Lucie Riu

The Mars Magnetosphere ATmosphere Ionosphere and Space-weather SciencE (M-MATISSE) mission is an ESA Medium-class (M7) Phase A candidate. Its twin orbiters—Henri and Marguerite—operate in complementary eccentric trajectories to sample Mars’s magnetosphere–ionosphere–thermosphere (MIT) system under varying solar-wind conditions. Science objectives include (1) mapping MIT coupling, (2) characterizing the radiation environment, and (3) probing ionosphere–surface interactions.The Science Ground Segment (SGS) at ESAC brings over two decades of mission-operations heritage—supporting Mars Express, ExoMars, BepiColombo, and JUICE, between others—providing end-to-end planning, health monitoring, and quick-look analysis using tools such as MAPPS/EPS-AGM and SPICE. The Mars Science Centre (MSC) adds specialist scientific oversight: defining observation strategies, refining event triggers, and ensuring agile responses to space-weather alerts and transient phenomena.Long-Term Planning (LTP), conducted at least six months before science operations, converts high-level objectives into: Observation Definitions (ObsDefs): generic templates for instrument modes (continuous, burst, event-driven), pointing and calibration requirements, and inter-instrument coordination. Resource Envelopes: power, data-rate, and thermal budgets for each ObsDef, generated via MAPPS/EPS-AGM to guarantee feasibility under worst-case margins. Preliminary Event Files: time-tagged orbital and geometric triggers—e.g., altitude crossings, solar-longitude markers, alignment windows—that drive ObsDef activation and feed into Medium-Term (MTP) and Short-Term Planning (STP). By front-loading these products, SGS and MSC ensure that all six instruments (COMPASS, M-EPI, M-MSA, M-SoSpIM, MaCro, M-AC) can seamlessly transition between routine monitoring and rapid-response campaigns, maximizing scientific return within spacecraft constraints.The LTP poster translates these products into a clear visual planning aid, highlighting representative mission-critical windows and sample plots rather than an exhaustive list. Key elements include: Annotated Eclipse & Occultation Intervals: shadow passages and Earth–line-of-sight losses, showing when instruments switch to safe or calibration modes. Flyby & Alignment Opportunities: selected Phobos/Deimos close approaches and inter-spacecraft proximity events, illustrating windows for radio-science occultations and coordinated measurements. Orbit-Regime Passages: representative sheath, magnetotail, and induced-magnetosphere boundary intervals, derived from SPICE-based analyses, indicating when to switch ObsDefs. Data-Rate Forecasts: sample bitrate-vs.-time curves annotated with solar-longitude markers, guiding allocation of high-data-volume burst modes. Trigger-Timeline Charts: simplified periapsis altitude and geometry plots labeled with example windows (e.g., terminator-ionosphere, dayside vs. nightside passes). Each figure is annotated with relevant parameters—solar longitude (Ls), solar-zenith-angle ranges, and spacecraft altitudes—to guide science and operations teams in correlating orbital geometry with ObsDef activation. By presenting a curated set of examples, the poster serves as an actionable blueprint, ensuring transparent communication of planning constraints and opportunities, and preparing M-MATISSE to capture both steady-state and transient Martian space-weather phenomena.

