E., and Turner, J.: Strofio Operations: A New Molecular Beam Facility, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20823, https://doi.org/10.5194/egusphere-egu24-20823, 2024.

We focus on the radial deformation of planet Mercury during its orbital period due to tidal forces exerted by the Sun. Bertone et al. (2021) obtained the first measurement of the tidal Love number h2 of Mercury via least squares minimization of height discrepancies at the cross-overs of the profiles obtained by the Mercury Laser Altimeter (MLA) onboard NASA’s MESSENGER spacecraft. However, height discrepancies at cross-overs, intersection points of profiles, can suffer from significant interpolation errors when the separation of consecutive footprints is large and the underlying terrain is rough. Here, we re-analyze the MLA profiles using new techniques of co-registration analysis that also include a post-correction procedure based on pseudo cross-overs. We have successfully applied these techniques to obtain the spatio-temporal thickness variations of the seasonal deposits on Martian poles (Xiao et al., 2022a, 2022b). Provided that a reference DTM is available, any particular pair of profile segments forms a pseudo cross-over. The height misfit at a pseudo cross-over is assigned as the difference in height corrections in the co-registrations of the profile pair, that form the pseudo cross-over, to the underlying reference DTM. Pseudo cross-overs can have great advantages over real cross-overs: (1) Lateral shifts of the profiles can be naturally compensated and interpolation errors avoided through the co-registration process in forming the height misfits at the pseudo cross-overs; (2) Since the profile segments do not necessarily have to intersect, the available number of "cross-overs" is normally multiplied in number; (3) Furthermore, the profile segment pair forming a pseudo cross-over can be widely separated across the research region, offering "global" constraints on the adjustment. For the uncertainty and sensitivity quantification, we create synthetic MLA observations by adding realistic errors and tidal deformation assuming an a priori tidal h2 and invert for the tidal h2 using the proposed techniques. Our measurement of tidal h2, combined with refined determination of the tidal potential Love number k2 from radio science experiments, will be used to discuss updated bounds of interior structure parameters of Mercury, especially the inner core size, which will improve our understanding of its thermal evolution and magnetic dynamo.

Bertone et al. (2021). JGR: Planets, 126(4), e2020JE006683.
Xiao et al. (2022a). PSS, 214, 105446.
Xiao et al. (2022b). JGR: Planets, 127(10), e2021JE007158.

How to cite: Xiao, H., Stark, A., Gutierrez, P. J., and Lara, L. M.: Measuring the tidal deformation of Mercury through co-registration of MLA profiles, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21257, https://doi.org/10.5194/egusphere-egu24-21257, 2024.

Venus' rotation is the slowest of all planetary objects in the solar system and the only one in the retrograde direction. It is commonly admitted that such a rotation state is the result of the balance between the torques created by the gravitational and atmospheric thermal tides¹. The internal viscous friction associated with gravitational tides drive the planet into synchronization (deceleration) while the bulge due to atmospheric thermal tides tend to accelerate the planet out of this synchronization^1,6. Other torque components (related to the two first one) also affect the rotation². This work first provide an estimate of the viscosity of Venus' mantle explaining the current balance with thermal atmospheric forcing. Second, this study quantify the impact of the internal structure and its past evolution on the gravitational tides and thus on the rotation history of Venus. Using atmospheric pressure simulations from the Venus climate database^4,5,7, we first estimated the atmospheric thermal torque and showed that topography and interior response to atmospheric loading, usually ignored in previous studies, have a strong influence on the amplitude of thermal atmospheric torque. Computing the viscoelastic response of the interior to gravitational tides and atmospheric loading³, we showed that the current viscosity of Venus' mantle must range between 2.3x10²⁰ Pa.s and 2.4x10²¹ Pa.s to explain the current rotation rate as an equilibrium between torques. We then evaluated the possible past evolution of the viscosity profile of the mantle considering different simple thermal evolution scenarios.  We showed that in absence of additional dissipation processes, viscous friction in the mantle cannot slowdown the rotation to its current state for an initial period shorter than 2-3 days, even for an initially very hot mantle. Beyond Venus, these results has implications for Earth-size exoplanets indicating that their current rotation state could provide key insights on their atmosphere-interior coupling.

¹Correia, A. C. M. and J. Laskar (2001), Nature.
²Correia, A. C. M. (2003), Journal of Geophysical Research.
³Dumoulin, C., G. Tobie, O. Verhoeven, P. Rosenblatt and N. Rambaux (2017), Journal of Geophysical Research.
⁴Lebonnois, S., F. Hourdin, V. Eymet, A. Crespin, R. Fournier and F. Forget (2010),  Journal of Geophysical Research.
⁵Lebonnois, S., N. Sugimoto and G. Gilli (2016), Icarus.
⁶Leconte, J., H. Wu, K. Menou and N. Murray (2015), Science.
⁷Martinez, A., S. Lebonnois, E. Millour, T. Pierron, E. Moisan, G. Gilli and F. Lefèvre (2023), Icarus.

How to cite: Musseau, Y., Dumoulin, C., Tobie, G., Gillmann, C., Revol, A., and Bolmont, E.:  Viscosity of Venus' mantle as inferred from its rotational state, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3129, https://doi.org/10.5194/egusphere-egu24-3129, 2024.

As part of a long-term monitoring program, full disk thermal maps of HDO (near 7 microns) and SO₂ (near 7 and 19 microns) have been obtained at the cloud top of Venus in 2023, using the TEXES(Texas Echelon Cross-Echelle Spectrograph)  imaging spectrometer at the Infrared Telescope Facility (IRTF) at Mauna Kea Observatory. Assuming a constant D/H isotopic ratio, the water abundance has been more or less constant since 2018, at about half its value in 2012-2016. In contrast, the SO₂ abundance, which was very high in 2018-2019 and very low between July 2021 and March 2023, has increased by a factor of about 5 between February and July 2023 (close to its maximum level of 2018-2019), and has remained at its high level in September 2023. The origin of these long-term variations is still unclear. In addition, stringent upper limits of NH₃ (at 927-931 cm^-1), PH₃ (at 1161-1164 cm^-1) and HCN at 744-748 cm^-1) at the cloud top have been obtained in July 2023. These results will be presented and discussed.

How to cite: Encrenaz, T., Greathouse, T., Giles, R., Widemann, T., Bezard, B., Lefevre, F., Lefevre, M., Shao, W., Sagawa, H., Marcq, E., and Arredondo, A.: Ground-based thermal mapping of Venus:  HDO and SO2 monitoring and upper limits of NH3, PH3 and HCN at the cloud top, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4022, https://doi.org/10.5194/egusphere-egu24-4022, 2024.

Coronae are crown-like, tectono-volcanic features found on Venus that typically range in diameter from 100-700 km. Diapirs of warm upwelling material impinging on the lithosphere are often invoked to explain coronae formation. With more than 500 coronae identified on the surface of Venus, if these diapirs are individually linked to a mantle plume, Venus must have a very different mantle structure than Earth. I consider three cases designed to assess the potential relationship between large-scale, long-wavelength lower mantle structure and smaller-scale upper mantle structure that could potentially form diapirs consistent with those that are envisioned to interact with the lithosphere and form coronae. I use the geoid and topography to identify the large-scale pattern of convection because the geoid contains and integral of the temperature anomalies over the depth of the mantle. Plume tails—narrow vertical conduits—integrate to give a positive geoid anomaly while small-scale, time-dependent drips or upwellings are minimized in the depth integration. The first case—the reference case—has a small, stepwise decreases in viscosity between the lower mantle (10²² Pa s), transition zone (10²¹ Pa s), and upper mantle (5x10²⁰ Pa s) with no phase transformations. This led to 20 ~1000-km diameter mantle plumes that remained stationary for more than 1.5 Gyr. This calculation is consistent with a number of geophysical observations it does not support the formation of coronae by plume-lithosphere interaction. To decouple the lower and upper mantle, I further decrease both the upper mantle and transition zone viscosities to 10²⁰ Pa s while leaving all other parameters unchanged. In this calculation the same 20 ~1000-km diameter mantle plumes formed and remained stationary for more than 1.5 Gyr. The geoid and topography are anti-correlated, inconsistent with the observed values on Venus and, the spatial scale, number, and topographic evolution of the plumes are not consistent with coronae. This calculation does not support the formation of coronae by plume-lithosphere interaction. In an attempt to further decouple the upper and lower mantle I add an endothermic phase transformation at the ringwoodite-bridgmanite boundary in addition to the decreased upper mantle and transition zone viscosities while leaving all other parameters unchanged. Unique to this calculation, a very large number of ~100-km diameter small topographic upwellings form some associated with the large-scale geoid high but never associated with the large-scale geoid low. The inclusion of a phase transformation decoupling the upper and lower mantle has the potential to create diapir-like structures in the upper mantle consistent with coronae formation.

How to cite: King, S.: Linking global-scale mantle flow with diapir-like coronae formation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5857, https://doi.org/10.5194/egusphere-egu24-5857, 2024.

The recent analysis of radar data from NASA’s Magellan mission suggests that volcanic activity is ongoing on Venus [1], providing unprecedented evidence that Venus’s evolution and present day state has been dominated by volcanic processes. Venus’s geodynamics and tectonics seem to be well characterized by the so-called “plutonic squishy lid” regime, where part of the melt that is formed in the interior rises to the surface but a significant part remains trapped in the crust and lithosphere forming intrusions [2]. These intrusions strongly influence the mantle’s thermal evolution, heat flow, and the present-day thermal state of the subsurface.

This study focuses on the effects of intrusive magmatism on the lithosphere thickness and thermal gradient. The latter is used to evaluate our models by comparing our results to estimates based on studies of the elastic lithosphere thickness [3,4,5]. We use the geodynamic code Gaia in a 2D spherical annulus geometry [6]. Our models vary the intrusive to extrusive ratio from a fully intrusive case to a fully extrusive one and the intrusive melt depth from 10 km to 90 km.

Our models show that depending on the percentage of extrusive melt and the depth of magmatic intrusions, the maximum thermal gradient varies from a few K/km up to almost 40 K/km at present day, with higher values obtained for higher percentages of intrusive melt and shallower the magmatic intrusions. Moreover, our results show that the thermal gradients have remained similar during the last 750 Myr. Models in which the extrusive magmatism is higher than 60% and the depth of magmatic intrusions lies deeper than 50 km cannot explain high local thermal gradients as suggested by studies of elastic lithosphere thickness [3,4,5].

In a recent study [7], the presence of a low viscosity layer (LVL) in the shallow Venusian mantle has been suggested to be related to the presence of partial melt. The LVL starts beneath the lithosphere at depths shallower than 200 km. This places constraints on the depth of melting that we can use to select successful models. Models that are compatible with partial melting starting at depth of 200 km or less beneath the surface require less than 40% extrusive magmatism and an intrusive melt depth strictly higher than 10 km.

We use our models to estimate ranges for melting conditions in the interior at present day. The range of melt temperatures lies between 2000 and 2250 K and the depth of melting between ~200 and 360 km. These estimations serve as a starting point for and will be compared with high-pressure-high-temperature laboratory experiments that will be performed at the University of Münster to select the most likely mantle compositions of Venus that can explain the Venera and Vega data.

References:

[1] Herrick & Hensley, Science, 2023. [2] Rolf et al., SSR, 2023. [3] Smrekar et al., Nature Geoscience, 2023. [4] Borelli et al., JGR, 2021. [5] Maia et al., JGR, 2022. [6] Hüttig et al., PEPI, 2013. [7] Maia et al., GRL, 2023.

How to cite: Herrera, C., Plesa, A.-C., Maia, J., Klemme, S., and Jennings, L.: Thermal evolution and magmatic history of Venus, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5946, https://doi.org/10.5194/egusphere-egu24-5946, 2024.

The Venusian atmosphere has rich and diverse chemistry and much of it remains to be explored. Here I present our recent work in identifying new reactions and quantifying their rate constants, along with UV-Vis spectral simulation using quantum chemistry calculations. The research focuses on elemental sulfur allotropes and sulfur oxides. Our UV-Vis spectral simulations are used to narrow the search of the unknown UV absorber by excluding molecules/isomers/conformers without the appropriate absorption and similarly include those with absorption profiles that fit the unknown absorber. Furthermore, we present a mechanism for how substituted sulfuric acid molecules can be formed in the Venusian atmosphere which can impact aerosol formation.

How to cite: Frandsen, B. and Skog, R.: Breaking New Ground in Venusian Atmospheric Sulfur Chemistry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7533, https://doi.org/10.5194/egusphere-egu24-7533, 2024.

Previous studies have inferred volcanic activity on Venus from indirect evidence, including variations in atmospheric composition and thermal emissivity data [1, 2, 3]. More recently, a study hypothesized ongoing volcanic activity on Venus, evidenced by a volcanic vent that collapsed between two different Magellan observing cycles [4]. Expanding upon this premise, we are investigating the surface geology of Venus using the extensive radar and altimetric data acquired by the Magellan spacecraft.

In particular, by properly processing the SAR images, we are conducting a detailed geomorphological analysis of Venus' surface, in order to identify and characterize various surface morphologies. Additionally, the altimetric data provided valuable insights into the topographical variations across Venus, further contributing to the geomorphological assessment.

Our research not only enhances the understanding of the geology of Venus but also underscores the significance of radar imaging in the study of planetary surfaces, where no other imaging techniques are available. The findings highlight the crucial role of continued exploration of Venus, which could be greatly advanced by upcoming missions such as VERITAS and EnVision [5, 6]. Equipped with superior radar technology, these missions are expected to provide images of Venus's surface at an unprecedented resolution and signal-to-noise ratio, far surpassing that of the Magellan SAR, thus enabling a more detailed characterization of Venus's surface morphology.

References

1. Truong, N. & Lunine, J. Volcanically extruded phosphides as an abiotic source of Venusian phosphine. Proceedings of the National Academy of Sciences 118, e2021689118 (2021).

2. Esposito, L. W. Sulfur dioxide: Episodic injection shows evidence for active Venus volcanism. Science 223, 1072-1074 (1984).

3. Smrekar, S. E. et al. Recent hotspot volcanism on Venus from VIRTIS emissivity data. Science 328, 605-608 (2010).

4. Herrick, R. R. & Hensley, S. Surface changes observed on a Venusian volcano during the Magellan mission. Science, eabm7735 (2023).

5. Hensley, S. et al. VISAR: Bringing Radar Interferometry to Venus. In Proceedings of International EnVision Venus science workshop, Berlin, Germany (2023).

6. Ghail, R. C. et al. VenSAR on EnVision: Taking earth observation radar to Venus. International journal of applied earth observation and geoinformation 64, 365-376 (2018).

Acknowledgments

G.M., D.S., and M.M. acknowledge support from the Italian Space Agency (2022-15-HH.0).

How to cite: Sulcanese, D., Mitri, G., and Mastrogiuseppe, M.: Investigating the volcanic activity on Venus with Magellan data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8135, https://doi.org/10.5194/egusphere-egu24-8135, 2024.

The Venusian atmosphere has everything to be an exciting natural sulfur laboratory. In addition to relatively high concentrations of sulfur dioxide, suitable conditions in the atmosphere make both thermo- and photochemical reactions possible, allowing for complex chemical reactions and the formation of new sulfur containing compounds. These compounds could explain or contribute to the enigmatic 320-400 nm absorption feature in the atmosphere. One of the proposed absorbers is polysulfur compounds. While some experimentally obtained UV-VIS spectra have been published, studying the different polysulfur species individually is extremely difficult due to the reactive nature of sulfur. In this work UV-VIS spectra for polysulfur species S₂ to S₈ were simulated using the nuclear ensemble approach to determine if they fit the absorption profile of the unknown absorber.

Geometries were optimized at the ωB97X-D/aug-cc-pV(T+d)Z level of theory, with the S₂, S₃, and S₄ structures also being optimized at the CCSD(T)/aug-cc-pV(T+d)Z level of theory. For the lowest energy isomers UV-VIS spectra were simulated using a nuclear ensemble of 2000 geometries, with vertical excitations calculated at the EOM-CCSD/def2-TZVPD or the ωB97X-D/def2-TZVPD levels of theory.

The simulated UV-VIS spectra for the smaller species were in quite good agreement with experimental results. Two different molecules were identified with substantial absorption cross sections in the range of the unknown absorber: The open chain isomer of S₃, and the trigonal isomer of S₄ However, the mixing ratios of these species in the Venusian atmosphere are also needed to make a more conclusive statement. Other polysulfur compounds have insignificant absorption cross sections in the 320-400 nm range and can therefore be excluded.

The calculated absorption cross sections can be used to calculate photolysis rates, which can be straight away added to atmospheric models of Venus. In addition, this work will help future space missions to Venus, for example by focusing their search for the unknown absorber.

How to cite: Skog, R., Frandsen, B., and Kurtén, T.: Simulating UV-VIS Spectra for Polysulfur Species in the Venusian Atmosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8798, https://doi.org/10.5194/egusphere-egu24-8798, 2024.

Venus’ mass and radius are similar to those of Earth. However, Venus’ interior structure and chemical composition are poorly constrained. Seemingly small deviations from the Earth might have important impacts in the long-term evolution and dynamics of Venus when compared to our planet and could help to explain the different present-day surface and atmospheric conditions and geophysical activity between these two planets. Shah et al. (ApJ 2022) presented a range of possible bulk compositions and internal structures for Venus. Their models, designed to fit Venus’ moment of inertia and total mass, predict core radii ranging from 2930-4350 km and include substantial variations in mantle and core composition. In this study, we pick ten different Venus models from Shah et al. (ApJ 2022) that range from a small to a big, and from a S-free to a S-rich core. We run mantle convection evolution models for the different scenarios using the code StagYY (Tackley, PEPI 2008; Armann and Tackley, JGR 2012) and explore how different interior structures and chemical compositions affect the long-term evolution and dynamics of Venus. In our models, the bulk composition of the mantle affects the basalt fraction and the solidus and liquidus temperature profiles. We investigate how the composition and size of the core affects magmatism hence outgassing of water and other volatiles to the atmosphere, the basalt distribution, heat flow, temperature of the mantle and lithosphere, and observables such as the moment of inertia and Love numbers. Since the tectonic regime active on Venus is still unknown, we test different evolution scenarios for a planet covered by a stagnant lid, an episodic lid, and a plutonic-squishy lid. The models produce a range of predictions that can be compared to observations by planned missions to Venus, including EnVision measurements by the VenSpec spectrometers, comprising outgassing of water and other volatiles and surface composition. These can be used to constrain Venus’ interior composition and structure, and reveal key information on the differences between Earth and Venus.

How to cite: Louro Lourenço, D., Tackley, P., Rolf, T., Grünenfelder, M., Shah, O., and Helled, R.: Influence of Possible Bulk Compositions on the Long-Term Evolution and Outgassing of Venus, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9470, https://doi.org/10.5194/egusphere-egu24-9470, 2024.

Venus has regained great interest from planetary scientists in recent years because of the multiple upcoming Venus missions (e.g., EnVision, DAVINCI+ and VERITAS). Studying Venus is crucial for understanding the evolution of terrestrial planets as well as projecting the Earth’s future. One important component of the Venus climate system, the sulfuric acid clouds, has exhibited spatial and temporal variabilities. These variabilities are closely connected with the interactions between dynamics, photochemistry, radiative transfer and cloud physics. Current modeling studies of the Venus atmosphere have shed light on the underlying physics of the cloud variabilities. However, none of them has resolved the cloud radiative feedback. As an essential step to fully understanding the complex interactions, we develop a state-of-the-art General-Circulation Model (GCM), with cloud condensation/evaporation and radiative feedback processes included. In this talk, I will quantify the radiative forcing caused by the acidic clouds and provide indications of how the radiative forcing can influence the Venus climate evolution.

How to cite: Shao, W., Mendonca, J., and Dai, L.: Cloud radiative feedback on the Venus climate simulated by a General-Circulation Model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10478, https://doi.org/10.5194/egusphere-egu24-10478, 2024.

The investigation into Venus's atmosphere has highlighted deficiencies in photochemical models when it comes to explaining the distribution of trace gas species, particularly crucial elements like CO and OCS, which play a vital role in Venus's sulfur cycle and cloud formation.

To gain a comprehensive understanding of the abundance and variability of these trace gases ahead of the DaVinci probe's descent, we initiated an observational study using NASA's IRTF telescope equipped with the high-resolution ISHELL spectrometer. Conducted from June 11 to June 30, 2023, our study involved capturing K, H, and J-band spectra of Venus's night side. We employed the SMART software to calculate synthetic spectra, considering various gas abundances and emission angles.

With our high-resolution spectral data (R=λ/Δλ~25,000), we successfully mapped the abundances of CO, H2O, and OCS in the equatorial region, revealing both daily and latitudinal variations. Our focus was on examining the delicate balance between chemistry and transport, evident in the observed anti-correlation between OCS and CO abundance with cloud opacity.

Through near-infrared observations, this study aims to unravel the intricate interplay between atmospheric dynamics and chemical reactions in Venus's cloud formation. By providing insights into observed cloud patterns and elucidating the relationship between atmospheric chemistry, dynamics, and cloud creation on Venus, we contribute crucial parameters to refine existing photochemical models.

How to cite: Liao, T.-J., Young, E., Bullock, M., crisp, D., and Yung, Y.: Unraveling Venus's Atmospheric Composition: Insights into CO, H2O, and OCS Abundances through Observations and Modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10655, https://doi.org/10.5194/egusphere-egu24-10655, 2024.

The spin period of Venus is anomalously large. With one Venusian day being 243 Earth days, the rotational bulge of
Venus has the amplitude of only tens of centimetres, making the Earth’s hotter twin the least rotationally stable planet in
the Solar System. Being a slow-rotator creates a unique link between internal and rotational dynamics. This is because,
on a slow-rotator, convection driven redistribution of mass may produce perturbations of the body’s inertia tensor that
are comparable in amplitude with the inertia of the rotational bulge. Venus thus may respond to mantle convection by
wobbling (Spada et al., 1996), and wobbling is detectable when both the rotational and the figure axes are measured
accurately. The present-day estimate of the angle between the two axes is 0.5°, but it is based on gravity models with a
limited resolution (Konopliv et al., 1999). Future missions to Venus, namely VERITAS and EnVision, are likely to provide
a more robust measurement.

The geodynamic regime of Venus’ mantle remains enigmatic. Observational data does not support the existence of
continuous plate tectonics on its surface, but some recent evidence of ongoing tectonic and volcanic activity (e.g. Herrick
and Hensley, 2023) and crater statistics analyses (e.g. O'Rourke et al., 2014) indicate that the planet is unlikely to be in a
stagnant lid regime (see also Rolf et al., 2022). Here we perform 3D spherical mantle convection simulations of the different
possible tectonic scenarios and compute the resulting reorientation of Venus. The reorientation is accompanied by a wobble
whose average amplitude we evaluate and compare to the present day estimate of 0.5° (Konopliv et al., 1999). Since the
different convective regimes predict vastly different rotational dynamics, the comparison provides a useful constraint on
the interior dynamics of Venus. This work was supported by the Czech Science Foundation through project No. 22-20388S.

References
Herrick, R., Hensley, S., 2023. Surface changes observed on a venusian volcano during the magellan mission. Science
doi:10.1126/science.abm7735.

Konopliv, A., Banerdt, W., Sjogren, W., 1999. Venus gravity: 180th degree and order model. Icarus 139, 3–18.
doi:10.1006/icar.1999.6086.

O'Rourke, J.G., Wolf, A.S., Ehlmann, B.L., 2014. Venus: Interpreting the spatial distribution of volcanically modified
craters. Geophys. Res. Lett. 41, 8252–8260. doi:10.1002/2014gl062121.

Rolf, T., Weller, M., Gulcher, A., Byrne, P., O’Rourke, J.G., Herrick, R., Bjonnes, E., Davaille, A., Ghail, R., Gillmann,
C., Plesa, A.C., Smrekar, S., 2022. Dynamics and evolution of venus’ mantle through time. Space Science Reviews 218,
70. doi:10.1007/s11214-022-00937-9.

Spada, G., Sabadini, R., Boschi, E., 1996. Long-term rotation and mantle dynamics of the Earth, Mars, and Venus.
J. Geophys. Res. Planets 101, 2253–2266. doi:10.1029/95JE03222.

How to cite: Patočka, V., Maia, J., and Plesa, A.-C.: The link between internal and rotational dynamics of Venus: The amplitude of mantle convection-driven wobble, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12316, https://doi.org/10.5194/egusphere-egu24-12316, 2024.

With the selection of multiple missions to Venus by NASA and ESA that are planned to launch in the coming decade, we will greatly improve our understanding of Venus. However, none of these missions have determining the seismicity of the planet as one of their primary objectives. Nevertheless, constraints on the seismicity remain crucial to understand the tectonic activity and geodynamic regime of the planet and its interior structure. 

Funded by the International Space Science Institute (ISSI) in Bern, Switzerland, we have gathered an interdisciplinary team of experts in seismology, geology, and geodynamics to assess the potential seismicity of Venus, specific regions that could be seismically active at present, and the methods to detect them.

Here, we present the findings from our second ISSI team meeting (January 29 - February 2, 2024), aiming to review knowledge on Venus's seismicity and interior and identify the best approaches for future missions. We present the feasibility, advantages, and disadvantages of different seismic observation techniques on the surface (e.g., broadband seismometers, distributed acoustic sensing methods), from a balloon (acoustic sensors), and from orbit (airglow imagers). We make a recommendation for the instrumentation of a future seismology-focused mission to Venus. 

We also suggest target regions with a high likelihood of significant surface deformation and/or seismicity. These targets are useful for the upcoming VERITAS (Venus Emissivity, Radio Science, InSAR, Topography and Spectroscopy) and EnVision missions and would specifically benefit from the repeat pass interferometry of VERITAS, which detects surface deformation and can therefore in principle constrain the maximum displacement of surface faulting at locations that are visited twice during the mission. 

How to cite: van Zelst, I., De Toffoli, B., Garcia, R. F., Ghail, R., Gülcher, A. J. P., Horleston, A., Kawamura, T., Klaasen, S., Lefevre, M., Lognonné, P., Maia, J., Näsholm, S. P., Panning, M., Plesa, A.-C., Sabbeth, L., Smolinski, K., Solberg, C., and Stähler, S.: Seismicity on Venus: optimal detection methods and target regions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12790, https://doi.org/10.5194/egusphere-egu24-12790, 2024.

EnVision radio science investigation will deepen our understanding of Venus’ gravity, interior structure and atmospheric properties. To address these scientific questions, a two-way link communication (configuration X/X/Ka-band) is established with the ESA ESTRACK ground stations enabling precise orbit determination (POD) during the science phase. An accurate modeling of the spacecraft’s dynamics, including the atmospheric drag acceleration, is key for retrieving EnVision’s trajectory and constraining Venus’ gravity field, tides and orientation parameters.

Dedicated radio occultation campaigns are designed to characterize electron density profiles in the ionosphere and atmospheric density, pressure and temperature in the mesosphere and upper troposphere of Venus. Furthermore, an accurate POD of the spacecraft also provides complementary information on the atmospheric density at the altitudes crossed by the probe, extending the science return of the EnVision mission.

The atmospheric drag perturbation strongly affects spacecraft trajectories that are characterized by a pericenter altitude above Venus’ surface of less than 220 km. By accounting for different Venus’ atmospheric models, e.g., the Venus Climate Database (VCD) and the Venus Global Reference Atmospheric Model (Venus-GRAM), we investigate the impact of potential errors and uncertainties in the predicted atmospheric properties on the orbit evolution of the spacecraft. We note significant inconsistencies between Venus’ atmospheric models at the spacecraft altitudes including atmospheric density differences of more than 200%. These discrepancies may be representative of the current knowledge of Venus’ upper atmosphere and thermosphere. Thus, we carried out a perturbative analysis of the dynamical forces by introducing a mismodeling in the atmospheric density profiles. We assumed the VCD for the simulation of the radio tracking measurements and we included as a priori model in the estimation process the Venus-GRAM. By developing a batch sequential filter that adjusts a set of atmospheric density scale factors, we compensated for the mismodeling and improved the quality of the dynamical model and of the orbit determination. The proposed approach enables an estimation of the atmospheric density at the spacecraft altitudes with an accuracy of 25% and accuracies in the orbit reconstruction of 1-2 m, 30-40 m and 20-30 m in the radial, transverse and normal directions.

How to cite: Gargiulo, A. M., Genova, A., Petricca, F., Del Vecchio, E., Andolfo, S., Torrini, T., Rosenblatt, P., Lebonnois, S., Marty, J.-C., and Dumoulin, C.: Estimation of Venus' atmospheric density through EnVision precise orbit determination, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13314, https://doi.org/10.5194/egusphere-egu24-13314, 2024.

The electrical environment of Venus has been investigated through extensive considerations of whether lightning has been detected in the atmosphere [1]. Although an important process, the presence or absence of lightning does not completely describe Venus’ electrical environment. Little consideration has been made of other related aspects, such as the possible presence of a global atmospheric electric circuit, as is present on Earth. In this context, lightning would be regarded as the source in a possible global circuit, which distributes charge across a planet. New arguments for and against a global electric circuit in Venus’ atmosphere are presented here which arise from re-analysis of data from the Venera 13 & 14 landers.

On Earth, the global atmospheric electric circuit connects regions of disturbed weather to distant regions of fair weather, by current flow between the conducting ionosphere and surface. Disturbed weather regions produce the potential difference between these conducting layers, which drives the current flow. The presence of a similar global circuit on other planets has been proposed, but their existence remains an open question, which motivates further work [2].

The Venera 13 & 14 landers descended through Venus’ atmosphere carrying a wealth of instrumentation. Each lander carried a point discharge sensor, which recorded electrical discharges between the spacecraft and the atmosphere [3]. The discharges recorded were difficult to explain using existing models of Venus’ environment, so it was previously proposed that low atmosphere haze layers could have caused them [4]. Further evidence for these haze layers has been provided by spectroscopic data from the Venera landers, which showed significant atmospheric extinction in the same region [5]. We have attempted to investigate whether it would be plausible for haze layers to cause both the electrical and extinction effects, and whether this favours a global electric circuit in Venus’ atmosphere.

To investigate this, a model describing electrical interactions in Venus’ atmosphere has been produced. The effects of different haze layers on Venus’ electrical environment were able to be studied, via different inputs to the model. The haze layer properties have been constrained by the spectroscopic observations. Results from the electrical modeling were compared with the electrical discharges recorded by the landers, allowing us to determine the conditions which best recreate these observations. Our investigations show that similar results to the observed Venera data can be produced by the electrical model when the effects of a global atmospheric electric circuit are included, but not when they are neglected. These findings are not definitive, but they do provide supporting evidence for the presence of a global electric circuit in Venus’ atmosphere.

References:
[1] R.D. Lorenz (2018). Progress in Earth and Planetary Science, 5. [2] K.L. Aplin (2006). Surveys in Geophysics 27. 63-108. [3] L. Ksanfomality et al. (1982). Soviet Astronomy Letters, 8. 230–232. [4] R.D. Lorenz (2018). Icarus, 307. 146-149. [5] B. Grieger (2003). Proceedings of the International Workshop Planetary Probe Atmospheric Entry and Descent Trajectory Analysis and Science. 63–70.

How to cite: McGinness, B., Harrison, G., Aplin, K., Airey, M., and Nicoll, K.: New Evidence for a Global Atmospheric Electric Circuit on Venus, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13391, https://doi.org/10.5194/egusphere-egu24-13391, 2024.

Studies of exoplanet habitability involving GCMs typically consider the potential for long-lived surface liquid water—or, in other words, climates that Earth-life may find survivable. However, the presence of life and remotely detectable biosignatures on an exoplanet additionally requires an independent origin of life and that life subsequently thrives rather than simply survives. The origin and proliferation of life are both strongly influenced by climate, and both can therefore be informed by GCM studies in parallel with traditional habitability metrics. 

Wet-dry cycles are thought to be an essential ingredient for the origin of life. Cyclic wetting and drying may arise from either diurnal or seasonal cycles, and thus the likelihood of an origin of life may differ between worlds with very different rotation rates, obliquities, or eccentricities. At the same time, seasonal mixing in aqueous environments can trigger highly productive blooms and amplify biosignatures relative to scenarios lacking temporal variability.  

We used ExoPlaSim (an atmospheric GCM) and cGENIE-PlaSim (a 3D model for ocean dynamics and marine biogeochemistry coupled to a 3D atmospheric GCM) to explore diurnal and seasonal cycles on other worlds—with an eye towards origin of life chemistry and biosignatures. This presentation will ultimately identify the planetary scenarios most conducive to exoplanet life detection. 

How to cite: Olson, S., Jernigan, J., Lafleche, E., and Brown, H.: Exploring origin of life chemistry and exoplanet biosignatures with GCMs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14161, https://doi.org/10.5194/egusphere-egu24-14161, 2024.

The NASA Magellan Mission (1990 to 1994) produced a valuable resource that planetary geologists continue to use three decades later to unravel the geological characteristics of Venusian Large Igneous Provinces. The ability to be the first to map the surface of Venus is a powerful engagement tool to inspire the next generation of planetary geologists, as illustrated by the size of the Mount Royal University (MRU) Venus geological mapping team (now 25, nearly ¼ of the MRU Geology Major program). MRU is a public undergraduate university. Students are recruited out of 1^st and 2^nd year courses. In year one (Y1) of the research program students learn how to use the ArcGIS software while being introduced to the geological features of Venus as they map their quadrant, in Y2 or Y3 the students present a poster at an internal research day. The goal by Y4 is for these students to publish a peer-reviewed journal article. Currently one student who ran into pandemic roadblocks through high school could be published while she upgrades her marks, before she is in the MRU Geology Major Program. Such opportunities could prove to be incentives to guide other students past similar roadblocks (we will start working with local junior and high school students in the near future). Collectively we are working towards completing the geological map of the Henie Quadrangle (V-58, south Venus). Detailed mapping (at 1:500,000) revealed that lava canali extend across the entire quadrangle, with evidence for at least three generations of canali. Three canali originate from corona features (e.g. the circumferential dykes around Fotla Corona) suggesting that some canali may be linked to corona formation. The orientation of compressional wrinkle ridges (WR) in northern Henie suggest that these WRs were formed due to strain associated with the formation of the Artemis tectonomagmatic feature which is directly north of Henie. Artemis is possibly the largest such feature in the Solar System. The extent of the Artemis influence is being constrained across the Henie Quadrangle. The source of strain that formed a differently oriented WR swarm to the south of Henie is unknown. There is no evidence for the strain localization into master faults that we see on Earth. More work is needed to develop a model for the formation of the paired Latmikaik-Xacau Coronae and the associated Tellervo Chasma, Sunna-Laverna Dorsae and the Sonmunde-Mdeb-Arubani Flucti. A fissure eruption out of the Sunna Dorsa is proposed as the origin for the surrounding Arubani Fluctus.      

How to cite: Boggs, K., Shackman, J., Demorcy, J., Pendleton, C., Hall, J., Chowdhury, M., Bley, H., Varga, E., Shustova, J., Dear, B., Fontaine, P., Dhami, L., Herrington, S., Ernst, R., El Balil, H., Bethell, E., and Hamner, S.: Henie Quadrangle (V-58, Southern Venus); Large Igneous Province Features, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14443, https://doi.org/10.5194/egusphere-egu24-14443, 2024.

Often termed the twin sister of the Earth, Venus represents an alternative outcome of the evolutionary path taken by large terrestrial planets. Given its extreme surface conditions, lack of surface water, and the absence of plate tectonics, the present-day thermal state of its mantle is likely very different from the Earth. Venus also remains the most enigmatic of terrestrial worlds in terms of interior structure. Both its tidal Love number k₂ and the moment of inertia factor, the main sources of information on the core size and interior structure, are known with a large uncertainty of about 10% [1, 2], and the magnitude of tidal dissipation, sensitive to the planet’s thermal state, has only been determined indirectly [e.g., 3]. Yet, the set of observables acquired by the Magellan and Pioneer Venus Orbiter missions can still be used to put constraints on the interior structure.

In this study, we perform a Bayesian inversion of several observational and theoretical constraints (such as the tidal Love number, maximum elastic thickness, or absence of intrinsic magnetic field) to gain insight into the present-day interior structure and thermal state of Venus. This is done by combining the calculation of a global tidal deformation with a 1d parameterised model of mantle convection in the stagnant-lid regime [4,5]. The convection model is based on the thermal boundary layer theory and incorporates partial melting, crustal growth, and inner core crystallization. The elastic structure of the mantle for three selected mineralogical models is obtained from the software Perple_X, based on the minimisation of Gibbs free energy [6]. Finally, to find the tidal parameters, we calculate the deformation of a layered compressible viscoelastic sphere [7]. The mantle is described by the Andrade rheological model, which has proven essential for distinguishing between a fully solid and a fully or partially liquid Venusian core [8]. We vary a large set of rheological, structural, and thermodynamic parameters and predict a range of mantle temperatures consistent with previous stagnant-lid models, average mantle viscosities between 10²⁰-10²² Pa.s, and a tidal quality factor of Q=50⁺⁷⁴_-24, corresponding to a phase lag of 1.12^+1.06_-0.67 degrees. Additionally, we discuss how the future measurements of the tidal deformation and the moment of inertia of Venus from EnVision [9] and VERITAS (Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy) [10] can improve our understanding of the planet's interior.

[1] Konopliv & Yoder (1995), doi:10.1029/96GL01589.

[2] Margot et al. (2021), doi:10.1038/s41550-021-01339-7.

[3] Correia & Laskar (2003), doi:10.1016/S0019-1035(03)00043-5.

