John Carter

We present a systematic detection and characterization of mesoscale atmospheric gravity waves in Martian clouds using High Resolution Stereo Camera (HRSC) imagery from Mars Express during Martian Years 34–37. Gravity wave packets were identified in the HRSC Cloud Atlas data set, and their morphology (horizontal wavelength, packet width/length, orientation) was measured on map‐projected products. Cloud top altitudes were derived from blue‐green parallax using HRSC's multi‐channel imaging geometry. For a subset of stereo–temporal “brooming” pairs separated by min, horizontal winds were derived by manual feature tracking, enabling direct estimates of observed and intrinsic phase speeds and implied vertical wavelengths at the packet scale. We cataloged 146 packets, of which 114 were morphologically characterized, measured 100 cloud top heights, and 11 had full dynamical characterization. Horizontal wavelengths span 2–117 km with an average of 29 km. Cloud tops show a dominant concentration between ≈15 and 40 km, and a less frequent extension to 60–100 km, with uncertainty ∼3–10 km, and clear spatial and seasonal variability. For the dynamical subset, observed phase speeds are 2.0–8.6 m/s, intrinsic phase speeds are 0.4–6.2 m/s, and implied vertical wavelengths are 0.2–3.4 km. These results demonstrate that HRSC repeat‐track imaging enables packet‐scale constraints on intrinsic gravity wave drag and mesoscale dynamics in Martian circulation models.

Atmospheric gravity waves (AGWs) are dynamically relevant in the Martian atmosphere [1], but orbital observations still provide an incomplete view of their morphology, altitude, and propagation conditions. Individual orbital images of clouds can identify wave packets and measure horizontal wavelengths, yet altitude, background wind, intrinsic phase speed, and vertical wavelength are only available when the observing geometry allows additional retrievals. This limits how far morphology alone can be interpreted dynamically. We compare three orbital datasets, that include clouds, each with different spatial resolution, coverage, and observing modes/geometry. They are not treated as a single climatology, because they cover different observing periods and have different sampling biases. Instead, we use them to test what part of the Martian AGW population each instrument can detect and characterize.OMEGA/Mars Express nadir observations [2] during MY26–29 provide the widest occurrence baseline (Figure 1- a), although with a limited total number of observations. In this dataset, 263 wave packets were detected and 125 were characterized, with horizontal wavelengths from 6 to 83 km and a mean of 21 km [3]. Detections are concentrated in the northern hemisphere, especially at mid-to-high latitudes, with seasonal peaks during northern spring and autumn and southern winter. Their spatial distribution is consistent with topographic forcing near Tharsis–Alba and with convective activity over the northern plains. HRSC/Mars Express stereo-temporal imaging [4] during MY34–37 adds altitude and motion information (Figure 1- b). Wave packets identified in the HRSC Cloud Atlas [5] were characterized using blue-green inter-channel parallax to retrieve cloud-top altitude and approximately 30-minute repeat-track pairs to estimate horizontal motion. Retrieved altitudes are mostly 15–40 km, with uncertainties of about 3–10 km and a smaller number of cases extending to 60–100 km. For 11 packets with altitude, wind, and wave-geometry constraints, the analysis gives intrinsic phase speeds of 0.4–6.2 m/s and implied vertical wavelengths of 0.2–3.4 km under linear gravity wave assumptions [6]. Comparison with MCD static stability and background winds [7,8] indicates that some packets lie close to critical or turning levels, which may affect whether they remain visible at cloud level.CaSSIS/ExoMars TGO imaging at 4 m/pixel [9] provides a substantially larger image dataset than HRSC, by roughly an order of magnitude, and samples smaller structures (Figure 1- c, Eira et al, in prep[10]). This part of the analysis remains preliminary, but it reaches sub-kilometer and few-kilometer horizontal wavelengths, below the OMEGA and HRSC detection ranges. A first comparison of spatiotemporal distribution, morphology, spatial scale, and observing geometry is used to assess instrument-dependent detection biases [10]. Whether the CaSSIS detections form the short-wavelength end of the OMEGA–HRSC population, or represent a separate subset controlled by different sources or visibility conditions, remains open.Taken together, the datasets connect measurements that are usually obtained separately: morphology from cloud images, altitude from stereo geometry, and propagation constraints from repeat imaging and background winds. The comparison separates morphology-only detections from cases where altitude and wind information allow dynamical interpretation. These are the quantities needed to test how gravity wave drag is represented in Mars general circulation models.Figure 1. Examples of Martian atmospheric gravity wave packets observed with (a) OMEGA/Mars Express, (b) HRSC/Mars Express, and (c) CaSSIS/ExoMars TGO, illustrating the different spatial scales and observing geometries used in the multi-instrument comparison. Acknowledgments: This work was supported by the Portuguese Fundação para a Ciência e a Tecnologia through the research grant UID/04434/2025, and through the grants of reference 2021.05455.BD, and 2020.06389.BD. GG acknowledges financial support from Junta de Andalucía 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 by MCIN/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 also thank Lucie Riu, Aurélien Stcherbinine, and the Mars Express and ExoMars TGO Teams for their support and encouragement in this work.References: [1] Fritts & Alexander, 2003; [2] Bibring et al., 2007; [3] Brasil et al., 2025; [4] Jaumann et al., 2007; [5] Tirsch et al., 2024; [6] Brasil et al. (under review); [7] Forget et al., 1999; [8] Millour et al., 2018; [9] Thomas et al., 2017; [10] Eira et al. (in prep.).