NH-rich compounds have been detected on Ceres (Sanctis et al., 2015), comet 67P (Poch et al., 2020) and possibly other asteroids (Rivikin et al., 2022), based on the 3.1 µm absorption in their infrared reflectance spectrum. This feature has never been found among the meteorite collections but recently reported on the returned Ryugu sample (Pilorget et al., 2022). Studying these compounds can help us understand the parent bodies evolution and the volatiles delivery within the Solar System. In 2023, NASA’s OSIRIS-REx mission returned ~120 g sample from the primitive asteroid Bennu (Lauretta et al., 2024). Preliminary analyses showed that Bennu samples share many chemical and mineralogical similarities with Ryugu samples. Here we search for the NH-rich compounds in the Bennu samples and compare them with Ryugu samples.Thanks to an agreement between NASA and JAXA, ~0.6 g of Bennu samples was delivered to the Extraterrestrial Sample Curation Center (ESCuC) of JAXA (Sagamihara, Japan). They are stored and measured under controlled environment (N2 purged) to avoid terrestrial contamination and alteration (Fukai et al., 2023). Samples are composed of 5 bulks, from which aggregate samples and mm-sized grains were extracted after a first campaign of analyses. Here we combined observations performed by the infrared-hyperspectral microscope MicrOmega (22.5 µm pixel size, 256x256 pixel, FOV 5x5 mm, spectral range 0.99-3.65 µm), a micro-FTIR spectrometer (single pixel, ~50-100 µm FOV, spectral range 2-13 µm) and a LEICA optical microscope (Bibring et al., 2017; Pilorget et al., 2022; Fukai et al., 2023). We have specifically searched for regions of interest (ROIs) with strong absorption around both 2.7 µm (OH) and 3.06 µm (NH).We have detected 8 NH-bearing ROIs (by 23rd December 2024), relatively rare compared to other minor phases such as carbonates. Their sizes vary from ~100 µm to ~1 mm, with different morphology, from rounded to elongated/irregular. For example, one of the ROIs shows a vein-liked shape, another one looks like a thin layer coating on the matrix material. The corresponding area in visible microscope images is often yellowish in color. In terms of brightness, they are generally much brighter in reflectance (~5-15%) than the surrounding matrix materials (2~3%). All the ROIs show much deeper (~40%) absorption around 2.7 µm than that of matrix materials (~10 %), which is similar to that of Ryugu ROIs if we average all the ROIs spectra for both datasets. Their band position is ~2.72 µm, similar to the matrix materials and those of Ryugu sample. All the ROIs also show deep absorption around 3.06 µm (~15%). The FTIR spectra are consistent with MicrOmega data in the overlapping wavelength region (2.0-3.6 µm). In the longer wavelength, these ROIs generally show bands around 6 µm (~1650 cm-1, water molecule), around 7 µm (~1430 cm-1, NH4+), and around 10 µm (~1020 cm-1, Si-O).These results show that ammonium (NH4+) is present in Bennu samples, with a possible connection with phyllosilicates. Importantly, we also observed similarities with NH-rich areas detected in Ryugu samples, thanks to the measurements on both collections by MicrOmega.

We present the detection and characterization of mesoscale waves on the lower clouds of Mars (20–40 km) using hyperspectral images from the Observatoire pour la Minéralogie, l’Eau, les Glaces et l’Activité (OMEGA) onboard the European Mars Express space mission. We used image navigation and processing techniques based on contrast enhancement and geometrical projections to semi‐manually detect and manually characterize morphological properties of the detected waves, such as horizontal wavelength or packet length. Our study covers 3 Martian years, spanning from January 2004 (Mars Year 26) to January 2010 (Mars Year 29). We detected 263 wave packets, of which we characterized 125, revealing an average horizontal wavelength of 21 km, with detected waves spanning horizontal wavelengths between 6 and 83 km. Wave activity exhibited spatial and temporal variability, with larger wave packets concentrated in the northern hemisphere and most detections occurring during daytime. Seasonal patterns revealed higher wave activity during northern spring and autumn and southern winter, linked to regional topography, atmospheric density perturbations, and diurnal heating cycles. These findings provide insights into Martian atmospheric gravity waves and demonstrate the OMEGA data set's value for future studies of Mars's atmospheric dynamics.

