Mars Express (MEX), launched in 2003, remains a highly productive mission in its third decade of operation at Mars. Recent science highlights include (1) discovery of englacial (internal) folding of the South Polar Layered Deposits, providing evidence of ice flow; (2) study of large-scale ionospheric ‘holes’ (plasma depletion events); (3) continuing development of digital elevation models and mosaics from the HRSC imager. Many of the key outcomes of two decades of Mars Express have been summarised in an article collection in Space Science Reviews titled “Mars Express: Pioneering Two Decades of European Science and Exploration of Mars”.
ExoMars Trace Gas Orbiter (TGO), launched in 2016, has now completed over four complete Mars years of science observations since reaching its nominal Mars orbit in April 2018. Recent science highlights include (1) detailed characterisation of the spatial and temporal variation of atmospheric hydrogen chloride (HCl), and modelling to understand its sources and sinks; (2) study of Mars’ water cycle, in particular relating to the transport of water to high altitudes and subsequent escape; (3) Repeated imaging of dust devils, allowing determination of near-surface wind velocities; (4) continued monitoring of radiation doses throughout the mission, including the most energetic event recorded yet in May 2024.
Acknowledgments: This abstract represents the work of hundreds of researchers and engineers across the MEX and TGO science and operations teams. MEX and TGO data are freely and publically available at ESA’s Planetary Science Archive (https://psa.esa.int/).
How to cite: Wilson, C.: Europe's Mars orbiters: status & highlights, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13295, https://doi.org/10.5194/egusphere-egu26-13295, 2026.
The ancient Martian sedimentary cycle remains poorly constrained because sedimentary deposits older than ~3.7 Gy are rare and sparsely exposed. In this study, we investigate rare ancient sedimentary exposures, where “sediments” are defined as accumulations of material formed by depositional processes, including volcanoclastic deposits.
We focus on deposits dated between ~4.0 and 3.7 Gy, specifically the Oxia Planum stratigraphic sequence (selected as the future landing site of the ExoMars 2028 Rover mission) and the basal sequence of Mawrth Vallis. Both sites are characterized by Fe/Mg-rich clay-bearing deposits, but exhibit distinct spectral types (vermiculite/saponite-bearing at Oxia Planum vs nontronite-bearing at Mawrth Vallis). Access to these stratigraphic records provides key insights into sedimentary processes during the Noachian period.
At both locations, we identified paleosurfaces, defined as remnants of ancient surfaces that were buried by younger deposits and later re-exposed by erosion. These paleosurfaces are recognized by flat-lying, cratered surfaces in which craters are infilled by overlying, younger, material. Some of these paleosurfaces extend over several thousand square kilometers and expose hundreds of preserved paleocraters, indicating prolonged sedimentary hiatuses.
We identified two major paleosurfaces. The older one, likely dated at ~4.0 Gy, is located between two sets of strata within the Oxia Planum sequence. The younger one, dated between ~4.0 and 3.7 Gy, occurs at the boundary between the Oxia Planum and Mawrth Vallis sequences. These paleosurfaces indicate time intervals during which the Noachian Martian sedimentary cycle was effectively halted: sedimentation ceased, as evidenced by crater accumulation, and erosion was minimal, allowing the preservation of paleocraters.
Using statistical analysis of preserved paleocraters observed at stratigraphic boundaries, we estimate the duration of these sedimentary hiatuses as a function of surface age. These results have significant implications for our understanding of the early Martian sedimentary cycle and planetary habitability, as they indicate very ancient periods of major climatic and environmental change embedded within this stratigraphic record, during which sedimentation ceased.
How to cite: Torres Auré, I., Quantin-Nataf, C., Carter, J., Fawdon, P., Millot, C., Dehouck, E., Pineau, M., and Volat, M.: Evidence for Sedimentary Hiatuses on Early Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7728, https://doi.org/10.5194/egusphere-egu26-7728, 2026.
Carbonates on Mars provide key insights into the planet’s past environmental conditions, as their formation typically results from interaction between CO2-bearing alkaline waters and ultramafic rocks commonly associated with a dense, CO2-rich atmosphere. While ferromagnesian (Fe,Mg-rich) clays are particularly widespread across the Martian surface [1,2], carbonates remain comparatively rare in orbital observations. This scarcity suggests that carbonates may be buried, altered, or spectrally obscured within clay-bearing rocks [3]. Here, we examine the presence of possible carbonates, along with clays, by analyzing approximately 517 near-infrared (1–4 µm) spectral cubes acquired by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). Our results reveal new carbonate-rich deposits and confirm earlier detections. A detailed investigation of the absorption bands near 2.3, 2.5 µm and around 3.4–3.5 µm indicates that carbonates on Mars are best represented as Fe–Mg solid solutions spanning the siderite–magnesite series, rather than pure endmembers [4]. Such compositions are geochemically plausible on Mars; they likely formed under reducing conditions and may have persisted despite later exposure to the more acidic, oxidizing surface environment [5]. Spectral mixing models better clarify the influence of clays on carbonate signatures and provide important constraints for further laboratory analog studies [6,7]. The recurring spatial asso-ciation of carbonates and clays across multiple outcrops implies either coprecipitation or closely related formation pathways within neutral to alkaline aqueous environments during the Noachian (3.7–4.0 Gyr ago), offering strong evidence for sustained liquid water and conditions potentially favorable to microbial life. Our results expand the known distribution of carbonates on Mars, emphasize their astrobiological relevance, and provide strategic guidance for future rover operations and sample-return site selection targeting preserved biomarkers (organic compounds). Overall, this work advances our understanding of early Martian habitability and the role of carbonates in recording ancient CO2-water interactions.