[4] Morschhauser et al. (2011), doi:10.1016/j.icarus.2010.12.028.

[5] Baumeister et al. (2023), doi:10.1051/0004-6361/202245791.

[6] Connolly (2009), doi:10.1029/2009GC002540.

[7] Takeuchi & Saito (1972), doi:10.1016/B978-0-12-460811-5.50010-6.

[8] Dumoulin et al. (2017), doi:10.1002/2016JE005249.

[9] Rosenblatt et al. (2021), doi:10.3390/rs13091624.

[10] Cascioli et al. (2023), doi:10.3847/PSJ/acc73c.

How to cite: Walterová, M., Plesa, A.-C., Baumeister, P., Rückriemen-Bez, T., Wagner, F. W., and Breuer, D.: Constraining the interior structure and thermal state of Venus, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14638, https://doi.org/10.5194/egusphere-egu24-14638, 2024.

Dynamics of the Venus atmosphere is still an unsolved fundamental problem in the planetary physics. ESA’s Venus Express collected long imaging time series in several wavelengths from UV to near-IR. It was later complemented by JAXA’s Akatsuki observations, thus providing the longest almost uninterrupted monitoring of the Venus atmosphere dynamics for about 26 Venus years. Tracking of cloud features allowed determination of wind speed at different levels within the cloud deck thus enabling significant progress in characterization of the mean atmospheric circulation. The analysis revealed wind variability including changes with altitude, latitude, local solar time as well as influence of the surface topography and long term 12.5 years periodicity.

The images also provided morphological evidences of dynamical processes at the cloud level. UV dark low latitudes were found to be dominated by convective mixing that brings UV absorbers from depth, while bright uniform clouds at middle-to-high latitudes are typical for the regions with suppresses vertical mixing. The latter feature correlates with drastic increase of the total cloud opacity poleward from ~60° latitude that likely indicates presence of a dynamical mixing barrier here. Similarity of the global UV cloud morphology at the cloud top (~70 km) and that in the deep cloud (50-55 km) observed in the near-IR on the night side suggested similar morphology shaping processes throughout the cloud deck. Venus Express observed gravity waves poleward of 65°N concentrated at the edges of Ishtar Terra likely indicating their generation by wind interaction with the surface. 

Venus Express performed about 800 radio occultations providing precise measurements of the atmospheric temperature structure and static stability parameter in the altitude range 40-90 km. The Richardson number latitude-altitude field derived from the wind and temperature measurements suggests presence of convection in the cloud deck and stable mesosphere above it with the convective layer extending to greater depth at high latitudes. The talk will present recent results on the atmospheric circulation, supplemented by a summary of the Venus Express observations related to the atmospheric dynamics and an outlook for further analysis of these data.  

How to cite: Titov, D., Khatuntsev, I., and Patsaeva, M.: Venus atmosphere dynamics: digging into the Venus Express observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14689, https://doi.org/10.5194/egusphere-egu24-14689, 2024.

The dynamic regime prevailing in the mantle of present-day Venus is still unknown. The surface of Venus seems uniformly quite young; it has  been proposed that it was due to a catastrophic resurfacing 150-700 Ma, and that the planet was in a stagnant lid regime since. Indeed, Magellan observations have failed to reveal a continuous set of accretion ridges and subduction zones, signatures of plate tectonics. But subduction features (trench, elastic bulge) are present in a number of localized spots, for exemple around two of the largest coronae, Artemis and Quetzelpetlal. There, subduction would be mainly by roll-back and could have been induced by the impingement of a mantle plume under the lithosphere, as predicted by our recent fluid dynamics laboratory experiments. Further analysis of our experiments suggest that subduction would be facilitated by the presence of a few % of a liquid phase in the asthenosphere. Melt would be most likely for the Venusian case, as anyway hinted by the amount of volcanic features on the surface of the planet. The experimental scaling laws further suggest that roll-back and subduction could be quite fast (10 cm/yr) because of the old age of the subducting lithosphere and the transformation to eclogite of the basaltic crust. This is turn would generate the rapid opening of a back-arc basin. Laboratory experiments show that for Venus temperature conditions, the produced crust and lithosphere could be quite disorganized with a contorted spreading center, large transforms and microplates. Moreover, the buoyancy of the newly created plate would cause it to remain quite elevated compared to the surrounding plains. Hence, inspection of the topography of Venus suggests several new plates created by subduction: beside the interior of Artemis coronae, Enyo Fossae and Asthik Planum could be plausible candidates. 

How to cite: Davaille, A.: Signatures of a regime of episodic localized subduction: from laboratory experiments to Venus, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16255, https://doi.org/10.5194/egusphere-egu24-16255, 2024.

The next ESA mission to Venus, EnVision, aims to study the planet as a whole, including its various constituting parts as well as their interactions and coupling processes. Several instruments will therefore compose the payload: a synthetic aperture radar (VenSAR, NASA), a subsurface radar sounder and a suite of three spectrometers (VenSpec) will be embedded, and a radioscience experiment will be implemented. Among them, the UV channel of the spectrometer suite, VenSpec-U, will observe the atmosphere above the clouds and will focus on the characterisation of the sulphured gases SO₂ and SO, the monitoring of the unknown UV absorber and dynamical processes. These four topics have been identified as the main science objectives of the instrument and have driven the elaboration of a preliminary design based on the requirements (e.g. spectral range, spectral and spatial resolution) that were formulated with respect to these goals.

The compliance of the current design with respect to these requirements, regarding in particular the precision of the retrieved science data, can then be assessed. Sensitivity studies are therefore performed using the Radiative Transfer Model (RTM), updated from the one used for SPICAV-UV/Venus Express retrievals (Marcq et al., 2020), that allows to link atmospheric features and UV reflectance spectra. Two types of perturbations are considered : errors of random nature arising from the presence of noise on the signal, or systematic errors caused by various effects that induce biases on the measurements. The first ones can be characterised through the influence of the Signal-to-Noise Ratio (SNR) on the uncertainties associated to each retrieved parameter through the fitting algorithm. Limits in terms of SNR can then be defined in order to ensure the compliance with the specifications. The second ones are referring to the impact of biases on the retrievals’ accuracy, and evaluate more specifically the effects of the similarities between the spectral characteristics of these biases and those of the atmospheric components aiming to be detected. The implemented method is based on the Effective Spectral Radiometric Accuracy (ESRA) requirement, previously defined within the framework of the ESA Sentinel missions. It allows to study biases independently as well as potential compensations, so that allowable envelopes of residual errors can then be estimated for each of the considered biases.

How to cite: Conan, L., Marcq, E., Lustrement, B., Rouanet, N., Vandaele, A. C., and Helbert, J.: Sensitivity studies for the VeSUV/VenSpec-U instrument onboard ESA’s EnVision mission, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16442, https://doi.org/10.5194/egusphere-egu24-16442, 2024.

Until now, the Venus PCM (Planetary Climate Model) was using precomputed tables for the distribution of the solar heating rates in the atmosphere of Venus. A new scheme is now implemented to compute online the radiative transfer of the solar flux, which allows more flexibility to study sensitivity to opacity sources. We have investigated the sensitivity of the temperature and circulation of the Venusian cloud region to the distribution of the UV absorber. Different vertical distributions of the UV absorber, as well as variations of this along latitudes, have been tested, and comparison is discussed of the vertical profile of computed solar heating rates, temperature distribution in the cold collar region, as well as the resulting mean zonal wind field.

How to cite: Han, P. and Lebonnois, S.: Influence of the UV absorber distribution on the temperature and circulation ofthe Venusian cloud region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16505, https://doi.org/10.5194/egusphere-egu24-16505, 2024.

The cause of the inhomogeneous near-ultraviolet absorption observed in the upper clouds of Venus remains a key question in Venusian research. One possible candidate in the literature is ferric chloride. The absorption spectrum of ferric chloride currently in use by models uses ethyl acetate as a solvent and does not reproduce the absorption features observed on Venus. The study of the optical properties and chemistry of ferric chloride in the sulphuric acid cloud droplets is required to draw valid conclusions regarding its suitability as a candidate for the near-UV absorption.

In this study, we measure the absorption spectrum of ferric chloride in sulphuric acid from 200 – 600 nm at a range of temperatures and measure the rate of conversion of the ferric chloride ions into ferric sulphate ions. We then use the resulting ferric chloride absorption coefficients in a 1D radiative transfer model and estimate the required concentration of ferric chloride in the clouds to be 0.6 – 0.9 wt% in the mode 1 (~0.3 µm radius) cloud droplets to match observations. We also predict the atmospheric concentrations of ferric chloride formed from the reaction of iron ablating from cosmic dust entering Venus’ atmosphere around 120 km with hydrogen chloride emitted by volcanic activity, and estimate the accumulation timescale of ferric chloride to produce the required concentrations in the clouds.

How to cite: Egan, J., Feng, W., James, A., Manners, J., Marsh, D. R., and Plane, J. M. C.: Laboratory studies and modelling of ferric chloride as the cause of the anomalous UV absorption in the Venusian atmosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16898, https://doi.org/10.5194/egusphere-egu24-16898, 2024.

High-resolution runs of the Venus PCM (1.25° in longitude and latitude) successfully simulated Venus atmospheric superrotation. The results show a clear spectrum and structure of atmospheric waves, primarily with periods of 5.65 days and 8.5 days. The simulation successfully reproduces long-term quasi-periodic oscillation of the zonal wind and primary planetary-scale wave seen in observations. These oscillations are obtained with a period of about 163-222 days close to the observations. The Rossby waves show robustness in wave characteristics and angular momentum transport due to Rossby-Kelvin instability by comparing the 5.65-day wave with the 5.8-day wave simulated by another Venus GCM, AFES-Venus. Similarities are also evident between the 8.5-day wave in our simulation and the 7-day wave obtained in AFES-Venus. Furthermore, the long-term variations in angular momentum transport indicate that the 5.65-day wave is the dominant factor of the oscillation on the superrotation, and the 8.5-day wave is the secondary. When the 5.65-day wave grows, its angular momentum transport is enhanced and accelerates (decelerates) the lower-cloud equatorial jet (cloud-top mid-latitude jets). Meanwhile, the 8.5-day wave weakens, reducing its deceleration effect on the lower-cloud equator region. Consequently, this flattens the background wind and weakens instability, leading to the decay of the 5.65-day wave. And vice versa when the 5.65-day wave is weak.

How to cite: Lai, D., Lebonnois, S., and Li, T.: Planetary-scale wave study in Venus cloud layer, simulated by the Venus PCM, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17524, https://doi.org/10.5194/egusphere-egu24-17524, 2024.

EnVision is ESA’s next mission to Venus, in partnership with NASA, where NASA provides the Synthetic Aperture Radar payload and mission support. The ESA mission adoption is scheduled for January 2024, and the launch for 2031. The start of the science operations at Venus is early 2035 following the mission cruise, and aerobraking phase around Venus to achieve a low Venus polar orbit. The scientific objective of EnVision is to provide a holistic view of the planet from its inner core to its upper atmosphere, studying the planets history, activity and climate. EnVision aims to establish the nature and current state of Venus’ geological evolution and its relationship with the atmosphere. EnVision’s overall science objectives are to: (i) characterize the sequence of events that formed the regional and global surface features of Venus, as well as the geodynamic framework that has controlled the release of internal heat over Venus history; (ii) determine how geologically active the planet is today; (iii) establish the interactions between the planet and its atmosphere at present and through time. Furthermore, EnVision will look for evidence of past liquid water on its surface.

The nominal science phase of the mission will last six Venus cycles (~four Earth years), and ~210 Tbits of science data will be downlinked using a Ka-/X-band communication system. The science objectives will be addressed by five instruments and one experiment, provided by ESA memberstates and NASA. The VenSAR S-band radar will perform targeted surface imaging as well as polarimetric and stereo imaging, radiometry, and altimetry. The high-frequency Subsurface Radar Sounder (SRS) will sound the upper crust in search of material boundaries. Three spectrometers, VenSpec-U, VenSpec-H and VenSpec-M, operating in the UV and Near- and Short Wave-IR, respectively, will map trace gases, search for volcanic gas plumes above and below the clouds, and map surface emissivity and composition. A Radio Science Experiment (RSE) investigation will exploit the spacecraft Telemetry Tracking and Command (TT&C in Ka-/X bands) system to determine the planet’s gravity field and to sound the structure and composition of the middle atmosphere and the cloud layer in radio occultation. All instruments have substantial heritage and robust margins relative to the requirements, with designs suitable for operation in the Venus environment, and were chosen to meet the broad range of measurement requirements needed to support the EnVision scientific objectives. The EnVision science teams will adopt an open data policy, with public release of the scientific data after verification and validation. Public calibrated data availability is <6 months after data downlink.

The mission phase B1 was concluded in December 2023 following the successful Mission Adoption Review and positive science review and recommendations by the ESA Solar System and Exploration Working Group (SSEWG) and Space Science Advisory Committee (SSAC). The mission adoption is scheduled for 25 January 2024. The scientific objectives and status of the EnVision mission preparations will be presented, including an overview of the scientific topics being studied and the next steps in the mission preparation.

How to cite: Straume-Lindner, A. G., Schulte, M., Pacros, A., Voirin, T., Bruzzone, L., Byrne, P., Carter, L., Dumoulin, C., Gilli, G., Helbert, J., Hensley, S., Jessup, K. L., Kiefer, W., Marcq, E., Mason, P., Moreira, A., Vandaele, A. C., and Widemann, T.: Science objective and status of the EnVision Mission to Venus, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18247, https://doi.org/10.5194/egusphere-egu24-18247, 2024.

Venus is a natural laboratory to study the atmospheric circulation on a slowly rotating planet. The dynamics of its upper atmosphere (60-120 km) is a combination of retrograde zonal wind found in the lower mesosphere and solar-to-antisolar winds that characterize the thermosphere, and it is subject to a strong turbulence and a dramatic variability both on day-to-day as well as longer timescales. Moreover, several wavelike motions with different length scales have been detected at these altitudes within and above the clouds and they are supposed to play an important role in the maintenance of the atmospheric circulation. The basic processes maintaining the super-rotation (an atmospheric circulation located at the clouds level and being 80 times faster than the rotation of the planet itself) and other dynamical features of Venus circulation are still poorly understood [1].

Different techniques have been used to obtain direct observations of wind at various altitudes: tracking of clouds in ultraviolet (UV) and near infrared (NIR) images give information on wind speed at cloud top (~70 km altitude) [2] and within the clouds (~61 km, ~66 km) [3], while ground-based measurements of doppler-shift in CO₂ band at 10 μm [4] and in several CO (sub-)millimeter lines [5,6] sound thermospheric and upper mesospheric winds, showing a strong variability.

In the mesosphere, at altitudes where direct observations of wind are not possible, zonal wind fields can be derived from the vertical temperature structure using the thermal wind equation. Previous studies [7,8,9] showed that on slowly rotating planets, like Venus and Titan, the strong zonal winds at cloud top can be successfully described by an approximation of the Navier–Stokes equation, the cyclostrophic balance in which equatorward component of centrifugal force is balanced by meridional pressure gradient.

We will present zonal thermal winds derived by applying the cyclostrophic approximation from the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) temperature retrievals. VIRTIS was one of the experiments on board the European mission Venus Express [10]. For this study, we will analyze the complete VIRTIS dataset acquired between December 2006 and January 2010 [11,12].

References

[1] Sanchez-Lavega, A. et al. (2017) Space Science Reviews, Volume 212, Issue 3-4, pp. 1541-1616.

[2] Goncalves R. et al. Atmosphere, 12:2., 2021. doi: 10.3390/atmos12010002.

[3] Hueso, R. et al. (2012) Icarus, Volume 217, Issue 2, p. 585-598.

[4] Sornig, M. et al. (2013) Icarus 225, 828–839.

[5] Rengel, M. et al. (2008) PSS, 56, 10, 1368-1384.

[6] Piccialli, A. et al. A&A, 606, A53 (2017) DOI: 10.1051/0004-6361/201730923

[7] Newman, M. et al. (1984) J. Atmos. Sci., 41, 1901-1913.

[8] Piccialli A. et al. (2008) JGR, 113,2, E00B11.

[9] Piccialli A. et al. (2012) Icarus, 217, 669–681

[10] Drossart, P. et al. (2007) PSS, 55:1653–1672

[11] Grassi D. et al. (2008) JGR., 113, 2, E00B09.

[12] Migliorini, A. et al. (2012) Icarus 217, 640–647.

How to cite: Piccialli, A., Grassi, D., Migliorini, A., Politi, R., Piccioni, G., and Drossart, P.: Zonal winds in Venus mesosphere from VIRTIS/VEx temperature retrievals, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18366, https://doi.org/10.5194/egusphere-egu24-18366, 2024.

Observations of Venus imply ongoing tectonic and volcanic activity, suggesting the planet is dynamically active^[1,2]. Tectonically altered regions, such as ridges or tesserae, indicate surface mobility. However, unlike Earth, no evidence of active plate tectonics has been identified. The tectonics and volcanism of terrestrial planets are closely tied to active mantle convection modes. Rheology, a crucial element in tectonics, is influenced by the presence of water^[3]. Despite this, the impact of water has largely been overlooked in Venus studies, as its interior is typically assumed to be dry. This assumption is being challenged by indications of significant hydrodynamic escape into space, requiring volcanic replenishment. Consequently, water is likely still present in Venus' interior, even if the concentrations are unknown. Importantly, the potential effects of water on Venus' dynamics and evolution remain poorly understood. The interplay between water, mantle dynamics, and volcanic activity would likely contribute to a more comprehensive understanding of Venus' evolution.  This underlines the need to consider complex dynamic thermo-magmatic models that account for water, including composition-dependent finite water solubilities.

In this study, we use the numerical code StagYY to perform state-of-the-art 2D models in a spherical annulus geometry to assess the effects of water on the tectono-magmatic evolution of Venus^[4,5]. Particular attention will be given to the way water influences mantle convection and tectonics. Indeed, results show that the presence of water can dramatically change the geodynamic regime through the rheology, melting and outgassing. With the introduction of composition-dependent water solubility maps, dehydration processes will redistribute water throughout the mantle^[6]. Since water content is directly related to the viscosity structure, the convective regime is expected to change as well. The main question we want to address is how dehydration processes and water distribution influence the convective and tectonic regimes of Venus. Studying the impact of water on Venus's interior may not only unveil insights into its tectonic evolution but also sets the stage for crucial future research, advancing our broader understanding of planetary processes and habitability.

^[1] Smrekar, S. E., Stofan, E. R., Mueller, N., Treiman, A., Elkins-Tanton, L., Helbert, J., ... & Drossart, P. (2010). Recent hotspot volcanism on Venus from VIRTIS emissivity data. Science, 328(5978), 605-608.

^[2]Gülcher, A. J., Gerya, T. V., Montési, L. G., & Munch, J. (2020). Corona structures driven by plume–lithosphere interactions and evidence for ongoing plume activity on Venus. Nature Geoscience, 13(8), 547-554.

^[3]Karato, S. I. (2015). Water in the evolution of the Earth and other terrestrial planets. Treatise on Geophysics, 9, 105-144.

^[4] Tackley, P. J. (2008). Modelling compressible mantle convection with large viscosity contrasts in a three-dimensional spherical shell using the yin-yang grid. Physics of the Earth and Planetary Interiors, 171(1-4), 7-18.

^[5]Tian, J., Tackley, P. J., & Lourenço, D. L. (2023). The tectonics and volcanism of Venus: New modes facilitated by realistic crustal rheology and intrusive magmatism. Icarus, 399, 115539.

^[6]Nakagawa, T. (2017). On the numerical modeling of the deep mantle water cycle in global-scale mantle dynamics: The effects of the water solubility limit of lower mantle minerals. Journal of Earth Science, 28(4), Article 4. https://doi.org/10.1007/s12583-017-0755-3

How to cite: Metternich, M., Tackley, P. J., Moccetti Bardi, N., and Lourenço, D. L.: Water and the tectonic regime of Venus, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19372, https://doi.org/10.5194/egusphere-egu24-19372, 2024.

A planet with a significant water content can give rise to a steam atmosphere (dominated by water vapor) when the incoming stellar flux exceeds the so-called runaway limit or after large impacts or accretion. All steam-atmosphere current models predict that the greenhouse effect of an ocean worth of water vapor is sufficient to generate a surface magma ocean. This has far reaching consequences for the early evolution of warm rocky planets and the coupling of their interior with the atmosphere. In this paradigm, the solidification of the mantle of Venus is believed to have happened only after the escape of its steam atmosphere to space, leaving the mantle desiccated.

However, these conclusions rely on the assumption that atmospheres are fully convective below their photosphere. This hypothesis was introduced in the 80s and is used in a large part of the literature on the subject. Its validity had however not been assessed thoroughly. We will present the results of a climate model that has been specifically designed to model the radiative-convective equilibrium of steam atmospheres without any a priori hypothesis on their convective nature. These results show that steam atmospheres are generally not fully convective, which yields much cooler surfaces than previous models. A runaway greenhouse does not systematically melt the surface. This changes completely our view of the early evolution of Venus', with even more drastic changes for planets around stars redder than the Sun.

The equilibrium thermal structure of a steam atmosphere, which affects observable signatures and mass-radius relationships of warm Earth-like to water-rich planets, becomes strongly dependent on the stellar spectrum and internal heat flow. Our current constraints on the water content of the internal Trappist-1 planets should for example be revisited. For ultracool dwarfs, these results even question the nature of the inner edge of the sometimes called habitable zone.

How to cite: Selsis, F., Leconte, J., Turbet, M., Chaverot, G., and Bolmont, E.: Steam atmospheres and the implications for Venus and Venus-like planets , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22187, https://doi.org/10.5194/egusphere-egu24-22187, 2024.

Global-scale Mars remote-sensing image datasets with accurate and consistent spatial positions contain a wealth of information on its surface morphology, topography, and geological structure. These data are fundamental for scientific research and exploration missions of Mars. Prior to China's first Mars exploration mission (Tianwen-1), none of the available global color-image maps of Mars with a spatial resolution of hundreds of meters were true-color products. On the other hand, there is currently a lack of global optical image datasets on a scale of several tens of meters with high-precision positioning and consistency that can be served as a reference frame for Mars.

Global remote sensing of Mars is one of the primary scientific goals of Tianwen-1. As of July 25, 2022, The Moderate Resolution Imaging Camera (MoRIC) onboard the orbiter has obtained 14,757 images, which have allowed acquiring global stereo images of the entire Martian surface. Additionally, the Mars Mineralogical Spectrometer (MMS) has returned 325 strips of visible and near-infrared spectral measurement data. These measurement data have laid the foundation for the development of a high-resolution global color-image map of Mars with high positioning accuracy and internal consistency. After processing of radiometric calibration (atmospheric correction, photometric correction and color correction), geometric correction (global adjustments and orthorectification) and global image cartography (global color uniformity, mosaicking and subdivision), the development of the Tianwen-1 Mars Global Color Orthomosaic and datasets based on these data was completed, with a spatial resolution of 76m and a planar position accuracy of 68m (a root mean square (RMS) residual of 0.9 pixels for tie points). This is currently the highest resolution global true color image map of Mars in the world, which can be served as a new Mars geodetic control network and reference frame. It can provide crucial foundational data for Mars scientific research and engineering implementation.

How to cite: Yan, W., Liu, J., Ren, X., Chen, W., Zeng, X., Wen, W., Li, C., Geng, Y., and Li, J.: A New Global Color Image Dataset and Reference Frame for Mars by Tianwen-1, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4948, https://doi.org/10.5194/egusphere-egu24-4948, 2024.

A joint analysis of subsurface sounding, topography and gravity data is presented in this study to provide constraints on the lateral density variations of the south polar layered deposits (SPLD). The enhanced resolution of the gravity field enables a thorough characterization of the signal associated with the polar deposits that highly correlates to the surface global topography. A novel iterative method is used to determine the radial gravity disturbances that depend on the density contrast and topography of the surface deposits across the polar cap. By using a constrained least-squares approach on localized three-dimensional mass concentrations (mascons), we locally inverted the bulk density from the gravity disturbances, leading to a new map of its lateral variations.

We thus leverage our retrieved map of the lateral density variations to provide bounds on the volumes of the main constituents of the SPLD. By assuming that the polar cap is composed of water ice, carbon dioxide ice and dust, a preliminary analysis of the compositional distribution is carried out. Our results show with unprecedented resolution extensive regions with bulk density consistent with pure water ice. The resulting map of the SPLD composition is fully consistent with complementary data, including the mass fraction of water-equivalent hydrogen measured through epithermal neutron and fast neutron counting rates acquired by the Mars Odyssey Neutron Spectrometer (MONS).

How to cite: Genova, A., Petricca, F., Andolfo, S., Gargiulo, A. M., Sulcanese, D., Mitri, G., and Chiarolanza, G.: Lateral variations of density and composition in the Martian south polar layered deposits, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6424, https://doi.org/10.5194/egusphere-egu24-6424, 2024.

In today’s extremely dry Mars, water vapor “adsorption” on regolith grains is thought to play crucial roles in subsurface water retention and water vapor exchange with the atmosphere (Fanale & Cannon, 1971; Zent et al., 1993, 1995, 2001; Böttger et al., 2005; Savijärvi et al., 2016, 2020). Global models that explicitly account for water diffusion in the shallow subsurface and calculate subsurface water distribution have assumed globally uniform regolith properties to simplify assumptions (Böttger et al., 2005; Schorghofer & Aharonson, 2005; Steele et al., 2017). However, Pommerol et al. (2009) examined the adsorption efficiency of six samples similar to the Martian regolith and found that the samples with smaller grain sizes store more adsorbed water due to their larger specific surface areas. Therefore, we have newly implemented a regolith scheme in a Mars Global Climate Model (MGCM), considering regolith properties like grain size, porosity, and the specific surface area. The grain size distribution was obtained from the empirical equation as a function of thermal conductivity (Presley & Christensen, 1997). The distributions of porosity and the specific surface area are also determined, referring to the laboratory experiments of Sizemore & Mellon (2008). Our results clarify that regolith grains with large specific surface areas in the northern low and mid-latitudes and the southern high latitudes, which have high adsorption coefficients, affect water storage. Subsurface water in the northern low and mid-latitudes exists up to 0.5–1wt% as adsorbed water. Regolith with high adsorption properties makes the depth of subsurface ice shallower in the southern high latitudes. Pore ice accumulates in regions poleward of 50°N and 50°S and the west of Elysium Mons and Olympus Mons, which is consistent with previous simulations. Also, with a homogeneous specific surface area, seasonal increases in pore ice were calculated at a depth of about 60 cm in mid-latitudes with low thermal inertia and high atmospheric water vapor content, but with the specific surface area map, the seasonal increases were not demonstrated. This study suggests that adsorption properties influence subsurface water dynamics, emphasizing the importance of considering inhomogeneous regolith properties in models of subsurface water distributions and the atmospheric water cycle including the regolith.

How to cite: Kobayashi, M., Kamada, A., Kuroda, T., Kurokawa, H., Aoki, S., Nakagawa, H., and Terada, N.: Effects of regolith properties on the Martian subsurface water distribution using a global climate model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7059, https://doi.org/10.5194/egusphere-egu24-7059, 2024.

Mars is an extremely cold and dry planet today, but it is thought to have been a water-rich planet in the past. Most of the water reservoir could represent hydrated crust and/or ground ice interbedded within sediments. Unlike Earth, Mars does not have a large satellite, so its obliquity varies greatly, and atmospheric circulation, water circulation, and subsurface water distribution are expected to change significantly over time. Currently, water ice is unstable at the pressure-temperature conditions found at the surface or subsurface of low/mid-latitude Mars, but recent observations by SHARAD revealed that large amounts of water remain beneath Utopia Planitia, which is thought to have formed during periods of high obliquity.

Here, we have newly developed a fully coupled global water circulation model for the atmosphere, hydrosphere, and cryosphere down to a depth of 1 km in the subsurface, and we used an iterative time integration scheme. We performed a series of simulations with changing Martian obliquity and eccentricity over the last few million years, and north polar layer deposit as an initial water reservoir. Our model implemented a water exchange scheme between the atmosphere and the regolith/crust for different porosities and grain sizes. We found that in the recent Milankovitch cycle, during the smaller obliquity periods, subsurface ice was mainly distributed around higher latitudes, but during the larger obliquity periods, the distribution of subsurface ice extended to lower latitudes of around 40^° N. It is possible that water ice with a volume content of more than 10% may remain at high latitudes above 60^° N. The abundance of water at such high latitudes could be an important indicator in the search for possible life on Mars, or a valuable water resource in future manned Mars missions.

How to cite: Kamada, A., Kuroda, T., Watanabe, Y., Kobayashi, M., Kodama, T., Greve, R., Nakagawa, H., Kasaba, Y., and Terada, N.: Long-term evolution of the subsurface water environment on Mars over the past million years, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7065, https://doi.org/10.5194/egusphere-egu24-7065, 2024.

Tianwen-1 mission is the first in the world to achieve Mars orbiting, landing and roving exploration through a single launch, and has developed technologies for planetary exploration launch and flight, planetary capture control, Mars entry and descent landing, Mars surface roving for Zhurong, scientific payload design and operation, long-distance deep space TT&C communication, etc. The mission has obtained a large number of scientific exploration data, formed a series of basic information such as true color image maps covering Mars surface, and a series of new discoveries such as new evidence of water and wind and sand activities in the Martian Utopia Plain. It enriches mankind's scientific understanding of Mars.

The report will introduce the progress and achievements of the Tianwen-1 mission in terms of technological development and scientific discovery.

How to cite: Geng, Y., Liu, J., Zhang, L., and Zhang, X.: Progress and achievement of Tianwen-1 mission, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7073, https://doi.org/10.5194/egusphere-egu24-7073, 2024.

Improving the data on the gravitational field of Mars can yield enhanced knowledge about Martian planetary dynamics and subsurface water reservoirs. In this study, we augment the VENQS software tool to perform simulations for a future dedicated satellite gravimetry mission at Mars following the archetype of GRACE-FO and as a result to study the challenges of such a mission.

The VENQS software tool consists of two parts: the VENQS App and the VENQS library. The VENQS App provides users with an easy access to a variety of simulation models, that can be combined to an individual VENQS library setup. These simulation models include amongst others orbit propagation of single satellites with embedded test masses, simulations of satellite constellations, and detailed disturbance analysis for satellites due to the space environment. Interaction with versioning systems allows the VENQS App to effectively track the software of the simulation models. In addition, a dedicated release management system enables the provision of different versions of the VENQS library.

Initially designed for satellites orbiting Earth, we are working on an augmentation of the VENQS library for interplanetary spacecraft or to be more precise for satellites orbiting arbitrary celestial bodies. In this context we want to propose the adaptation of VENQS for precise orbit propagation at Mars, which can assist the assessment of different mission influences on gravity field recovery (via dedicated software tools such as GRAVFIRE). We present the general simulation procedure including the modelling of perturbating forces along with gravitational acceleration for the orbit integration. Furthermore, we explain the differences to simulations of terrestrial spacecraft and outline occurring challenges with Martian atmosphere, time and reference frames, solid Mars tides as well as more complex satellite geometries inducing micro-vibrations and the non-availability of GNSS, that may deteriorate gravity field solutions.

How to cite: Bredlau, M., Bremer, S., Schilling, M., and Wassermann, N. K.: Simulation of a satellite gravimetry mission at Mars, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9136, https://doi.org/10.5194/egusphere-egu24-9136, 2024.

Our research leverages state-of-the-art deep learning techniques to automate surface mapping and continuous monitoring on planetary bodies. We are also developing tools to analyze the model uncertainty and decision-making in AI models with evaluation in our surface mapping projects and beyond.

We focus on one of the solar system's most dynamic Earth-analog environment on terrestrial planets - Mars' northern polar region, a repository of the planet's climatic history within its extensive ice-layered dome. We detect small blocks [1] and their sources yielding a reliable method for monitoring mass wasting activity with valuable present-day erosion rate results [2].

In parallel, we investigate and map polygonal patterns on both Earth and Mars to assess the global distribution of polygons and their potential as indicator for climate conditions and changes. On Earth, polygons are indicators of the volume of ground ice and provide insights into permafrost vulnerability to climate change. On Mars, similar young landforms could be linked to geologically recent freeze-thaw cycles. This would be conflicting with the current environment and would have implications for the recent hydrologic past of the planet. The distribution of polygonal ground on Mars can provide valuable information on the role of liquid water in the recent past by shedding light on the formation mechanism.

We use AI models for automated surface mapping because they achieve highly complex decision-making. However, they are usually treated as Black-Box systems. To tackle this problem, we are developing software tools for analyzing model uncertainty and decision-making within an application-independent framework. Typical questions are why did the model produce exactly this response and how certain is it about the correctness of its results?

References: [1] Martynchuk O. et al., 2024. EGU 2024. [2] Su S. et al., AGU 2023.

How to cite: Fanara, L., Su, S., Martynchuk, O., Hauber, E., Schlegel, A., Ludwig, J., Melching, D., Hänsch, R., and Gwinner, K.: Unraveling the climate evolution on Mars and Earth with AI-driven surface mapping and explainable AI, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10083, https://doi.org/10.5194/egusphere-egu24-10083, 2024.

Surface water ice is unstable on present-day Mars outside of the polar regions. However, prominent geological features show that during its recent past the surface of Mars was covered, on multiple occasions, by a « latitude-dependent mantle » (LDM) of water ice, from the polar regions to the tropics [1].

Different studies conducted with Global Climate Models, in particular the Mars PCM (previously Mars LMD-GCM) led to the formulation of a climate scenario for the emplacement of ice ages : during high obliquity phases (>45°, as opposed to present-day ~25°), strong destabilization of the Northern Cap allowed for the aerial deposition of ice on the flank of tropical volcanoes, forming glaciers. When returning at lower obliquity, these glaciers were in turn destabilized but ice accumulated in the mid and high latitudes, and thus formed the observed surface ice deposits (LDM) [2]. However, the 45° obliquity excursions occurred before the last 5 million years, while the last ice age occurrence is dated of 400 000 years at most.

Previous numerical experiments did not account for the radiative effect of water-ice clouds. Previous studies show that, even though somewhat negligible in the present-day Martian climate, this effect is overriding at higher obliquity with the intensification of the water cycle [3]. We have conducted new experiments at 35° obliquity with the Mars PCM using an improved physical package for the radiatively active clouds (RACs) and surface ice. Here, we present the resulting climate regime in our simulations. At 35° obliquity, the atmosphere is almost two orders of magnitude wetter than present-day, due to the greenhouse effect of RACs over the polar regions. In the high to mid latitudes, the seasonal winter ice accumulation is increased dramatically, while the summer sublimation is dampened by the latent heat cooling. Surface water ice thus accumulates at rates corresponding to tens of meters at each high obliquity excursion, reconciling the climatic scenario with the inferred age of emplacements of the LDM.

References:

[1] Head et al. (2003), Recent ice ages on Mars, Nature, 426, 797.

[2] Madeleine et al. (2009), Amazonian northern mid-latitude glaciation on Mars: A proposed climate scenario, Icarus, 203, 390

[3] Madeleine et al. (2014), Recent Ice Ages on Mars: The role of radiatively active clouds and cloud microphysics, Geophysical Research Letters, 41, 4873

Acknowledgements:

This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement No 835275).

How to cite: Naar, J., Forget, F., Millour, E., Vos, E., Segonne, C., Lange, L., Clément, J.-B., and Montmessin, F.: Recent ice ages on Mars by destabilization of the Northern Polar Cap at 35° obliquity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10784, https://doi.org/10.5194/egusphere-egu24-10784, 2024.

Previous studies have constrained the lithosphere at the north and south poles of Mars to be thick and cold, with elastic thicknesses of 330 to 450km [1], and >150km [2], respectively. The elastic thickness characterizes the stiffness of the lithosphere in response to loading and is directly linked to the thermal state of the lithosphere and the surface heat flow. Thus, elastic thickness estimates at the north and south poles provide crucial constraints on the present-day surface heat flow on Mars. Additional information on the present-day planetary thermal state comes from evidence of ongoing melting in the mantle, as indicated by the presence of both young lava flows in Tharsis and Elysium provinces and an active mantle plume beneath Elysium Planitia [3,4,5]. 

In this study we explore the thermal evolution of Mars using global 3D geodynamic models. These models improve upon our previous work [6] by including updated interior structure information from the InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission [7,8] and by considering constraints on the present-day thermal state of the planet as noted above. Thermal evolution models using the most recent crustal thickness estimates [8,9], require that the crust contains more than half of the total amount of heat producing elements (HPEs) to explain localized recent volcanic activity on Mars [8]. 

We find that the crustal thickness variations control the surface heat flow and the elastic thickness pattern, as well as the location of melting zones in the present-day Martian mantle. The strongest constraint for the thermal history and present-day state of the interior is given by the elastic thickness at the north pole. While at the south pole, all models show values >150km, compatible with the latest estimate [2], only a few models present an elastic thickness >300km at the north pole, with values still lower than the recent estimate of [1].  A larger elastic thickness at the north pole could indicate: 1) a northern crust less enriched in HPEs, 2) a colder lithosphere due to a weaker blanketing effect caused by a thinner or higher-conductivity crust on the northern hemisphere, 3) ongoing viscoelastic relaxation, suggesting that the observed surface deflection beneath the north polar cap is not the final one [1], or a combination thereof. 

In contrast to the cold lithosphere inferred for the Martian polar regions, recent volcanic activity suggests a warmer interior beneath Tharsis and Elysium provinces [3,4]. This reveals an important spatial variability in the thermal state and thickness of the Martian lithosphere. Our work shows that only a narrow range of models can match elastic thickness estimates at the polar caps and explain Mars’ recent volcanic activity, thereby providing important insights into the structure and thermal evolution of the interior.