In deserts on Earth, aeolian (wind-blown) and fluvial (river) (AF) processes display considerable interactions, which have an impact on dune and river trajectories, morphologies, geometries, and distributions. These interactions can lead to water loss to the subsurface and the formation of sabkhas, which are interdune ponds that transform into salt flats. These pools are where primordial continental life on Earth is hypothesized to have emerged, evidenced by microbial mats. Lithified dunes and interwoven inverted river channels, and the discovery of aqueously altered lithified dunes by the Curiosity rover, indicates synergy between AF interactions on ancient Mars.We report the results of the pilot study by the Working group on Aeolian-Fluvial Terrain Interactions (WAFTI), based at the European Space Agency, which examines the effects of these processes in synergy under ancient Martian conditions, using a combination of modelling and geomorphological analysis. Our Martian Aeolian-Fluvial Interactions (MAFI) model is a landscape evolution model based on a coupled implementation of the Caesar-Lisflood fluvial model, and Discrete ECogeomorphic Aeolian Landscape model (DECAL) dunes model. It routes water over a Digital Elevation Model (DEM) and calculates erosion and deposition from fluvial and slope processes changing elevations accordingly. Aeolian material is discretized into slabs on the DEM, and slabs are moved across the space according to a set of simple rules.We conduct simulations of various scenarios to model the interactions between perennial and ephemeral rivers, actively migrating dunes, and different types of terrain (bedrock and unconsolidated sediment). These simulations incorporate factors such as evaporation and water loss to the subsurface. We measure changes in the grainsize distribution of the river sediment both upstream and downstream of a dunefield, and analyse the effects of dune migration on river morphology and pond evolution over hundreds of years of AF interactions.These interactions have a number of salient impacts: meandering inverted channels, the sediment size and distribution of Martian rivers, the formation of interdune pools, and the preservation of Martian valley networks.

ExoMars Trace Gas Orbiter (TGO) was launched by the European Space Agency in March 2016 and started operating around Mars in April 2018 after the nominal science orbit was reached. Four instruments are mounted on the spacecraft: The Atmospheric Chemistry Suite (ACS), the Colour and Stereo Surface Imaging System (CaSSIS), the Fine Resolution Epithermal Neutron Detector (FREND), and the Nadir and Occultation for MArs Discovery (NOMAD) instrument. The ACS and NOMAD instruments are dedicated to studies of the Martian atmosphere. The CaSSIS visible camera is equipped with a rotation mechanism allowing to acquire images of the same target with different viewing angle in the same overflight pass, enabling stereo images. Specific regions can be targeted by rolling the spacecraft in across-track direction. The FREND instrument requires nadir or near-nadir pointing during a large fraction of time to map the hydrogen abundance in the sub-surface. The Science Operations Centre (SOC) based at the European Space Astronomy Centre (ESAC, Spain) is responsible for the implementation of science operation timelines, considering the instrument team requests and the mission's science priorities, while at the same time complying with spacecraft and operational constraints (B. Geiger et al., 2018, M. Ashman et al., 2018). We describe here the overall planning strategy for TGO and its evolution. The planning is divided into specific segments: long, medium, and short term, corresponding to 6-months, 4-weeks and 1-week planning periods. The strategy is set for a long-term planning period (LTP) and revised if/when necessary. For each 6-month or LTP period, the planning is such that solar occultations opportunities are computed for the overall period. On average, since the beginning of the mission, we find that a LTP period comprises ~3500 occultations opportunities amongst which ~60% are eventually scheduled. The scheduled occultation pointings are partitioned between the ACS and NOMAD instrument. Additionally, it is possible to indicate in the schedule that ACS can ride-along a percentage of prime occultations allocated to NOMAD. Depending on the location at the surface and/or the Solar Longitude (Ls, i.e., the local season) the occultations can be considered with higher priority. Starting from MTP012 (in February 2019), occultations covering the equatorial regions were considered with highest priority. Thus, no other type of observations can be implemented during periods of equatorial occultations. Moreover, based on instrument teams requests a list of regions of interest (ROI) is also used to flag amongst the occultations opportunities the ones with high priority. This list was started during MTP020 in October 2019 and the last addition to the list is dated to April 2024. We do not exclude that this list will evolve in the future to respond to scientific requirements/discoveries. To this day, 7 ROIs