La planète Mars a connu une période où l'eau liquide était durablement stable. Outre les vestiges morphologiques d'une activité hydrologique en surface, l'interaction chimique de l'eau avec la croûte basaltique s'est traduite par la formation d'argiles et de sels hydratés en surface et en profondeur. Ces minéraux hydratés ont été détectés à la surface de Mars en 2004 grâce à l'instrument OMEGA, l'imageur hyperspectral infrarouge proche embarqué sur la sonde européenne Mars Express. Leur étude permet de reconstruire l'histoire de l'activité aqueuse sur Mars et de caractériser une période ancienne où l'environnement a pu être favorable à l'apparition d'une chimie pré-biotique. Ce travail de thèse s'intéresse aux environnements aqueux de Mars en couplant les données minéralogiques des imageurs hyperspectraux embarqués OMEGA/Mars Express et CRISM/Mars Reconnaissance Orbiter avec la morphologie. De nouveaux outils de traitement et d'analyse des données sont développés et ont permis la détection et la caractérisation spectrale de plus d'un millier de dépôts de minéraux hydratés sur Mars, fournissant une vue d'ensemble de l'altération. Celle-ci a eu lieu principalement dans la première partie du Noachien et a surtout formé des phyllosilicates ferro-magnésiens de la famille des vermiculites et smectites. Une importante diversité minérale est par ailleurs constatée avec une dizaine de familles minérales différentes, traçants des conditions géo-chimiques variées. Placés dans leur contexte géologique, certaines détections permettent de proposer l'existence passée d'un système hydrologique sur l'ensemble de la planète qui a donné naissance à un cycle des argiles similaire au cycle terrestre. Il apparait par ailleurs que les cratères d'impact sont le contexte privilégié des minéraux hydratés, mais le lien entre ces derniers et les processus d'impact demeure ambigu. La découverte d'un cycle des argiles est compatible avec l'hypothèse d'une planète potentiellement habitable au Noachien mais qui devra être vérifiée par l'exploration in-situ.

The Jupiter and Icy Moons Explorer (JUICE) mission of the European Space Agency (ESA) will investigate the Jovian system with multiple instruments over several years, beginning in early 2031. This paper describes the historical context and state of knowledge, as well as JUICE’s scientific goals and measurement techniques of the satellites that will not be encountered in close flybys. These include the large volcanically active moon Io, the four small inner moons Metis, Adrastea, Amalthea, and Thebe, and the numerous small Irregular (outer) moons. JUICE will provide multiple opportunities to observe Io from relatively remote distances of hundreds of thousands of kilometers. These observations will enable monitoring of Io’s surface for changes, and for the study of its neutral clouds and plasma torus. Io observations will be performed with the four optical remote sensing instruments and with the Particle Environment Package. For the small inner moons it is planned to obtain complete geographic longitude (scales up to 8 km/px), solar-phase and multi-color coverage, oblique polar views, and UV to near-IR spectra. Astrometric measurements will also be performed. The Irregular moons will mostly appear unresolved to the JUICE instruments. Nonetheless, long-duration disk-integrated lightcurves will be acquired to derive rotation periods, object dimensions, pole-axis orientations, and colors for most objects for the first time. From these data, convex-shape models will be generated and phase curves determined. Furthermore, the precision of the orbital elements will be improved via accurate astrometry. UV and near-IR measurements will be attempted for the largest of these objects.