References:

[1] Broquet et al., 2020. [2] Broquet et al., 2021. [3] Voigt et al., 2023. [4] Hauber et al., 2011. [5] Broquet & Andrews-Hanna, 2023. [6] Plesa et al., 2018. [7] Stähler et al., 2021. [8] Knapmeyer-Endrun et al., 2021. [9] Wieczorek et al., 2023.

How to cite: Plesa, A.-C., Broquet, A., Voigt, J. R. C., Wieczorek, M. A., Hauber, E., and Breuer, D.: Thermal state of the Martian interior at present day as constrained by elastic lithosphere thickness estimates and recent volcanic activity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12473, https://doi.org/10.5194/egusphere-egu24-12473, 2024.

Understanding the intricate thermal dynamics on Mars is crucial for accurate scientific measurements, particularly for seismological studies. The InSight Mission to study the interior structure and composition of Mars has recorded the Mars seismograms and in-situ data for the initial assessment of Mars' geothermal heat flow. Given that these measurements are obtained in close proximity to the lander at the surface, a primary concern is the presence of thermo-elastic noise, originating from fluctuations in solar radiation, within the collected data. Experiments such as those conducted by SEIS on Mars have specifically identified this phenomenon, detecting noise during the eclipse of Phobos (Stähler et al, 2020). While managing periodic temperature variations of instruments is feasible, challenges arise with other factors, such as those associated with moving shadows on the ground and solar radiation fluctuations. This implies that the presence of the lander will introduce thermal perturbations, causing alterations in both local surface and subsurface temperature measurements. These challenges necessitate numerical quantification due to difficulties in filtering them from the data. Hence, this study investigates first how the shadowing effect from the lander's structure and solar radiation variations impacts subsurface soil temperatures and consideration of this effect on the tilt recorded on the seismometers. We develop a 3D numerical model within Comsol Multiphysics 6.1 finite element package. The key element in adapting this model for use on Mars is accurately replicating the illumination conditions on the surface. Based on sub solar latitude and longitude derived using the JPL Horizons Ephemeris output, an illumination model is set at the instrument site for a desired duration. Unlike the Moon, where no atmospheric contribution affects temperature variations, Mars possesses a thin atmosphere that contributes to convective heat transfer. First, an analytical model is employed to find the transient solution of temperature at any given depth and time instances. The solution to the energy balance analysis determines the boundary conditions at the ground surface, which are then applied in the heat conduction equations governing subsurface temperature distribution.  The numerical temperature distribution output at an unperturbed location, far away from the lander is then compared with the analytical solution.  Once the 3D model is calibrated, the resulting temperature profiles can be utilized to assess the tilt of the seismometer feet and the sensitivity to additional solar radiation fluctuations. The findings suggest that the presence of a lander can exert substantial effects on the surrounding temperature environment under Martian conditions. This can introduce noise into the data collected by the seismometer, emphasizing the importance of accounting for and mitigating such influences in both the design and data analysis.

How to cite: Kizhaekke Pakkathillam, S., Lognonne, P., De Raucourt, S., and Kawamura, T.: Lander Induced Thermo-Elastic Noise at InSight Location on Mars, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12497, https://doi.org/10.5194/egusphere-egu24-12497, 2024.

The excellent performances of quantum accelerometers, due to their very good behaviour in the low frequency measurement bandwidth and to their intrinsic stability, which does not call for periodic calibration of the sensors, foster their application to extra-terrestrial investigations. In particular, the study of Mars and of its planetary composition, evolution, density and surface properties is going to be of great importance in the next decades for many reasons, both for the enhancement of the scientific knowledge and for applications in future missions.

So far, the gravity models of Mars have been derived from tracking data of different missions. Preliminary simulations performed at POLIMI considering a one-arm gradiometer pointing in the radial direction, flying on a polar orbit and acquiring data for a time span of two months show that a significant improvement in the knowledge of the gravity field of Mars could be achieved by launching a dedicated mission collecting gravity gradiometry observations by means of a quantum sensor. Even taking into account a degradation of the solution due to more realistic conditions, allowing for a possible mission lifetime of a few years (which is feasible under Mars conditions) would mean that the already available CAI technology could lead to very high benefits in terms of the scientific knowledge of the Martian gravity field.

How to cite: Reguzzoni, M., Rossi, L., and Migliaccio, F.: A quantum gradiometry mission concept for the improvement of Mars gravity field models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12635, https://doi.org/10.5194/egusphere-egu24-12635, 2024.

Martian polar caps consist of both H₂O and CO₂ ice. While H₂O ice is mainly passive on modern Mars, it may have not been the case in recent Martian history, when its obliquity was higher, or when it was changing rapidly. The distribution of ice species in the snowpack affects its physical and thermodynamic properties. In the upper layers, it determines its albedo and thermal emissivity. Thus understanding the mutual effect between these ices and their interaction with the atmosphere is crucial for understanding the evolution of Martian polar regions. In this study, we employ a newly-developed Exotic Ices snow model coupled to the NASA Goddard Institute for Space Studies (GISS) ROCKE-3D planetary General Circulation Model (GCM) [1]  to study the behavior of Martian polar caps. ROCKE-3D is a planetary GCM developed at NASA GISS as an extension of its Earth climate model, modelE [2]. It has been extensively used to simulate climate of various planets, including Mars (e.g. [3,4]).

The Exotic Ices snow model was specially developed for planetary applications which involve more than one condensable in the atmosphere, in which case snow can contain multiple species of ice (CO₂ and H₂O in the Mars case). For each species of ice, the model uses their proper physical properties and phase diagram, but otherwise it treats all species of ice on an equal footing.  The combined effects on albedo, thermal inertia and mutual insulation are treated accordingly. The snowpack interacts with the atmospheric dust cycle, and can accumulate a prognostic amount of dust, though the effect of dust on snow properties is not currently treated explicitly, and is prescribed. 

In this study, we first validate our model against the modern Martial climate, for which we use mission results from Mars Climate Sounder (atmospheric temperature and dust optical depth), SPICAM on Mars Express (atmospheric water), and Viking 2 (surface pressure). We investigate the effect of snow radiative properties on CO₂ and water cycles and the ability of our model to accurately reproduce those with minimal model tuning. We then perform simulations for several obliquities from a recent Martian past, and investigate the behavior of the Martian polar caps in such conditions.

References: [1] Way, M. J. et al. (2017) ApJS, 231, 12. [2] Kelley, M. et al. (2020) J. Adv. Model. Earth Syst., 12, no. 8, e2019MS002025. [3] Schmidt, F. et al. (2022) Proc. Natl. Acad. Sci., 119, no. 4, e2112930118. [4] Guzewich, S.D. et al. (2021) J. Geophys. Res. Planets, 126, no. 7, e2021JE006825.

How to cite: Aleinov, I., Glaser, D., Guzewich, S., Perlwitz, J., Tsigaridis, K., Way, M., and Wolf, E.: Study of Martian Polar Caps with GISS ROCKE-3D GCM, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13493, https://doi.org/10.5194/egusphere-egu24-13493, 2024.

Due to its axial tilt of ~25°, Mars has seasons. During its fall and winter, when temperature drops, there exist two depositional mechanisms of atmospheric CO₂, that is, precipitation as snowfall and direct surface condensation in the form of frost (Hayne et al., 2012). Up to one third of the atmospheric CO₂ exchanges with the polar surface through the seasonal deposition/sublimation process. Therefore, accurate measurements of the evolution of the seasonal polar caps can place crucial constraints on the Martian climate and volatile cycles. 

Recently, by reprocessing and co-registering the MOLA profiles, Xiao et al. (2022a, 2022b) derived both spatial and temporal thickness variations of the seasonal polar caps at grid elements of 0.5° in latitude and 10° in longitude. However, the MOLA-derived results can suffer from biases related to various processes, for example, pulse saturation due to high albedo of the seasonal deposits, non-Gaussian return pulses due to rough terrain and dynamic seasonal features, incomplete correction for the global temporal bias, and penetration of the laser pulses into the translucent slab ice. Furthermore, MOLA altimetric observations are limited to Mars Year 24 and 25 which prevents the detection of possible interannual variations in the CO₂ seasonal transport. 

In this contribution, we will show how the shadow variations of fallen ice blocks at the bottom of steep scarps of the North Polar Layered Deposits (NPLDs) allow us to infer the thickness evolution of the seasonal deposits (Xiao et al., 2024). For this, we utilize the High Resolution Imaging Science Experiment (HiRISE/MRO) images with a spatial resolution of up to 0.25 m/pixel (McEwen et al., 2007). We successfully conduct an experiment at a steep scarp centered at (85.0°N, 151.5°E). We assume that no, or negligible, snowfall remains on top of the selected ice blocks, the frost ice layer is homogeneous around the ice blocks and their surroundings, and no significant moating is present. These assumptions enable us to separately determine the thickness of the snowfall and frost. We find that maximum thickness of the seasonal deposits at the study scarp in MY31 is 1.63±0.22 m to which snowfall contributes 0.97±0.13 m. Interestingly, our thickness values in the northern spring are up to 0.8 m lower than the existing MOLA results (Smith et al., 2001; Aharonson et al., 2004; Xiao et al., 2022a, 2022b). We attribute these differences mainly to the remaining biases in the MOLA heights. Furthermore, we demonstrate how the long time span of the HiRISE images (2008—2021; Mars Year 29—36) allows us to measure the interannual variations of the deposited CO₂. Specifically, we observe that snowfall in the very early spring of Mars Year 36 is 0.36±0.13 m thicker than that in Mars Year 31. 

Hayne et al. (2012). JGR: Planets, 117(E8).

Xiao et al. (2022a). JGR: Planets, 127(7), e2022JE007196.

Xiao et al. (2022b). JGR: Planets, 127(10), e2021JE007158.

Xiao et al. (2024). JGR: Planets (In Revision).

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How to cite: Xiao, H., Xiao, Y., Su, S., Schmidt, F., Lara, L. M., and Gutierrez, P. J.: Thickness of the seasonal deposits by examining the shadow variations of the fallen ice blocks at Martian North Pole, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14925, https://doi.org/10.5194/egusphere-egu24-14925, 2024.

Mars harbors two geologically young (<100 Ma) and large (~1000 km across) polar ice caps, which represent the only million-year-old surface features that induce measurable surface deformations. In the absence of in situ heat flow measurements, analyses of these deformations is one of the few methods that give access to the present-day planetary thermal state. The latter is indicative of the concentration of radiogenic elements in the interior, which is an important metric to determine the planet’s bulk composition, structure, and geologic evolution (Plesa et al., 2022). In previous work, we have imaged the deformed basements beneath the two polar caps and have determined the present-day thermal state of Mars (Broquet et al., 2020; 2021). The results of these studies are currently widely used as firm constraints on Martian thermal evolution models (e.g., Plesa et al., 2022). However, these models struggle to explain both the thick lithospheres inferred at the poles and the planet’s young volcanism and ongoing plume activity (e.g., Broquet & Andrews-Hanna, 2023). Importantly, Broquet et al. have assumed the polar deformations to be at equilibrium, which is only valid if the time elapsed since the polar caps’ formation is greater than the time required for viscous adjustments. This assumption is central to these models and depends upon the poorly known age of the polar caps and the internal viscosity structure of Mars. In this work, we couple a novel viscoelastic modelling approach of the polar deformations to thermal evolution models that account for InSight seismic measurements and observational constraints on recent volcanic activity. Our preliminary investigations reveal that viscosity structures, outlined in the thermal models presented in Plesa et al. (2022), lead to polar deformations reaching equilibrium in a few Myr and up to hundreds of Myr. These findings demonstrate that viscoelastic relaxation can surpass the polar caps’ ages, emphasizing the necessity for a comprehensive exploration of polar viscoelastic relaxation. This approach will yield critical insights into the internal viscosity structure of Mars together with the polar caps' age and formation history, ultimately leading to a better understanding of the planet’s geologic and climatic evolution.

Broquet A., et al., (2021). The composition of the south polar cap of Mars derived from orbital data. JGR:Planets 126, e2020JE006730. 10.1029/2020JE006730.

Broquet A. et al., (2020). Flexure of the lithosphere beneath the north polar cap of Mars: Implications for ice composition and heat flow. GRL 47, e2019GL086746. 10.1029/2019GL086746.

Broquet A., & Andrews-Hanna J. C., (2023). Geophysical evidence for an active mantle plume underneath Elysium Planitia on Mars. Nat. Astro. 7, 160–169. 10.1038/s41550-022-01836-3.

Plesa A.-C., et al., (2022). Interior Dynamics and Thermal Evolution of Mars – a Geodynamic Perspective. Adv. Geophys. 63, 179–230. 10.1016/bs.agph.2022.07.005.

How to cite: Broquet, A., Wieczorek, M. A., and Breuer, D.: Viscoelastic relaxation of the lithosphere beneath the Martian polar caps: Implications for the polar caps’ formation history and planetary thermal evolution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15270, https://doi.org/10.5194/egusphere-egu24-15270, 2024.

Introduction: Data by the MGS MOLA [1] instrument provide a dense global network of laser shots with unprecedented height precision for Mars. The extraction of planetary radii from laser pulses requires precise knowledge of spacecraft trajectory and the instrument’s orientation in space. Limited knowledge of these extrinsic parameters causes deviating height information at cross-over points of the laser tracks and occasionally substantially offset outlier profiles. Applying adjustment techniques, the final mission data products [2] minimized the cross-over residuals while still showing considerable variability in height differences when compared to HRSC Mars quadrangle DTMs [3].

We accurately co-register MOLA profiles to existing HRSC DTMs allowing to increase the accuracy of the co-registration of the single laser tracks while providing similar internal a-posteriori cross-over accuracies as in [2]. The method applies Evolution Strategy (ES) [4] to directly solve for extrinsic observation parameters. Combined HRSC / MOLA DTMs will provide a most comprehensive, best resolved global data product currently available for Mars.

Method: Starting with a seed vector the ES repeatedly creates sets of random parameter vectors that are evaluated by the quality function. The latter is defined by the RMS of the height difference between DTM and corrected laser shots. The lowest RMS vector of each generation will be the seed for the next generation random vectors.

The optimization of the parameter vector for each laser data segment is performed on an equatorial HRSC half-quadrangle and parameters are applied to all data of a laser data segment reaching from North to South pole.

Results: ES-based adjustment of MOLA tracks was applied using two existing equatorial HRSC DTM half-quadrangles (MC-13E and MC-21E) and the laser track segments intersecting these quadrangles. The quality of the adjustment was evaluated by visual inspection of gridded DTM data products generated from the adjusted tracks and by analyzing the consistency of the results in terms of height residuals at cross-overs. Inspection of DTM products is sensitive to outlier track detection, that commonly occur in the uncorrected MOLA data but also appear in the ES adjusted DTMs. The average absolute residual height differences at cross-overs amount to 4.44 m for the nominal profile solutions, 4.58 m in the crossover-adjusted version [2], and to only 2.78 m with ES-adjusted profiles. The same values are also derived eliminating globally the 3s-blunder height differences. The corresponding values are then 3.48 m (nominal case), 2.93 m [2], and 2.09 m (ES-adjusted). The method establishes a high-quality co-registration between MOLA and HRSC DTMs considered very promising for future joint HRSC/MOLA DTMs. We discuss the potential to re-assess temporal variation in the MOLA data record not uniquely resolved in the past, such as estimates of the seasonal deposition  and sublimation in the polar areas.

References:
[1] Smith, D. E. et al. JGR 106, 23689-23722 (2001). Doi:10.1029/2000JE001364
[2] Smith, D. E. et al. NASA PDS (2003). MGS-M-MOLA-5-MEGDR-L3-V1.0.
[3] Gwinner, K. et al. PSS 126, 93-138 (2016). Doi: 10.1016/j.pss.2016.02.014
[4] Rechenberg, I. Evolutionsstrategie 94. Vol. 1 (Frommann-Holzboog, 1994).

How to cite: Willner, K., Gwinner, K., Stark, A., Elgner, S., and Hussmann, H.: Evolution Strategy-Based Approach for Joint Analysis of Laser Altimeter Tracks and Photogrammetric Stereo DTMs: MOLA and HRSC, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19019, https://doi.org/10.5194/egusphere-egu24-19019, 2024.

Mass wasting activity, in the form of ice block falls, has been observed as the main erosion process at steep scarps of the North Polar Layered Deposits (NPLD) [1,2]. Our study focuses on leveraging a state-of-the-art deep learning technique to map the sources of such events throughout the entire NPLD region. By quantifying water ice loss, we derive the current erosion and retreat rate for each active NPLD scarp. We notice that these scarps have varying degrees of erosion, from less than 0.01 up to 0.88 m³ per Mars Year per meter along the scarp. The current most active scarp shows a retreat rate of ~6 mm per Mars Year. We want to compare our results to the detected ice block falls at the underlying Basal Unit (BU) region [3], to understand the difference between the two units’ geological processes, and help to constitute important constraints to the present-day mass flux of the north polar region.

References

[1] Herkenhof et al., 2007. Science, 317(5845), pp.1711-1715.

[2] Dundas et al., 2021. J. Geophys. Res. Planets, 126(8), p.e2021JE006876.

[3] Martynchuk, et al., 2023. AGU23, 11-15 Dec.

How to cite: Su, S., Fanara, L., Xiao, H., Hauber, E., and Oberst, J.: Erosion rate of the north polar steep scarps on Mars, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19493, https://doi.org/10.5194/egusphere-egu24-19493, 2024.

There is ample evidence to conclude that the ice deposits on solar system bodies—aside from Earth—have complex chemical constitutions. Carbon dioxide ice is prevalent at the poles of Mars and owing to its substantial reflectivity and seasonal variability, it significantly influences the planet's energy budget. Recent evidence of the existence of CO₂ ice glaciers on Mars explains the volumetric distribution and accumulation of CO₂ ice into the curvilinear basins at the south pole of Mars. While spectral measurements of martian ice have been made, no model of the dusty martian firn or CO₂ glacier ice exists at present. Due to their significant effects on snow and ice's albedo reduction, dust and snow metamorphism must be taken into consideration. Here, we adapt the terrestrial Snow, Ice, and Aerosol Radiation (SNICAR) model and apply it to martian glaciers by incorporating CO₂ ice capabilities in the model and validating with the observed remote sensing data. Compared with CO₂ snow, we find that CO₂ glacier ice albedo is much lower in visible and near-infrared (NIR) spectra. CO₂ ice albedo is more sensitive to layer thickness than CO₂ snow. We observe a noticeable transition between snow albedos and firn/glacier ice albedos. In particular, the absorption features at 1.435 µm and 2.0 µm caused by asymmetric stretching overtones and combinations of fundamental vibrational modes become damped. At these two wavelengths, the albedo is very small; the glacier ice has a higher albedo than coarse-grained snow because of specular reflection. We observe that small amounts (<1%) of Martian dust can lower the albedo of CO₂ ice by at least 50%. Once validated, our model can be used to characterize orbital measurements of martian CO₂ ice and refine climate-model predictions of ice stability. In the future, we plan to study the spectral albedo of other exotic ices in the solar system (N₂ and methane ice in case of Pluto, CO ice on Umbriel).

How to cite: Singh, S., Singh, D., and Whicker, C. A.: Spectral Albedo of Dusty Martian CO2  Snow and Ice, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19665, https://doi.org/10.5194/egusphere-egu24-19665, 2024.

The Laser Ranging Interferometer (LRI) technology demonstrator on-board the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission has proved an unmatched sub-nanometer per square root of Hertz ranging performance above 100 mHz surpassing the noise floor of the until then state-of-the-art K/Ka-band ranging instrument by orders of magnitude. The LRI’s reliability and its outstanding performance have led to the decision of implementing LRI-like systems as primary instruments for the measurement of the intersatellite range in all currently planned NASA, DLR and ESA Earth gravity missions.

Interferometric laser ranging has proven to be an indispensable technique for the long-term monitoring of Earth’s gravitational field and its spatial and temporal variations, enabling in-depth analyses of many Essential Climate Variables (ECVs). We propose to bring this proven technology to an application in a constellation of satellites dedicated to Mars gravity research as outlined in the paper titled “MaQuIs—Concept for a Mars Quantum Gravity Mission”.

In this talk we will give an overview of the architecture of the LRI as it is currently flying on GRACE-FO as well as the measurement principle and its consequences for the overall mission design. Additionally, we are going to highlight a few of the following development activities, which could be applied for a mission around Mars: enhancement of the long-term stability of the laser frequency, improved redundancy schemes as well as a novel sensor type for the acquisition and maintenance of the constellation. Progress with respect to these aspects will yield a next generation of intersatellite laser interferometers with improved performance and enhanced reliability.

How to cite: Koch, A., Bergmann, G., Fock, M., Grossel, K., and van den Toren, J.: Next Generation Intersatellite Laser Ranging Interferometry for Mars Gravity Research, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20145, https://doi.org/10.5194/egusphere-egu24-20145, 2024.

The north polar region of Mars is one of the most active places of the planet with avalanches and ice block falls being observed every year on High Resolution Imaging Science Experiment (HiRISE) data. Both phenomena originate at the steep icy scarps, which exist on the interface between two adjacent geological units, the older and darker Planum Boreum Cavi unit, also called Basal Unit (BU) and the younger and brighter Planum Boreum 1 unit, which is a part of the so called North Polar Layered Deposits (NPLD). These exposed layers of ice and dust contain important information about the climate cycles of the planet. We are primarily interested in monitoring the current scarp erosion rate (quantified through analyzing ice debris) at the same time differentiating between the activity originating in the NPLD [1] from that originating in the BU

The large scale of the region of interest, combined with a growing amount of available satellite data makes automation key for this project. To achieve the latter we propose a computational pipeline consisting of three consecutive steps, namely: scarp segmentation, single image super-resolution and ice-block detection. For the final analysis Mean Average Precision (mAP.95) was used as a benchmark metric. The performance value of 93.6% was obtained on a test dataset, leading us to conclude that the network is able to perform even on small ice fragments (which comprise the majority of the debris). On a system running 4 RTX3090 GPUs the finished pipeline processes a single HiRISE product in just under 20 minutes, returning the scarp outline and precise ice boulder coordinates. Using this pipeline, we next plan to robustly monitor the mass wasting activity in the whole north polar region and throughout the entire Mars Reconnaissance Orbiter (MRO) mission.

[1] Su, S. et al., 2024. EGU 2024.

How to cite: Martynchuk, O., Fanara, L., Gwinner, K., and Oberst, J.: Computer vision model for monitoring block falls in the Martian north polar region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22233, https://doi.org/10.5194/egusphere-egu24-22233, 2024.

To study the emission of energetic neutral atoms (ENAs) at Titan, we have developed a novel model that takes into account a spacecraft detector’s limited field of view and traces energetic magnetospheric particles backward in time. ENAs are generated by charge exchange between Titan’s atmospheric neutrals and energetic magnetospheric ions. By tracing these ions through the draped electromagnetic fields in Titan’s environment, we generate synthetic ENA images and compare them to Cassini observations from the TA flyby. Our model can reproduce the intensity and morphology of the observed images only when field line draping is included. Using a realistic detector geometry is necessary to determine the influence of this draping on the ENA images: the field perturbations eliminate a localized feature in the emission pattern, which is a different effect than found by previous models utilizing an infinitely extended detector. We demonstrate that ENA observations from TA contain signatures of the time-varying Saturnian magnetospheric environment at Titan: the modeled ENA emission morphology and the effect of field line draping are different for the background field vectors measured during the inbound and outbound legs of TA. The visibility and qualitative effect of the draping on observed ENA images vary strongly between different detector locations and pointings. Depending on the viewing geometry, field line draping may add features to the synthetic ENA images, remove features from them, or have no qualitative effect at all. Our study emphasizes the challenges and the potential for remote sensing of Titan’s interaction region using ENA imaging.

How to cite: Tippens, T., Roussos, E., Simon, S., and Liuzzo, L.: A Novel Backtracing Model to Study the Emission of Energetic Neutral Atoms at Titan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3, https://doi.org/10.5194/egusphere-egu24-3, 2024.

The atmosphere of Titan is a unique natural laboratory for the study of atmospheric evolution and photochemistry akin to that of the primitive Earth (1), with a wide array of complex molecules discovered through infrared and sub-mm spectroscopy (2) (3). Here, we present the results of the exploration of original, ground-based, very high-resolution visible spectra of Titan, obtained with VLT-UVES (4). We have developed a new, Doppler-based line detection method which allowed to retrieve an empirical, high resolution (R = 100.000) line list of methane between 525 nm and 618 nm, for which no similar line lists are yet available (5), identifying and characterising more than 90 new high energy CH₄ absorption lines at low temperature (T = 150 K).

Furthermore, we searched for the predicted, but previously undetected carbon trimer molecule, C₃, (6) (7), on the atmosphere of Titan, at its 405.1 nm band, by comparing VLT-UVES Titan spectra with a line-by-line (8) model spectrum of Titan’s atmosphere with C₃. Our results are consistent with the presence of C₃ at the upper atmosphere of Titan, with a column density of 10¹³ cm^-2. This study of Titan's atmosphere with very high-resolution visible spectroscopy presents a unique opportunity to observe a planetary target with a CH₄-rich atmosphere, from which CH₄ optical proprieties can be studied (9). It also showcases the use of a close planetary target to test new methods for chemical retrieval of minor atmospheric compounds, in preparation for upcoming studies of cold terrestrial exoplanet atmospheres (10).

References: (1) Hörst S., 2017; J. Geophys. Res. Planets, doi:10.1002/2016JE005240; (2) Nixon C., et al, 2020; The Astronomical Journal, doi:10.3847/1538-603881/abb679; (3) Lombardo N., et al, 2019, The Astrophysical Journal Letters, 2019, doi:10.3847/2041- 658213/ab3860; (4) Rianço-Silva R., et al, 2023, submitted to Planetary and Space Sciences (under peer-review). (5) Hargreaves R., et al, 2020; The Astrophysical Journal Supplement Series, doi:10.3847/1538-4365/ab7a1a; (6) Hérbad E., et al, 2013; Astronomy & Astrophysics, doi:10.1051/0004-6361/201220686; (7) Dobrijevic M., et al, 2016; Icarus, doi.org/10.1016/- j.icarus.2015.12.045; (8) Schmidt M., et al, 2014; MNRAS, doi.org/10.1093/mnras/stu641; (9) Thompson M., et al, 2022; PNAS, doi.org/10.1073/pnas.2117933119; (10) Tinetti G., et al, 2018; Experimental Astronomy, doi:10.1007/s10686-018-9598-x;

How to cite: Rianço-Silva, R., Machado, P., Martins, Z., Lellouch, E., Loison, J.-C., Dobrijevic, M., Dias, J., and Ribeiro, J.: A study of very high resolution visible spectra of Titan: Line characterisation in visible CH4 bands and the search for C3, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-691, https://doi.org/10.5194/egusphere-egu24-691, 2024.

Atmospheric gravity waves are oscilatory disturbances that occur on a specific layer of the atmosphere and whose restoration force is buoyancy [2]. Because of this, these waves can only exist in a continuously stably stratified atmosphere. These waves play an essential role in the global circulation of a planets atmosphere. They are responsible for very important dynamic phenomena such as, for example, the vertical transfer of energy, momentum and chemical species (atmospheric gravity waves transport energy and momentum from the troposphere and deposit it in the thermosphere and mesosphere) since they can form on one region of the atmosphere and travel through it, sometimes over great distances [1]. As such, the study of the properties of atmospheric gravity waves is an essential tool to answer some of the fundamental questions regarding the Venusian atmosphere dynamics, in particular, the fascinating mechanism of superrotation of the atmosphere.

With this work we present observations of wave-like structures on the dayside of Venuss atmosphere using the ultraviolet wavelength of 365nm from Akatsuki’s UVI instrument. The main goal is to evaluate the population of atmospheric waves in Akatsuki’s public database by measuring their physical properties(crest number, horizontal wavelength, packet length, width and orientation ), dynamical properties and distribution in order to establish possible links with previous studies of waves. This work follows a previous study performed by Peralta et al. (2008)[1] and by Silva et al. (2021) [3].

[1] Peralta et al., Characterization of mesoscale gravity waves in the upper and lower clouds of venus from vex-virtis images. Journal of Geophysical Research: Planets, 113(E5), 2008.
[2] Piccialli et al., High latitude gravity waves at the venus cloud tops as observed by the venus monitoring camera on board venus express. Icarus, 227:94 111, 01 2014.
[3] Silva et al., Characterising atmospheric gravity waves on the nightside lower clouds of Venus: a systematic analysis, AA 649 A34, 2021.

How to cite: Espadinha, D., Machado, P., Peralta, J., Silva, J., and Brasil, F.: Exploring the Venusian clouds: Atmospheric Gravity Waves with Akatsuki UVI instrument, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-793, https://doi.org/10.5194/egusphere-egu24-793, 2024.

Diurnal solar radiation forces global oscillations in pressure, temperature, and wind fields. They are called atmospheric or thermal tides and are additionally modified by topography, surface properties, and atmospheric absorber consentration. They propagate around the planet in periods that are integer fractions of a solar day and are only relevant in the upper atmosphere on Earth, but they represent a very large part of the atmospheric circulation on Mars. First two harmonic components (diurnal and semi-diurnal), with periods of 24 and 12 hr at the locations of InSight and Mars Science Laboratory (MSL) are represented here with the comparison to Mars Climate Database (MCD) predictions.

Both of these landers are located in the tropics, InSight on Elysium Planitia (4.5°N, 135.6°E) and MSL within the Gale Crater (4.6°S, 137.4°E). In this study, we utilized observations of the time period from Martian year (MY) 34 solar longitude (Ls) 296° to MY 36 Ls 53°. Diurnal amplitude was larger than semi-diurnal amplitude on both platforms and similar sensitivity to atmospheric dust content was found. However, the amplitude of the semi-diurnal component was smoother than the diurnal amplitude due to its sensitivity to global atmospheric dust content. One clear difference between the platforms was the average amplitude of the diurnal tide, which was 17 Pa for InSight and 33 Pa for MSL. Lateral hydrostatic adjustment flow, generated by the topography causes this difference since it increases the diurnal range of pressure within the Gale. Diurnal tide phase at the InSight was lower than that at the MSL, with averages of 03:39 and 04:25 LTST. In addition, MSL detected roughly contant diurnal tide phase, but InSight observed much more variation. Semi-diurnal phase pattern was very similar on both platforms.

Diurnal tide amplitude predicted by the MCD mimicked the observations quite well at both locations, except during MY 35 Ls 0°–180°. During that time, MCD amplitudes were lower than observed. This is very likely explained by the atmospheric dust conditions, due to the sensitivity of the diurnal tide to the local atmospheric dust loading. MCD dust optical depth was in good agreement with MSL observed optical depth during MY 35 Ls 180°–360°, but was lower than observed during MY 35 Ls 0°–180°. MCD semi-diurnal amplitudes mimicked the observations well throughout MY 35 due to its sensitivity to global atmospheric dust loading.

How to cite: Leino, J., Harri, A.-M., Banfield, D., de la Torre Juárez, M., Paton, M., Rodriguez-Manfredi, J.-A., Lemmon, M., and Savijärvi, H.: Atmospheric Tides Near the Equator on Mars, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1333, https://doi.org/10.5194/egusphere-egu24-1333, 2024.

The Martian atmosphere experiences large diurnal variations due to its small thickness and low heat capacity. Driven by diurnal solar insolation and influenced by topography and radiative drivers (clouds and dust), diurnal temperature changes propagate from lower atmosphere into higher altitudes as forms of atmospheric tides. However, our understanding of diurnal variations in the Martian atmosphere is poor due to the lack of observations, especially those covering the entire planet and all local times, until recent. In its novelly designed high-altitude orbit, instruments onboard the Hope probe of the Emirates Mars Mission (EMM) could obtain a full geographic and local time coverage of Mars every 10 Martian days (Almatroushi et al., 2021). The Emirates Mars InfraRed Spectrometer (EMIRS, Edwards et al., 2021) observes surface temperature, temperature profile, dust content, water clouds, and water vapor in the lower atmosphere. Diurnal variations of such properties are derived on a planetary scale for the first time without significant gaps in local time or interference from seasonal changes. Such a rapid full planetary-scale coverage is ideal for investigating the fast-changing dust storms on Mars. In this talk, we present results of diurnal temperature variations and thermal tides before, during, and after several regional dust storms in Martian Year (MY) 36 and 37, and their coupling with dust and clouds. The results are also compared with numerical simulations by the Mars Planetary Climate Model (PCM), providing valuable information on physical processes controlling the diurnal climate of Mars.

Almatroushi, H., AlMazmi, H., AlMheiri, N., AlShamsi, M., AlTunaiji, E., Badri, K., et al. (2021). Emirates Mars Mission Characterization of Mars Atmosphere Dynamics and Processes. Space Science Reviews, 217(8), 89. https://doi.org/10.1007/s11214-021-00851-6

Edwards, C. S., Christensen, P. R., Mehall, G. L., Anwar, S., Tunaiji, E. A., Badri, K., et al. (2021). The Emirates Mars Mission (EMM) Emirates Mars InfraRed Spectrometer (EMIRS) Instrument. Space Science Reviews, 217(7), 77. https://doi.org/10.1007/s11214-021-00848-1

How to cite: Fan, S., Forget, F., Smith, M., Guerlet, S., Badri, K., Atwood, S., Young, R., Edwards, C., Christensen, P., Deighan, J., Almatroushi, H., Bierjon, A., Liu, J., and Millour, E.: Diurnal Temperature Variations and Thermal Tides in the Martian Atmosphere before and during Regional Dust Storms Observed by EMIRS, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2981, https://doi.org/10.5194/egusphere-egu24-2981, 2024.

By utilizing progress in millijoule-level pulsed fiber lasers operating in the 1.96 µm spectral range, we propose a novel concept introducing a differential absorption barometric lidar designed for remote sensing of Martian atmospheric properties on an orbiter. Our emphasis is on the online wavelength situated in the trough region of two absorption lines, chosen for its insensitivity to laser frequency variations, thereby mitigating the need for stringent laser frequency stability. Our investigation centers around a compact lidar configuration, featuring reduced telescope dimensions and lower laser pulse energies. These adjustments are aimed at minimizing costs for potential forthcoming Mars missions.

The primary measurement objectives include determining column CO2 absorption optical depth, columnar CO2 abundance, surface atmospheric pressure, as well as vertical distributions of dust and cloud layers. By combining surface pressure data with atmospheric temperature insights obtained from sounders and utilizing the barometric formula, the prospect of deducing atmospheric pressure profiles becomes feasible. Simulation studies validate the viability of our approach. Notably, the precision of Martian surface pressure measurements is projected to better than 1 Pa when the aerial dust optical depth is anticipated to be under 0.7, a typical airborne dust scenario on Mars, considering a horizontal averaging span of 10 km.

How to cite: Liu, Z., Campell, J., Lin, B., Yu, J., Geng, J., and Jiang, S.: Remote Sensing of Column CO2, Atmospheric Pressure, and Vertical Distribution of Dust and Clouds on Mars using Differential Absorption Lidar at 1.96 µm on an Orbiter, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3253, https://doi.org/10.5194/egusphere-egu24-3253, 2024.

We model the long-term evolution of Venus through volatile exchanges and compare observed and simulated present-day states. This work focuses on quantifying the effect of different parameterizations for loss processes on the overall evolution.

Due to both the striking similarities and the obvious differences between Earth and Venus, understanding Venus might hold keys to how planets become -and cease to be- habitable. It has been suggested that the divergence between Earth and Venus could occur during the first few hundred million years due to interaction between the interior of the planet, its atmosphere and escape mechanisms. 

We develop coupled numerical simulations of the atmosphere and interior to test what evolutionary paths can reproduce the observed present-day state of Venus. They include modeling of mantle dynamics, core evolution, volcanism/outgassing, surface alteration, atmospheric escape (hydrodynamic and non-thermal), volatile deposition and loss through impacts. Impact histories representing different possible scenarios for late accretion are generated using n-bodies simulations.

Our previous efforts used hydrocode results to model impact erosion. A new parameterization has since been proposed by Kegerreis et al. (2020), with increased losses for high-energy collisions. We test if these results induce divergences between different impact histories (e.g., giant impact vs. small impactors) and combine these different parameterizations depending on impactor size.

Post-hydrodynamic escape, non-thermal loss mechanisms can remove low amounts of water and oxygen, from the surface/atmosphere (4 mbar to a few bar), making it quite difficult to accommodate large bodies of water, especially during Venus’ recent past. Trapping oxygen on the surface through oxidation of newly emplaced volcanic material through solid-gas reactions appears inefficient (totalling loses similar to non-thermal escape). Runaway greenhouse resulting in a molten surface could lead to the loss of multiple bars of oxygen but still leaves behind a significant atmospheric inventory. These results imply a maximum limit to water delivery by impacts.

Atmospheric delivery and erosion by impacts seem to be the largest source/sink of volatile species during evolution. The choice of parameterization for erosion can induce a large difference in total inventory (up to several 1-10 bar of H₂O and CO₂). However maximum delivery by impactors over Late Accretion are still limited by loss processes. Previously obtained upper limits for water content of the Late Accretion (95-98% dry enstatite chondrite, 2-5% of carbon chondrite) are revised upward to 5-10% Carbon chondrites for efficient atmospheric erosion models.

How to cite: Gillmann, C. and Golabek, G.: Consequences of Impact Erosion and Volatile Loss Processes on the Evolution of Venus., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5297, https://doi.org/10.5194/egusphere-egu24-5297, 2024.