are defined: Gale Crater, Jezero Crater, Green Valley, Utopia Planitia, Elysium Planitia, Alba Mons and Arsia Mons (for the detection of Elongated Clouds). Nominally, the instrument allocation for “highly valuable occultations” on ROIs is 50/50 between the ACS and NOMAD instruments while trying to get similar spatial coverage on each region for both instruments. The CaSSIS instrument team provides a list of images (Nadir pointing or targeted pointing, the latter resulting in off-nadir angle) at Medium Term planning (MTP). On average ~2500 nadir images and ~1400 targeted images are acquired per LTP-period. Targeted images are important to fill gaps on the surface and/or to point to locations that cannot be reached while observing in Nadir mode. Although this puts constraints on the space-craft operations, the off-nadir angle allowed for these observations have recently been increased from 5 to 7 degrees to allow for better access to regions that can rarely be observed.At MTP-level, other types of observations can be implemented. Mostly, observations that are not part of the standard repetitive pointing timeline and that result in large off-nadir angle. These specific observations, labelled as “Special Pointings”, are limited in number to 5 per STP (i.e., per week) due to their operational constraints. They correspond to calibration measurements, Phobos or Deimos observations and limb observations. Special pointing calibrations measurements were included in the planning strategy since the beginning of the mission with an allocation of 1 special pointing per STP. This number has increased with time (5 to this day) thanks to the scientific benefit of these pointings. The first limb measurement occurred in MTP014, in April 2019; the first Phobos measurement occurred in MTP045, in September 2021 and the first Deimos measurement took place in MTP049, in December 2021. The limb measurements are usually used by the NOMAD instrument to detect and characterise airglow (day- or night- glow) and auroras (Gérard et al., 2020a,b; Soret et al., 2022; Soret et al., 2023; Gérard et al., 2023). Recently, experimental measurements for limb observations with CaSSIS were also carried out. These CaSSIS observations are promising (Thomas et al., 2024) and are implemented as special pointings on the basis of ~1 per MTP. Based on instrument team requests, moon observations for ACS have stopped in May 2022.Reference: B. Geiger et al., Long Term Planning for the ExoMars Trace Gas Orbiter Mission: Opportunity Analysis and Observation Scheduling, 2018 Space Ops. Conference; M. Ashman et al., Science Planning Implementation and Challenges for the ExoMars Trace Gas Orbiter, 2018 Space Ops. Conference; Gérard et al., 2020, Detection of green line emission in the dayside atmosphere of Mars from NOMAD-TGO observation, Nature Astronomy Letters; Gérard et al., 2020, First Observation of the Oxygen 630 nm Emission in the Martian Dayglow, GRL; Soret et al., 2022, The Mars Oxygen Visible Dayglow: A Martian...

Atmospheric gravity waves (GWs) are mesoscale atmospheric oscillations that propagate vertically in stable, stratified planetary atmospheres [1], significantly shaping weather and climate by influencing temperature, wind patterns, and cloud formations. In this study, we present preliminary results of GWs in the Martian atmosphere using the High-Resolution Stereo Camera (HRSC) [2] onboard the European Mars Express (MEx) spacecraft [3]. By taking advantage of high-altitude observations (200-800 m/px) with a field of view from limb to limb, we can investigate the morphological and dynamical properties of GWs. Previous studies using the OMEGA instrument [4] were limited by a narrow field of view, preventing them from capturing the full extent of wave packets.We have morphologically characterised the wave packets in the high-altitude observations, considering the number of crests, horizontal wavelength, packet width and length, and orientation. Additionally, we retrieved cloud heights using a new method adapted from [5] that utilises the RGB channels of HRSC to measure the altitudes of waves present in the images. In addition to pairs of high-altitude observations taken 30 minutes apart, we estimated wind speeds by tracking the displacement of features between the two images.Our findings indicate a varied range of altitudes for different cloud types, including water ice clouds ranging from 15-45 km (±5 km error), CO₂ ice clouds from 60-85 km (±5 km error), and dust clouds from 5-10 km (±3 km error). Wind speeds of 5-15 m/s (±10% error) were estimated, and we created regional wind maps across cloud-rich regions (Figure 1). These wind maps reveal the dynamics of mesoscale cloud structures, illustrating how GWs influence wind patterns across the Martian atmosphere. Future research will incorporate OMEGA's spectral data to classify cloud types accurately. Figure 1 - Gravity waves detected in high-altitude HRSC observations of the region at 40°S, 70°W during Mars Year 36. Red markers pinpoint specific features in wave packets (50 tracers), measured in paired images taken 34 minutes apart. These coordinates are used to