Sedimentary volcanism, whereby material is brought to the surface by fluid overpressure, has been proposed to explain some of the periglacial landforms, including pitted cones, in the Northern Plains of Mars. However, in the absence of convincing mineralogical evidence, the origin for these deposits has never been conclusively determined. Here we conduct a remote sensing-based mineralogical survey to identify hydrated minerals within the Thumbprint Terrains and neighbouring Vastitas Borealis Formation. We detect several occurrences of hydrated silica along with sulfate salts in candidate mud volcano-like morphologies which likely formed during the Early Amazonian period, supporting the sedimentary volcanism origin. Buoyancy-driven analytical modelling suggests the hydrated silica and sulfate salts are sourced from reservoirs at depths of several 10 s and 100 s of metres, respectively below the Thumbprint Terrains and Vastitas Borealis Formation. The exposed sulfates may have been derived from ancient buried evaporite deposits suggesting, at least locally, a salt-rich aqueous origin for the Vastitas Borealis Formation, and would be consistent with the presence of a past northern ocean on Mars.

Currently, there is a considerable effort from the science community to study planetary atmospheres, in order to understand the role of climate change in planetary evolution. In particular, for Mars, climate history plays a key role in understanding the conditions that could have allowed the presence of liquid water in the past and its consequences for comparative planetology and potential past habitability. However, knowledge of the mechanisms that dominate the atmospheres of planets is still limited. Current research projects have contributed significantly to understand the temporal and spatial variability of winds on Mars, the role of cloud formation, dust storms and gravity waves in atmospheric circulation [1]. The goal of this work was, then, to detect clouds in the ExoMars/TGO CaSSIS stereo camera dataset, measure cloud altitudes [2] and cloud structure, retrieve wind velocities and related wind fields, and todetect and characterize atmospheric gravity waves in the atmosphere of Mars, in order to improve our understanding of the planet’s atmospheric dynamics. Gravity waves have already been detected by Mars Express [3], although there is still an important dataset from ExoMars/TGO CASSIs completely unexplored. Through this, we aim to build a catalogue of winds and atmospheric gravity waves using data from ExoMars’ CaSSIS enabling the comparison with Mars Express cameras’ data, namely OMEGA and HRSC. In order to have the most complete cloud catalogue possible, a Machine Learning (ML) algorithm was considered, besides manual verification, to go through the CaSSIS dataset.Through the CaSSIS Observations website and the CaST (CaSSIS Suggestion Targeting) tool, manual verification of almost 9000 CaSSIS images – including basically all stereo pairs – was made, in order to check for the existence of clouds in each one. In the future, to complete out catalogue, the Yolov5X algorithm [4] will be trained with 1500x1500 tiles, where cloud detections were annotated with recourse to Roboflow, and then deployed on the CaSSIS dataset to signal other possible cloud images. ML has already been deployed effectively in similar research projects [5,6], so the potential in this case is exciting as we intend to present. Altitude measurements will be performed based on a work by Scholten et al. (2010) [7] and developed and fine-tuned in Brasil et al. (2024) [2], while wind measurements were made via cloud tracking in stereo pairs. Both the former and latter procedures, as well as the characterization of waves were facilitated through the navigation and processing of the images in ArcGIS Pro.Through manual verification, to date, we have detected clouds in over 200 CaSSIS images, including more than 80 that belong to one of over 40 stereo pairs. These detections were mostly made in the northern hemisphere (Fig. 1 & 2), suggesting a contribution from the higher humidity related with a larger permanent polar cap [8], although most CaSSIS stereo pairs can be found in the southern hemisphere [9]. The peaks in cloud detection happen around the northern and southern spring equinoxes (𝐿! = 0∘ and 𝐿! = 180∘, respectively) possibly related with an intensification of the water ice and vapour sublimation cycle, whereas it dips just after the beginning of the summer season in the northern (𝐿! = 90∘) and southern (𝐿! = 270∘) hemispheres (Fig. 2.), possibly due to lesser weather activity [10].There could also be an observational bias during the second half of the Martian year related with the Dust Storm season, with CaSSIS being actively directed away from regions with ongoing weather activity, fog or dust lifting.We intend to continue our work in completing our cloud image catalogue, adding the images suggested by the ML model in development. Navigation of stereo pairs and wave images will be made in order to perform the measurements described earlier and to make available new data from an unexplored dataset which will enable us to better constrain our interpretation of temporal and spatial variations in the Martian atmosphere.References: [1] A. Cardesin-Moinelo et al. “First year of coordinated science observations by Mars Express and ExoMars2016 Trace Gas Orbiter”. Icarus 353 (2021). [2] F. Brasil et al. “Morphological and dynamical characterisation of Gravity Waveson Mars atmosphere using the High-Resolution Stereo Camera on Mars Express”. In: Europlanet Science Congress 2024. [3]Brasil et al., 2025. JGR: Planets, 130(3), e2024JE008726. [4] J. Glenn. Ultralytics YOLOv5. Version 7.0. 2020. [5] V. T. Bickelet al. “Exploring CaSSIS with Machine Learning – The Search for Chloride Deposits on Mars”. Lunar and Planetary ScienceConference 2023, [6] V. T. Bickel et al. “Exploring CaSSIS with Machine Learning – The Search for Dust Devils on Mars”.Lunar and Planetary Science 2023. [7] F. Scholten et al. “Concatenation of HRSC colour and OMEGA data for the determinationand 3D-parameterization of high-altitude CO2 clouds in the Martian atmosphere”. Planetary and Space Science 58.10 (2010). [8]D. Davies. “The Mars water cycle”, Icarus 45.2 (1981). [9] C. Re et al. “CaSSIS-based stereo products for Mars after three yearsin orbit”. Planetary and Space Science 219 (2022). [10] J. R. Barnes et al. “The global circulation”. Cambridge University PresseBooks. 2017.