The structure and evolution of Titan’s daytime planetary boundary layer (PBL) are investigated through large eddy simulation (LES) modeling.  The PBL is the interface between the surface and the free atmosphere through which energy, mass, and momentum are exchanged via turbulent eddies.  The sounding from the Huygens probe provided the only direct, vertically resolved measurement of the structure of the PBL at a single moment in time. How the observed structures develop and evolve remain uncertain, and the turbulent exchange processes are challenging to constrain from the single profile. LES techniques provide a mechanism for understanding the observed structure and dynamics of the PBL, better constraining turbulent atmosphere-surface exchange, and improving the parameterization of the PBL in larger-scale models.  Results from LES studies forced by diurnally-varying radiation are presented for Titan.  The development of three distinct PBL layers are noted: 1) a near-surface layer dominated by frictional dissipation; 2) a mixed-layer of near neutral stability; and 3) a relatively deep entrainment layer capping the top of the PBL.  The three layers are similar in character to what is often observed in the Earth’s convective PBL. The interpretation of the modeled structures and PBL evolution in the current LES study differs significantly from previous mechanisms inferred from GCM studies and shows important differences from prior work that lacked diurnally-varying radiative forcing.

How to cite: Rafkin, S., Chin Canche, G., and Soto, A.: The Structure and Evolution of Titan’s Daytime Planetary Boundary Layer, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6486, https://doi.org/10.5194/egusphere-egu24-6486, 2024.

Highly variable ionospheric structures on Mars have been recently observed via spacecraft measurements. Acoustic-gravity waves (AGWs) could be an underlying mechanism. Studying the response of the Martian ionosphere to AGWs could provide us with an important understanding of the neutral wave-ionospheric coupling process. To explore the plasma-neutral coupling driven by AGWs in the lower ionosphere of Mars, a linearized wave model has been developed. This model can describe the propagation and dissipation of AGWs in a realistic atmosphere and first incorporates plasma behaviors associated with photochemistry and electromagnetic fields. We adopted a full-wave model as the first part of our coupled model to delineate wave propagation in a realistic atmosphere. The second part of our model consists of the governing equations describing the plasma behaviors. Therefore, our model not only replicates the result of the full-wave model but also investigates the wave-driven variations in the plasma velocity and density, electromagnetic field, and thermal structures. Our model results reveal that ions are mainly dragged by neutrals and oscillate along the wave phase line below ~200 km altitude. Electrons are primarily subject to gyro-motion along magnetic field lines. The wave-driven distinct motions among charged particles can generate the perturbed electric current and electric field, further contributing to localized magnetic field fluctuations. Major charged constituents, including electrons, O⁺, O₂⁺, and CO₂⁺, have higher density amplitudes when interacting with larger-periodic waves. The presence of photochemistry leads to a decrease in the plasma density amplitude, and there exists a moderate correlation between plasma density variations and those in the neutrals. Our numerical results indicate that the wave-driven variations range from several percent to ~ 80% in the plasma density and from ~ 0.2% to 17% in the magnetic field, which are consistent with the spacecraft observations. Further calculations reveal that the wave-induced plasma-neutral coupling can heat the neutrals yet cool the plasmas. Electrons are cooler than ions in the coupling process. The wave-driven heating by neutral-ion collisions exceeds that by neutral-electron collisions but tends to be lower than the wave dissipative heating and photochemical heating. Our model has potential applications in studying the AGWs-driven variable ionospheric structures and can be used for other planets.

How to cite: Wang, X., Xu, X., Cui, J., Yi, S., Gu, H., Zhou, Z., Man, H., Luo, L., He, P., and Yang, P.: A Linearized Coupled Model of Acoustic-gravity Waves and the Lower Ionosphere at Mars, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7015, https://doi.org/10.5194/egusphere-egu24-7015, 2024.

Venus is well known for extreme heat at its surface and being shrouded in clouds composed of sulphuric acid. However, there are regions of Venus’ atmosphere around 120 km that are cold enough to harbour ice clouds, under conditions similar to the upper mesospheres of Earth and Mars where ice clouds form. In this presentation we will show, using published satellite products and numerical modelling, that the upper mesosphere of Venus can be cold enough for both H₂O and CO₂ to condense and form particles. Amorphous solid water particles (ASW) are likely to nucleate both heterogeneously on meteoric smoke (formed from the condensation of the metallic vapours which ablate from cosmic dust particles entering  Venus’ atmosphere) and also homogeneously, resulting in clouds of nano-scaled particles at around 120 km that will occur globally. The temperatures may become cold enough (below ~90 K) that CO₂ particles nucleate on ASW particles. Taking account of the uncertainty associated with retrievals of temperature in the upper mesosphere (using the SOIR instrument on Venus Express), CO₂ ice cloud formation could occur more than 30% of the time poleward of 60^o. Since the main component of Venus’ tenuous atmosphere is CO₂, any CO₂ crystals that form will grow and sediment on a timescale of a few minutes. Mie calculations show that these Venusian mesospheric clouds (VMCs) should be observable by contemporary satellite instruments, although their short lifetime means that the probability of detection is small. We suggest that VMCs are important for the redistribution of meteoric smoke and may serve as a cold-trap, removing some water vapour from the very upper mesosphere of Venus through the growth and sedimentation of cloud particles, and possibly reducing the loss of water to space.

How to cite: Plane, J., Murray, B., Mangan, T., and Määttänen, A.: Ephemeral Ice Clouds in the Upper Atmosphere of Venus, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8133, https://doi.org/10.5194/egusphere-egu24-8133, 2024.

While extensive studies have been conducted on Mars' dayside airglow emissions using instruments of various missions (Mariner, Mars Express, MAVEN, TGO and EMM), only the ultraviolet and infrared emissions have been investigated on the nightside (MEx and MAVEN). The middle ultraviolet spectrum is dominated by the v’=0 δ and γ bands of nitric oxide excited by radiative association of nitrogen and oxygen atoms. Although this emission is present at all latitudes and local times, extensive mapping has shown that it is enhanced in winter at high latitudes in both hemispheres (Schneider et al., 2020). This seasonal brightening at high latitudes is the signature of the global transport of O and N atoms ascending from the sunlit summer polar regions that are carried downward by vertical winds and diffusion to the 40-60 km region of the dark winter hemisphere. The O₂ nightglow at 1.27 μm has already been monitored as well (Bertaux et al., 2012). However, nightglow emissions in the visible domain have begun only very recently with the NOMAD-UVIS instrument, which can, for the first time, simultaneously monitor the UV and visible domains in the Martian atmosphere. Gérard et al. (2023) have discovered the presence of the (0,5) to (0,11) bands of the O₂ Herzberg II system between 400 and 650 nm in the nightglow. We present here a comprehensive statistical analysis of this nightglow based on a dedicated NOMAD-UVIS campaign of 30 orbits acquired between May and October 2023 in the southern hemisphere during the winter season. Combining both the inertial and limb tracking modes allows for intensity retrieval, latitudinal variability analysis, and the generation of limb profiles.

The O₂ emission is expected to solely originate from the three-body recombination of O atoms O + O + M → O₂* + M.  The oxygen density can therefore directly be retrieved from the Herzberg II observations. Furthermore, simultaneous NO nightglow observations with NOMAD-UVIS combined with the retrieved oxygen density, allows to calculate the nitrogen density and its downward flux. As atomic oxygen serves as a precursor to both NO and O₂ nightglows, arising from O atom recombination with either oxygen or nitrogen, this dual investigation presents a remarkable opportunity to unravel their shared characteristics (stemming from oxygen density) and their distinguishing features (emanating from nitrogen), including variations in brightness and altitudes. It will provide valuable constraints for improving 3-D models that simulate global circulation and dynamic processes. In particular, it will help solving the current discrepancy between the predicted and modeled altitude distribution of the NO nightglow, a proxy of insufficiently vigorous downward transport of N atoms.

References:

Bertaux et al. (2012), First detection of O₂ 1.27 µm nightglow emission at Mars with OMEGA/MEX and comparison with general circulation model predictions, JGR, 117, E00J04, doi:10.1029/2011JE003890.

Gérard et al. (2023). Observation of the Mars O2 visible nightglow by the NOMAD spectrometer onboard the Trace Gas Orbiter. Nature Astronomy, https://doi.org/10.1038/s41550-023-02104-8

Schneider et al. (2020) Imaging of Martian circulation patterns and atmospheric tides through MAVEN/IUVS nightglow observations. JGR Space Physics 125(8), e2019JA027318.

How to cite: Soret, L., Gérard, J.-C., González-Galindo, F., Thomas, I., Ristic, B., Vandaele, A.-C., and Hubert, B.: Probing the Mars upper atmosphere through simultaneous NOMAD/UVIS observations of the NO ultraviolet and O2 visible nightglow, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9716, https://doi.org/10.5194/egusphere-egu24-9716, 2024.

The Zhurong rover conducted in-situ spectral investigations of southern Utopia Planitia, where orbital observations revealed the presence of spectrally featureless dust. However, in-situ reflectance spectra collected by the Short Wave Infrared (SWIR) spectrometer exhibit hydrated features for all observations along the traverse. These features have been interpreted as being associated with groundwater (Liu Y. et al., 2022) or ocean (Liu C. et al., 2022; Xiao et al., 2023) or atmospheric water (Zhao et al., 2023). Here, we combine the Multispectral Camera (MSCam) and SWIR data to characterize the spectra of landing site and provide some new insights into the surface composition diversity.

Multispectral images suggest that most of surfaces are consistent with the presence of dust whereas a few of rock surfaces exhibiting dark tones are compositionally distinct. The co-observational SWIR data can be used to further constrain the surface compositions. With Principal Component Analysis (PCA) and unmixing analysis of the SWIR data, we found that these dusty surfaces are ubiquitously characterized with faint 1900 and 2200 nm absorptions and the dark rock surfaces exhibit strong blue slopes in the NIR.

The hydrated dust features seem to contrast with previous knowledge, that the dust does not exhibit obvious NIR hydration features from orbital observations. Such discrepancies were also observed at Jezero crater, where the fine soils or dusty rocks exhibit a 1900 nm H₂O absorption but without 2200 nm band (Mandon et al., 2023). Spectral variation may reflect distinct surface dust compositions between the Perseverance and Zhurong landing site, indicating different dust reservoirs or dust alteration processes. The surface dust of different sites may be mixtures of globally well-mixed fine materials and local/regional distinct hydrated phases. Another possibilities is that the dust underwent different post-deposition aqueous alteration.

The dark rock surfaces may represent less dust-coated surfaces. The strong blue slope features have been previously attributed to coatings on a dark substrate. Furthermore, the morphological properties show that these surfaces exhibit relatively fragile surface context, consistent with surface coatings or rinds.

How to cite: Zhang, Q., Carter, J., Vincendon, M., Poulet, F., Pineau, M., Guo, L., Luo, Y., Liu, D., Bibring, J.-P., Liu, J., and Li, C.: New insight into the surface composition of Zhurong landing area, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10193, https://doi.org/10.5194/egusphere-egu24-10193, 2024.

We report two extreme cases of clouds in Mars, on the one hand what we call “isolated dot clouds” and on the other hand new cases of extremely “elongated long and narrow clouds” reminiscent in their shape of the one that develops in Arsia Mons. We use the images obtained by the VMC-camera on board the Mars Express mission that from its advantageous polar elliptical orbit allows to image Mars at different local times (in particular at twilight hours).

We present the properties of the “dot clouds” that develop abundantly in the Terra Cimmeria region, particularly around the Kepler crater (longitude 140.9 East and 46.8 South) in Mars solar longitudes Ls from 30 to 100 deg. These are compact rounded clouds with sizes of about 50 km in diameter and altitudes in the range 50-80 km as measured from their shadows. Sometimes they appear isolated at dawn, others in twilight clusters, but we also present a singular case in which they exhibited a ringed shape. We discuss possible mechanisms underlying their formation, such as convection and the possible intervention of the crustal magnetic field concentrated in this region.  On the other hand, we report new cases of extremely narrow and elongated clouds observed at mid and high latitudes in both hemispheres. We study in particular the properties of these clouds in the volcanic region of Alba Patera, in Thaumasia Highlands and in Lyot crater, where they can reached lengths from 1,000 km to 2,000 km and widths of 50 km.  

How to cite: Sanchez-Lavega, A., Hernandez-Bernal, J., Larsen, E., del Rio-Gaztelurrutia, T., Sánchez-Cano, B., and Määttäanen, A.: Mars Singular Clouds: Dots, Rings and Narrow-Elongated, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10357, https://doi.org/10.5194/egusphere-egu24-10357, 2024.

Alpha Particle X-ray Spectrometers (APXS) were an integral component of the science payload that flew on the twin Mars Exploration Rovers (MER) Spirit and Opportunity. An updated version of the MER APXS instrument, further optimized for in situ geochemical analyses on Mars, is currently operational within Gale crater onboard the Mars Science Laboratory (MSL) rover Curiosity. APXS on MER and MSL were designed and calibrated for high-precision in situ analyses of geologic materials on Mars. The use of curium-244 sources provides high sensitivity to lower-Z elements. This low-Z sensitivity is important for characterizing the abundance of rock forming elements such as Na, but also enables analyses of Ar, which makes up ~2% of the Martian atmosphere, and thus ~40% all non-condensable gas species.

Atmospheric dynamics on Mars are driven in large part by condensation flow. The temperature and pressure at the winter pole leads to the deposition of carbon dioxide (which makes up ~95% of the atmosphere) onto the polar cap. The following spring, carbon dioxide sublimates from the cap, a cycle which creates a pressure gradient across the planet. Non-condensable gases, such as Ar, are not deposited on the polar cap and become enriched relative to carbon dioxide. Most environmental monitoring hardware flown to Mars can measure the absolute pressure of the atmosphere, but not specifically the abundance of non-condensable species. In the case of the Sample Analysis at Mars (SAM) instrument on MSL, atmospheric constituents can be deduced with great accuracy, but not with a high frequency.

We summarize efforts on MER and MSL to characterize variability in non-condensable gas density on Mars using instruments designed to measure the composition of rocks and regolith. Analyses by Spirit enabled calibration of the MER APXS for atmospheric analyses. The Opportunity mission, spanning ~5000 sols, acquired around 2250 hours of atmospheric data with its APXS. This data set revealed an annual short-lived Ar enrichment occurring around L_s 150, previously unreported in the literature and not present in climate models at that time. This phenomenon has since been regularly targeted on MSL with APXS (and SAM), with ~800 hours of atmospheric analyses conducted by APXS thus far. We report recent findings from Mars Year 37, where dedicated high-frequency APXS atmospheric campaigns were conducted, coinciding with solar conjunction and extended holiday plans, significantly improved constraints on the timing of this short-lived enrichment at Gale crater, and compare the observed results to those from Opportunity.

How to cite: VanBommel, S., Gellert, R., Berger, J., Christian, J., Knight, A., McCraig, M., O'Connell-Cooper, C., Thompson, L., Yen, A., and Boyd, N.: Monitoring Condensation Flow on Mars with Landed X-ray Spectrometers: A Summary of 11,000 Sols Across Three Landing Sites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12597, https://doi.org/10.5194/egusphere-egu24-12597, 2024.

Due to gravitational perturbations from nearby planets, Mars has undergone large obliquity variations through its history. Modeling suggested that in the past 10 million years, the obliquity of Mars has varied by up to 20°, from 15° to 35°. During time periods of high obliquity, the polar regions of Mars received more solar insolation and became warmer, leading to more rapid sublimation of water ice and higher atmospheric water content. During periods of low obliquity, on the contrary, water vapor condensed in polar regions and the atmosphere became dry. This variation has a significant impact on the photochemistry of the Martian atmosphere, as HO_x radicals, which are photolytic products of water vapor, are key catalysts to the photochemistry of the Martian atmosphere. It is then of interest to explore the photochemistry of Mars at different obliquities and its effects on the climate and surface of Mars, as part of the objectives of the “Mars Through Time” European Research Council project. In preparation for future Mars sample return missions, it is important to evaluate the preservability of potential organic matter buried in the shallow subsurface with different oxidizing capacities of the atmosphere at different obliquities.

In view of the three-dimensional nature of the sublimation, transport, and condensation of water, we employ a fully coupled photochemical-radiative-dynamical model—the Mars Planetary Climate Model, developed at LMD in collaboration with other institutions—to simulate the photochemistry of the recent Martian atmosphere at obliquities between 15° and 35°. We find that at high obliquities, water content of the Martian atmosphere could exceed the present-day value by more than one order of magnitude, and the OH concentration could be higher by up to two orders of magnitude. These drastic changes result in a significantly lower CO concentration. Opposite effects are observed from low-obliquity simulations. The nonlinearity in the photochemical system, however, has led to more complex behaviors of the HO₂ and H₂O₂ concentrations. We will explain the mechanisms behind these effects and discuss their implications in the paleoclimate of Mars and the preservation of potential biogenic organic matter in the shallow subsurface. We will also address the long-standing “CO-deficit” problem in Mars photochemical modeling, and show how the state-of-the-art 3D photochemical modeling helps to mitigate the problem.

How to cite: Luo, Y., Lefèvre, F., and Forget, F.: Photochemistry of the Recent Martian Atmosphere at Different Obliquities, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12803, https://doi.org/10.5194/egusphere-egu24-12803, 2024.

Recurring Slope Lineae (hereinafter RSL) are seasonal dark flows observed on steep slopes (≳ 25°) of Mars that are overall dark (slope albedo < 0.2) (McEwen et al., 2011). These movements of up to a few hundred meters long appear and grow downwards (more or less incrementally), fade (partially or totally) more or less progressively, and recur almost every year. After considering it as liquid water or brine flows, the RSLs are now widely considered as granular flows of dark sand or dust, both involving dust at different levels. Mechanisms that may drive these movements are however not precisely understood. One of the main common features between RSL and dust is seasonality: major RSL formations are for example observed during the dust storm season, and RSL formation is enhanced after global dust storms. Here, we aim to better understand the role of dust and winds in these movements.

We have first concentrated our study on Hale crater (323.48°E, 35.68°S), a well-studied RSL site located within an area of higher dust storm detections in the OMEGA/Mars Express dataset. Images taken by the HiRISE camera onboard Mars Reconnaissance Orbiter (during Martian Years 31, 32 and 33) have been used to characterise the RSL annual activities. We defined 3 intensity levels to classify formations and disappearances. Then, we compared these RSL activities to atmospheric dust optical depth measurements and Mars Climate Database (MCD) predictions of dust deposition and winds. Finally, we computed the effective reflectance values of several consecutive HiRISE images, taking into account the local slope of the surface, to quantify darkening and brightening.

We observed that RSL formation and disappearance are correlated with the atmospheric dust optical depth variations. We also noticed that the prediction of dust deposition rate reaches two maxima during the dust storm season that occur simultaneously with intermediate and high RSL disappearance levels. Reflectance variations showed that RSL can disappear both by brightening and darkening, with relative variations from a few per cent to 40%, suggesting that RSL can also disappear by widespread dust removal all over the RSL slope. We also identified some correlations between RSL activities and wind predictions: the maximum of surface wind stress is reached during the first period (of the year) of high RSL formation level, and the convective winds reach high values during the dust storm season (L_s ~ 180-360°), corresponding to intermediate and high RSL formation levels. Overall, these results suggest that dust deposition/removal and winds are involved in the RSL disappearance and formation mechanisms at Hale crater.

How to cite: Leseigneur, Y., Vincendon, M., and Zhang, Q.: The Martian Recurring Slope Lineae: Granular Flows Linked with Wind and Dust , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15988, https://doi.org/10.5194/egusphere-egu24-15988, 2024.

Clouds have been observed on Venus, Mars and Titan, and a growing number of exoplanets, yet the connection between planetary rotation rate and cloud distribution has not previously been extensively investigated. Using an idealised climate model incorporating seasonal forcing, we investigate the impact of rotation rate on the abundance of clouds on an Earth-like aquaplanet, and the resulting impacts upon albedo and seasonality. We show that the cloud distribution varies significantly with season, depending strongly on the rotation rate, and is well explained by the large-scale circulation and atmospheric state. Planetary albedo displays non-monotonic behaviour with rotation rate, peaking around one half of Earth’s rotation rate. Clouds reduce the surface temperature and total precipitation relative to simulations without clouds at all rotation rates, and reduce the dependence of precipitation on rotation rate. Clouds also affect the amplitude and timing of seasonality, in particular by modifying the width of the Hadley cell at intermediate rotation rates. The timing of seasonal transitions varies with rotation rate; the addition of clouds further modifies this phase lag, most notably at Earth-like rotation rates. Our results may inform future characterisation of terrestrial exoplanets, in particular informing estimates of planetary rotation for non-synchronous rotators.

How to cite: Williams, D., Ji, X., Corlies, P., and Lora, J.: Clouds and Seasonality on Terrestrial Planets with Varying Rotation Rates , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16259, https://doi.org/10.5194/egusphere-egu24-16259, 2024.

We have developed a new version of the IPSL Titan GCM, now called the Titan Planetary Climate Model (Titan PCM), including a new microphysical model for haze and clouds. Observations of Titan have long revealed the presence of seasonal cycles on Titan (haze, clouds, organic compounds), the ins and outs of which are still poorly understood. In particular, the lack of information on the different flows that govern these cycles prevents us from understanding all the phenomena taking place in Titan’s atmosphere. The need to develop a complete climate model, including microphysics, therefore becomes essential.

The latest improvements in the Titan PCM radiative transfer, now based on a flexible correlated-k method and up-to-date gases spectroscopic data, lead to a better modelling of the temperature profiles in the middle atmosphere. The photochemical solver extends computation of the composition above the top of the PCM (roughly 500 km) up to 1300 km. Radiative transfer is coupled with a new microphysics model in moments. This model includes phenomena such as the nucleation and condensation of clouds, and precipitation that shape the satellite’s landscape.

We are now able to model the processes involved in the formation of tropospheric (CH4) and polar (C2H2, C2H6 and HCN) clouds on Titan. Cloud formation induces new seasonal cycles, particularly at the tropopause where clouds empty the lower layers of the atmosphere of aerosols, featuring two boundary, the main haze layer and a layer of condensed organic compounds. Higher up, in the lower stratosphere, the haze follows a new cycle constrained solely by the circulation, leading to a better modelling of the temperature profiles in the low stratosphere and the troposphere.

From the results of coupled simulations, we can discuss multiple questions raised by observations. Special interest is bear on the overall control of the thermal structure, and impact of the coupling on equinoctial circulation reversal. We also discuss the radiative destabilization of the lower polar winter stratosphere, observed by Cassini radio-occultations.

How to cite: Lebonnois, S., de Batz de Trenquelleon, B., Rosset, L., Vatant d'Ollone, J., and Rannou, P.: The Titan PCM : a fully coupled climate model to study thermal structures, haze, clouds and their seasonal variations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16561, https://doi.org/10.5194/egusphere-egu24-16561, 2024.

The Nadir and Occultation for MArs Discovery (NOMAD) spectrometer has been collecting Mars observations since 2018, providing a massive amount of information regarding its atmospheric composition, its vertical structure and bridging the gap between the previous knowledge of the lower atmosphere and the data from other missions (e.g., MAVEN) regarding atmospheric escape. The capability of the Solar Occultation (SO) channel to map the vertical structure of the atmosphere with a very high (>1000) signal-to-noise ratio, at a very high spectral resolution (>17000) and a high vertical sampling (0.5 to 2 km) is valuable in many contexts, ranging from the search for trace species in the lower atmosphere (10 to 40 km) to mapping the isotopic composition of the main atmospheric constituents (H₂O, CO₂, CO) or exploring the vertical structure of dust, water ice and CO₂ ice clouds.

Aerosols are some of the main drivers of the Martian climate, and the study of their spatial distribution and microphysical properties can advance our knowledge of their impact on the climate of the planet and on their formation and dynamics. This work will show the extension of previous investigations focused on dust, water ice and CO₂ ice using NOMAD data, by presenting the mapping of these atmospheric components on a global scale over 3 Martian Years (MY34 Ls 160 to MY37 Ls 170). The acquisition by NOMAD of several diffraction orders during a single occultation allows in fact to obtain spectrally broad information that can be used to map dust and water ice vertical distributions and particle sizes. The information content of NOMAD data about particle sizes of water ice has been demonstrated to be particularly high and to give important information about the nucleation processes of water ice. NOMAD data can also be used to look for CO₂ ice by combining broad spectral information with localized CO₂ ice features at 3600 and 3710 cm^-1, which are well identifiable in the NOMAD spectra.

Besides presenting the climatology of aerosols, we will illustrate specific features occurring during the Martian Year and their repeatability; more specifically, we will look into the differences between MY 34, characterized by a Global Dust Storm, and following years, to highlight the impact of dust-induced heating over cloud formation. We will also give some insights into CO₂ ice cloud formation, which was confirmed to be surprisingly heterogeneous compared to results obtained before TGO operations.

How to cite: Liuzzi, G., Villanueva, G., Aoki, S., Trompet, L., Daerden, F., Neary, L., Viscardy, S., Faggi, S., Stone, S. W., Thomas, I., Patel, M., and Vandaele, A. C.: A 3 Martian Year climatology of aerosols with ExoMars TGO-NOMAD: seasonal cycles and new insights, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17142, https://doi.org/10.5194/egusphere-egu24-17142, 2024.

The NOMAD (“Nadir and Occultation for MArs Discovery”) spectrometer suite onboard the ExoMars Trace Gas Orbiter (TGO) is composed of three spectrometers. In this work, we will use the UVIS channel in occultation mode. An aerosol climatology had been produced covering the second half of MY 34 up to the end of MY 36. 
Aerosols are an important part of the Martian atmosphere and have a strong relationship with the atmospheric temperature. They are composed of dust, H2O ice, and CO2 ice. Dust is the main aerosol and has a significant contribution to the radiative transfer budget, as it absorbs solar radiation, leading to local heating of the atmosphere. Dust is confined to lower altitudes during the aphelion season and can reach higher altitudes during the perihelion, especially during dust storms that frequently arise on Mars during this period. The ice clouds are more present during the aphelion when the temperature is colder and follow a seasonal pattern. Several types of clouds can be found throughout the year, contrary to the dust they reflect the sunlight and cool locally the atmosphere. 
Using only the spectral range of UVIS dust, H2O ice, and CO2 ice cannot be differentiated because the three aerosols have similar spectral features in the UV-visible. Dust represents most of the aerosols present in the atmosphere, therefore only dust refractive indices are used in this work. Detection of CO2 and water ice will be investigated in future work using the infrared channel of NOMAD. Nevertheless, we presented a way of indirectly recognizing the composition of the aerosols using indirect parameters such as the temperature or comparison with other datasets.It is possible to distinguish the particle size between 0.1 to 0.8 µm with confidence. When the particles are larger it is not possible to retrieve the precise size. 
In conclusion we present a climatology of Martian aerosols, including vertical extinction profiles as well as vertical profiles of particle size distributions. The seasonal cycle of the dust is observed and recurring structures over different Martian years such as dust storms or ice clouds are detected. We also present a comparison with water vapor profiles and aerosol profiles during regional dust storms, we showed that the water vapor during the storm could condense to water ice due to the presence of dust condensation nuclei at high altitudes. The thermal and dynamical structure of the atmosphere, and chemical species are all sensitive to the aerosol’s abundance and size.

How to cite: flimon, Z., Erwin, J., Robert, S., Neary, L., Piccialli, A., Trompet, L., Willame, Y., Daerden, F., Bauduin, S., Wolff, M., Thomas, I., Ristic, B., Bellucci, G., Patel, M., Depiesse, C., Vandaele, A.-C., Mason, J., Lopez-Moreno, J. J., and Vanhellemont, F.: Martian aerosol Climatology on Mars as Observed by NOMAD UVIS on ExoMars TGO, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17539, https://doi.org/10.5194/egusphere-egu24-17539, 2024.

The Moon is subjected to a variety of influences in the space environment. One of these is the solar wind, a plasma stream consisting of mostly H⁺ and He²⁺ ions, that impinges on the lunar surface. As a consequence, material is released through the process of ion sputtering, mostly on an atomic level. These ejecta subsequently take part in the formation of the lunar exosphere [1]. Constraining their physical properties, most notably the parameters sputtering yield, ejecta angular distribution and their energy distribution, is thus crucial to properly model the exosphere creation [2]. Such investigations have been of interest for decades and have recently been carried out with samples representative for the lunar mineralogy [3–6].

In this contribution, we present our current investigations on the aforementioned parameters using samples prepared from material collected during the Apollo 16 mission. Using a quartz crystal microbalance (QCM), we are able to measure mass changes due to sputtering caused by H and He ions and therefore also the sputtering yield. Additionally, we place another QCM in the experimentation chamber in a rotatable manner that collects the ejecta. Doing so enables us to probe the angular distribution of the ejecta. For these experiments, we use two types of samples: flat vitreous films as well as pellets pressed from lunar regolith and prepared according to [7]. Along with numerical simulations considering the sample morphology, this allows us to untangle intrinsic material properties from modifications thereof due to surface roughness. Lastly, we will present plans for future measurements to experimentally resolve the ejecta energy distribution. These energy distributions of particles sputtered from compound materials (rather than monatomic ones) are an actively researched area, especially from a numerical standpoint [8–11] – experimental data are scarce, however. This study combining the three physical quantities describing the sputtering process will therefore close a knowledge gap and be applicable not only to the Moon, but also to the sputtering of other planetary bodies.

[1] B. Hapke, J. Geophys. Res. Planets 106 (2001) 10039–10073
[2] P. Wurz, et al., Icarus 191 (2007) 486–496
[3] P.S. Szabo, et al., Icarus 314 (2018) 98–105
[4] H. Biber, et al., Nucl. Instrum. Methods. Phys. Res. B 480 (2020) 10–15
[5] H. Biber, et al., Planet. Sci. J. 3 (2022) 271
[6] M.J. Schaible, et al., J. Geophys. Res. Planets 122 (2017) 1968–1983
[7] N. Jäggi, et al., Icarus 365 (2021) 114492
[8] L.S. Morrissey, et al., J. Appl. Phys. 130 (2021) 013302
[9] H. Hofsäss, A. Stegmaier, Nucl. Instrum. Methods. Phys. Res. B 517 (2022) 49–62
[10] L.S. Morrissey, et al., ApJL 925 (2022) L6
[11] R.M. Killen, et al., Planet. Sci. J. 3 (2022) 139

How to cite: Brötzner, J., Biber, H., Jäggi, N., Nenning, A., Fuchs, L., Szabo, P. S., Galli, A., Wurz, P., and Aumayr, F.: A comprehensive study on the sputtering of the lunar surface, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18377, https://doi.org/10.5194/egusphere-egu24-18377, 2024.

Dust storms on Mars cause variations in atmospheric temperatures and dynamics due to direct solar heating and its dynamic response. These effects are most intense during the dust storm season (Ls 180º - 360º), when most global and regional storms occur and when the suspended dust reaches higher altitudes in the atmosphere. The thermal impact of these events affects the regional and global circulation of Mars. Thanks to measurements taken by the Thermal Emission Spectrometer (TES) onboard the Mars Global Surveyor (MGS) and the Mars Climate Sounder (MCS) onboard the Mars Recoinnasance Orbiter (MRO) it is possible to study the spatial and temporal variability of these storms over the last 12 Martian years (Martín-Rubio et al., 2024). Although each storm must be considered independently, it is possible to observe how the storms recur seasonally following specific patterns that allow them to be grouped according to their time of occurrence and evolution, with the recurrence patterns named as type A, B and C (Kass et al., 2016). Late northern winter large regional storms (C-type storms) show the highest variability; it appears that the occurrence of Global Dust Storms does not have a simple direct effect in the intensity of the subsequent C-type storm. We analyze recent intense type C storms (MY 34, 35 and 36, with particular focus on MY 34, when a Global Dust Storm occurred), studying the vertical, latitudinal and longitudinal dust distribution that occurred between solar longitudes Ls = 318° - 335°. This study is important to better understand the interannual variability of regional dust storms on Mars, as well as dust transport during late northern winter regional storms.

References:

Martín Rubio, C., Vicente-Retortillo, A., Gómez, F. and Rodríguez-Manfredi, J.A., 2024. Interannual variability of Regional Dust Storms between Mars Years 24 and 36, Icarus (under review).

Kass, D. M., Kleinböhl, A., McCleese, D. J., Schofield, J. T., Smith M.D. 2016. Interannual similarity in the Martian atmosphere during the dust storm season

How to cite: Martín-Rubio, C., Vicente-Retortillo, A., Martínez-Esteve, G., Gómez, F., and Rodríguez-Manfredi, J. A.: Interannual Variability of Dust Storms between Mars Years 24 and 36 and analysis of dust vertical distribution of the MY 34 late-storm., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18637, https://doi.org/10.5194/egusphere-egu24-18637, 2024.

The Curiosity rover has traversed more than 30 km from the landing site at the very bottom of Gale crater and has climbed more than ∼750 m into the Mt. Sharp foothills over more than five Martian years. Modeling and observations strongly suggest that the rover has ascended to elevations above a cold pool of air at the bottom of the crater [Ruíz-Pérez et al. 2024 in preparation]. During nighttime, downslope winds originating from both Mt. Sharp and crater rims would prevent the nighttime accumulation of methane released along the slopes above the cold pool and facilitate the convergence and accumulation of methane in the bottom of the crater. As a result, any methane released along the slopes at night is quickly transported downslope. After sunrise, the crater circulation transitions to an upslope regime. The reversal of the circulation should transport the methane accumulated in the bottom of the crater upslope as shown in MRAMS model tracer fields, that also indicate a substantial horizontal mixing that rapidly dilutes the methane-enriched air mass. Any methane released along the slopes is transported horizontally and vented out of the crater. MRAMS model predicts a methane front of peak values to pass higher elevations at increasingly later times after sunrise, moreover later in the morning (~10:00 LMST), but usually with highly and increasingly diluted with time methane values. At mid-morning, upslope circulation along surface rims is fully developed and there is a clear horizontal divergence at bottom of crater where methane is highly diluted due to 3-D atmospheric mixing and increasingly advected upslope out of crater. At dusk, downslope winds starts to develop through sloped surfaces of Mt. Sharp, as well as the cold pool of air at the bottom of the crater, which begins to trap methane released from the ground to start the cycle again. Consistent with [Pla-García et al. 2019] and [Moores et al. 2019] the 3-D crater circulation supplemented by the growth and collapse of the PBL is necessary to explain the TLS-SAM methane observations.

How to cite: Pla-Garcia, J., C.R. Rafkin, S., Ruíz-Pérez, M., and Atreya, S.: MSL TLS-SAM measurements consistent with localized methane containment and transport by 3-D atmospheric circulation in Gale crater, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19315, https://doi.org/10.5194/egusphere-egu24-19315, 2024.

We present numerical studies of star/planet interactions, specifically the effects of Stellar Energetic Particles (SEPs) on the atmospheres of terrestrial (exo)planets. This work was performed as part of the INCREASE project (INfluence of strong stellar particle Events and galactic Cosmic Rays on Exoplanetary AtmoSpherEs) funded by the German Research Council (DFG).

We have developed and applied a new Model Suite which couples magnetospheric and atmospheric propagation and interaction models PLANETOCOSMICS (Desorgher et al. 2006) and AtRIS (Banjac et al. 2019) with the atmospheric chemistry and climate models 1D-TERRA (e.g., Wunderlich et al. 2020) and ExoTIC (Sinnhuber et al., 2012).

We are able to assess the influence of the stellar activity on the planetary atmospheric structure, its chemical composition, and infer spectroscopic observables as well as the effects on biosignatures.

How to cite: Grenfell, L., Iro, N., Sinnhuber, M., herbst, K., Bartenschlager, A., Scherer, K., and Taysum, B.: Modelling Stellar Energetic Particles effects on the atmospheres of terrestrial (exo)planets: INCREASE, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19629, https://doi.org/10.5194/egusphere-egu24-19629, 2024.

Dome-shaped uplifted and fractured terrain observed at the surface of the Moon and Mars includes floor-fractured impact craters. Such deformation features are inferred to form by the emplacement and inflation of sill- and laccolith-shaped magma bodies in the shallowest 1-2 km of a planetary body’s rocky crust. Only the final surface deformation features can be observed from space, modelling helps to understand the emplacement dynamics and the deformation of the overlying rock. A mismatch exists, however, between the complex mechanical response of host rocks to magma-induced stresses observed on Earth in exposed volcanic plumbing systems and the linearly elastic deformation assumed by most of the often-used numerical models.

We have implemented simulations of the inflation of a laccolith intrusion in a particle-based host medium in the two-dimensional (2D) Discrete Element Method (DEM). Our approach allows us to investigate magma-induced, highly discontinuous, deformation and dynamic fracturing and visualizes the localization of subsurface strain. We systematically varied a range of numerical model parameters that govern host rock strength (bond cohesion, bond tensile strength, bond elastic modulus), and specific gravity known for the Moon, Mars and Earth. For equal rock stiffness and amounts of intruded magma, our model results show that we can expect more vertical surface displacement on the Moon due to the lower gravity there compared to Mars, and Earth. Rock toughness and rock stiffness control the amount of fracturing more than gravity does.

We also tested how host rock strengths in our 2D DEM model could be upscaled from intact strengths of rock samples collected at Earth analogue sites, or by implementing a digital crack network that simulates the highly fractured conditions of the intensively impacted Lunar and Martian crusts. Our results show that laccolith inflation in pre-cracked host rocks results in higher surface displacements and a higher amount of magma-induced cracking in broader fractured zones. We expect that our model results will induce a better understanding of the emplacement and architecture of shallow magmatic intrusions below magma-induced uplifted terrain and floor-fractured craters on the Moon and Mars.