calculate wind speeds, aiding in the creation of wind maps with velocities ranging from 5 to 15 m/s, with an error margin of 10%. Acknowledgements: This work was supported by the Portuguese Fundação Para a Ciência e a Tecnologia of reference PTDC/FIS-AST/29942/2017, through national funds and by FEDER through COMPETE 2020 of reference POCI-01-0145-FEDER-007672, and through a grant of reference 2021.05455.BD. GG acknowledges financial support from Junta de Andalucia through the program EMERGIA 2021 (EMC21_00249) and from the Severo Ochoa grant CEX2021-001131-S funded by MCIN/AEI/ 10.13039/501100011033. IAA is also supported by grant ID2022-137579NB-I00 funded byMCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”. Funded by the ESA Faculty Research Contract and Science Exchange Programme, which is in the frame of the MWWM - Mars Wind and Wave Mapping project of reference ESA RFP/3-17570/22/ES/CM. We thank the Mars Express Team for their support and encouragement in starting this work. References:[1] Fritts, D. C., & Alexander, M. J. (2003). Gravity wave dynamics and effects in the middle atmosphere. Reviews of geophysics, 41(1).[2] Jaumann, R., et al., 2007. The high-resolution stereo camera (HRSC) experiment on Mars Express: Instrument aspects and experiment conduct from interplanetary cruise through the nominal mission. Planetary and Space Science 55, 928-952.[3] Cardesin-Moinelo, A., et al., 2024. Mars Express: 20 Years of Mission, Science Operations and Data Archiving. Space Science Reviews, 220(2), 25.[4] Brasil, F., et al., 2024. Atmospheric Gravity Waves in Mars’s Lower Atmosphere: Nadir Observations from OMEGA/Mars Express data. Astronomy and Astrophysics (under revision).[5] Scholten, F., et al., 2010. Concatenation of HRSC colour and OMEGA data for the determination and 3D-parameterization of high-altitude CO2 clouds in the Martian atmosphere. Planetary and Space Science, 58(10), 1207-1214.

The surface of Titan displays evidence of fluvial and aeolian activity. Rainfall on Titan results in fluvial landforms (FLs), lakes, and seas. Unlike Earth, this rainfall is predominantly liquid methane. Titan’s surface conditions allow for liquid methane and ethane to be stable. Although the rainfall is primarily methane, this methane (liquid density ~424 kg/m3) can be photolyzed to form ethane (liquid density ~544 kg/ m3), resulting in lakes and rivers of ethane. Liquid ethane is more likely to be fed back into rivers and lakes by springs and play a formative role in the lower reaches of rivers. Changes in fluid density from the source (methane) to the terminus (ethane) of Titan’s rivers may affect the flow dynamics of the river. Methane fed rivers are likely episodically active since rainfall, which is concentrated in the poles, lasts 10-100 hours each Titan year (30 Earth years). Although precipitation is limited in the mid-latitudes, FLs have been observed in these regions. Titan is also covered by vast regions of active dune fields, primarily within the equatorial latitudes. They are composed of hydrocarbon and nitrile sand-sized particles forming from photochemical reactions in Titan’s atmosphere. Although observations of Titan are limited, interactions between rivers and dunes have been observed. Limited data availability means modelling fluvial and aeolian processes is one of the best methods to understand active and previously active processes on Titan. Here we report the initial study by the Working group on Aeolian-Fluvial Terrain Interactions (WAFTI), based at the European Space Agency, which examines the effects of these processes in synergy under Titan conditions, using a combination of modelling and geomorphological analysis. We hypothesise that these interactions could have implications for the distribution and planforms of Titan FLs. To simulate the interactions between fluvial and aeolian processes on Titan, we developed the Titan Aeolian-Fluvial Interactions model. This is a landscape evolution model based on a coupled implementation of the Caesar-Lisflood fluvial model, and Discrete ECogeomorphic Aeolian Landscape model (DECAL) dunes model. The Caesar-Lisflood fluvial model routes water over a digital elevation model and calculates erosion and deposition from fluvial and slope processes and changes elevations accordingly. The DECAL model is based on the Werner slab model of dunes, which simulates dune field development through self-organization. Several scenarios shall be modelled: (1) a continuous methane river, flowing in a straight channel with linear dunes migrating towards the channel parallel to its length; (2) a continuous methane river flowing towards a dune field with crest lines perpendicular to the direction of flow; (3) simulation scenario (1) but altered slope to represent the three different reaches (source, mid-reaches, and termination) of the channel and simulate for both methane and ethane flows by altering fluid density; (4) simulation scenario (1) with an episodically active river and continually active dunes. The findings of these simulations may help understand the drainage patterns and distribution of FLs and methane/ethane across Titan.