Atmospheric gravity waves (AGWs) significantly influence Mars’ climate by facilitating energy and momentum exchanges, thus modulating atmospheric circulation, cloud formation, and dust distribution processes [1]. Despite recent advances in the characterization of Martian AGWs using observations from Mars Express/OMEGA [2], this study was limited by the narrow field of view and restricted spatial coverage. Here, we present an extended analysis using data from the High-Resolution Stereo Camera (HRSC) [3], likewise onboard Mars Express (MEx), benefiting from its higher spatial coverage, resolution (map scales between 200-800 m/px), and consistent imaging quality.We examined HRSC high-altitude imagery covering Mars Years (MY) 34-37 [4], identifying and characterizing over 100 distinct wave packets, nearly doubling the number previously analyzed. Our refined cloud-altitude measurement technique significantly improved the accuracy and robustness of cloud height retrievals, resulting in estimated altitudes of 15-40 km for water-ice clouds and 60–100 km for CO2-ice clouds, with uncertainties around ±2 km. Wind speeds were determined through precise cloud displacement analyses from HRSC double-broom imagery, taken with an interval of 30 minutes apart, consistently yielding values between 5-20 m/s and uncertainties of approximately ±1 m/s, though these uncertainties likely underestimate the total error due to unresolved spacecraft pointing inaccuracies. Additionally, by retrieving the wind speeds of wave packets and the background, we derived preliminary phase speed estimates for the detected wave packets. Comparison with local background winds suggests a range of intrinsic wave behaviours, which reflect differences in their generation mechanisms or propagation environments.Our enhanced dataset allows us to establish seasonal and spatial patterns of gravity wave occurrence, highlighting a prominent hemispheric asymmetry with significantly more wave observations in the northern hemisphere. This raises new questions about observational biases potentially related to spacecraft observational strategies. Additionally, the measured wind speeds remain consistently lower than mesoscale model predictions from the Mars Climate Database [5,6], suggesting that current atmospheric models may inadequately represent mesoscale dynamics associated with gravity waves.Collaborations with the OMEGA and TGO/CaSSIS teams are now extending this analysis further, incorporating spectral information for cloud composition (OMEGA) and complementary observational geometries (CaSSIS), crucial for addressing the limitations identified in this work. These multi-instrument synergies will allow better discrimination of physical processes involved in wave formation, propagation, and dissipation.This comprehensive analysis using HRSC data provides critical insights into Martian atmospheric dynamics, which can be used to improve current atmospheric models using the parameterization of gravity waves characterized in this work. Acknowledgments: 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 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 by MCIN/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 also thank Lucie Riu, Aurélien Stcherbinine, and the Mars Express Team for their support and encouragement in this work. References[1] Fritts et al., 2003. Reviews of Geophysics, 41(1).[2] Brasil et al., 2025. JGR: Planets, 130(3), e2024JE008726.[3] Jaumann et al., 2007. Planetary and Space Science 55, 928-952[4] Tirsch, et al. 2024. EPSC2024-44, DOI:10.5194/epsc2024-44.[5] Forget et al., 1999. JGR: Planets, 104(E10), 24155-24175.[6] Millour et al., 2017, EGUGA, 12247

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.

We report here about the currently foreseen scientific activity of the MAJIS instrument during the two planned JUICE flybys of Europa in 2032. MAJIS [1] (Moon and Jupiter Imaging Spectrometer) is a two-channel imaging spectrometer onboard JUICE, covering the spectral range 0.5-5.55 μm, splitted in a VISNIR channel (0.5-2.36 μm,

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.