How to cite: Poppe, S., Morand, A., Harnett, C. E., Cornillon, A., Awdankiewicz, M., Heap, M., and Mège, D.: Modelling magma-induced surface uplift and dynamic fracturing around laccoliths on the Moon, Mars, and Earth, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2138, https://doi.org/10.5194/egusphere-egu24-2138, 2024.

The rock and rock-ice mixtures of the core-enveloping spherical shells comprising terrestrial body interiors have thermally determined viscosities well described by an Arrhenius dependence. Accordingly, the implied viscosity contrasts determined from the activation energies (E) characterizing such bodies can reach values exceeding 10⁴⁰, for a temperature range that spans the conditions found from the lower mantle to the surface. In this study, we first explore the impact of implementing a cut-off to limit viscosity magnitude in cold regions. Using a spherical annulus geometry, we investigate the influence of core radius, surface temperature, and convective vigour on stagnant lid formation resulting from the extreme thermally induced viscosity contrasts. We demonstrate that the cut-off viscosity must be increased with decreasing curvature factor, ƒ (=r_in/r_out, where r_in and r_out are the inner and outer radii of the annulus, respectively), in order to obtain physically valid solutions. We find that for statistically-steady systems, the mean temperature decreases with core size, and that a viscosity contrast of at least 10⁷ is required for stagnant lid formation as ƒ decreases below 0.5. Inverting the results from over 80 calculations featuring stagnant lids (from a total of approximately 180 calculations), we apply an energy balance model for heat flow across the thermal boundary layers and find that the non-dimensionalized temperature in the Approximately Isothermal Layer (AIL) in the convecting layer under a stagnant lid is well predicted by T'_AIL=½{ -(2T'_out+γ) + √[γ² + 4γ(1+T'_out)] } where γ is a function of E and ƒ, and T'_out is the non-dimensionalized surface temperature. Moreover, the normalized (i.e., non-dimensional) thickness of the stagnant lid, L', can be obtained from a measurement of the non-dimensional surface heat flux once T'_AIL is determined. Stagnant-lid thicknesses increase from 10 to 30 percent of the shell thickness as ƒ is decreased, and thick lids can overlie vigorously convecting underlying layers in small core bodies, potentially delaying secular cooling and suggesting that small objects with small cores may have developed thick elastic outer shells early in the solar system's history while maintaining vigorously convecting interiors. However, we also find that for the small number of 3-D calculations that we examined, parametrizations based on 2-D calculations overestimate the temperature of the convecting layer and the thickness of the conductive lid when ƒ is small (less than 0.4).

How to cite: Javaheri, P., Lowman, J., and Tackley, P.: Spherical geometry convection in a fluid with an Arrhenius thermal viscosity dependence: the impact of core size and surface temperature on the scaling of stagnant-lid thickness and internal temperature, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3226, https://doi.org/10.5194/egusphere-egu24-3226, 2024.

Nearly three decades of investigation has made steady progress towards self-consistently generating multiple features of plate tectonics from global mantle convection models.  Accordingly, the modelling of dynamic plates with migrating boundaries and evolving areas has become commonplace in both 2-D and 3-D geometries. Investigating the properties required for obtaining durable deep mantle formations similar to the Large Low Shear-wave Velocity Provinces (LLSVPs) has received similar attention. In this study, we model LLSVPs by assuming their composition is persistent  (i.e, we assume steady-state chemistry). To this end, we incorporate a Compositionally Anomalous Intrinsically Dense (CAID) mantle component comprising 2–3.5 per cent of the total mantle volume. We explore the impact of both an intrinsic contrast in density and viscosity for the CAID component, in an effort to stimulate the formation of a pair of LLSVP-like structures and a surface that exhibits the principle features of terrestrial plate tectonics; including recognizable and narrowly focused divergent, convergent and (in 3-D) transform plate boundaries that separate 8–16 distinct plate interiors. Although we find that a pair of CAID material provinces can be readily obtained in 2-D calculations while maintaining a surface exhibiting plate-like behaviour, specifying the same system parameters in 3-D calculations does not yield a pair of enduring provinces for any values of the parameters investigated.  In addition, CAID component inclusion in the calculations can affect global geotherms, so that in comparison to the surface behaviour obtained for the initial condition isochemical model, the cases incorporating the dense component do not yield surfaces that simulate plate tectonics. In general, CAID material components that are 3.75–5 percent denser than the surrounding mantle (at surface temperatures), and up to a factor of 100 times greater in intrinsic viscosity, form layers populated by voids, or nodes connected by ridges that reach across the core–mantle boundary (CMB), rather than distinct piles resembling the morphology of the LLSVPs. However, due to their temperature, we find the CAID material forms masses on the CMB that are relatively less dense (0.625–1.5 per cent) and viscous than the adjacent mantle material, in comparison to the percentage differences obtained at common temperatures. By adjusting our yield stress model to account for the influence of the CAID material on the geotherm, we find a highly satisfactory plate-like surface can be re-attained. Nevertheless, the formation of a pair of LLSVP-shaped masses remains elusive in 3-D calculations with plate-like surface behaviour and we suggest that caution is required if inferring the physical properties of the LLSVPs from 2-D models.

How to cite: Lowman, J., Langemeyer, S., and Tackley, P.: Model geometry determined contrast in the feedback between compositionally originating LLSVPs and dynamically generated plates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4709, https://doi.org/10.5194/egusphere-egu24-4709, 2024.

The Earth/Moon system likely results from a giant impact between a Mars-size object and the proto-Earth 70 to 110 Myrs after the formation of the first solids of the Solar System. This high-energy context leads to extreme conditions under which volatile elements would not normally be preserved in the protolunar disk. However, recent measurements of lunar samples highlight the presence of a significant amount of water in the Moon's interior (1.2 to 74 ppm). The aim of the present work is to quantify the water contribution of the late accretion on the early Moon. Here, we use a 2D axisymmetric model with the hydrocode iSALE-Dellen to study the fate of a large impactor on a target body similar to the early Moon with a crust, a magma ocean, and a mantle. For this purpose, we compute different models to monitor the depth to which the impacted material is buried at the end of the impact event and the degree of devolatilisation of the impactor. Three parameters are explored: the crustal thickness (ranging from 10 to 80 km), the impactor radius (ranging from 25 to 200 km) and the impactor velocity (ranging from 1 to 4 times the target escape velocity). Our models show that impactors with a radius greater than 50 km impacting a partially molten lunar body with a crust thinner than 40 km could significantly contribute to the water content of the lunar mantle even for impact velocities of less than 5 km s^-1. For larger impact velocities (≥ 10 km s^-1) the impactor material is significantly molten and its water content is devolatilised within the lunar atmosphere. Depending on the water content of the impactor material and the ability of the lunar magma ocean to maintain chemical heterogeneities, the late lunar accretion following the Moon-forming giant impact could explain the differences in water content between the lunar samples.

How to cite: Engels, T., Monteux, J., Boyet, M., and Bouhifd, A.: Large impacts and their contribution to the water budget of the Early Moon., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6343, https://doi.org/10.5194/egusphere-egu24-6343, 2024.

High-resolution images taken by the Lunar Reconnaissance Orbiter show the existence of many boulder tracks within the Finsen crater. Current research suggests that shallow moonquakes and meteorite impacts are likely to be the cause of boulder falls. Based on a simplified model, we simulate the rolling process of the boulder along the slope when the lunar surface shakes and provide the critical PGA (peak ground acceleration) required for the boulder to start rolling under different conditions. The results show that boulders may roll down slopes within one or more cycles under strong ground shaking. The critical PGA of seismic waves required for a boulder to conduct slope rolling is related to the size of the boulder, the slope at the initial location, the dominant period of the seismic wave, and the ratio of horizontal and vertical peak ground accelerations. Except for rolling against the slope, in some cases, boulders may jump and roll downhill. Using the high-resolution images taken by the LRO to determine how the boulders rolled downhill, we can then estimate the lower limit of the magnitude of moonquakes in the region under different conditions. Finally, we provide a preliminary estimation of the lower limit of the paleo-moonquakes magnitude in the Finsen Crater.

How to cite: Tao, S., Shi, Y., and Zhu, B.: Magnitude estimation of Paleo-moonquakes from boulder tracks in Finsen crater, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6814, https://doi.org/10.5194/egusphere-egu24-6814, 2024.

The Large Low-Velocity Provinces (LLVPs) beneath West Africa and the Southern Pacific are characterized by low seismic wave velocities and are associated with plate-unrelated magmatism such as hotspots, large igneous provinces, and kimberlite. Despite their significance, the structure, origin, and feeding processes of LLVPs remain elusive.

Previous studies have suggested that the LLVPs have remained stationary for over 300 million years, but their morphology appears to have changed. While geodynamic simulations favor denser LLVPs, a recent free-oscillation analysis has suggested lighter ones. The High-Velocity Region (HVR), which surrounds the LLVPs, is located beneath present and past subduction zones. Plumes of varying morphology are imaged between hotspots and LLVP margins, with intensive plumes revealing ultra-low velocity zones (ULVZs) at their roots. Ocean island basalts (OIBs) from hotspots are geochemically enriched and originate from multiple reservoirs. Interestingly, OIB chemistry does not correlate with seismic plume imaging and differs between the two LLVPs. OIB near the African LLVP is influenced by fluid-related subducted materials.

In the light of these results, I propose the following new model for the LLVPs. The LLVPs are at higher temperatures than the HVR and the surrounding mantle. They are composed of Fe-enriched mono-mineral bridgmanite rock, called bridgmanitite. The large grain size of bridgmanitite results in high viscosity despite the high temperatures, thereby stabilizing the LLVPs. The LLVPs are block-structured and the relative movement of the blocks changes the LLVP morphology. Bridgmanitite was formed by the solidification of a primordial magma ocean. Its deposition at the core-mantle boundary forms LLVP precursors in the early mantle. These LLVP precursor blocks can be moved by the thrust and sweep of subducted slabs to form the present-day LLVPs. Erosion and plume formation have reduced the volume of the LLVPs and resulted in different LLVP heights. The HVR consists of harzburgite brought from the surface by subduction. It contains only a limited amount of basaltic rock because the basaltic rock was detached from slabs in the mid-mantle due to suppressed grain growth. As a result, the HVR material is high-density due to the low temperature but is intrinsically low-density due to its chemistry. The HVR material has been heated using the LLVP heat to form plumes. Plumes are geochemically depleted when they have formed in the deep mantle. However, they are enriched in incompatible elements and volatiles in the shallow mantle. This enrichment results from melt migration due to the temperature gradient around the plume. Thus, although LLVP heat drives plume formation, the plate-unrelated magmas such as OIB are not directly derived from the LLVPs.

How to cite: Katsura, T.: Large Low-Velocity Provinces (LLVPs): a new model for their structure, origin, and evolution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8054, https://doi.org/10.5194/egusphere-egu24-8054, 2024.

Recent years have seen the discovery of a huge number of exoplanets, including several planets with very high densities suggesting that they also have rocky interiors which may be 9 – 10 times more massive than Earth. Mineralogy of these so called ‘super-Earth’ planets have been an interesting topic, as it gives implications on the planetary processes (Plate tectonics, geodynamo, etc.) and their habitability. Many studies concluded that such planets may contain ultra-high-pressure analogues of Earth’s lower mantle minerals. (Mg,Fe)O, a binary solid solution of MgO-FeO system is the second most abundant mineral of Earth’s lower mantle. If these super-Earth’s interior can have high pressure analogue of perovskite which is another most abundant phase of lower mantle of Earth as shown by some recent studies then there is a possibility of finding high pressure phase of (Mg,Fe)O also in the lower mantle of those super-Earths. MgO is stable in a NaCl structure (B1) in lower mantle condition of earth. It transforms to CsCl₂ (B2) at high pressure (p) and Temperature (T) conditions. However, FeO is stable in B1 structure which transforms to a rhombohedral phase first and then to NiAs-type structure (B8) with increasing p. Finally, above 240 GPa and 4000 K, FeO transforms directly from B1 to B2. Along with structural phase transitions, FeO also undergoes a spin transition from high spin (HS) to low spin (LS) state with increasing pressure. In this study, we performed first principles DFT calculations on the structural phase transitions of Mg_xFe_1-xO (x % = 0, 25, 50, 75 & 100) from B1 to B2 coupled with spin transition. Their mechanical and thermal properties under pressures ranging from 0 – 500 GPa relevant to super-earth planets have also been estimated. Our investigations have confirmed the presence of B1 phase of (Mg,Fe)O in lower mantle of earth with a spin transition from HS -LS which is thought to be responsible for the seismic anomalies of lower mantle of Earth. Spin transition of magnesiowustite and its effect on mechanical and thermal properties have been the topic for several experimental studies for many years. Most of them tried to explain the shear anisotropy of lower mantle with the help of (Mg,Fe)O with various Fe concentrations. Present study attempts to explore the stable phases of Mg_xFe_1-xO relevant to super-Earth conditions. Both mechanical and dynamical behaviour have been investigated in the entire pressure range. Results show a new tetragonal phase of Mg_0.25Fe_0.75O above 125 GPa, which is found to be both mechanically and dynamically stable. These findings will also attempt to predict the mineralogy and seismicity of those giant planets.

How to cite: Karangara, A. and Das, P. K.: High pressure phase of Magnesiowustite: Implications to the mineralogy of super-Earths, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8194, https://doi.org/10.5194/egusphere-egu24-8194, 2024.

Isotopic systems and trace elements are ideal proxies to constrain the production and recycling of crust (both mafic and felsic) over time. Within the Rubidium-Strontium (Rb-Sr) system, Rb-87 decays to Sr-87 and due to the preferential partitioning of Rb into the crust (relative to Sr) during partial melting, ⁸⁷Sr/⁸⁶Sr ratio of the crust is higher than that of the mantle over time. Trace elements such as Niobium (Nb) and Uranium (U) do not fractionate when mantle melts to form mafic magma (oceanic crust) but they do fractionate when oceanic crust is recycled and undergoes fluid-present melting, i.e., during the production of felsic magmas (continental crust) [Hofmann et al., 1986], thereby resulting in a lower Nb/U of the felsic crust compared to the mantle. In this work, we couple the evolution of the above-mentioned geochemical proxies with the melting processes in global convection models using the code StagYY [Tackley, 2008]. Results from these geodynamic models are then compared with geochemical data obtained from olivine-hosted melt inclusions extracted from komatiites of 3.27 Ga Weltevreden formation (Barberton Greenstone Belt, South Africa).

These models self-consistently generate oceanic and continental crust while considering both plutonic and volcanic magmatism [Jain et al., 2019] and incorporate a composite rheology for the upper mantle. Pressure-, temperature-, and composition-dependent water solubility maps calculated with Perple_X [Connolly, 2009] control the ingassing and outgassing of water between the mantle and surface [Jain et al., 2022]. These models show intense production and recycling of continental crust during the Hadean and the early Archean, which is in agreement with new geochemical data [Vezinet et al., in review] and previous geochemical box models [Rosas & Korenaga, 2018; Guo & Korenaga, 2020]. The thermal evolution is also consistent with cooling history of the Earth inferred from petrological observations [Herzberg et al., 2010].

As the estimates of total amount of water (at the surface and in the deep interior) vary from 5-15 ocean masses (OMs) based on magma ocean solidification models to 1.2-3.3 OMs based on petrological models [Nakagawa et al., 2018], different initial values of water are also tested, which show a strong influence on the amount of felsic melts produced. Ongoing work includes incorporating the effect of water on the density and viscosity of mantle minerals and adapting the lithospheric strength with surface topography.

How to cite: Jain, C., Sobolev, S., Sobolev, A., and Vezinet, A.: Thermochemical models of early Earth evolution constrained by geochemical data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9734, https://doi.org/10.5194/egusphere-egu24-9734, 2024.

The radial density of planets increases with depth due to compressibility, leading to impacts on their convective dynamics. To account for these effects, including the presence of a quasi-adiabatic temperature profile and entropy sources due to dissipation, the compressibility is expressed through a dissipation number proportional to the planet's radius and gravity. In Earth's mantle, compressibility effects are moderate, but in large rocky or liquid exoplanets (super-earths), the dissipation number can become very large. We explore the properties of compressible convection when the dissipation number is significant. We start by selecting a simple Murnaghan equation of state that embodies the fundamental properties of condensed matter at planetary conditions. Next, we analyze the characteristics of adiabatic profiles and demonstrate that the ratio between the bottom and top adiabatic temperatures is relatively small and probably less than 2. We examine the marginal stability of compressible mantles and reveal that they can undergo convection with either positive or negative superadiabatic Rayleigh numbers. Lastly, we delve into simulations of convection in 2D Cartesian geometry performed using the exact equations of mechanics, neglecting inertia (infinite Prandtl number case), and examine their consequences for super-earth dynamics.

How to cite: Ricard, Y., Alboussière, T., and Labrosse, S.: Compressible convection in large rocky planets, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9939, https://doi.org/10.5194/egusphere-egu24-9939, 2024.

Plate tectonics is a fundamental framework for understanding the geodynamic processes shaping our planet, including seismicity, volcanism, mountain building, and even the long-term climate system and habitability of our planet. However, how plate tectonics evolved over 4.5 billion years remains a major unanswered question. In this study, we employ dynamically self-consistent three-dimensional thermochemical geodynamic models to simulate plate tectonics evolution with physically realistic parameters. Our results demonstrate that plate tectonics undergoes three main stages due to differing dominant mantle cooling modes. Initially, magmatism dominates surface heat transport, with extrusive volcanism leading to a mobile heat-pipe mode, characterised by a high level of volcanism, large surface heat flux, and highly mobile plates in the first 1.5 billion years. This differs from the "heat-pipe" mode occurring on Jupiter's satellite Io by additionally having plate-like behaviour as well as crustal delamination and lithospheric dripping. As the mantle cools, it transitions to a stable mode where mantle convection patterns and their surface expressions become stable for around 1-2 billion years, followed by a smooth evolution to present-day plate tectonics. Our model matches key observations of the surface heat flux, strain rate, plate velocity, and plate distribution patterns, indicating that the early mobile heat pipe mode plays a crucial role in efficiently extracting heat from the mantle. Magmatic intrusion is also expected to have important effects, which we will examine. This study may provide insights into the Earth's dynamic processes and mantle-atmosphere feedback related to plate tectonics and the dynamic evolution of other terrestrial planets, which ultimately affect the long-term climate system and habitability of our planet.

How to cite: Yan, J. and Tackley, P.: How did plate tectonics evolve? Insights from 3-D spherical thermochemical convection simulations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11554, https://doi.org/10.5194/egusphere-egu24-11554, 2024.

The Earth is the only planet in our Solar System with active plate tectonics. Answering questions such as why plate tectonics started on Earth and which tectonic regime came before are fundamentally important for understanding the evolution of the early Earth. Currently, the most popular answers are (i) before plate tectonics on Earth, there was stagnant lid or plutonic-squishy-lid tectonic regime with no or minor contribution of subduction; (ii) plate tectonics took over when the initially high mantle temperature on Earth dropped by 100-200K due to secular cooling. In this work, we challenge both these statements based on published and new data and models.

Plenty of observations suggest that plate tectonics started on Earth during mid-Archean. At the same time, the numerical models and petrological data on the thermal evolution of the Earth show that mid-Archean was likely the time of the highest temperature of the Earth’s mantle and that significant secular cooling took place later in the Proterozoic. Moreover, previously published and our new thermochemical models also suggest that among all proposed tectonic regimes, only mobile-lid regime (i.e. plate tectonics) can lead to significant cooling of the Earth. Therefore, we conclude that plate tectonics in mid- or early Archean was unlikely to be initiated due to the significant secular cooling of the Earth’s mantle. The existence of no-subduction regimes, such as stagnant-lid or plutonic-squishy-lid, prior to plate tectonics are challenged by the new geochemical data which suggest extensive subduction and continental crust production already in the Hadean and early Archean.

Here we present global geodynamic models of Earth’s evolution computed using StagYY and ASPECT codes in 2D spherical annulus and 3D geometries respectively. StagYY models suggest that during the Hadean and the early Archean, the tectonic regime was oscillating between plume-induced subduction and plutonic-squishy-lid. The mantle temperature remains high during this time, but significant amount of continental crust is produced in these models, which is in agreement with the new geochemical data (melt inclusions from Weltevreden komatiites). After the emergence of continents in the mid- to late Archean, we decrease the effective friction of the oceanic lithosphere in the models to mimic the lubricating effect of continental sediments in subduction channels. This leads to a transition of the tectonic regime from oscillatory to continuous mobile-lid and to an efficient secular cooling of Earth, which is consistent with petrological observations. Being 2D, all plume-induced subduction zones in StagYY models are global. With the preliminary 3D ASPECT models, we show how a number of plume-induced regional subduction zones in early Earth evolve into a global network of plate boundaries and result in plate tectonics.

How to cite: Sobolev, S., Jain, C., and Pons, M.: Why does Earth have plate tectonics and what was before?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12766, https://doi.org/10.5194/egusphere-egu24-12766, 2024.

How to cite: Tian, J. and Tackley, P.: The influence of deep mantle thermal conductivity on the long-term thermal evolution of Earth's mantle and core, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12993, https://doi.org/10.5194/egusphere-egu24-12993, 2024.

Outgassing from the interior is a key process influencing the evolution of the atmospheres of rocky planets. For planets with a stagnant lid tectonic mode, previous models have indicated that increasing planet size very strongly reduces the amount of outgassing, even to zero above a certain planet mass (Dorn et al., A&A 2018). This is because melt is buoyant only above a certain depth, which becomes shallower with increasing planet size (hence "g"); for large enough planets this depth may even lie within the lithosphere, preventing eruption and outgassing.

            However, uncertainties in rheology strongly influence the temperature structure of planets, hence (i) the depth at which melt is generated and (ii) the thickness of the lithosphere. One major uncertainty is the rheology of post-perovskite, which constitutes a large fraction of the mantle in large super-Earths. Ammann et al. (Nature 2010) find that diffusion is anisotropic; it is not clear whether the "upper bound" or "lower bound" is relevant to large-scale deformation, but both result in high viscosity at very high pressures, strongly influencing the radial temperature profile (Tackley et al., Icarus 2013). In contrast, Karato (2011, Icarus) argues that a different mechanism - interstitial diffusion - acts to make viscosity almost independent of pressure and relatively low in the post-perovskite regime.

            Another uncertainty is the reference viscosity (the viscosity at a reference temperature, pressure and stress), as this depends on bulk composition, water content, grain size and other properties. Lower reference viscosity results in thinner lithosphere and crust (e.g., Armann & Tackley, JGR 2012).

            Thus, numerical simulations are performed of the long-term (10 Gyr) thermo-chemical evolution of stagnant-lid planets (coupled mantle and core) with masses between 1 to 10 Earth masses, varying the reference viscosity and the rheology of post-perovskite. The simulations are based on the setup of Tackley et al. (2013 Icarus) with the addition of partial melting and basaltic crustal production, and outgassing of a passive tracer that partitions into the melt and outgasses 100% upon eruption.

            Results indicate that:

• the previously-found trend of lower percentage outgassing with larger planet size is reproduced, but
• outgassing does not fall to zero even in a 10 Earth mass planet. Outgassing of between 15% and 70% is found for 10 Earth mass planets (up to ~100% for Earth mass planets).
• Post-perovskite rheology (interstitial, lower-bound or upper-bound) makes only a minor difference to long-term outgassing, but does influence the timing of outgassing.
• Reference viscosity makes a large difference to outgassing, with lower viscosities leading to substantially larger outgassing percentages.
• Internal heating plays a major role: stagnant-lid planets initially heat up due to low heat transfer efficiency, thinning the lithosphere and producing widespread melting.

How to cite: Tackley, P.: Outgassing on Stagnant-Lid Planets: Influence of Rheology, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13059, https://doi.org/10.5194/egusphere-egu24-13059, 2024.

How to cite: Récalde, N., Davies, J. H., Panton, J., Porcelli, D., and Andersen, M.: Investigating the stability and composition of LLSVP-like material in mantle convection models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13510, https://doi.org/10.5194/egusphere-egu24-13510, 2024.

Plate tectonics is the most prominent surface manifestation of mantle convection in Earth. Current observational results suggest that Earth is the only planet displaying plate tectonics. However, whether plate tectonics has accompanied the entire evolutionary history of Earth is a key question. If not, questions such as when plate tectonics began and what kind of tectonic mode prevailed before plate tectonics, have always been at the forefront and hot topics in the field of Earth science.

In this study, we employed three-dimensional spherical mantle convection numerical simulations to explore various mantle convection modes. Results indicate that, under different parameter frameworks, mantle convection modes can be categorized into five types: I) non-plate active lid convection mode, where the surface exhibits multiple concentrated weak zones, resulting in relatively fragmented plates; II) plate-like mobile lid convection mode, characterized by a higher number of subduction zones and mid-ocean ridges on the surface, which spontaneously form, develop and disappear over time, dividing the surface into about 10 plates; III) episodic plate-like mobile lid convection mode, where the surface experiences plate-like mobile lid mode for most of the time, interspersed with transient surface stagnation; IV) episodic stagnant lid convection mode, characterized by long periods of surface stagnation interspersed with short periods of surface movement with the surface mostly featuring only one subduction zone. V) stagnant lid convection mode, where the surface appears as a single rigid layer.

We mainly analyze the influence of lithospheric strength, i.e., yielding stress, Rayleigh number and internal heat rate on these five mantle convection modes. We can better explain the plate tectonics of the present Earth using mode Ⅱ. Because of the higher internal heat rate, higher mantle temperature and lower mantle viscosity, resulting in a larger Rayleigh number, our research suggests that the early Earth was in mode III or IV. Our results suggest that even if there was some type of plate tectonics in the early Earth, it is different from present plate tectonics. Before the onset of plate tectonics, the Earth might have experienced episodic lid convection. The results hold important scientific significance for understanding the evolution of the Earth's plate tectonics.

How to cite: Xiang, S. and Huang, J.: Mantle convection modes in 3D mantle convection simulations and its implications for the evolution of Earth’s plate tectonics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13588, https://doi.org/10.5194/egusphere-egu24-13588, 2024.

One of the most informative ways of studying the interior structure and geodynamics of terrestrial planets is the joint investigation of gravity and topography data. In the case of Venus, this is in fact one of the only sources of information about the planet's interior, along with estimations of the tidal Love number [1], moment of inertia factor [2], and the absence of an internally generated magnetic field [3].

Early gravity and topography studies that made use of Pioneer Venus and later Magellan data revealed unique properties of Venus's interior. They showed that Venus has a notably higher gravity-topography correlation for long wavelengths compared to Earth and a globally large apparent depth of compensation [4]. Considering these characteristics and analyzing the wavelength-dependent ratio between gravity and topography, the so-called spectral admittance, [5] concluded that the long-wavelength topography of the planet was supported dynamically, i.e., through convection in the mantle.

Since then, several studies have investigated the gravity and topography signature of Venus with the goal of understanding the planet’s interior by constraining geophysical properties of the mantle, such as the mantle viscosity. Some estimated the dynamic geoid contribution from three-dimensional geodynamic simulations [6,7]. Others adopted the analytical viscous flow model by [11] to study the viscosity structure of Venus's mantle [8,9,10]. The main advantage of the latter method is that it is computationally inexpensive, allowing for the performance of inversions. However, it is a simplified model which neglects lateral viscosity variations.

In this study, we estimate the dynamic topography and geoid signatures from the geodynamical models by [12], which include a strongly temperature-dependent viscosity, hence lateral viscosity variations, to evaluate the influence of different parameters such as the increase of viscosity with depth, the presence of viscosity jumps, and the ratio between intrusive and extrusive magmatism. In a second step, we plan to systematically evaluate the influence of lateral viscosity variations on the geoid and topography and thus to quantify the importance of the simplifications adopted in the analytical model.

Our first results show that the increase of viscosity with depth should be no more than 2 orders of magnitude, since larger values strongly decrease the spectral correlation and admittance at long wavelengths which is inconsistent with the observations. In addition, scenarios where extrusive magmatism dominates tend to overestimate the admittance due to the generation of thick thermal lithospheres in excess of 300 km thickness. These results underscore the importance of gravity and topography analyses for deciphering the geodynamical evolution and tectonic style of Venus.

[1] Konopliv and Yoder (1996) GRL, 23; [2] Margot et al. (2021) Nat Astron; [3] Phillips and Russel (1987) JGR, 92; [4] Sjogren et al. (1980) JGR, 85;  [5] Kiefer et al. (1986) GRL, 13; [6] Huang et al. (2013) EPSL, 362; [7] Rolf et al. (2018) Icarus, 313; [8] Pauer et al. (2006) JGR, 111; [9] Steinberger et al. (2010) Icarus, 207; [10] Maia et al. (2023) GRL, 50; [11] Hager & Clayton (1989) Mantle Convection; [12] Plesa et al. (2023) EGU.

How to cite: Maia, J., Plesa, A.-C., Tosi, N., and Wieczorek, M.: Constraining Venus's interior with gravity and topography predictions from geodynamic models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15952, https://doi.org/10.5194/egusphere-egu24-15952, 2024.

So far, most numerical models focused on understanding different aspects of the Earth’s system, such as mantle convection, tectonics, or atmospheric dynamics, have typically adopted a limited perspective constrained to the specific region of interest. Recently, efforts have been made to couple these simulations, enabling them to interact seamlessly with one another. Abstaining from doing so may lead to results that don't accurately represent how the various systems interact.

Achieving the successful integration of the deep carbon cycle and water transport into our mantle dynamics code (StagYY) represents a crucial step towards this goal - a comprehensive, large-scale model of our planet, encompassing phenomena from the Earth's core to the uppermost layers of the atmosphere resulting from a collaborative effort between different research groups. We adopt a thermodynamic approach to quantify the H₂O solubility of important water-carrying minerals within the mantle, with the goal of faithfully coupling geodynamic models and realistic transport/incorporation of water across the silicate part of our planet. The details of the numerical implementation are yet the subject of ongoing discussion; however, several crucial considerations must be thoroughly evaluated. These include the assessment of density variations resulting from water integration into nominally anhydrous minerals, the complex multi-stage degassing process of subducting slabs, and the inclusion of exotic phases that are currently absent from the thermodynamic databases being utilized.

The anticipated effects of a water-bearing mantle on the overarching dynamics are still under investigation. Nevertheless in-gassing, degassing, and the internal transport of water within the mantle exert a direct influence on various aspects. These include the governing viscosity field, the extent of H₂O-induced melting, and atmospheric CO₂ concentrations, among others. If water can, in fact, permeate deep into the mantle, it has the potential to introduce significant deviations in the dynamics of lower mantle convection compared to what current models predict. Furthermore, recent considerations of the stability regime of hydrous phases also point towards interesting implications in the study of water-rich exoplanets as stronger gravity profiles should result in colder geotherms, significantly expanding the thermodynamical stability of water-transporting phases across the P-T parameter space.

Quantifying this process will provide valuable insights for the geodynamic modeling community and help advance our understanding of the deep-Earth system. Furthermore, the distinct chemical exchange dynamics arising from our applications can be investigated further and prove advantageous for the study of exoplanetary atmospheres, especially those around bodies characterized by abundant water, such as water worlds and hycean planets.

How to cite: Moccetti Bardi, N., Tackley, P. J., and Metternich, M. A.: Mantle hydration and implications for Earth and exoplanetary research, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16140, https://doi.org/10.5194/egusphere-egu24-16140, 2024.

Crystallization processes, a partial or complete overturn of the early mantle and other processes can lead to a compositionally stably stratified mantle which may hinder of even prevent convective currents. In the classical view, the layer will be stable if the restoring force, generated by the compositional stratification will exceed the driving force as provided by heating the layer from the core. The situation resembles the diffusive scenario of double diffusive convection, characterized by the fast diffusing component (heat) being the driving force, while the slowly diffusing component (composition) acts as the restoring force. If perturbed, subcritical convection can eventually take plain ce.  While in  pure thermal convection , subcritical flow only develops as localized patterns, in the double diffusive case, a perturbation can lead to a global destabilization (blue sky bifurcation) of the system, due to a sufficient finite  amplitude perturbation. . In this study we have investigated the influence of a finite amplitude perturbation of varying magnitudes , namely realze by an impact on a stably stratified mantle. Numerical experiments in 2- and 3D, cartesian and spherical simulations, based on a Finite Volume scheme  have been conducted to study the evolution of such a system. Key parameters  which characterize the evolution are the (1) initial stratification and the structure f the perturbation. The viscosity structure is a further influencing factor.

The experiments show that an impact into a stably stratified mantle can lead to a global destabilization, giving rise to complex flow patterns, including local and transient layering of the mantle flow. An evolutionary path of a planet from a stably stratified state to a complex layered period and/or to a full convection mode seems sensitive.

How to cite: Hansen, U. and Dude, S.: Spontaneous destabilization of a compositionally stably stratified mantle in the Early Earth, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16401, https://doi.org/10.5194/egusphere-egu24-16401, 2024.

We present a numerical model of a cooling magma ocean (MO) and the atmosphere degassing from it. The solidification of the MO leads to the enrichment of the silicate melt in volatiles, thus favoring degassing. Both reservoirs interact via heat and volatile exchange, where the volatiles are H2O and CO2. The aim of this model is to explore the influence of the atmosphere on the surface conditions after the MO stage, and especially the conditions required for the condensation of a water ocean to occur. For example, for an early Earth at 1 AU initially containing 1 Earth's water ocean mass, a water ocean could form for initial CO2 content as large as 1,000 bars. Moreover, a tenth of the actual Earth's water ocean mass would be sufficient to generate a water ocean on early Venus. Liquid water could also be present on the surface of the two exoplanets Trappist-1e and 1f. Comparing our results with other recent models, we discuss the relative influence of the model hypotheses, such as mantle composition, the treatment of the heat transfer in the atmosphere, and the treatment of the last stages of the MO solidification.

How to cite: Massol, H., Davaille, A., Sarda, P., and Delpech, G.: Early formation of a water ocean as a function of initial CO2 and H2O contents in a solidifying rocky planet, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16653, https://doi.org/10.5194/egusphere-egu24-16653, 2024.

 New high-pressure, high-temperature layered partial melting experiments have been performed to simulate the interaction between the last stage, dense Fe-Ti-rich cumulate layer that remained after about 99.5% crystallization of the lunar magma ocean (LMO), and the underlying solidified Mg-rich mantle. For this, a synthetic assemblage of an upper Fe-Ti-rich cumulate layer (6.1 wt.% TiO₂ and 39.7 wt.% FeO) and a lower forsteritic olivine layer (Mg# = 92.8) has been taken in 1:4 weight ratio, respectively, and subjected to experiments at pressures ranging between 1 to 3 GPa and temperatures varying between 1100 ⁰C and 1525 ⁰C using a piston cylinder apparatus. In the top cumulate layer, phases such as Fe-rich clinopyroxene, Fe-poor clinopyroxene, pigeonite, orthopyroxene, rutile, ilmenite, quartz and melt were formed, depending upon different P-T conditions. The Fe-Ti-rich basaltic melts (5-18.5 wt.% TiO₂, 13-28.6 wt.% FeO, and 35-59 wt.% SiO₂) produced in this cumulate layer at different degrees of partial melting approach the lunar mare basalts in their compositions and can be used to explain the huge variation in TiO₂ enrichment that is observed in lunar basalts (between 0 to ~17 wt. %). Following LMO crystallization, the last stage dense mineral-melt cumulate layer is expected to undergo a gravitational overturn due to density instability. This work aims to simulate the partial melting of the cumulates in this layer as a result of the overturn. The consequent compositional heterogeneity of the lunar mantle is used to justify the observed variation in Ti-rich basalt compositions on the lunar surface. The basaltic melts produced in these experiments are mostly Al, Mg-poor compared to available lunar basalt samples. However, this deficiency may be addressed by assimilation of these melts into low-Ti, Mg-rich basalt magmas that would have subsequently erupted from the underlying mantle. Simulations of such assimilation using thermodynamic modelling have also been done and the results support this theory. The possible fate of the last stage melt of the LMO has thus been studied and used to understand the variable compositions of lunar basalts.

How to cite: Moitra, H., Ghosh, S., Mukherjee, T., and Gupta, S.: Understanding the variability in the titanium contents of lunar basalts using high-pressure, high-temperature layered partial melting experiments and thermodynamic modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17525, https://doi.org/10.5194/egusphere-egu24-17525, 2024.

The InSight mission's SEIS instrument has provided a unique opportunity to probe the deep interior of Mars. This seismic exploration of the Martian interior has emerged as a promising avenue for revealing the enigmatic geophysical properties and dynamic processes within the planet's mantle.

In this study, we present an analysis of the seismic signature of marsquakes which transit deep into the mantle, providing crucial information on the seismic velocity profile and potential heterogeneities. The quakes show a characteristic late emergence of the first energy at higher frequencies which can be analysed as due to the scattering of seismic energy as it transits the mantle. From this we are able to quantify the size distribution of the mantle's small-scale heterogeneity as well as to constrain the rheological properties and convective vigor of the Martian mantle.

As unlike Earth, Mars has sealed its mantle contents under a stagnant lid, we use our observations to provide evidence about the early stages of planetary formation and differentiation on Mars. Our findings contribute to the better understanding of the Martian mantle's geodynamics and allow a comparative assessment of the evolution of planetary interiors that likely apply to other planets that lack plate tectonics.