Aeolian and fluvial processes on Earth show significant interactions. Within terrestrial desert environments, analysis of ~200 locations has revealed that where ephemeral or episodic rivers flow across a dune field the predominant processes alternate between aeolian and fluvial, and that when rivers and dunes are active, they interact with one another. Avulsions can be major, with channels in the northern Kalahari having cumulative diversions of 10s of km. Considering Mars likely had an arid environment during the period of peak fluvial activity, the presence of fossilised Martian dunes, and observations by the Curiosity rover of fluvially altered aeolian deposits, it is apparent that Mars likely experienced simultaneous fluvial and aeolian processes, and periods of fluvial inactivity where aeolian processes persisted. At present, Martian aeolian and fluvial processes have only been studied independently, and their interaction has not been explored.Here we report the initial study by the Working group on Aeolian-Fluvial Terrain Interactions (WAFTI), based at the European Space Agency, which examines the effects of these processes in synergy under ancient Martian conditions, using a combination of modelling and geomorphological analysis. We hypothesise that these interactions could have implications for a number of Martian phenomena, for example: the prevalence of meandering inverted channel systems, the distribution of organic material, the discordance of Martian valley networks, and the sediment size and distribution of Martian rivers. In this study, we simulate the interactions between migrating dunes and different reaches of an active river channel, under ancient Martian conditions to determine the effects on the channel’s morphology and geometry.Our Martian Aeolian-Fluvial Interactions (MAFI) model is a landscape evolution model based on a coupled implementation of the Caesar-Lisflood fluvial model, and Discrete ECogeomorphic Aeolian Landscape model (DECAL) dunes model. It routes water over a Digital Elevation Model (DEM) and calculates erosion and deposition from fluvial and slope processes changing elevations accordingly. Aeolian material is discretized into slabs on the DEM, and slabs are moved across the space according to a set of simple rules.At EGU we will present the results of our simulations of aeolian and fluvial interactions on an inclined plane with a central channel and a continuously flowing Martian river. Typically on Mars, channels are housed within valleys with V or U-shaped cross-sections. Additionally, the topography of Mars is heavily altered by impact craters, many of which are sediment sinks. Finally, the profiles and immaturity of Martian valleys indicate that they were likely ephemeral/episodic, so flow was unlikely to be continuous. We, therefore, plan to expand our study to simulate the following: (1) simulate continuous flow for a DEM with a V-shaped valley and central channel; (2) “” U-shaped valley and central channel; (3) “” for a DEM with a crater present adjacent to the part of the valley; (4) simulate episodic fluid flow with periods of no fluvial activity, but continued aeolian activity. Understanding these two major surface processes in synergy will aid in the reconstruction of Mars’ ancient paleoenvironments in a way that has not previously been explored.