How to cite: Charalambous, C., Pike, T., Fernando, B., Samuel, H., Bill, C., Lognonné, P., and Banerdt, B.: Small-scale Structure of the Martian Mantle, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17640, https://doi.org/10.5194/egusphere-egu24-17640, 2024.

Geodynamic modelling is increasingly dependent on the initial conditions. Non-steady-state planetary evolution models are complex enough that several solutions can be achieved with small variations in the initial temperature, composition, etc. Models of magma ocean evolution predict an overturn of a layer enriched in iron and incompatible elements. The absence of this layer in any tomographic inversion of the Earth suggests that our models of magma ocean evolution are missing key phenomena. Since these models are the basis for the initial conditions of Earth-applied geodynamic planetary models, there is an urgency to find the origin of the discrepancies between our idea of magma ocean crystallization and the current state of the Earth.

To advance our understanding of the consequences of magma ocean crystallization, we carry out high resolution models of mantle flow coupled with (1D) magma ocean evolution (including melting and crystallization processes). We allow two different forms of topography to arise with a sticky air (sticky magma ocean) approximation: dynamic topography and thermodynamic topography. We explore how different equilibration times affect melt segregation and magma ocean composition, as well as how crystal settling influences solid state convection and differentiation. We calculate, as well, chemical exchange between the solid and liquid parts of our model by expanding on previous work, studying different equilibrium constants and allowing the system to self-regulate.

Preliminary results suggest a competition effect between the two forms of topography mentioned above. This competition implies that the equilibrium constant of chemical exchange, as well as melting segregation speed and crystal growth and settling, will have an essential role in the equilibration between the solid mantle and the liquid magma ocean. This and other results have implications for Earth, but also for other discovered magma oceans such as those on the Moon, Mars or even exoplanets.

How to cite: Manjon Cabeza Cordoba, A., Ballmer, M. D., and Shorttle, O.: Melting and Remelting in a Crystallizing Magma Ocean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19267, https://doi.org/10.5194/egusphere-egu24-19267, 2024.

The origin of the martian crustal dichotomy is a long-standing mystery since its discovery in the Mariner 9 era. Among various proposed hypotheses, a single giant impact origin (i.e. the Borealis impact) is the most well known, and the most studied. However, studies that include realistic impact models often adapt a simplified geological and geophysical model for predicting the final crustal distribution, while long-term mantle convection studies have mostly employed an over-simplified parametrization of the impact. Here we use a coupled SPH-thermochemical approach to first simulate an impact event, and then use the result of this realistic model as the initial condition for the long-term mantle convection model. We demonstrate that a giant impact collision results in a mantle-deep magma pond, which upon crystallisation leads to a thicker crust production on the impacted hemisphere. In other words, an impact-origin of Mars's southern highlands requires the giant impact to occur in the southern hemisphere. We find that both the impact scenario and the mantle properties affect the geometry of the impact-induced crust ("highlands'') and the subsequent state of the interior, and that the formation of "highlands'' extends beyond the initial magma pond.  We show that a near head-on (15^o from the normal) impact event with impactor radius of 750 km, together with a mantle viscosity of 10²⁰ Pa s, can best reproduce the southern highlands of Mars with a geometry similar to that of present-day observations.

How to cite: Cheng, K. W., Ballantyne, H., Golabek, G., Jutzi, M., Rozel, A., and Tackley, P.: Combined impact and interior evolution models in three dimensions indicate a southern impact origin of the Martian Dichotomy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22090, https://doi.org/10.5194/egusphere-egu24-22090, 2024.

In this study, we use the Direct Simulation Monte Carlo (DSMC) method [1] to investigate the collisional fraction of the atmospheres of Europa, Ganymede, and Callisto. The extent of the collisional atmosphere of the icy moons is still subject to ongoing debate. While Europa’s atmosphere is tenuous and effectively collisionless, the exobase for Ganymede and Callisto is expected to be located above a thin collision-dominated atmospheric layer [2].

In the 2030s, both ESA's Jupiter Icy Moons Explorer (JUICE) and NASA's Europa Clipper mission are set to explore Jupiter's icy moons from up close, using high-resolution mass spectrometers to sample their atmospheres. The Neutral gas and Ion Mass spectrometer (NIM) of the Particle Environment Package (PEP) onboard JUICE [3] and the MAss Spectrometer for Planetary EXploration (MASPEX) onboard Europa Clipper [4] will determine the atmospheric composition of the moons and potentially sample plume material on Europa. The collisional fraction of their atmospheres affects the abundances of the various species that will be measured, and hence also the deduction of the underlying surface composition. Therefore, obtaining a comprehensive understanding of atmospheric structures, including the collisional fraction, is imperative for both missions. This knowledge is essential to ensure the correct interpretation of the measured data once it becomes available.

The DSMC method is a computation technique, where rarefied gas flows are simulated by tracking the motion of individual particles, including their collisions and interactions, to provide insight into the macroscopic gas dynamics. Therefore, this method is ideal for studying thin atmospheres that transition from being collisional near the surface to ballistic at higher altitudes, such as the atmospheres of the icy Galilean moons. The model [5, 6] used herein includes different physical and chemical processes that create the atmospheres of the icy moons, such as sputtering due to interactions with Jupiter's magnetosphere, the sublimation of surface ice, and photochemical reactions.

[1] Bird, G. A. (1994). Molecular gas dynamics and the direct simulation of gas flows.
[2] Schlarmann, L., et al. (2024), in preparation.
[3] Grasset, O., et al. (2013). Planetary and Space Science, 78, 1-21.
[4] Phillips, C. B., and Pappalardo, R. T. (2014). Eos, Transactions AGU, 95(20), 165-167.
[5] Carberry Mogan, S. R., et al. (2021). Icarus, 368, 114597.
[6] Carberry Mogan, S. R., et al. (2022). Journal of Geophysical Research: Planets, 127(11).

How to cite: Schlarmann, L., Vorburger, A., Carberry Mogan, S. R., and Wurz, P.: Exploring the Collisionality of the Icy Galilean Moon Atmospheres., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-352, https://doi.org/10.5194/egusphere-egu24-352, 2024.

Characterizing Europa’s subsurface ocean is critical to assessing Europa’s habitability. Measurements of the magnetic field induced in the conducting Europan ocean in response to Jupiter’s magnetosphere is a proven technique that has successfully demonstrated the existence of subsurface oceans at Io (magma), Europa, and Callisto. In the case of Europa, the dynamic, magnetized plasma flow in the Jovian magnetosphere causes strong magnetic perturbations comparable to those of the induced field strength. Thus, accurate characterization of the ocean by magnetic sounding requires an accurate characterization of the plasma properties. The Plasma Instrument for Magnetic Sounding (PIMS) will launch on the Europa Clipper mission in October 2024 onboard a Falcon Heavy rocket and will measure the plasma properties in Jupiter’s magnetosphere and in Europa’s tenuous atmosphere. PIMS measurements will advance our understanding of the Jovian environment near Europa’s orbit and the interaction of Europa’s atmosphere and surface with Jupiter’s plasma and magnetic field. These scientific advances will, in turn, improve modeling efforts that will ultimately enable a highly accurate separation of the magnetic field due to induction in Europa’s interior from the highly variable magnetic perturbations due to the plasma interactions exterior to Europa. Thus, PIMS will enable the full potential of the induction technique in probing Europa’s interior to be realized, and will help constrain the average thickness of the ice shell and average thickness and salinity of the ocean, as well as characterize the composition and sources of the plasma and volatiles. In this presentation we will overview the PIMS instrument and its final calibration before it was integrated onto the spacecraft.

How to cite: Luspay-Kuti, A. and the The PIMS Science and Engineering team: The Plasma Instrument for Magnetic Sounding (PIMS): Measuring the Plasma Influence on Magnetic Induction on the Europa Clipper mission  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1266, https://doi.org/10.5194/egusphere-egu24-1266, 2024.

One of the most important realizations that planetary scientists have come to in the last 20 years is that in the search for potential habitability in our solar system, the focus need not only be on planetary bodies close to the Sun, where water on the surface is in liquid state. Based on Galileo and Cassini observations in the Jupiter and Saturn systems, there are many potential places in our solar system where sub-surface liquid water oceans may exist.

JUICE magnetometer (J-MAG) measurements (such as those made by the magnetometers on the Galileo and Cassini spacecraft) enable an understanding to be gained of the interior structure of the icy moons of Jupiter, specifically those of Ganymede, Callisto and Europa. Of particular interest are knowledge of the depth at which the liquid oceans reside beneath their icy surfaces, the strength of any internal magnetic fields such as at Ganymede and the strength of any induced magnetic fields arising within these oceans.

The primary science objectives of JUICE which will be constrained by the magnetic field observations and which drove the performance requirements of the J-MAG instrument include:

• At Ganymede:
• Characterization of the extent of the ocean and its relation to the deeper interior
• Characterization of the ice shell
• Characterization of the local environment and its interactions with the Jovian magnetosphere
• Description of the deep interior and magnetic field generation
• At Europa, further constrain the depth of the liquid ocean and its conductivity
• At Callisto, characterize the outer shells, including the ocean

How to cite: Dougherty, M.: Using magnetic field observations from the Galilean moons to diagnose ocean properties, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1416, https://doi.org/10.5194/egusphere-egu24-1416, 2024.

JUICE is an ESA L-Class interplanetary mission to the Jupiter system that was launched on the 14th April 2023 from Kourou, French Guiana. It will make in-situ and remote sensing measurements of Jupiter and the Galilean moons during a three-year science operation phase starting in July 2031. The tour will include a high-latitude phase, fly-bys of Callisto and Europa culminating in elliptical and circular orbits of Ganymede down to an altitude of 200 km. Detection and characterization of potential sub-surface oceans on Europa and Ganymede are a key science goal of the mission as is the interaction between Ganymede’s internal magnetic field with the Jovian field.  Constraining the depth and conductivity of any subsurface ocean on Ganymede will be achieved through measurement of response to two magnetic inducing signals, one at Ganymede’s orbital period (171.7 hrs) and the other at Jupiter’s synodic period (10.5 hrs) which together drive a requirement for in-flight accuracy of 0.2nT. The combination of such low frequency and low amplitude scientific signals places a unique set of EMC cleanliness requirements on the spacecraft system and on the performance of the instrument configuration.

J-MAG is the DC magnetometer instrument on JUICE measuring the low frequency magnetic field vector in the range [0-64 Hz]. It is composed of a conventional dual fluxgate design together with a Coupled Dark State Magnetometer (CDSM) absolute scalar sensor and an electronics box accommodated within a vault on the main platform. All three sensors are mounted on the outer segment of a 10.6 m boom. The scalar sensor is included to enable calibration of the fluxgate sensors during the Ganymede phase where the magnetic field is highly variable and traditional techniques for fluxgate offset calibration (such as spacecraft rolls or analysis of incompressible waves in the solar wind) are not viable.  

We report on the instrument design and challenges presented by the mission environment and trajectory. We will present the performance of the magnetometer on ground and a summary of the initial results from the near-Earth commissioning phase that took place during May 2023.

How to cite: Brown, P. and the The J-MAG Instrument Team: The J-MAG Magnetometer: Instrument design, performance, and initial in-flight results., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1750, https://doi.org/10.5194/egusphere-egu24-1750, 2024.

The interiors of the icy moons of Jupiter hold a key to understanding habitability in the Solar System and beyond. They could serve as prototypes to comprehend similar bodies that might have the potential to sustain life. The magnetic field observations from the Galileo mission between 1996 and 2003 suggest large oceans below the icy crusts of Europa and Callisto and a probable subsurface ocean at Ganymede. It also discovered that Ganymede has an intrinsic magnetic field and a dynamic magnetosphere.

NASA’s Europa Clipper and ESA’s Jupiter ICy moons Explorer (JUICE) missions have been designed to better understand and characterise these icy moons. They aim to confirm the existence of a subsurface ocean at the three moons, in particular, Ganymede and Europa, and constrain their internal structure. The missions would also explore the magnetosphere of Jupiter and its interactions within the Jovian system. Ganymede is the largest moon of our Solar System, capable of producing its own dynamo field and possibly possessing an ocean beneath its surface. However, separating the intrinsic field from the induced field is a difficult problem. Galileo measurements provided two models for Ganymede’s overall internal field- a dipole and quadrupole model or a dipole and induction model. Both the quadrupole and induction signals are quite small and well represent the observations together with the dipole field.

Latest trajectory information for Europa Clipper assuming an October 2024 launch, and the predicted JUICE trajectory following the successful launch in April 2023 show initial close Ganymede flybys. In this study, we use them to understand their trajectories and highlight their importance in confirming the induced signal and thereby the ocean as well as for modelling the dynamo field. The first 2 Clipper and the first 3 JUICE flybys occur within an altitude of 500 km from Ganymede’s surface and are hence useful for overall internal field modelling. We predict the measurements that would be observed from the two internal sources as well as the external magnetospheric source to better understand the signals and decipher their differences. For the intrinsic and external fields, we use dynamo and magnetohydrodynamic models respectively while for the induced field, we use Jupiter’s background field along with the induction equation at the spacecraft locations.

The 5 flybys independently as well as together with the data from the Galileo flybys would enhance our understanding of the different magnetic sources at Ganymede and the fields they produce. These joint early flyby observations will enable us to be better equipped to model the magnetic field components near Ganymede in the orbital phase of the JUICE mission.

How to cite: Sharan, S., Bunce, E., Dougherty, M., Jia, X., and Kivelson, M.: Understanding the interior magnetic fields of Ganymede using flybys of the Europa Clipper and JUICE missions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2170, https://doi.org/10.5194/egusphere-egu24-2170, 2024.

Under low pressure and temperature, most rocks have extremely low electrical conductivities (< 10^-9 S/m) which rise dramatically at temperatures encountered in deep interiors of solid bodies. The presence of ferric iron (Fe³⁺), whose abundance is related to the oxygen fugacity of the rock, lowers the activation energy of conduction and enhances rock conductivity further. Most models of the interior of Europa are consistent with the presence of a highly-conducting metallic iron core with a radius between 200 and 700 km (e.g., Kuskov and Kronrod, 2005). Thus, the mantle and the core of Europa are likely highly conducting and are expected to create measurable induction response. Accounting for this deep conductivity would not only improve the modeling of the physical parameters of the ocean but help further constrain the properties of Europa’s deeper interior.

Since the discovery of induction response from Europa’s ocean (Khurana et al., 1998), numerous studies have reexamined the electromagnetic induction signatures obtained by the Galileo spacecraft using increasingly sophisticated techniques to model the induction field and the moon/plasma interaction field (see e.g. Zimmer et al. 2000; Schilling et al. 2007; Vance et al. 2021). However, these studies have ignored the effect of induction from the deeper interior. Also, no studies have been performed for lower conductivities of the ocean and for longer period waves (such as the orbital period of Europa = 85.2 h) which can probe deeper even through a highly conducting ocean.

To address this problem, we have used the recursive method of Srivastava (1966) for a multiple layer model of Europa’s deep interior. The results from this preliminary exploration show that for a range of core radii and mantle conductivities, the deeper interior modifies the signal from the ocean by several nT at the two primary frequencies. The 85.2 h period penetrates through the ocean and elicits increasing response from the deep mantle as its conductivity is increased (from generation of stronger eddy currents). The 11.1 h period on the other hand produces a weaker response  with increasing mantle conductivity because the eddy currents are already at their highest level (100% induction from the ocean) but begin to follow a deeper path through the mantle and thus their magnetic response at the surface appears weaker.

Khurana, K.K., M.G. Kivelson, D. J. Stevenson, and others (1998) Induced magnetic fields as evidence for subsurface oceans in Europa and Callisto, Nature, 395, 777-780.

Kuskov O.L. and V.A. Kronrod (2005) Internal structure of Europa and Callisto, Icarus, 177, 550-569.

Srivastava, S.P. (1966) Theory of the magnetotelluric method for a spherical conductor, Geophys. J. Roy. Astro. Soc. 11, 373-387.

Vance, S. D., Styczinski, M. J., Bills, B. G., Cochrane, C. J., Soderlund, K. M., Gomez-Perez, N., & Paty, C. (2021). Magnetic induction responses of Jupiter's ocean moons including effects from adiabatic convection. J. Geophys. Res. : Planets, 126, e2020JE006418.

Zimmer, C., K.K. Khurana, and M.G. Kivelson (2000) Subsurface oceans on Europa and Callisto:  Constraints from Galileo magnetometer observations, Icarus, 147, 329.

How to cite: Khurana, K., Cao, H., and Stixrude, L.: The Impact of Europa’s Deep Interior on the Electromagnetic Induction Signal from Europa’s Ocean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4522, https://doi.org/10.5194/egusphere-egu24-4522, 2024.

With its subsurface ocean, Europa raises intriguing possibilities about the potential for extraterrestrial life beneath its icy crust. Its unique surface features present a dynamic and complex geophysical landscape that offers valuable insights into its evolution. This study explores the plume dynamics and deposition of icy dust particles on Europa. Utilizing a Direct Simulation Monte Carlo (DSMC) modeling of Europa's gaseous plumes, we use a hybrid model to understand dust dynamics entrained in the plumes. This approach allows us to consider various parameters such as production rate, initial velocity of gas and dust, and size distribution of dust particles, providing a comprehensive view of plume dynamics and highlighting their impact on Europa's surface characteristics. The results showing distinct plume morphologies and dust deposition patterns offer clues to our understanding of Europa's ongoing geological activity and subsurface ocean.

How to cite: Tseng, W.-L., Lai, I.-L., Ip, W.-H., Hsu, H.-W., and Tzeng, Y.-S.: Surface Deposition of Icy Dust Entrained in Europa’s Plumes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4968, https://doi.org/10.5194/egusphere-egu24-4968, 2024.

Volcanic activity at Europa’s seafloor is one of the key questions regarding the habitability of its subsurface ocean. The suitable conditions for hydrothermalism on Europa’s seafloor are conditioned by the heat released from the underlying silicate mantle, supplied by both radiogenic and tidal heating. The orbital resonance between Io, Europa, and Ganymede forces their orbit and maintains non-zero eccentricities. Tidal heating due to eccentricity tides on Io is so extreme that it  produces intense volcanism.  Even though tidal heating  in Europa’s silicate mantle is expected to be much weaker than on Io due to its greater distance to Jupiter,   Běhounková et al. [1] showed that it may still be sufficient to maintain Europa’s mantle in a partially molten state  for several tens to hundred millions of years, particularly during periods of increased eccentricity. Due to inefficient melt transport through the thick lithosphere of Europa [2], melt produced during periods of enhanced eccentricity may accumulate and in turn affect the tidal heating, as it is the case for Io, implying a possible runaway melt process in the silicate interior of Europa.

In this context, the goal of this study is to evaluate the effect of melt accumulation on the tidal heat production of Europa’s silicate mantle. For that purpose, we follow the approach developed to model the solid tides in Io’s partially molten interior [3], taking into account the effect of melt on the viscoelastic properties of the mantle. We adapt it to the context of Europa, corresponding to a deeper and thinner asthenosphere than on Io. We show that, whatever the partially molten layer thickness, melt accumulation increases tidal heat production and tidal dissipation even exceeds radiogenic heating. For equivalent volume of accumulated melt, the thinner the layer, the more pronounced this effect is. Our results show that the accumulation of melt, over timescales consistent with the 3D model prediction of Běhounková et al. [1], may significantly affect the tidal dissipation amplitude and its pattern. The potential presence of such melt accumulations may be tested by future measurements by Europa Clipper and JUICE from the combined analysis of gravimetric, altimetric and magnetic data, which might reveal long-wavelength anomalies which could be confronted to our model prediction.

[1] Běhounková et al., GRL, 48(3), e2020GL090077 (2021),  [2] Bland and Elder, GRL, 49(5), e2021GL096939 (2022). [3] Kervazo et al., A&A, 650, A72 (2021)

How to cite: Kervazo, M., Tobie, G., Behounkova, M., Dumoulin, C., and Choblet, G.: Impact of melt accumulation on tidal heat production in Europa’s mantle, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6113, https://doi.org/10.5194/egusphere-egu24-6113, 2024.

Launched in April, 2023, ESA’s JUpiter ICy moons Explorer (JUICE) is en route to the Jupiter system. Upon arrival in 2031, the spacecraft will orbit Jupiter for 3.5 years, making 35 total encounters with Ganymede, Europa, and Callisto, before going into orbit about Ganymede for 1 year.  NASA’s Europa Clipper is scheduled to launch in October 2024, and arrives in the Jupiter system in 2030, a year before JUICE. Orbiting Jupiter, the Clipper spacecraft will spend a year in the system before focusing on ~52 flybys of Europa during a nominal four-year primary mission phase, while also making multiple serendipitous flybys of Ganymede and Callisto. Having two highly instrumented spacecraft in close proximity in time and space affords unprecedented opportunities for synergistic observations of Europa, Ganymede, Callisto, Io, Jupiter’s atmosphere, magnetosphere and environment, and Jupiter’s small satellites and rings, as well as opportunities for unique heliospheric and magnetosphere science during the JUICE and Clipper missions’ cruise and Jupiter-approach phases.

Analysis of potential joint science opportunities is underway by a small team of scientists from the JUICE and Clipper mission teams. Ideas have been collated from JCSC members as well as from three joint Clipper-JUICE workshops (2018, 2019, 2022), and the Science Traceability Matrix from a prior joint ESA-NASA study, the Europa Jupiter System Mission (EJSM). We recently produced a report on science that can be accomplished during the two spacecrafts’ cruise and Jupiter approach phases (Bunce et al., this meeting), and are now investigating potential opportunities once JUICE and Clipper are in orbit around Jupiter. Multiple opportunities exist for joint science at several different targets within the Jovian system, including two opportunities near Europa where the spacecraft are within 0.5Rj of each other and only a few hours apart. Scientific objectives may fall into one or more categories: (1) time dependent, in which both spacecraft must acquire data at same time, or one spacecraft’s observations inform the other’s observations; (2) space dependent, in which each spacecraft acquires data from specific parts of the Jovian system, or both observe the same target with similar, or different viewing geometries; and (3) an increase in science data (e.g. temporal or spatial coverage) made possible due to the availability of additional instrument types or data collection opportunities.

There are currently no firm commitments from NASA or ESA to accomplish science beyond that of each mission’s primary science objectives. However, discussions are ongoing and we are optimistic that our recommendations for the unprecedented opportunities afforded by the two missions’ alignment will enable funding support to be found. In this paper, we discuss some of the potential combined science from JUICE and Clipper that could further enhance understanding of the of the Jupiter system and the origin and habitability of the Galilean moons.

How to cite: Prockter, L., Bunce, E., and Choukroun, M. and the JUICE-Clipper Steering Committee: Exploring the Jupiter System through unique joint JUICE and Europa Clipper observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6262, https://doi.org/10.5194/egusphere-egu24-6262, 2024.

On 14 April 2023, the JUpiter ICy moons Explorer (JUICE) of ESA was launched from Europe's Spaceport in French Guiana. It will arrive at Jupiter and its moons in July 2031. Here we describe how JUICE will investigate the interior of the three icy Galilean moons, Ganymede, Callisto and Europa. Best insights into their interior, such as from an induced magnetic field, tides, rotation variations, and radar reflections, will be obtained during close flybys of the moons with altitudes of about 1000 km or less and during the Ganymede orbital phase at an average altitude of about 500 km and less. The 9-month long orbital phase around Ganymede, the first of its kind around another moon than our moon, will allow an unprecedented and detailed insight into the moon’s interior, from the central regions where a magnetic field is generated to the internal ocean and outer ice shell. Multiple flybys of Callisto will constrain the density structure, clarify the differences in evolution compared to Ganymede and will provide key constraints on the origin and early evolution of the Jupiter system. JUICE will visit Europa only during two close flybys and will perform geophysical investigations on selected areas, complementary to those performed by Europa Clipper.

We emphasize the synergistic aspects of the different geophysical investigations, showing how different instruments will work together to probe the hydrosphere, internal differentiation, dynamics, and evolution of these icy moons. In situ measurements and remote sensing observations will support the geophysical instruments to achieve these goals by providing complementary information about tectonics, potential plumes, surface composition, and exchange processes between ocean, ice and surface. Additional insight into the dissipative processes in the Jupiter system will be provided by accurate tracking of the JUICE spacecraft.

How to cite: Van Hoolst, T., Tobie, G., and Vallat, C. and the JUICE WG1 SSR: Investigating the interior of Ganymede, Callisto and Europa with JUICE, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6318, https://doi.org/10.5194/egusphere-egu24-6318, 2024.

At the beginning of the next decade, the Europa Clipper Flight System will enter orbit around Jupiter and, over a four-year period, will fly by Europa nearly 50 times to explore the habitability of this planet’s moon Europa. The Flight System comprises (1) the Propulsion Module, which provides the thermally-controlled spacecraft structure, propulsion subsystem, and solar array; (2) the Avionics Module, which enables spacecraft guidance, navigation, and control operations, provides power conditioning and computer resources which stores and prioritizes science data for downlink; (3) the Radio-Frequency Module, which provides telemetry uplink and science data downlink capabilities; and (4) a highly capable suite of remote-sensing and in-situ instruments to achieve the science objectives of the mission. The remote sensing payload consists of the Europa Ultraviolet Spectrograph (Europa-UVS), the Europa Imaging System (EIS), the Mapping Imaging Spectrometer for Europa (MISE), the Europa Thermal Imaging System (E-THEMIS), and the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON). The in-situ instruments comprise the Europa Clipper Magnetometer (ECM), the Plasma Instrument for Magnetic Sounding (PIMS), the SUrface Dust Analyzer (SUDA), and the MAss Spectrometer for Planetary Exploration (MASPEX). Gravity and radio science will be achieved using the spacecraft's telecommunication system, and valuable scientific data will be acquired by the spacecraft’s radiation monitoring system. The mission is presently in the assembly, testing, and launch operations (ATLO) phase. The Propulsion and RF Modules have been delivered from the Johns Hopkins Applied Physics Laboratory (APL) to the Jet Propulsion Laboratory (JPL). The flight system integration and environmental testing has been completed at the Jet Propulsion Laboratory. The flight system is presently undergoing a series of operations tests. In May 2024, it will be shipped to Kennedy Space Center, where it will be integrated with the solar array, which was delivered to the location earlier this year. The launch period begins on 10 October 2024, and once lifted off, the Europa Clipper will be cruising to the Jupiter System with gravity assists by Mars followed by Earth on the way. Go Europa Clipper!

How to cite: Korth, H., Pappalardo, R., and Buratti, B. and the Europa Clipper Flight System Engineering Team: The Europa Clipper Flight System on its Path to Launch , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6577, https://doi.org/10.5194/egusphere-egu24-6577, 2024.

Recent JWST observations reveal a higher abundance of endogenic CO₂ at Tara Regio, a prominent leading hemisphere chaos (Villanueva et al., 2023; Trumbo and Brown, 2023). Prior findings from Keck also show an excess of H₂O₂ in the same region (Trumbo et al., 2019). Could the emplacement of the ocean-derived CO₂ onto Europa’s surface influence radiolytic chemistry to boost peroxide yields in these enigmatic chaos regions? Increased H₂O₂ at fractured chaos terrains where ocean-surface exchange is more likely is exciting from a habitability stance, as it may facilitate oxidant delivery to the subsurface ocean.

We present laboratory results that show H₂O₂ synthesis increases by 2-3 folds in the presence of trace amounts of CO₂ (< 3 %) when compared to radiolysis of pure water ice. We also discuss correlations between CO₂ and H₂O₂ abundances in the JWST datasets to determine whether Europa’s endogenous CO₂ indeed conspires to inflate H₂O₂ at Tara Regio and possibly other chaos terrains. These JWST observations combined with emerging laboratory measurements set the stage for detailed mapping of CO₂ (via its 2.7 and ~4.23-4.29 µm absorptions) and H₂O₂ (via its 3.5 µm absorption) with MISE (Europa Clipper) and MAJIS (JUICE) at unprecedented spatial resolution.

References:

• Villanueva, G. L. et al., (2023) Science, 381, 1305–1308 
• Trumbo, S. K and Brown, M. E. (2023) Science, 381, 1308–1311
• Trumbo, S. K. et al. (2019) Astronomical Journal, 158, 127

How to cite: Raut, U., Protopapa, S., Mamo, B. D., Villanueva, G., Cartwright, R. J., Teolis, B. D., Retherford, K. D., and Blaney, D. L.: Can endogenic CO2 inflate radiolytic H2O2 in Europa’s Chaos?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6579, https://doi.org/10.5194/egusphere-egu24-6579, 2024.

The MAss Spectrometer for Planetary EXploration (MASPEX) is a multi-bounce time-of-flight neutral gas mass spectrometer with unprecedented spaceborne mass resolution and sensitivity. It is capable of measuring and identifying minor and trace gases requiring mass resolution of m/Δm ~ 25,000 at abundances of parts-per-million in Europa’s exosphere. Exospheric sources of gases include exsolved, sublimed, sputtered, and radiolytically produced volatiles from Europa’s surface and interior. These gases can be used to characterize surface composition and identify volatiles outgassed from Europa’s interior. Of particular relevance in characterizing Europa’s habitability are the ratios of organic compounds such as alkanes, alkenes, alkynes, alcohols, ethers, aldehydes, amides, amines, and nitriles that undergo chemical transformations, which can be used to determine oxidation states, pH, temperature, and free energy availability of an interior ocean, perched lake, or a gas source region in the ice shell (e.g., a diapir).

This paper presents: 1) the principles and ground-calibrated performance of the MASPEX instrument that is now integrated onto the Europa Clipper spacecraft and planned to be launched in October of 2024, 2) the planned scientific investigation and its critical role in the study of Europa’s habitability, 3) the operational plans, and 4) the anticipated data products from the MASPEX investigation. The paper will also discuss the complexity of the investigation and its requisite need for the acquisition of supporting geochemical, impact fragmentation, and sputtering/radiolytic data sets that help to characterize the geochemical reaction framework and the anticipated modification of chemical species due to impacts with the instrument’s thermalizing chamber, and from radiolysis and sputtering. In the latter context we present the science team’s efforts to generate the necessary data sets, and we encourage interested scientists to contribute to this important endeavor, which is essential for the maximum success of the MASPEX investigation.

How to cite: Waite, J. H., Burch, J. L., Brockwell, T., Young, D. T., Miller, K., Glein, C. R., Wyrick, D. Y., Teolis, B. D., Bolton, S. J., Choukroun, M., McGrath, M. A., McKinnon, W. B., Mousis, O., Sephton, M. A., Shock, E., Zolotov, M. Y., Persyn, S. C., Stone, J. M., Perryman, R., and Ray, C. and the MASPEX Science and Instrument Teams: The Europa Clipper MASPEX Investigation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6809, https://doi.org/10.5194/egusphere-egu24-6809, 2024.

The ionospheres of Jupiter’s icy moons have been observed by in situ plasma measurements and radio occultation. However, their spatial structures have not yet been fully characterized. To address this issue, we developed a new ray tracing method for modeling the radio occultation of the ionospheres using Jovian auroral radio sources. Applying our method to radio observations with the Galileo spacecraft, we derived the electron density of the ionosphere of Ganymede and Callisto. For Ganymede’s ionosphere, we found that the maximum electron density on the surface was 150 cm^-3 in the open magnetic field line regions and 12.5 cm^-3 in the closed magnetic field line region during the Galileo Ganymede 01 flyby. The difference in the electron density distribution was correlated with the accessibility of Jovian magnetospheric plasma to the atmosphere and surface of the moons. These results indicated that electron impact ionization of the Ganymede exosphere and sputtering of the surface water ice were effective for the producing Ganymede’s ionosphere. For Callisto’s ionosphere, we found that the densities were 350 cm^-3 and 12.5 cm^-3 on the night-side hemisphere during Callisto 09 and 30 flybys, respectively. These results combined with previous observations indicated that atmospheric production through sublimation controlled the ionospheric density of Callisto. This method is also applicable to upcoming Jovian radio observation data from the Jupiter Icy Moon Explorer, JUICE. 

How to cite: Yasuda, R., Kimura, T., Cecconi, B., Misawa, H., Tsuchiya, F., Kasaba, Y., Satoh, S., Sakai, S., and Louis, C.: Ray tracing for Jupiter’s icy moon ionospheric occultation of Jovian auroral radio sources, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6850, https://doi.org/10.5194/egusphere-egu24-6850, 2024.

The Galileo spacecraft performed close flybys of the moon Ganymede between 1996 and 2001. We reanalysed data of the energetic particles detector EPD onboard Galileo and derived the particle fluxes, energy spectra, and pitch angle distributions in the energy range of several keV to MeV during Ganymede flybys G2, G7, G8, G28, and G29. We find sharp dropouts in ion and electron fluxes as signatures of the loss cones inside the Ganymede magnetosphere as well as trapped electron distribution. Additionally, bi-directional field-aligned and butterfly distributions were found as well. We discuss these findings compared with simulation results in charactering Ganymede’s magnetosphere and in the context of future measurements with the Particle Environment Package PEP onboard the Juice mission which will be in orbit around Ganymede in 2032.

How to cite: Krupp, N., Roussos, E., Fränz, M., Kollmann, P., Clark, G., Paranicas, C., Khurana, K., Barabash, S., and Galli, A.: Energetic particle measurements near Ganymede: Galileo EPD data revisited and perspectives for Juice PEP, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7724, https://doi.org/10.5194/egusphere-egu24-7724, 2024.

Solid-state convection has been proposed to occur within Europa’s ice shell based both on the interpretation of observed geological activity during Galileo spacecraft exploration and theoretical investigations. Laboratory experiments have investigated the effect of grain size insensitive creep and grain size sensitive creep on the ductile behaviour of polycrystalline ice. The ice grain size and the ice impurities content and, consequently, the viscosity of the ice within Europa’s ice shell are poorly constrained, limiting the possibility to understand if solid-state convection can occur under Europa’s ice shell conditions. To investigate how diurnal tidal flexing and the internal dynamics of Europa’s ice shell influence the ice grain crystals’ evolution, we adopted a thermal-mechanical numerical model that uses finite differences and marker-in-cell techniques, implementing the dynamic recrystallization of the ice and the ice grain evolution in a self-consistent way with the numerical model. We found that solid-state convection within Europa’s ice shell can occur if it is diurnally tidally deformed, as the tidal stresses within the ice shell operate to reduce the ice grain sizes and the ice viscosity. We discuss future radio science experiments, in combination with radar sounder investigations, that will be capable of characterizing the possible presence of solid-state convection within Europa’s ice shell.

Acknowledgements: G.M. acknowledges support from the Italian Space Agency (2023-6- HH.0).

How to cite: Mitri, G.: Dynamic recrystallization within Europa’s ice shell: Implications for solid-state convection , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8353, https://doi.org/10.5194/egusphere-egu24-8353, 2024.

At the very end of its growth, Jupiter became surrounded by a disk composed of gas and dust, where the Galilean moon presumably formed. It is supposed that satellitesimals formed by streaming instability and grew by pebble accretion. Once the satellitesimals reacedh a significant size, they undergone an inward type I migration by gravitational interaction with the disk. In the early stages of the circumplanetary disk, the migration of satellitesimals occurred over so short timescales that most bodies fell onto Jupiter, suggesting that the Galilean moons formed later during the disk’s evolution.  Other studies suggest that the moons sequentially formed and migrated inward. This suggests that the moons were trapped in mean motion resonances, halting their migration.  In the coming years, the ESA mission JUICE and NASA mission Europa-Clipper will study the Galilean moons composition and provide hints on their formation conditions.

In this context, we aim to model the evolution of a 2-dimensional circumplanetary disk around Jupiter. To do this, we have constructed a quasi-stationary circumplanetary disk model that considers viscous heating, accretion heating, and heating of the upper layers of the circumplanetary disk by Jupiter. The thermal structure is determined by a grey atmosphere radiative transfer model. We show that the heating by Jupiter of the upper layers of the disk induces flaring and disk self-shadowing effects, which locally increase and decrease the disk temperature, respectively. The resulting temperature variations can be up to 50 K relative to the surrounding disk temperature. Consequently, the circumplanetary disk can produce transient hotter and colder regions that can last up to 10 kyr. The alternance of hot and cold regions in the Jovian circumplanetary disk has then profound implications for the formation conditions of the Galilean moons.

How to cite: Schneeberger, A., Mousis, O., and Lunine, J.: Impact of Jupiter's heating and self-shadowing on the structure of its circumplanetary disk , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8573, https://doi.org/10.5194/egusphere-egu24-8573, 2024.

The magnetosphere of Jupiter is apart from the Sun the strongest source of charged particles in the Solar system. The interaction of these particles with the exospheres of the Jovian moons forms one of the most complex plasma laboratories encountered by human space flight. For this reason the plasma analyzer package forms a crucial experiment of the Jupiter Icy Moon Explorer (JUICE). As part of the Plasma Environment Package (PEP) we describe a combined electron and ion spectrometer which is able to measure the electron and ion distribution functions in the energy range 1 to 50000 eV with high sensitivity and time resolution. This instrument is called the Jovian Electron and Ion Analyzer, JEI. We report on the general performance of the instrument and on first observations of the solar wind during commissioning of the instrument in space.

How to cite: Fränz, M., Bambach, P., Fischer, H., Heumüller, P., Krupp, N., Kühne, W., Roussos, E., Labudda, R., and Barabash, S.: The Jovian Electron and Ion Spectrometer (PEP-JEI) for the JUICE mission, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9464, https://doi.org/10.5194/egusphere-egu24-9464, 2024.

The rocky Jovian moon, Io, exhibits global volcanism that is driven by heat dissipated by tidal deformation. The large rate of heat exported by this volcanism, in conjunction with evidence in the form of magnetic induction, suggests that the mantle may contain a significant fraction of partial melt. This melt may be present in regions where both solid and liquid coexist at the macroscale. Nevertheless, existing models to investigate the location and magnitude of tidal heating consider an internal structure consisting of layers of pure solid or liquid. Such models are not appropriate for tidal deformation of partially molten materials. Building upon recent advancements in the theory of gravitational poroviscoelastic dynamics, we model tidal heating within Io, taking into account the effect of a two-phase, partially molten asthenosphere. 

The solid regions are modelled as a Maxwell viscoelastic material, and the top and bottom of the asthenosphere are treated as impermeable boundaries. We find that tidal dissipation within the fluid-filled pores depends on the ratio of the asthenosphere’s permeability to the melt’s viscosity. Thus, a low-viscosity melt and highly permeable pore-network favour enhanced tidal dissipation within the fluid. When this ratio, representing the Darcy drag, is large enough, fluid dissipation can exceed that within the solid grains when solid viscosity is high (> 10¹⁷ Pa s) or ultra-low (< 10¹¹ Pa s). Tidal dissipation by the pore-hosted melt exhibits its own distinct tidal heating pattern, which always produces enhanced heating towards low latitudes.

How to cite: Hay, H., Katz, R., and Hewitt, I.: Tidal Dissipation in a Partially Molten Asthenosphere on Io, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9753, https://doi.org/10.5194/egusphere-egu24-9753, 2024.

The presentation discusses the accuracy of the scalar Coupled Dark State Magnetometer on board the Jupiter Icy Moon Explorer (JUICE) mission of the European Space Agency. The scalar magnetometer MAGSCA is part of the J-MAG instrument.

MAGSCA is an optical, omni-directional scalar magnetometer based on coherent population trapping, a quantum interference effect, within the hyperfine manifold of the ⁸⁷Rb D₁ line. The measurement principle is only based on natural constants and therefore, it is in principle drift free and no calibration is required. However, the technical realisation can influence the measurement accuracy.
The most dominating effects are heading characteristics, which are deviations of the magnetic field strength measurements from the ambient magnetic field strength.

The verification of the accuracy and precision of the instrument is required to ensure its compliance with the performance requirement of the mission: 0.2 nT (1-σ).
The verification is carried out with four dedicated sensor orientations in a Merritt coil system, which is located in the geomagnetic Conrad observatory. The coil system is used to compensate the Earth’s magnetic field and to apply appropriate test fields to the sensor. 

A novel method is presented which separates the heading characteristics of the instrument from residual (offset) fields within the coil system by fitting a mathematical model to the measured data. It allows verifying that the MAGSCA sensor unit does not have a measurable remanent magnetisation as well as that the desired accuracy of 0.2 nT (1-σ) is achieved by the MAGSCA flight hardware for the JUICE Mission.

How to cite: Amtmann, C., Pollinger, A., Ellmeier, M., Dougherty, M., Brown, P., Lammegger, R., Betzler, A., Agú, M., Hagen, C., Jernej, I., Wilfinger, J., Baughen, R., Strickland, A., and Magnes, W.: Accuracy of the Scalar Magnetometer aboard ESA's JUICE Mission, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10327, https://doi.org/10.5194/egusphere-egu24-10327, 2024.

Chemically stratified layers in the deep oceans of icy moons may strongly influence the oceans’ dynamics, thermal and chemical evolution, and therefore their habitability. Such layers can form during the differentiation of the refractory cores as they heat up due to the decay of long-lived radioactive elements. In the case of Ganymede, salts could be transported through the high-pressure ice layer to form a denser salt water layer at the base of the ocean. Such a layer would inhibit ocean convection, limiting chemical and thermal transport. It is therefore crucial to understand how these layers form and what specific signatures they may leave in geophysical observations of future space missions. The present work describes numerical simulations of the formation of stratified layers and the predicted observables that could be detected by instruments on the JUICE spacecraft.

3-D numerical simulations of Ganymede’s rotating ocean are performed with the PARODY code. Rayleigh-Bénard convection is imposed. We investigate the effect of either a constant flux of heavy salts or a fixed composition at the base of the ocean. Two regimes are identified by varying the dimensionless chemical Rayleigh (buoyancy over viscosity) and Schmidt numbers (viscosity over diffusivity). In the first regime, heavy salts are entrained and mixed in the convective region. In the second regime, the entrainment is too weak and a chemically stratified layer develops, eventually filling the entire ocean.

Extrapolation to Ganymede suggests the current existence of a chemically stratified layer at the base of the ocean with a thickness close to 30 km. By considering different stratifications in Ganymede’s ocean in the PlanetProfile and ForcedTides codes, we show that signatures of stratified layers might be detected in the gravity field, induced magnetic field, and tidal deformation responses. The problem of non-uniqueness in the individual observations points to the need to jointly invert these datasets from the JUICE mission to constrain the existence and properties of stratified oceanic layers.

How to cite: Pinceloup, M., Bouffard, M., Vance, S., Melwani Daswani, M., and Styczinski, M.: Formation of chemically stratified layer in Ganymede’s ocean: implications for upcoming JUICE mission, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10976, https://doi.org/10.5194/egusphere-egu24-10976, 2024.

How to cite: Haslebacher, C., Prockter, L. M., Leonard, E. J., Schenk, P. M., and Thomas, N.: Extraction of topographic profiles of double ridges on Europa , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11349, https://doi.org/10.5194/egusphere-egu24-11349, 2024.

Spiked, icy features, akin to the ‘penitentes’ on Earth [1], have been found on other airless bodies in the solar system as well, such as the 'bladed terrains' of Pluto [2] and the 'spires' of Callisto [3]. These features, thought to be formed due to sublimation erosion, are present in young, crater-less regions and hence represent an active response of the surfaces of these bodies to changing seasonal and climatic conditions. Interestingly, penitente formation has also been hypothesized on Europa [4], albeit the feasibility of that process on Europa has been questioned [5]. A fundamental limitation of testing this hypothesis for Europa is the lack of images at the resolution of the proposed penitente features (~ 15 m), unlike the images of the bladed terrains of Pluto from New Horizons and spires of Callisto from Galileo which clearly show these features. 

Photometric roughness models peer below the resolution limit of the camera to offer a glimpse of any surface roughness that is in the geometric optics limit.  Our roughness model [6], which has been successfully fit to a range of planetary bodies [7,8], will enable us to probe the surface roughness of Europa and test the penitente-hypothesis. We are locating Galileo images from the equatorial regions of Europa (within an equatorial zone restricted to ±24° where they are hypothesized to exist) and extracting scans of specific intensity (I/F) with backplanes of geometric coordinates. We will fit these I/F curves with our photometric model to derive roughness values, which will be compared to the proposed roughness of ~ 60° [4]. This predicted roughness is very high, so its effect on the light reflected from the surface should be easily detectable. To get a useful point of comparison for the roughness values we obtain for Europa, we will also perform a roughness analysis of the spires of Callisto, which are in a similar size regime of ~ 100 m. 

[1] Claudin, P. et al. (2015), Phys. Rev. E, 92(3), 033015; [2] Moore, J., et al. 2018, Icarus 300, 129-144, [3] Howard, A. D., & Moore, J. M. (2008). GRL, 35(3), L03203 [4] Hobley, D.E.J. et al. (2018). Nat. Geosci., 11(12), 901-904. [5] Hand, K.P. et al. ( 2020). Nat. Geosci., 13(1), 17-19. [6] Buratti, B. J., & J. Veverka (1985), Icarus 64, 320-328; [7] Buratti, B. J. et al. (2006). Planet. & Space Sci. 54, 1498-1509 [8] Lee, J. et al.  (2010), Icarus 206, 623-630.

How to cite: Mishra, I. and Buratti, B.: Testing the penitente hypothesis on Europa via photometric roughness, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11367, https://doi.org/10.5194/egusphere-egu24-11367, 2024.

Juice is the first large mission chosen in the framework of ESA’s Cosmic Vision 2015-2025 program.

The focus of Juice is to characterize the conditions that might have led to the emergence of habitable environments among the Jovian icy satellites, in particular Ganymede, Europa and Callisto. Juice will also perform a multidisciplinary investigation of the Jupiter system as an archetype for gas giants.

The spacecraft payload consists of 10 state-of-the-art instruments (and one experiment that use the spacecraft telecommunication system with ground-based instruments) that will perform remote and in-situ measurements of Jupiter, its moons and their environment.

From a trajectory’s point of view, the mission calls for a three-year orbital survey of the Jupiter system followed by an additional 9 months in orbit around Ganymede for an in-depth characterization of Ganymede as a planetary object and possible habitat. During the Jupiter orbital phase, Juice will perform a sequence of 67 orbits of different periods and inclinations around the planet including several flybys of the Galilean moons, 2 of which as close as 400km altitude from Europa in July 2032.

The Juice top level Europa science goals are the determination of the composition of the non-ice materials and understanding their origin (deep interior vs exogenic), the search for liquid water under active sites and the study of the activity processes at play on the moon.

A representative detailed science operations plan has been developed by the science team covering a 24 hour-period around the first flyby of Europa in July 2032. The plan considers the latest knowledge on instrument and spacecraft resources and performances available at the time of the study.

This work presents the geometry and mission constraints associated to the flyby as well as the observation strategy chosen by the different payload; the remote sensing package’s strategy includes exosphere characterization (including potential plume detection) through limb observations and surface characterization at different scales and wavelengths, both on the inbound (dayside) and outbound (nightside) part of the flyby. At low altitude and centered around closest approach, the geophysics package will perform topography and surface roughness measurement using the laser altimeter as well as surface sounding down to a depth of up to ~ 9 km with the ice penetrating radar. Radio science range rate measurement will support the estimate of the main quadrupole coefficients and the testing of the hydrostatic hypothesis. The in-situ package will operate continuously to monitor the Europa plasma, neutral and electromagnetic wave environment. The resulting harmonized operations timeline, together with resources limitations and the assessment on the expected science return is discussed.

How to cite: Vallat, C., Lorente, R., and Altobelli, N. and the The Juice Science Team: A detailed science and operations analysis of the first flyby of Europa by the Juice spacecraft, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11664, https://doi.org/10.5194/egusphere-egu24-11664, 2024.

How to cite: Beth, A., Galand, M., Modolo, R., Leblanc, F., Jia, X., Huybrighs, H., and Carnielli, G.: Ionospheric environment of Ganymede during the Galileo flybys, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11772, https://doi.org/10.5194/egusphere-egu24-11772, 2024.

The Jovian Energetic Neutrals and Ions (JENI) Camera and the Jovian Energetic Electrons (JoEE) belong to the six-sensor suite Particle Environment Package (PEP) on board the JUICE mission. JENI is a combined ion and ENA camera with 90˚x120˚ Field-of-View and an energy range from a few keV to 110 keV for ENAs and 5 MeV for ions. Only one mission, Cassini, has captured ENA images of the Jovian system before during its distant flyby. Those images revealed emissions coming from the Europa neutral gas torus, but were too distant to resolve details on its spatial distribution and variability. The Juno mission has detected ENA emissions originating from both the Europa and also the Io torus, that indicate azimuthally asymmetric distributions. In ENA mode, JENI will image the Europa and Io tori, to investigate their spatial distribution and long-term variability providing global constraints to physical models of their sources. Although a predominant fraction of the ENAs from the tori originate from charge exchange between magnetospheric energetic ions and the neutral gas, a significant fraction may originate from charge exchange between the energetic ions and the ambient plasma in the tori. This opens up the intriguing possibility to also diagnose the plasma dynamics and distribution of the tori. JENI also targets the explosive recurrences of vast regions of heated plasma in the Jovian magnetotail (“injections”) that may be the engine behind the periodic radio emissions from rotating, magnetized planets, such as Saturn, Jupiter and perhaps even brown dwarfs. In ion mode, JENI will provide the detailed in-situ measurements of the energetic ion environment necessary to understand the physical heating and transport processes underlying the global context provided by the ENA images. JoEE is an electron spectrometer that near-simultaneously provide the energetic electron spectrum in multiple look directions over the energy range from 28 keV up to 2 MeV. JoEE’s prime objectives are to investigate the acceleration mechanisms of Jovian radiation belt electrons and their interaction with the Jovian moons. The Juno mission has recently made important electron measurements that provides useful guidance for deepening the JoEE objectives.

In this presentation an overview is given of JENI and JoEE, with emphasis on the ENA observations and their expected science return. This includes imaging of the Europa and Io tori distribution and variability, quasi-periodic magnetospheric injections, and their relation to rotationally periodic radio emissions from planets and brown dwarfs.

How to cite: Brandt, P., Clark, G., Kollmann, P., Mitchell, D. G., Gkioulidou, M., Haggerty, D., Barabash, S., Wurz, P., Krupp, N., Roussos, E., Paty, C., Jia, X., Khurana, K., Allegrini, F., Pontoni, A., and Smith, H. T.: Energetic Neutral Atom (ENA) Imaging and In-Situ Energetic Particle Exploration of the Jovian Magnetosphere and Moon Environment from JUICE/PEP, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12178, https://doi.org/10.5194/egusphere-egu24-12178, 2024.

ESA’s Jupiter Icy Moons Explorer (JUICE) mission scientific payload includes a 2-channels (visible to near-infrared (VISNIR) and infrared (IR)) cryogenic imaging spectrometer instrument called the Moons And Jupiter Imaging Spectrometer (MAJIS). During its ground calibration campaign, this instrument was tested at different operative temperatures, and calibration measurements were acquired to derive the spatial, spectral, and radiometric performances. Following the launch of the JUICE mission to the Jovian System, the first in-flight measurements were acquired during the near-Earth commissioning phase (NECP). In flight, the internal calibration unit (ICU) was used to monitor the instrument’s response.  In particular, the ICU signal provides full illumination of the instrument's field of view. It exhibits several absorption bands thanks to a didymium and a polystyrene filter placed in front of the VISNIR and IR sources, respectively.

The performances of the instrument are evaluated through several metrics, including the absolute spectral calibration, the full width at half maximum of the response (spatial and spectral), the distortions (keystone and smile), and the impact of the optical head temperature.

The flight acquisitions will be presented and compared to the ground calibration analyses, and the current performances of the instrument will be discussed in the context of MAJIS main scientific goals.

How to cite: Haffoud, P., Langevin, Y., Poulet, F., Vincendon, M., Filacchione, G., Piccioni, G., Carter, J., Guiot, P., Lecomte, B., Dumesnil, C., Barbis, A., Tommasi, L., Rodriguez, S., Stefania, S., Tosi, F., Pilorget, C., and De Angelis, S.: Monitoring the performances of MAJIS from ground to flight calibration measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12317, https://doi.org/10.5194/egusphere-egu24-12317, 2024.

Ion precipitation onto Ganymede, shaped by interaction between the Jovian plasma and Ganymede’s magnetosphere, has been connected to brightness patterns and radiolysis products on its surface [1,2]. JUICE will measure ion fluxes in-situ at around 500 km altitude, leaving uncertainties for the precipitation patterns on the surface [3]. At Earth’s Moon, backscattered Energetic Neutral Atoms (ENAs) have been shown to be suitable for studying the ion-surface interaction from an orbiting spacecraft [4]. We now present the first modeling of ENAs created by backscattered H, O and S ions at Ganymede, which will enable JUICE to remotely observe the ion impacts. Using the SDTrimSP code [5], which has been verified for backscattered ENAs at the Moon [6, 7], we account for inputs of magnetospheric plasma precipitation from hybrid simulations [8] and Ganymede’s surface composition from telescopic observations [9].

Our simulation results support that backscattering is an important formation process mainly for atomic H and O populations, whose properties are directly related to the precipitation conditions. Especially backscattered H ENAs dominate over any sputtered ENAs [10] above at least around 1 keV, making them ideal candidates for observing the plasma-surface interaction at Ganymede. Compared to lunar ENAs, backscattering probabilities are lower, but extended high-energy tails occur due to energetic ion populations in the Jovian plasma. The backscattering process thus creates neutral atom contributions that are candidates for observation with both JUICE’s JNA and JENI instruments.

[1]          S. Fatemi, et al., Geophys. Res. Lett. 43 (2016), 4745.

[2]          S.K. Trumbo, et al., Sci. Adv. 9 (2023), eadg3724.

[3]          C. Plainaki , et al., Astrophys. J. 940 (2022), 186.

[4]          Y. Futaana, et al., Gephys. Res. Lett. 40 (2013), 262.

[5]          A. Mutzke, et al., IPP Report 2019-02 (2019).

[6]          P.S. Szabo, et al., Geophys. Res. Lett. 49 (2022), e2022GL101232.

[7]          P.S. Szabo, et al., J. Geophys. Res.: Planets 128 (2023), e2023JE007911.

[8]          A.R. Poppe, et al., J. Geophys. Space Phys. 123 (2018), 4614.

[9]          N. Ligier, et al., Icarus 333 (2019), 496.

[10]       A. Pontoni, et al., J. Geophys. Space Phys. 127 (2022), e2021JA029439.

How to cite: Szabo, P. S., Poppe, A. R., Mutzke, A., Liuzzo, L., and Carberry Mogan, S. R.: Constraining Ion Precipitation onto Ganymede’s Surface with Backscattered Energetic Neutral Atoms, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13075, https://doi.org/10.5194/egusphere-egu24-13075, 2024.

Introduction. Europa, the most visibly active icy moon of Jupiter, is a prime target for the search for life in the outer solar system. Two spacecraft missions, Europa Clipper from the National Aeronautics and Space Administration (NASA) and the Jupiter Icy Moon Explorer (JUICE) from the European Space Agency (ESA), will conduct extensive observations of its surface, gravity field and environment starting 2030. It has been proposed that liquid briny water reservoirs could be injected and stored in Europa’s ice shell, causing the formation of various geological features. In particular, these reservoirs could occasionally trigger eruptions [1], resulting in flows on the surface and vapor plumes in the atmosphere.

If shallow liquid brine reservoirs are indeed present in Europa's ice shell, they would leave surface evidence that future missions could detect, including local thermal anomalies, ice shell thickness change, and erupted briny solutions with time varying salinity. We present a novel simulation that models thermal, physical, and compositional ice shell and reservoir evolution and eruption, and that predicts the various signatures detectable by future robotic exploration.

Cryomagma chemistry. We conserve enthalpy to solve the coupled chemical evolution and pressurization of freezing brines stored in Europa’s ice shell using current best estimates of the oceanic composition [2] to predict the composition of erupted cryolava. This composition varies with time, as salts concentrate during freezing [3], which could lead to erupted brines of varying composition depending on the reservoir frozen fraction when the eruption is triggered. The equilibrium freezing of oceanic brines is modeled using the software PHREEQC to obtain the liquid and solid fraction of each component of the aqueous solution as a function of the temperature. 

Ice shell and reservoir modelling. We simultaneously model the ice shell and reservoir thermal, physical, and compositional evolution self-consistently building upon the framework of [4]. We solve for the conservation of enthalpy using conservative finite differences in a one-dimensional (1D) spherical shell, propagated explicitly forward in time. The thermophysical properties of the multiphase model are temperature-, pressure-, and composition dependant, thus the composition and physical state are consistently updated at every time step. Finally, modeled eruption frequency and eruptive characteristics are dependent on the properties and their gradients in ice surrounding the reservoir.

Results. Outputs of the model include the temporal evolution of the temperature in the ice shell, reservoir, and at the surface, and the time of eruptions and erupted cryomagma composition (Fig. 1).

Figure 1: Temporal evolution of signatures of a 1 km thick cryomagma reservoir located 1 km bellow the surface.

Acknowledgements. Portions of this research were carried out at the Jet  Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA). This work was supported by NASA’s Solar System Workings program (grants #80NM0018F0612 and #80NSSC20K0139)

References. [1] Lesage et al. (2022) PSJ 3(7), 170, [2] Melwani Daswani et al. (2021) GRL 48(18), [3] Naseem et al. (2023) PSJ 4(9), 181, [4] Howell, S. M. (2021) PSJ 2(4), 129.

How to cite: Lesage, E., Howell, S. M., Miller, J. W., Naseem, M., Villette, J., Neveu, M., Melwani Daswani, M., and Vance, S. D.: Cryovolcanism inside out: Signatures of past and present cryovolcanism on Europa, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13816, https://doi.org/10.5194/egusphere-egu24-13816, 2024.

Scheduled to launch in October 2024, NASA’s Europa Clipper will set out on a journey to explore the habitability of Jupiter’s icy ocean world Europa. After a 5.5 yr cruise that includes gravity assists at Mars and Earth, the spacecraft will enter orbit around Jupiter and will perform nearly 50 flybys of Europa over a four-year period. To explore Europa as an integrated system and achieve a complete picture of its habitability, the Europa Clipper mission has three main science objectives to characterize: (1) the ice shell and ocean including their heterogeneity, properties, and surface–ice–ocean exchange; (2) Europa’s composition including any non-ice materials on the surface and in the atmosphere, and any carbon-containing compounds; and (3) Europa’s geology including surface features and localities of high science interest. Additionally, several cross-cutting science topics will be investigated through searching for any current or recent activity in the form of thermal anomalies and plumes, performing geodetic and radiation measurements, and assessing high-resolution, co-located observations at select sites to provide reconnaissance for a potential future landed mission. These science objectives will be accomplished using a highly capable suite of remote-sensing and in-situ instruments. The remote sensing payload consists of the Europa Ultraviolet Spectrograph (Europa-UVS), the Europa Imaging System (EIS) consisting of a wide and a narrow angle camera (WAC, NAC), the Mapping Imaging Spectrometer for Europa (MISE), the Europa Thermal Imaging System (E-THEMIS), and the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON). The in-situ instruments are the Europa Clipper Magnetometer (ECM), the Plasma Instrument for Magnetic Sounding (PIMS), the SUrface Dust Analyzer (SUDA), and the MAss Spectrometer for Planetary Exploration (MASPEX). Gravity and radio science will be obtained using the spacecraft's telecommunication system, and valuable scientific data will be acquired by the spacecraft’s radiation monitoring system.

Assembly, test, and launch operations (ATLO) of the Europa Clipper spacecraft are progressing well, and the flight system integration and environmental testing has been completed at the Jet Propulsion Laboratory. Currently, the flight system is undergoing operations testing, and in May 2024, the spacecraft will be shipped to NASA’s Kennedy Space Center at Cape Canaveral, Florida. There, the remaining integration activities will occur for the solar array and REASON antennas followed by final flight system tests. The launch period begins on 10 October 2024. To provide details on the mission’s instruments and planned investigations, the Europa Clipper science team is publishing manuscripts in a special issue of Space Science Reviews, and the team continues to work towards optimizing science return through preparation of the mission’s Strategic Science Planning Guide. As well, collaborative science opportunities with ESA’s JUpiter ICy moons Explorer (JUICE) mission, which will overlap in its tour period at Jupiter and make observations of Europa, are being discussed informally among the science teams. Onward to Europa!

How to cite: Craft, K. L., Pappalardo, R., Buratti, B., Korth, H., Daubar, I., Phillips, C., Klima, R., Howell, S., Leonard, E., Matiella Novak, A., Ray, T., Kampmeier, J., and Paczkowski, B. and the Europa Clipper Science Team: The Europa Clipper Mission and its Final Stretch to Launch, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14097, https://doi.org/10.5194/egusphere-egu24-14097, 2024.

It is generally assumed that the large icy satellites of Jupiter and of Saturn are, like our Moon, in an equilibrium rotation state called a Cassini State. In this state, the rotation of the satellite is synchronous with the orbital motion and the precession rate of the rotation axis is equal to that of the normal to the orbit. Moreover, the spin axis of the satellite, the normal to its orbit and the normal to the inertial plane remain coplanar and the obliquity (the angle between the normal to the orbit and the spin axis) is constant over time. For satellites with a slow orbital precession rate like the large icy satellites, up to four Cassini states are possible, characterized by a (theoretically) constant obliquity close to 0 (CSI), ± π/2 (CSII and IV) and π (CSIII). From these four states, only two are stable: CSI and CSIII.

We here model these two stable Cassini States of triaxial satellites using an angular momentum approach. In our model, the motion of the spin motion in space is coupled with the polar motion of the satellite and, contrary to what is usually done in the classical Cassini States studies, we do not average the external gravitational torque over short period terms. We can therefore compute the mean obliquity value of the different satellites but also the nutations (small periodic variations) both in obliquity and in longitude, which are due to the periodic variations of the gravitational torque acting on the satellites. We identify and study two causes for the polar motion and their effects on the obliquity: the semi-diurnal polar motion due to the inclination and node precession and the long period polar motion due to the eccentricity and pericenter precession.

How to cite: Coyette, A., Baland, R.-M., and Van Hoolst, T.: Modeling the Cassini States of large icy satellites with an angular momentum approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15429, https://doi.org/10.5194/egusphere-egu24-15429, 2024.

The JUpiter ICy moons Explorer (JUICE) mission is a cornerstone of the European Space Agency (ESA). The mission was launched in April 2023 from Kourou with an Ariane V launcher and is expected to arrive at Jupiter in 2031. JUICE will investigate the gas giant planet Jupiter, its atmosphere, magnetosphere, and its icy moons, Ganymede, Europa and Callisto. The mission will focus on Ganymede, during the low altitude circular and polar orbital phase.

The spacecraft will carry a suite of scientific instruments, including a camera, a spectrometer, a radar system, a laser altimeter, and a suite of instrumentation dedicated to radio science experiments: the Ka-band Transponder (KaT), the Ultra Stable Oscillator (USO) and the High Accuracy Accelerometer (HAA).

The Gravity & Geophysics of Jupiter and Galilean Moons experiment (3GM) instrumentation will be used to study the gravity field up to degree and order 40 of Ganymede and the extent of internal oceans on the icy moons. Furthermore, during radio occultations, the 3GM experiment will investigate the structure of the neutral atmospheres and ionospheres of Jupiter and its moons.

The HAA accelerometer will play a fundamental role during the 3GM experiment even if it will not directly measure any of the physical quantities connected with the experiment scientific goals. It aims to measure the perturbations of non-gravitational forces that the JUICE spacecraft will undergo during 3GM measurements with an accuracy of  in the frequency band of  Hz. Such perturbations are mainly induced by the propellant sloshing within the tanks, especially during the moon flybys. These perturbing accelerations are included in the orbital determination algorithm. In this work we show the first inflight data collected by the HAA instrument during the cruise. We present the data collected after launch (April-June 2023) during the deployment of the spacecraft moving appendages such as the RIME antenna, the Langmuir probes and the magnetometer boom. The analysis of these data aims to preliminary characterize the instrument behaviour and the spacecraft dynamic environment. Additionally, we show the analysis of the HAA data collected during the first payload checkout (January 2024), with a focus on the preliminary assessment on the instrument in-flight scientific performances.  

How to cite: De Filippis, U., Cappuccio, P., Di benedetto, M., and Iess, L.: Analysis of the first data collected by the High Accuracy Accelerometer (HAA) onboard the JUICE spacecraft, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17407, https://doi.org/10.5194/egusphere-egu24-17407, 2024.

The Surface Dust Analyser (SUDA) is a dust impact mass spectrometer onboard of the Europa Clipper mission for investigating the surface composition of the Galilean moon Europa. The instrument is a Time--Of--Flight (TOF) impact mass spectrometer derived from previously flown dust compositional analyzers on Giotto, Stardust, and Cassini. SUDA uses the technology of the successful Cosmic Dust Analyzer (CDA) operating on Cassini and employs advanced reflectron-type ion optics for increased mass resolution. The instrument will measure the mass, speed, charge, elemental and isotopic composition of impacting grains.

Atmosphereless planetary moons such as the Galilean satellites are wrapped into a ballistic dust exosphere populated by tiny samples from the moon's surface produced by impacts of fast micrometeoroids. SUDA will measure the composition of such surface ejecta during close flybys at Europa to obtain key chemical constraints for revealing the satellite's composition, history, and geological evolution. Because of their ballistic orbits, detected ejecta can be traced back to the surface with a spatial resolution roughly equal to the instantaneous altitude of the spacecraft.

SUDA will detect a wide variety of compounds from Europa's surface over a concentration range of percent to ppm and connect them to their origin on the surface. This allows simultaneous compositional mapping of many organic and inorganic components, including both major and trace compounds, with a single instrument. Any recent tectonic activity, cryovolcanism, or resurfacing event is detectable by variations in the surface composition. This can be linked to corresponding geological features, including the analysis of compositional variations across large craters on Europa. SUDA will further the understanding of Europa's surface couples to its interior source regions.

In this presentation, we will discuss SUDA's unique capabilities to collect compositional ground truth from orbit and how SUDA contributes to the Europa Clipper science goals.

How to cite: Kempf, S. and the SUDA Science Team: SUDA: A SUrface Dust Analyser for compositional mapping of the Galilean moon Europa, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17570, https://doi.org/10.5194/egusphere-egu24-17570, 2024.

The NASA Galileo spacecraft explored the Jupiter system between 1995 and 2003. The spacecraft was equipped with the Near-Infrared Mapping Spectrometer instrument (NIMS), able to probe Jupiter’s atmosphere and the icy moons’ surface composition in the near-infrared with its 17 detectors operating between 0.7 to 5.2 microns [1]. The Galileo NIMS dataset was collected during flybys, which resulted in a series of very diverse data cubes, viewing geometries and spatial resolutions. In addition, depending on the instrument mode used to collect the data, and on the instrument’s own health status, the NIMS infrared spectra were collected with a varying spectral sampling (between 15 and 408 wavelengths), and an evolving absolute wavelength calibration over the course of the mission. Despite its heterogeneity and complexity of use, the Galileo/NIMS dataset is one of the most valuable resource to model and map the surface properties (composition, grain size, roughness, phase function) of Jupiter’s moons, which are the prime targets of the Europa Clipper [2] and ESA JUICE [3] missions in this decade.

We converted the Galileo/NIMS calibrated dataset publicly available on the PDS Imaging Node (as g-cubes) into a MySQL relational database, which allows to quickly select and extract radiance factors (I/F), geometry data, and metadata from the entire NIMS data set. The smallest element in the database is a spectrum (i.e. one pixel). Using SQL queries relying on the pixel viewing geometry (incidence, emission, phase, and azimuth) and the geographic pixel location (latitudes and longitudes on a target), phase curves and/or collections of spectra can be easily retrieved. Individual g-cubes data can also be accessed upon request. We used this database framework, together with Bayesian inversion methods and the Hapke model [4,5], to perform detailed compositional studies on Europa’s dark lineaments [6,7], and spectro-photometric modeling of broader regions of interest located in different hemispheres [8].

References

[1] Carlson et al., Space Science Reviews, 60, 457-502, 1992.

[2] Howell and Pappalardo, Nat Commun 11, 1311, 2020.

[3] Grasset et al., Plan Spac Sci 78, 1-21, 2013.

[4] Hapke, Icarus 221, 1079-1083, 2012.

[5] Hapke, Cambridge University Press, 1993.

[6] Cruz Mermy et al., Icarus 394, 115379, 2023.

[7] Andrieu et al., EPSC 2022.

[8] Belgacem et al., EPSC, 2022.

How to cite: Cornet, T., Cruz-Mermy, G., Belgacem, I., Andrieu, F., and Schmidt, F.: Studying the icy moons of Jupiter using a database framework, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19302, https://doi.org/10.5194/egusphere-egu24-19302, 2024.

ESA’s JUpiter ICy moons Explorer (JUICE) launched on April 14, 2023, beginning an eight-year journey to the Jupiter system. Arriving in 2031, JUICE will make 35 total flybys of Ganymede, Europa, and Callisto before going into orbit about Ganymede. NASA’s Europa Clipper is scheduled to launch in October 2024, arriving in the Jupiter system in 2030, a year ahead of JUICE. Clipper will spend a year in the system before undertaking 49 flybys of Europa during a nominal three-year primary mission phase, while also making multiple serendipitous flybys of Ganymede and Callisto. Having two highly instrumented spacecraft in close proximity in time and space affords unprecedented opportunities for synergistic observations during the missions’ main orbital phases, and unique heliospheric and magnetosphere science during cruise and Jupiter approach.

While there are currently no firm commitments from NASA or ESA to accomplish science beyond that of each mission’s primary science objectives, discussions are ongoing and the task of the appointed JUICE-Clipper Steering Committee (JCSC) is to provide recommendation of compelling joint science opportunities between the two missions.

This paper will focus on the cruise and Jupiter approach phases. We have identified a number of potential opportunities for investigating the evolution of the solar wind plasma and interplanetary magnetic field and related structures such as monitoring Coronal Mass Ejections (CMEs) or Corotating Interaction Regions (CIRs) during times when the two spacecraft are radially aligned (i.e. at similar heliocentric longitudes) or at similar heliocentric distances, as well as radio science observations of the solar wind and/or Solar Energetic Particle (SEP) events that could be observed throughout interplanetary transfer. There is also potential for investigating the evolution of solar wind structures and disturbances when both spacecraft are “connected” through Parker Spiral field lines. The cruise science return from JUICE and Clipper could be further enhanced by data from other operational spacecraft (e.g., BepiColombo, Solar Orbiter, Parker Solar Probe, MAVEN, IMAP, Psyche), thus expanding the catalogue of opportunities for these identified configurations, as well as simultaneous observations by ground and space-based observatories (e.g., JWST, Keck, etc.). The >1 year Jupiter approach phase of the JUICE spacecraft while Clipper orbits within the jovian magnetosphere provides an unrivalled opportunity to study the complexity of the solar wind-magnetosphere interaction and aurora at Jupiter, a topic where there remain many open questions. This phase would provide a unique opportunity for preparatory joint observations to understand if and how the solar wind influences the moon’s local space environment, and the related interaction with Jupiter’s rapidly rotating magnetosphere.

How to cite: Bunce, E., Prockter, L., and Choukroun, M. and the JUICE Clipper Science Committee: ESA JUICE and NASA Europa Clipper: Joint Science Opportunities during Cruise and Jupiter Approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20110, https://doi.org/10.5194/egusphere-egu24-20110, 2024.

The JUICE mission has been launched by an Ariane 5 launcher on April 14, 2023 and is now on its way to reach Jupiter and its icy moons in 2031. The focus of JUICE is to characterise the conditions that may have led to the emergence of habitable environments among the Jovian icy satellites, with special emphasis on the internally active ocean-bearing worlds, Ganymede and Europa. Following a Jupiter Touring phase of 4 years, JUICE will become the first orbiter of a moon that is not our own, entering Ganymede orbit in 2034.

The spacecraft passed its commissioning review successfully on July 19, 2023, following the Near Earth Commissioning Phase (NECP), and, despite a few hickups, the ESA and multi-national instruments teams are now operating our interplanetary ship successfully. The preparation of the first combined flyby of the Earth and the Moon  in the history of space exploration (August 2024) is on-going. The first planning training exercise was completed by the Science Ground Segment, complementing the preparation of the strategic science planning of the Jupiter Tour.

How to cite: Altobelli, N., Witasse, O., Vallat, C., Tanco, I., Dietz, A., and Erd, C. and the JUICE TEAMS: The JUICE mission - an overview, since launch and beyond , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20679, https://doi.org/10.5194/egusphere-egu24-20679, 2024.

The Jupiter bound JUICE mission (JUpiter ICy moons Explorer) was successfully launched on April 14, 2023 and is currently executing its 8-year interplanetary cruise phase. JUICE carries three comprehensive instrument suites to fully characterize particles, fields, and waves. The JUICE space plasma instrumentation constitutes the most comprehensive and capable heliophysics payload ever flown, or planned, in the important but not-well explored the solar system region between 1 and 5 au.

Science objectives that can be addressed by the JUICE payload include solar wind evolution, collisionless shock interactions and propagation, and particle acceleration, solar energetic particles, pick-up ion (PUI) origin and evolution, turbulent interactions, energetic neutral atom (ENA) imaging, and interplanetary hydrogen observations.

JUICE enables an expansion of inner heliospheric science, connecting to observations in the outer heliosphere and Very Local Interstellar Medium (VLISM) by NASA’s New Horizons, Voyager, and Interstellar Mapping and Acceleration Probe (IMAP) (to launch Feb 2025). New science opportunities are also enabled by the simultaneous observations from Europa Clipper in the same region. JUICE will spend the next six years between 0.7 au and 2.5 au, and in 2029-2031 it will explore the region out to Jupiter. JUICE has no thermal constraints past 1.34 au and the data volume from relevant sensors live well within the available data downlink through its weekly passes using the European Space Tracking (ESTRACK).

In this presentation, we discuss the unique heliophysics observations the six-sensor suite Particle Environment Package (PEP) on board can do in conjunction with other space physics measurements on board JUICE and Europa Clipper. The PEP-suite measures species-resolved energy and angular distributions of electrons (~ 1 eV to ~1.5 MeV), ions (~1 eV to > 10 MeV; energy rage is species dependent); and ENA (~ 5eV to 300 keV). In addition to the PEP instrument suite, JUICE also carries a radiation monitor (RADEM) that can provide complimentary energy and species resolved measurements of very energetic electrons and ions in the solar wind.

How to cite: Barabash, S., Brandt, P., Wurz, P., Clark, G., Krupp, N., Roussos, E., Stenberg Wieser, G., Wittmann, P., Fränz, M., Shimoyama, M., Wieser, M., Kollmann, P., and Mitchell, D.: Unique Heliospheric Measurement Opportunities with the ESA JUICE mission: Science Case for Particle Environment Package (PEP), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20774, https://doi.org/10.5194/egusphere-egu24-20774, 2024.