Icy bodies are the most numerous and diverse bodies in the Solar System, but only a few have been visited yet by space probes. Some of these icy bodies, mostly giant planet satellites like Callisto, are called ocean worlds as they likely host most of the liquid water of our Solar System within sub-glacial oceans [Sotin & Tobie 2004]. The presence of liquid water under the icy crusts of these bodies raises questions relative to exobiology. In the coming years and decades, these ocean worlds will be the focus of major planetary science missions, firstly with JUICE (ESA, launch scheduled in April 2023) and Europa Clipper (NASA, launch scheduled in October 2024) which will be targeting the Galilean moons, then with still conceptual missions as we speak such as (i) Uranus Orbiter and Probe and (ii) Enceladus Orbilander. Despite not being the prime target of any of these missions, Callisto will be investigated by JUICE and Europa Clipper through multiple flybys. One way to get information about Callisto’s sub-glacial ocean is to look at the moon’s surface, which may highlight markers of past or current activity and could lift the veil on its chemical composition. Spectroscopy is a powerful technique for such study, especially in the near-infrared domain where spectral signatures of H2O-ices, silicates, salts are detectable. Consequently, in preparation for future infrared spectroscopic data, and specifically those of the infrared imaging spectrometer MAJIS of the JUICE mission, a ground-based campaign was led with an instrument sharing some similar and also complementary characteristics: SINFONI (SINgle Faint Object Near-infrared Investigation), which was mounted on the UT4 of the VLT at ESO. Here we present the results derived from the analysis and the modeling of four full-disk observations acquired with this instrument. SINFONI combines an integral field spectrometer operating with different gratings with an adaptive optics module [Eisenhauer et al. 2003]. Our four observations were performed using the H+K grating, ranging from 1.46 µm to 2.41 µm, with a spectral resolution R = 1.500, but each spectrum acquired was automatically resampled in order to get a spectral sampling of 5 x 10-4 µm. The campaign took place from January 2015 from March 2016, and the observations were acquired near the opposition to optimize the angular resolution with Callisto’s angular diameter close to 1.5 arcsec. As SINFONI’s field of view is 0.8 x 0.8 arcsec2 divided into 64 x 64 pixels, one observation actually corresponds to a mosaic of ten overlapping acquisitions, as described in a paper about Ganymede using the exact same technique [Ligier et al. 2019]. All in all, after removing the high solar incident angle pixels we could not recover after applying photometric corrections (basically all pixels above latitude 60°, north and south), our dataset covers approximately 70% of Callisto’s entire surface with a spectral and spatial sampling (~40 km/pix) which allow to detect and map the spectral absorptions that may exist in this wavelength range of the Callisto’s spectrum. Spatial resolution is in par with that of the partial Callisto mosaic from the NIMS imaging spectrometer of the NASA Galileo probe. The first results obtained concerns the physical properties of the moon’s surface directly derived from the reduction process and the photometric corrections; one obtains satisfactory results using the qualitative photometric model of Oren-Nayar, which is a generalization of the Lambertian model with the surface roughness (σ) as only additional parameter [Oren & Nayar 1994]. In the case of our study, the best results were obtained with  ranging between 17° and 19° whatever the observation. These values are much lower than the values in the 30° – 45° range provided by previous studies [Buratti 1991, Domingue & Verbiscer 1997], however these values were obtained through the modeling of the solar phase curve via the Hapke model [Hapke 1984, Hapke 1986] using a combination of telescopic observations and Voyager data; the major differences between the approaches make the respective results hard to compare (our data are < 10° emergence angle). Our second result concerns the global shape and spectral signatures in the surface spectra: overall, they are much flatter and more distorted than those of Europa and Ganymede, especially the quite large 2-µm H2O-ice band. To the exception of crystalline ice absorptions at ~1.50 µm, ~1.57 µm, ~1.65 µm and the 2-µm band, Callisto does not show other clear signatures (figure 1). However, very subtle signature(s), like the one at ~2.21 µm (figure 1), might actually be observed and are being investigated to confirm the detection(s). If confirmed it could suggest the presence of hydrated materials like salts or silicates. We will address this point during the meeting. Figure 1: Comparison between Ganymede’s (blue) and Callisto’s (red) mean spectrum of the entire dataset. And lastly our third main result comes from spectral modeling, where both linear and non-linear unmixing were performed. Unlike previous studies on Ganymede and Europa [Ligier et al. 2019, Ligier et al. 2016], the linear model shows that all of Callisto’s spectra are satisfactorily modeled without needing any hydrated salt and that the only two constituents would be (i) a darkening agent, with abundances always exceeding 80% even for the iciest spectra, and (ii) multiple grain sizes of the crystalline form of H2O-ice, with an average abundance of 7% and exhibiting a strong latitudinal gradient for the smallest grains typical of the influence of the Jovian magnetospheric environment (figure 2). Such a low concentration overall of H2O-ice challenged us about the legitimacy of the linear unmixing approach, so we decided to run the Shkuratov non-linear unmixing model...