The habitability of icy moons in the outer Solar System is linked to their ability to maintain warm subsurface oceans through time. While most heat generation in response to tidal forcing is thought to occur in icy crusts and water oceans, the actual response of silicic material to deformation under relevant planetary conditions has not previously been studied comprehensively in a laboratory setting. Similar meteoritic material is often studied at room pressure instead of at the 10s to 100s of MPas of pressure present at depth in moons, and subjected to dynamic forces to simulate impacts rather than observed under quasistatic loading and deformation. In the absence of laboratory constraints on peak strength and deformation behavior, large errors remain for estimates of heat contribution from the mantles, as well as in models of seismic and elastic properties of icy moon interiors.

We experimentally deformed samples of the Kilabo meteorite, an LL6 chondrite, under axial strain rates of 10^-5 s^-1 and confining pressures up to 100 MPa. We recorded the strength of the material, calculated energy dissipation through acoustic emission events, and measured how ultrasonic wavespeeds evolved as a function of confining pressure. Dissipative microcracking events occurred at all pressures, even at low stresses during isotropic pressurization and nominally “elastic” deformation. These events were most common at low confining pressures. The mechanical behavior of the meteoritic material also evolved as a function of confining pressure: peak strength occurred at 50 MPa laboratory confining pressure, and material continuously stiffened as pressure increased. These pressure-dependent properties indicate that larger icy planetary bodies may have stiffer, less deformable silicate layers than those found in small icy satellites. Rocky interior deformation could therefore contribute to the bulk heat budget required to maintain subsurface oceans in Ariel and Miranda, along with many other smaller icy moons in the outer Solar System.  

How to cite: Seltzer, C., O. Ghaffari, H., and Peč, M.: Experimental constraints on tidal dissipation in silicate cores of icy satellites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-762, https://doi.org/10.5194/egusphere-egu24-762, 2024.

Uranus and Neptune have atmospheres dominated by molecular hydrogen and helium. In the upper troposphere (between 0.1 and 10 bars), methane is the third main molecule and condenses, yielding a vertical gradient in methane. Because it is heavier than the H₂/He background, methane condensation can inhibit convection and moist convective storms. Previous studies derived an analytical criterion on the methane vapor amount, above which moist convection is inhibited. In ice giants, this criterion yields a critical methane abundance of 1.2% at 80K (this corresponds approximately to the 1 bar level).

Using a 3D cloud-resolving model, we have shown (Clement et al. 2024, submitted in A&A) that this critical methane abundance governs storms inhibition and formation, concluding that the intermittency and intensity of storms depends on the methane abundance. Where methane exceeds this critical abundance in the deep atmosphere (at the equator and the middle latitudes on Uranus, and all latitudes on Neptune), frequent but weak storms form. Where methane remains below this critical abundance in the deep atmosphere (possibly at the poles on Uranus), storms are rarer but more powerful.

We use the insights of our 3D small-scale simulations to build a 1D parameterization of diffusion and convection for radiative-convective and global climate models. As 3D cloud-resolving simulations require long computation times, a radiative-convective model is needed to extrapolate heating tendencies. The combined use of these models should enable us to estimate more realistic periods between convective storms and explain the observed latitudinal sporadicity of methane clouds over a long period of time.

How to cite: Clement, N., Leconte, J., Spiga, A., Guerlet, S., Milcareck, G., Le Saux, A., and Selsis, F.: Convective storms and methane clouds on Uranus & Neptune: sporadicity and latitudinal variations revealed by a 3D cloud-resolving model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1905, https://doi.org/10.5194/egusphere-egu24-1905, 2024.

Both Voyager 1 and 2 are equipped with Plasma Science (PLS) instruments: four Faraday cups that measure the properties (density, temperature and flow) of low energy ions and electrons. During the Voyagers journey towards the interstellar space and the flybys from the gas giants PLS gave us the first in-situ data of the solar wind in such great distances, the magnetospheric plasma properties at the gas giants, and the extent of our heliosphere along with the conditions of the interstellar medium.

Voyager was particularly important for the study of the gas giants, as it was the first time we had in-situ plasma measurements from inside the magnetospheres, and PLS helped in studying not only the morphology of the magnetosphere, but also the plasma sources, dynamics, interaction with the moons, and ultimately its interaction with the solar wind plasma.

Jupiter and Saturn were visited from both Voyager 1 and 2, but only Voyager 2 visited Uranus and Neptune. The PLS data for Jupiter have been re-calibrated and archived by Bagenal+ [2017], Dougherty+ [2017], and Bodisch+ [2017]. They also developed an IDL package, VIPER (Voyager Ion PLS Experiment Response) for their analysis. For this work we re-analyzing the Voyager PLS data for Uranus and in this poster we present our methodology, the adaptation of VIPER for the Uranian conditions and the results of the re-analysis.

How to cite: Xystouris, G., Bagenal, F., and Wilson, R.: Re-analysis of Uranus Data from Voyager 2 Plasma Science Experiment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3184, https://doi.org/10.5194/egusphere-egu24-3184, 2024.

Albedo changes of Neptune related to the 11-year solar cycle have been reported since the 1970s (Lockwood and Thompson, Nature 280, 1979). For nearly two decades a clear anti-correlation between solar activity and Neptune’s brightness was observed but the relationship appeared to break down between the late 1980s (Lockwood and Thompson, Nature 349, 1991) and mid 1990s (Lockwood and Jerzykieicz, Icarus 180(2), 2006) where signs of a direct correlation instead appeared. Recent results indicate a direct correlation sustained over two solar cycles (Chavez et al, Icarus 404, 2023) prompting renewed interest in attempting an explanation.

Several parameters vary with the solar cycle, one being UV light which has a much higher variation than that of visible light. This could affect the photochemistry of Neptune’s atmosphere which is rich in methane that photolyzes at wavelengths below 200 nm and can produce haze (Romani and Atreya, Icarus 74(3), 1988). Another parameter that varies is the flux of galactic cosmic rays (GCRs) which is modulated by the solar wind. GCRs can ionize molecules leading to ion-induced nucleation (Moses et al, GRL 16(12), 1989) but only for the energies of particles which are allowed entry to the planetary atmosphere by the magnetic field. Solar activity modulates GCRs of energies up to about 20 GeV so a solar variation due to GCRs is only possible if particles of those energies can enter the atmosphere. The parameter used to describe GCR entry is the cutoff rigidity (in GV).

In this work we have used the magnetic field model of Neptune (Connerney et al, ASR 12(8), 1992) and a particle trajectory program (the Geomagnetic Cutoff Rigidity Computer Program by Smart and Shea, 2001, Tech. Rep. No. 20010071975) to calculate a cutoff rigidity map for Neptune for vertical GCR entry. Since the magnetic field is very tilted compared to the rotational axis (by about 45 degrees) the cutoff rigidity map has interesting features as the GCRs are guided by the magnetic field lines. Thus, lower energies and therefore a higher GCR flux more susceptible to solar cycle changes are allowed to enter the atmosphere at mid latitudes, as opposed to most planets where this happens as the poles since their magnetic field is more closely aligned with the rotational axis.

Furthermore, we have used fitted GCR energy spectra in combination with the cutoff rigidity map to produce a map of solar cycle variations in GCR flux at a height of 49 km, which is at the pressure level where cosmic ray showers are initiated at Earth and also close to where Neptunian clouds are found. Where the cutoff rigidity is lowest the solar cycle variations of GCR are several tens of percents which could affect cloud formation significantly.

How to cite: Enghoff, M. B., Romani, P. N., Connerney, J. E. P., and Jørgensen, J. L.: Galactic cosmic ray cutoff rigidity and solar cycle variation at Neptune, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5294, https://doi.org/10.5194/egusphere-egu24-5294, 2024.

Uranus is observed to have fast surface zonal winds with speeds reaching up to 200 ms⁻¹ relative to its assumed bulk rotation. The exact decay behaviour of the winds is uncertain, but there is indirect evidence that they must decay rapidly in relatively shallow layers of Uranus. By analysing thousands of Uranus interior structure models our study investigates the Uranian zonal wind decay via past zonal gravitational harmonics measurements, as well as understanding our limitations of future zonal wind constraints with a prospective Uranus mission (as proposed by NASA’s Planetary Science and Astrobiology Decadal Survey 2023-2032). In addition, we explore the effect of zonal wind decay on planetary shapes, the relationship of zonal wind decay and planetary bulk rotation, and the effect of alternative surface zonal wind profile fits to surface wind measurements on aforementioned phenomena.

How to cite: Soyuer, D., Helled, R., Neuenschwander, B., and Morf, L.: Zonal Winds of Uranus: Analysis, Modelling and Prospects, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9646, https://doi.org/10.5194/egusphere-egu24-9646, 2024.

The international consortium GEPP has been set to conceptualize probe designs with appropriate payloads that would remain within the typical budget allocated for ESA M-class missions (currently 500 M€). The aims of the consortium are i) to conceptualize a line of generic planetary entry probes that could be targeted to the giant planets with very few modifications, ii) to make the international science community, ESA and its member states, conscious that there is an opportunity to supply a series of entry probes as part of future international collaborations, for example as part of the future NASA flagship mission towards Uranus (Uranus Orbiter Probe) or to any future NASA-led mission to the outer planets for an affordable budget, and iii) to demonstrate that an M-class budget could even fund several entry probes with well-prioritized science objectives. The model payload capabilities of each concept will be defined according to a carefully-designed science traceability matrix. Two extreme concepts shall be investigated by the GEPP Consortium, namely a highly capable parachute-descent probe including a typical payload of 30 kg of scientific instruments down to 10 bars, and a smaller parachute-descent probe designed to address top priority science objectives with selected key measurements that would address the ESA Cosmic Vision 2050 science objectives. This presentation will detail the scientific objectives for each entry probe design, as well as the content, organization and planning of the study, which is assumed to be completed by the end of 2025.

How to cite: Mousis, O. and the GEPP team: Generic Entry Probe Program (GEPP) – an international initiative promoting the development of European descent modules dedicated to the in situ exploration of giant planets, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13379, https://doi.org/10.5194/egusphere-egu24-13379, 2024.

In the last twenty years, spectroscopic imaging observations of Uranus and Neptune, the solar system’s ‘Ice Giants’, have revolutionised our understanding of the atmospheres of these cold, distant worlds. In spectroscopic imaging observations, each pixel in the resolved image of the planet contains a continuous spectrum, which can be used to probe gaseous abundances as well as the precise vertical distribution of scattering particles, which is something that filter imaging alone cannot achieve. For example, observations made near 800 nm with the STIS instrument on Hubble Space Telescope have determined that the abundance of methane varies strongly with latitude in these atmospheres, with roughly a factor of two depletion at polar latitudes compared to the equator. At longer wavelengths (~1.5 μm), observations made with the NIFS instrument at Gemini-North have revealed not only the presence of hydrogen sulphide, but also hints of its latitudinal variation.

In this presentation we will highlight recent advances made with spectral imaging observations, using HST/STIS and also the MUSE instrument at the ESO Very large Telescope. On both planets the weight of evidence supports an atmospheric aerosol structure comprised of: 1) a deep layer of aerosol/H₂S ice near the H₂S condensation level at p > 5 bar;  2) a middle layer of aerosol/CH₄-ice near the CH₄ condensation level at p = 1 – 2 bar; and 3) an upper layer of photochemical haze. Variation in opacity and scattering properties of the middle aerosol layer near 1 – 2 bar are found to be responsible for the bulk difference in colour between Uranus and Neptune, and also for the seasonal cycle of Uranus’s colour. Meanwhile, variations in the reflectivity of the particles in the deep layer are found to be responsible for the dark spots seen in Neptune’s (and occasionally Uranus’s) atmosphere and in Neptune’s dark South Polar Wave near 60°S. In addition, a new class of deep bright cloud has been identified in Neptune’s atmosphere using VLT/MUSE, which hints at deep, vigorous convection.

While it is important that HST/STIS and VLT/MUSE monitoring observations will continue, the James Webb Space Telescope has recently observed both Uranus and Neptune using the NIRSpec instrument in Integral Field Unit (IFU) mode (i.e., spectroscopic imaging) at even longer wavelengths from 1.6 to 5.2 μm. These observations will advance even further our understanding of these distant worlds, although we note that extending such observations to NIRSpec’s shorter wavelengths would allow JWST to also recover the latitudinal variation of hydrogen sulphide, a key tracer of deep convection.

How to cite: Irwin, P., Dobinson, J., Teanby, N., Fletcher, L., Roman, M., Simon, A., Wong, M., Orton, G., Toledo, D., and Perez-Hoyos, S.: Aerosol layers, clouds, spots and the colours of Uranus and Neptune, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16799, https://doi.org/10.5194/egusphere-egu24-16799, 2024.

Over the last twenty years, a still very limited number of extended numerical simulations of the Uranus magnetosphere, showed that large scale magnetic vortices form tailwards of the planet. Their structure is strongly time-dependent on daily and seasonal time scales, both,   because of both, the unusually large 59 deg angle between the magnetic axis and the rotation axis of the planet and the small angle (unique in the solar system) between the rotation axis and the orbital plane. Based on results from 3D magnetohydrodynamic simulations, we comment on the nature and the structure of the vortices at both solstice and equinox. 

How to cite: Pantellini, F. and Griton, L.: Vortices in the magnetic tail of Uranus, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18135, https://doi.org/10.5194/egusphere-egu24-18135, 2024.

Understanding the atmospheric dynamics of Uranus and Neptune remains a challenging endeavour due to the limited observational data available. In this study, we employ a sophisticated General Circulation Model (GCM), known as the Generic Planetary Circulation Model, to investigate the complex meteorological phenomena of the Ice Giants, with a focus on the role of convection in the troposphere Our attention is directed towards the parametrization of convection, a crucial driver of atmospheric circulation, as it significantly impacts the transport of energy and the distribution of chemical species throughout the atmosphere. One of the unique aspects of our study lies in the consideration of methane condensation in the convection parametrization scheme based on a thermal plume model initially developed for the Earth atmospheric boundary layer (Rio & Hourdin 2008). However, unlike for the Earth, the condensable species are heavier than the surrounding atmosphere mainly composed of hydrogen. This phenomenon is suggested to be a powerful driver of intermittent storms activity detected in the atmospheres of the Ice Giants (Guillot 2022). The improved fidelity of our GCM simulations offers valuable implications for interpreting observational data and refining our understanding of the atmospheric processes governing these enigmatic outer planets.

How to cite: Le Saux, A., Guerlet, S., Spiga, A., Leconte, J., Clement, N., and Milcareck, G.: Investigating Atmospheric Dynamics of Uranus and Neptune: A General Circulation Model Approach with a Parametrization of Convection, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18317, https://doi.org/10.5194/egusphere-egu24-18317, 2024.

Neutral Tori are generally a result of particles escaping from a planetary atmosphere, its rings or satellites through internal source mechanisms or interactions with the magnetosphere. These particles then form a population of co-orbiting neutral particles that provide a source of plasma to the magnetosphere as well as drive dynamics and chemistry. Thus, understanding neutral tori provides key (sometimes unique) insight into planetary magnetospheres, moon source characterization and understanding, and ultimately can provide insight to past, present and future of magnetospheres. Current increased neutral torus research had provided significant insight into Saturn and Jupiter’s magnetosphere and gas giants in general. These results indicated great potential for improving our understanding the magnetospheres of Uranus and Neptune whose orientations offer the possibility of magnetospheric configurations not previously observed. Here, we will discuss how the Gas Giant neutral torus state of understanding has signifcaintly increased and may provide an analogy for what we may expect from studying these features on Ice Giants. We also present some preliminary modeling to speculate on the possible presence of neutral tori at Uranus and Neptune.

How to cite: smith, H.: The potential for neutral tori at Uranus and Neptune, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20711, https://doi.org/10.5194/egusphere-egu24-20711, 2024.

With its extended mission, JUNO is getting close to Io and performs moon flybys. It is therefore time to (re)analyse the already available magnetometer data from close flybys of Io by Galileo. Earlier studies of the J0 flyby showed the presence of ion cyclotron waves generated by the pick-up of SO2+ and determined the density of the picked-up ions. In this presentation we study all five Io flybys by Galileo and investigate the presence of ion cyclotron waves for three different species. SO2+, SO+ and S+. Through Fourier analysis and calculation of the cross-spectral matrix and strong criteria on power, polarization and ellipticity, we determine intervals of significant wave activity. Under the assumption of bi-spherical scattering of the pick-up ions in the velocity ring-distribution, an estimation of the pick-up ion density can be obtained. Through an assumption of the ionization frequency, this can be converted into a neutral density to obtain a value of the total neutral gas emitted per second and compare it to the usually assumed 1000 kg/s. Naturally, the five flybys will also give information about differences generated by local time, longitude and latitude.

How to cite: Volwerk, M., Bagenal, F., Dols, V., Kivelson, M., Khurana, K., Lammer, H., Schmid, D., Simon Wedlund, C., and Jia, X.: Ion cyclotron waves at Io: Pick-up rate and outgassing, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1243, https://doi.org/10.5194/egusphere-egu24-1243, 2024.

A common problem in space physics is how the energetic particles we observe in space are accelerated to high energies. In the magnetospheres and radiation belts of magnetized planets like the Earth and Saturn, we find electrons with up to MeV energies. There are two fundamental acceleration processes. Electrons can gain energy when they are transported closer to the planet (radial acceleration), where the magnetic field is stronger. The alternative is that the electrons are accelerated locally, through fluctuating electric or magnetic fields and wave-particle interaction. In this work, we use a modified version of the Versatile Electron Radiation Belts code to perform the simulations of the radiation belts at Saturn. Using convection terms of a modified Fokker-Planck equation, the zebra stripes and banana orbit signature is reproduced in the convection-diffusion code. Using the flexibility of our simulation framework, we explore the effects of radial diffusion, coulomb scattering and the local diffusion. Throughout the series of simulations, we aim to understand the role of the controlling processes of the radial transport acceleration (e.g., due to variable electric field) and the role of local acceleration, as well as any other processes needed to reproduce the observations.

How to cite: Drozdov, A., Kollmann, P., Hao, Y., and Wang, D.: Modeling of Saturn’s radiation environment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2578, https://doi.org/10.5194/egusphere-egu24-2578, 2024.

The inward plasma transport at Saturnian magnetosphere is examined using the flux tube interchange stability formalism developed by Southwood and Kivelson (1987).  Seven events are selected.  Three cases are considered: (1) the injected flux-tube and ambient plasmas are nonisotropic; (2) the injected flux-tube and ambient plasmas are isotropic and (3) the injected flux-tube plasma is isotropic but the ambient plasma is nonisotropic.  Case (1) may be relevant for fresh injections while case (3) may be relevant for old injections.  For cases (1) and (2), all but one events have negative stability condition, suggesting that the flux-tube should be moving inward.  For case (3), the injections located at L > 11 have negative stability condition, while 4 out of 5 of the injections at L < 9 have positive stability condition.  The positive stability condition for small L suggests that the injection may be near its equilibrium position and possibly oscillating thereabouts---hence the outward transport if the flux tube overshot the equilibrium position.  The flux-tube entropy plays an important role in braking the plasma inward transport.  When the stability condition is positive, it is because the entropy term, which is positive, counters and dominates the effective gravity term, which is negative for all the events.  The ambient plasma and drift out from adjacent injections can affect the stability and the inward motion of the injected flux tube. The results have implications to inward plasma transport in Jovian magnetosphere as well as other fast rotating planetary magnetospheres.

How to cite: Wing, S., Thomsen, M., Johnson, J., Ma, X., Mitchell, D., Allen, R., and Delamere, P.: The roles of flux-tube entropy and effective gravity in the inward plasma transport at Saturn, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2951, https://doi.org/10.5194/egusphere-egu24-2951, 2024.

The abrupt brightening of an Energetic Neutral Atom (ENA) blob or cloud has been interpreted as plasma injection in the Saturnian magnetosphere (termed ENA injection herein). Morphologically, there appears to be two types of abrupt ENA cloud brightening: (1) the brightening of a large cloud usually seen at distances > 10-12 Rs (Rs = 60,268 km) in the midnight or postmidnight region; (2) the brightening of a smaller cloud usually seen at distances < 10-12 Rs around 21-03 magnetic local time (MLT). Among many radio waves observed at Saturn, type 2 ENA injections correlate best with the 5 kHz narrowband waves. Using Cassini INCA and RPWS data, we examine the periodicities of the type 2 ENA injections and the 5 kHz narrowband emissions as well as their cross-correlations, which have been previously used to measure the lag times or phase differences. Because correlational analysis can only establish linear relationships, we also use mutual information to establish linear and nonlinear relationships. On average, the peak of the 5 kHz narrowband emission lags those of the type 2 ENA injection by about a few minutes to 2 hr. The injection of hot plasma into the inner magnetosphere can lead to temperature anisotropy, which can generate electrostatic upper hybrid waves, which upon encountering the high density gradient at the outer edge of the Enceladus density torus, can mode convert to the Z mode and then to O mode. The 5 kHz narrowband waves commonly propagate in the O mode.

How to cite: Ma, X., Wing, S., Brandt, P., Johnson, J., Mitchell, D., Kurth, W., Menietti, J., and Delamere, P.: Periodic narrowband radio wave emissions and inward plasma transport at Saturnian, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3227, https://doi.org/10.5194/egusphere-egu24-3227, 2024.

Juno’s Extended Mission has expanded the scientific reach of Juno’s low-light Stellar Reference Unit (SRU) star camera to multiple new targets within the Jovian system. Close flybys of the dark sides of Ganymede and Europa (illuminated by Jupiter-shine) have yielded high-resolution SRU surface images that enabled significant improvements to the geomorphologic maps of these icy moons and revealed sites of potential present day surface activity on Europa (providing high quality baselines for Europa Clipper and JUICE). Close flybys of Jupiter’s dark side began in Spring 2023, launching the SRU’s Extended Mission study of lightning in the northern latitudes at resolutions as high as a few kilometers per pixel, and the geometry has also allowed the SRU to image Jupiter’s faint dust ring from vantage points inside the ring. The Mission’s planned flybys of Io in December 2023 and February 2024 will present additional opportunities for low-light high-resolution SRU surface imaging on the dark side of the volcanic moon. Our presentation will discuss new Extended Mission results from Juno’s SRU. 

How to cite: Becker, H. N., Florence, M., Brennan, M., Lunine, J., Schenk, P., Hansen, C., Martos, Y., Bolton, S., and Alexander, J.: New Extended Mission Results from Juno’s Stellar Reference Unit , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3269, https://doi.org/10.5194/egusphere-egu24-3269, 2024.

Recently, it has been shown that the secular variation of Jupiter's magnetic field, which has been observed by the Juno spacecraft, is in large part due to eastward advection of the Great Blue Spot (a localized, equatorial region of intense magnetic field) by fluid flow in the deep interior. More recent observations  by Juno suggest that the drift rate of the spot is varying rapidly in time. These time variations can be fit with a sinusoidal variation of the flow speed with a period of approximately four years.  Here, we discuss both the mechanism of this time variability and the constraints that its observability place on the structure and dynamics of the deep interior.

How to cite: Bloxham, J., Cao, H., Stevenson, D., Connerney, J., and Bolton, S.: Rapidly time-varying zonal flow in Jupiter's deep interior, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4667, https://doi.org/10.5194/egusphere-egu24-4667, 2024.

The presence of carbonaceous matter is envisaged on the surface of many outer solar system bodies, including the Galilean moons. Density and moments of inertia of icy moons and dwarf planets also suggest the presence of this material in their refractory cores. The initial carbonaceous matter would have been composed of complex organic molecules (COMs) that possibly formed when the building blocks of the moons were in the forms of pebbles and icy grains in the protosolar nebula. Experimental studies indeed show that COMs can be formed from the UV irradiation of icy grains under nebular conditions.

A baseline scenario is the formation of the Galilean moons in a circumplanetary disk that was too cold to vaporize the solids originating from the protosolar nebula. In this scenario, only the thermodynamic conditions of the protosolar nebula play a crucial role in determining the composition of the building blocks of the moons. Here we aim to assess the thermodynamic conditions of the protosolar nebula that enable the formation and the delivery of COMs to the formation location of the Galilean moons in the context of the aforementioned scenario. To do so, we have developed a two-dimensional model that describes the transport of pebbles/dust particles during the evolution of the protosolar nebula, using a Lagrangian scheme. This allows us to calculate the interstellar flux received by the particles as they migrate through the nebula.

How to cite: Benest Couzinou, T., Amsler Moulanier, A., and Mousis, O.: Delivery of organic matter to the Galilean moons, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5889, https://doi.org/10.5194/egusphere-egu24-5889, 2024.

Ganymede’s atmosphere is one of the most complex among the moons of our solar system. As the only known satellite in our solar system to feature an intrinsic global magnetic field, Ganymede forms a small magnetosphere within the much larger magnetosphere of Jupiter. The interaction between the two magnetospheres makes Ganymede's plasma environment highly variable both in space and time. Consequently, the moon's atmosphere, predominantly shaped by the interplay between the plasma environment and Ganymede's surface, likely exhibits a corresponding high degree of variability.

The recent Juno spacecraft flyby of Ganymede has provided us with unprecedented insights into the moon's electron and ion environment. This study capitalizes on electron data collected by the Jovian Auroral Distributions Experiment (JADE) during Juno's traversal of Ganymede's magnetopause current layer, employing these measurements as a proxy for the electron conditions within Ganymede's auroral region. Our simulations reveal that these electrons play a pivotal role in governing Ganymede's H₂ and O₂ atmospheres, representing the predominant constituents of its atmospheric composition. Furthermore, the abundance of atomic O and H, crucial factors in Ganymede's atmospheric mass loss, is intricately influenced by these electrons, underscoring their significance in shaping the complex dynamics of Ganymede's atmospheric behavior.

Our current understanding of Ganymede's atmosphere predominantly stems from spectroscopic observations. However, it's crucial to acknowledge that the interpretation of spectroscopic data heavily relies on certain assumptions. Our analysis underscores the significance of acquiring a comprehensive understanding of Ganymede's atmosphere. To achieve this, it is imperative to conduct simultaneous observations encompassing the moon's surface, its atmospheric conditions, and the entirety of its plasma environment, including both thermal and energetic ions and electrons. 

How to cite: Vorburger, A., Fatemi, S., Carberry Mogan, S. R., Galli, A., Liuzzo, L., Poppe, A. R., Roth, L., and Wurz, P.: Influence of Ganymede's electron environment as measured by JADE on Ganymede's atmosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6024, https://doi.org/10.5194/egusphere-egu24-6024, 2024.

Our understanding of the giant planets in our solar system has been significantly advanced by the Juno and Cassini missions. These planets provide us with the unique opportunity to understand the interior structure of giant exoplanets. Recent insight into Jupiter’s atmospheric composition indicates a water concentration of 2-7 times solar in the equatorial region, surpassing the subsolar findings of the precursor Galileo mission. In this study, we conduct radiative transfer calculations for Jupiter's deep atmosphere including these enhanced water enrichment results and the presence of condensates predicted by chemical equilibrium models. Our primary focus is to derive a new temperature-pressure profile and assess the existence of potential radiative zones within the deep atmosphere. The presence of a radiative zone can have a profound impact on the internal structure of a planet and thus, a detailed analysis of Jupiter's temperature profile is essential for a comprehensive study of its interior structure.

How to cite: Siebenaler, L. and Miguel, Y.: Exploring the temperature profile of Jupiter's deep atmosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6119, https://doi.org/10.5194/egusphere-egu24-6119, 2024.

Juno arrived at Jupiter in 2016 and was inserted into a polar orbit with its closest approach (“perijove”) near Jupiter’s equator.  One of Juno’s first major discoveries was the existence of circumpolar cyclones covering both of Jupiter’s poles. Over the course of Juno’s prime and extended missions, the line of apsides of the orbit has experienced a constant northward migration due to Jupiter’s asymmetric gravity field. One result of this migration is the lowering the spacecraft’s altitude over Jupiter’s north pole.  Recently, the altitude over the north pole has reduced sufficiently to allow Juno’s microwave radiometer (MWR) to resolve Jupiter’s circumpolar cyclones.  The observations provide new insights into how the circumpolar cyclones evolve with depth.  We will present results from multi-wavelength observations of Jupiter’s polar cyclones including visible light images (JunoCam), the infrared images (JIRAM) and microwave images (MWR).  The combined data set reveals information on how the circumpolar cyclones compare and evolve with depth. 

How to cite: Bolton, S., Brueshaber, S., Orton, G., Hansen, C., Levin, S., Mura, A., Grassi, D., Fletcher, L., Rogers, J., Eichstädt, G., Wong, M., Ingersoll, A., Ermakov, A., and Li, C.: Multi-wavelength Observations of Jupiter’s Northern Circumpolar Cyclones, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6708, https://doi.org/10.5194/egusphere-egu24-6708, 2024.

    Juno’s Microwave Radiometer (MWR) is providing the unprecedented opportunity to explore the dynamical properties and composition of Jupiter’s deep atmosphere, which is arguably one of the most visibly heterogeneous and time variable in the solar system. Since its arrival on 27 August 2016, the MWR has observed variability in microwave emission at wavelengths between 1.3 and 50 cm, sensing from 0.7 bar to over 100 bars of atmospheric pressure at over 57 close approaches to the atmosphere, known as “perijoves”. There has been a concerted effort to collect contextual information from other Juno instruments, as well as ground- and space-based observations to help interpret the MWR results. The space-based observations have included those from Juno’s own visible camera (JunoCam) and its Jupiter Infrared Auroral Mapper (JIRAM), as well as the Hubble Space Telescope (HST). The ground-based observations have included images and spectra from both professional and citizen-science astronomers.

     We report here observations that are constrained to spatial resolutions of 2 degrees in latitude or better, and have been subject to recent improvements in the calibration drift for all MWR’s channels with an improved relative calibration uncertainty of 0.5% or better over the entire mission.  This has allowed us to evaluate zonal-mean temperatures and variability with improved confidence that these are real and not an artifact of receiver drift. The region that by far shows the greatest variability from a zonal mean is the North Equatorial Belt, (NEB: 12^oN-16^oN planetocentric) with a 2% standard deviation from the mean at all levels sensed by the MWR except for the 50-cm channel that senses variability in temperature and ammonia and water composition at pressures in excess of 100 bars of pressure. Among the strongest variability associated with discrete features in the atmosphere is a major upwelling and subsequent clearing of cloud cover in the North Temperate Belt (NTB: 20^oN-26^oN) in August-September of 2020.  In general, the microwave antenna temperature variability often but not always correlates with visible or near- to mid-infrared variability. In some regions, such as the Equatorial Zone (EZ: 3^oS-6^oN), substantial variability is detected not only in regions above the level of the water-condensate cloud (~10 bars) but also at great depth (>100 bars). An important part of our next steps will be to examine where variabilities in the zonal-mean microwave brightness are the result of zonally discrete features in the atmosphere, particularly the NEB.

How to cite: Orton, G., Zhang, Z., Levin, S., Fletcher, L., Oyafuso, F., Li, C., Brueshaber, S., Wong, M. H., Momary, T., Bolton, S., Baines, K., Dahl, E., and Sinclair, J.: Probing the Depths of Spatial and Temporal Variability in Jupiter from Juno Microwave Radiometer Observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6795, https://doi.org/10.5194/egusphere-egu24-6795, 2024.

On June 7, 2021, and September 29, 2022, the NASA Juno spacecraft flew by Jupiter’s Galilean moons, Ganymede, and Europa, respectively.  The closest approach distance was only ~1000 km above Ganymede, and only ~350 km above Europa. More recently, on December 30, 2023, Juno passed by Io at a distance of 1500 km and is planned do so a second Io flyby on February 3, 2024 at a similar distance.  The close flybys were the first encounters with the moons in over two decades and provided the first opportunity to map the subsurface of the their shells at multiple microwave frequencies using Juno’s Microwave Radiometer (MWR).  The observations provided several swaths across the moons at six frequencies, ranging from 600 MHz to 22 GHz.  The ice transparency at microwave frequencies is dependent on its purity; assuming pure ice, the observations probe depths ranging from meters to kilometers. The MWR observations represent the first resolved interrogation of Ganymede and Europa’s subsurface ice shell revealing new constraints on porosity, fracturing, differences in terrain type and possibly the thickness of the ice shell. These unprecedented measurements of Io, Europa and Ganymede will allow comparative studies of the surfaces and subsurface structures of the Jovian satellites. The Juno MWR measurements complement previous ground-based radar and microwave radiometry observations, which provided early characterization of these surfaces.  A comparison of the microwave spectra for all three satellites will be presented, as well as a detailed analysis and interpretation of the Ganymede MWR data that provide new constraints on ice subsurface properties.

How to cite: Ermakov, A., Bolton, S., Zhang, Z., Levin, S., Akiba, R., Lunine, J., Feng, J., Hand, K., Keane, J., Misra, S., Hartogh, P., Stevenson, D., Siegler, M., and Bonnefoy, L.: Juno Microwave Radiometer Observations into the Subsurface of the Ice Shells of Io, Europa and Ganymede, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6820, https://doi.org/10.5194/egusphere-egu24-6820, 2024.

Various characteristic frequencies observed in the plasma wave spectrum inward of Io have revealed a durable electron density profile that includes a localized relative maximum near M = 4.8 with a local minimum between this and the much greater densities closer to Io.  Scale heights relative to the centrifugal equator are of order one Jovian radius, thought to be too large for a cold heavy ion population leading to the conclusion that protons are likely responsible for the large scale height.  In this paper we show evidence of the low-frequency cutoff of the z-mode at the L=0 frequency, a polarization change at the local electron plasma frequency and low-frequency cutoff of ordinary mode waves.  The determination of the electron plasma frequency and electron cyclotron frequency from the measured magnetic field strength also allow the calculation of the upper hybrid resonance frequency and R=0 cutoff of the extraordinary mode.  Often, all of these spectral features can be found in the Juno plasma wave spectra obtained in the inner Io torus.

How to cite: Kurth, W., Hospodarsky, G., Faden, J., Menietti, J. D., Sulaiman, A., Elliott, S., Connerney, J. E. P., Allegrini, F., and Bolton, S.: Io Torus Electron Densities inward of Io's M-shell, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6867, https://doi.org/10.5194/egusphere-egu24-6867, 2024.

Strong and persistent zonal winds at the cloud level characterize both Jupiter and Saturn. Based on  Juno and Cassini's measurements of the low-order gravity harmonics up to J₁₀,  it was shown that the observed cloud-level winds penetrate inward parallel to the planet's spin axis and decay at a depth of around 3,000 km and 9,000 km, respectively. However, because of the limited number of measured gravity harmonics, the latitudinal structure of the flows could not be uniquely determined, so only an overall estimate of their depth was obtained.

Here, we present new gravity analyses for both gas giants, based on the original Juno and Cassini measurements,  but in which the magnitude of harmonics higher than J₁₀ is constrained at the less observable high latitudes. This enables resolving the gravity field up to J₄₀ for Jupiter and J₂₀ for Saturn, while being consistent with the previous gravity measurements.  We then use the high harmonics to better constrain the structure of the zonal flows below the observed cloud level, revealing the latitudinal variations in the depth of the flows. We show that for Saturn, the mid-to-high latitude jets must be shallower than the low-latitude winds, while in Jupiter, the low-latitude winds dominate the gravity signal. In the talk, we will review the similarities and differences between the two gas giants arising from our results and discuss their implications for our understanding of gas giant dynamics.

How to cite: Galanti, E., Kaspi, Y., Durante, D., and Iess, L.: The structure of Jupiter and Saturn's winds below the cloud level - insights from high harmonics gravity measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7242, https://doi.org/10.5194/egusphere-egu24-7242, 2024.

The magnetospheres of gas giants are characterised by their strong magnetic fields, the fast rotation of the planet and the presence of embedded active moons (Io at Jupiter, Enceladus at Saturn), releasing neutral gas and, from there, plasma in the innermost regions of the systems. Their dynamics is believed to be controlled by a balance between the centrifugal force acting on cororating plasmas trapped in the planetary magnetic field, plasma pressure gradients and magnetic forces. This balance determines the rate of outward transport of mass, angular momentum and energy and has a strong influence on the global configuration and dynamics of the magnetospheres. It results in the formation of a magnetodisk of plasma at the planetary equator, and a global outward transport of plasma from the innermost source regions to the outer magnetosphere where it is lost through magnetospheric boundaries or downtail. 
    Until now, description of this transport has followed two different approaches in the literature. “Corotation enforcement” models focus on the description of angular momentum transport in a disk exchanging momentum with the planetary thermosphere/ionosphere via electric current systems transferring magnetic torques. They assume mass and conservation but do not explicitly describe the transport processes through the magnetodisk. On the contrary, radial diffusion models do not explicitly take into account angular momentum transport nor exchanges between the planet and the magnetospheric plasma, but they describe radial transport of mass and energy assuming a certain state of turbulence in the magnetodisk.
    We present a unifying approach of the radial transport of mass, angular momentum and energy, using turbulent diffusion and including sources and sinks of plasma of arbitrary radial distribution throughout the disk. Our set of coupled equations independently describes momentum exchange with the two conjugate ionospheres, thus allowing for the study of interhemispheric asymmetries, such as the ones revealed by Juno, in this coupling. We will present solutions of our coupled set of transport equations that explore the different possible causes and effects of interhemispheric asymmetries in magnetodisk/planet coupling, with emphasis on the cases of latitudinally thin and thick disks corresponding respectively to the cases of Jupiter and Saturn. We will compare the outputs of our models with recent observational constraints brought by the Juno and Cassini missions.

How to cite: Devinat, M., André, N., and Blanc, M.: A self-consistent model of radial transport in the magnetodisks of gas giants including interhemispheric asymmetries, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8604, https://doi.org/10.5194/egusphere-egu24-8604, 2024.