In the past decades, numerous hydrated silicates have been detected at the surface of Mars from orbital and in situ characterization. Understanding the hydrated mineralogy of Mars constitutes an important goal to retrace its water history and to evaluate its resource assets in terms of water budget. In addition to providing information on the past aqueous subsurface and surface environments, the aqueous alteration minerals (e.g., secondary phases) have a major exobiological potential and are prospective resources for human exploration and in situ resource utilization (ISRU, [1]). As such they are key drivers in the selection of current and upcoming landing sites for robotic and human missions to Mars. With a more global and quantitative view of the altered mineralogy (as presented in [2]) the modal composition can be accessed and the water content stored in hydrated silicates present at/near the surface can be evaluated. By quantifying the content of each minerals at the hydrated sites, the estimation of the water content stored at the surface within these minerals is then quite straightforward. The global mineralogical maps of [2] were used. They were derived using the full dataset of the OMEGA instrument, where the global abundances of 11 hydrated silicates can be found: Fe-Mg dominated smectite, Al-smectite, AlSiOH, Opal, Mg-carbonates, Chlorite, Fe/Mg-Micas, Serpentine and Fe-hydroxide. A set of non-hydrated minerals is also included in the mixture but is not used to derive the water content as they do not contain OH or H2O. To evaluate the water content of each individual end-member, the potential chemical formula of each end-member was first evaluated and then the weight percent of H2O or OH in the formula was estimated. This methodology is based on [3]. Thus, for each end-member several estimations of the water content are computed. They depend on the selected formula (the exact formula being unknown at Mars) and on the estimated hydration state (being also unknown) of each mineral. Then, the abundance of each end-member in water content is evaluated by multiplying their abundance with their individual water weight percent and by summing at each location (i.e., each pixel of the map) all the resulting water contributions. The resulting global map of water content at a resolution of ~ 1 km per pixel at the equator is shown on Figure 1.   The average content of water, based on the content stored in hydrated silicates, is estimated to be slightly above 5 wt%, with some rare occurrences > 20 wt% (examples of such occurrences are shown on Figure 1). These values are in good agreement with previous orbital estimations of the water content at Mars based on other estimations techniques ([4],[5]) that predicted 2-7 wt% on average at the surface. Figure 1 - Global map of water content (wt%) at Mars, as stored in hydrated silicates. The red arrows point at location of 100s km2 were the water content at the surface is consistently > 10 wt%. Three zoomed maps are shown to illustrate specific settings that provide a high-water content at the surface. The orange arrows and circles highlight the large deposits of Marwth Vallis, Nili Fossae and Meridiani Planum.   The ongoing studies now aim at a detailed analysis of the water distribution in order to look for new regions with high past aquability (stable liquid water) potential and/or exobiological potential, if such locations exist. The map will be studied locally (see Figure 1) in combination with high resolution images in order to correlate the high-water content with their context and highlight new regions of interest. Incorporation of ground-truth knowledge from Perserverance at Jezero crater is foreseen so as to refine the mineral endmembers, and make abundance comparisons on the larger mineral units which will be sampled.    References [1] Abbud-Madrid, A., et al. (2016). Mars Water In-Situ Resource Utilization (ISRU) Planning (M-WIP) Study 90. [2] Riu, et al. (2022). The M3 project: 3 – Global abundance distribution of hydrated silicates at Mars. Icarus 374, 114809. https://doi.org/10.1016/j.icarus.2021.114809 [3] Wernicke, L.J. & Jakosky, B.M. (2021). Martian Hydrated Minerals: A Significant Water Sink. J. Geophys. Res. Planets 126. https://doi.org/10.1029/2019JE006351 [4] Audouard, J., et al. (2014). Water in the Martian regolith from OMEGA/Mars Express: Mars 3 µm absorption and water mobility. J. Geophys. Res. Planets 119, 1969–1989. https://doi.org/10.1002/2014JE004649 [5] Milliken, R.E. et al. (2007). Hydration state of the Martian surface as seen by Mars Express OMEGA: 2. H 2 O content of the surface: HYDRATION STATE OF THE MARTIAN SURFACE. J. Geophys. Res. Planets 112. https://doi.org/10.1029/2006JE002853