This study closely aligns with the objectives of ESA’s “Rosalind Franklin” mission [8], whose rover will explore Oxia Planum and investigate clay-bearing terrains and possible carbonates in the search for well-preserved biosignatures throughout subsurface rocks and soils [9-11]. This work is thereby financially supported by the Italian Space Agency (ASI) [Grant ASI-INAF n. 2023–3–HH.0].
References: [1] Carter et al. (2013) JGR Planets 118, 831–858. [2] Brossier et al. (2026) JGR Planets 131, e2025JE009393. [3] Ehlmann et al. (2008) Science 322, 1828–1832. [4] Beck et al. (2024) Earth and Space Science 11, e2024EA003666. [5] Niles et al. (2013) Space and Science Reviews 174, 301–328. [6] Bishop et al. (2013) JGR Planets 118, 635–650. [7] Bishop et al. (2021) Earth and Space Science 8, e2021EA001844. [8] Vago et al. (2017) Astrobiology 17, 471–510. [9] Quantin-Nataf et al. (2021) Astrobiology 21, 345–366. [10] Mandon et al. (2021) Astrobiology 21, 464–480. [11] Brossier et al. (2022) Icarus 386, 115114.
How to cite: Brossier, J., De Sanctis, M. C., Altieri, F., Raponi, A., Saggese, V., Ferrari, M., Bruschini, E., and De Angelis, S.: Tracking Down Carbonates Lurking in Martian Clay-Rich Rocks, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8145, https://doi.org/10.5194/egusphere-egu26-8145, 2026.
Oxia Planum, the landing site of the Rosalind Franklin Mission (RFM), is located between the ancient highlands of Arabia Terra and the younger plains of Chryse Planitia [1]. The region preserves clear evidence of past water-rock interactions, particularly layered clay-rich deposits that are considered prime targets for astrobiological investigation [2, 3]. This study focuses on a selection of Regions of Interest (ROIs), areas with the highest concentrations of ferromagnesian clays as identified through remote sensing analyses. We derive local digital terrain models from stereo photogrammetry and quantify horizontal and vertical accuracy [4], a key requirement for interpreting water-related processes and stratigraphic relationships in the low-relief Oxia Planum. Our objective is to examine how clay distribution relates to other geologic elements, in particular fractures [5, 6], to better constrain their geologic interpretation and stratigraphic context [7], contributing to strategies for guiding the selection of drilling sites once the rover arrives on Mars.
This work is funded by the Italian Space Agency (ASI) [Grant ASI-INAF n. 2023–3–HH.0].
References: [1] Quantin-Nataf et al. (2021) Astrobiology 21, 345–366. [2] Mandon et al. (2021) Astrobiology 21, 464–480. [3] Brossier et al. (2022) Icarus 386, 115114. [4] Trisic Ponce et al. (2026), this conference. [5] Apuzzo et al. (2025) PSS 267, 106169. [6] Rasmussen et al. (2026), this conference. [7] Fawdon et al. (2024) Journal of Maps 20, 2302361.
How to cite: Altieri, F., Rasmussen, M., Brossier, J., Frigeri, A., Trisic Ponce, J., De Sanctis, M. C., Bruschini, E., De Angelis, S., Ferrari, M., Formisano, M., Rossi, L., and Ammannito, E.: Clay-rich deposits at Oxia Planum: from orbital spectroscopic evidence to their geology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17330, https://doi.org/10.5194/egusphere-egu26-17330, 2026.
The ESA ExoMars mission will land at Oxia Planum to search for signs of life on Mars [1, 2]. In this study, we analyze aeolian linear features in the landing ellipse using CTX (6 m/pixel), CaSSIS (5 m/pixel), and HiRISE (25 cm/pixel) imagery.
We identified bright wind streaks oriented towards the S-SSW (mean azimuth 189°), consistent with formative winds blowing from the N-NNE. Their orientation reveals slight variations, allowing us to distinguish distinct sub-populations that appear controlled by the local topography.
In contrast, dark-toned stripes form a 'streaky' pattern with a main NE-SW trend. In the western sector, they consist of elongated dark patches covering the bright, clay-enriched unit (the mission’s main target [2]). Crucially, the presence of small scarps suggests a degree of material consolidation or cementation. These stripes are preferentially preserved in the lee of impact craters (~600 m diameter), suggesting formative winds from the NE, thus differing substantially from the orientation of the nearby bright streaks.
In the SE sector, SSE-oriented dark stripes are associated with a ~2 km diameter impact crater. Both CaSSIS and HiRISE data confirm that these features consist of a dark ejecta blanket preferentially preserved along the crater's southern rim, directly overlying the bright clay-enriched bedrock. Their orientation is slightly divergent but comparable to the bright wind streaks in this area, suggesting control by the current regional wind regime.
We propose that these findings indicate a new class of Martian aeolian feature. Unlike typically described wind streaks, the features presented here appear composed of consolidated material. Specifically, the dark ejecta stripes can be interpreted as 'aeolian preservation streaks'. This feature arises from the differential erosion of a consolidated unit (e.g., crater ejecta blanket) by winds from the N-NNW; the crater rim creates a wind shadow that preserves the ejecta downwind while the surrounding area is removed, exposing the underlying Noachian bedrock.
The orientation of these preservation streaks suggests that a N-NNW wind regime has been dominant in shaping the landscape over geological timescales. Even the dark stripes in the western sector, particularly where clustered behind topographic obstacles, may share this origin. Although their degree of consolidation remains to be definitively determined, their divergence from bright streaks suggests either a different formation timeline or strong local topographic control. These hypotheses regarding consolidated aeolian features and paleo-wind regimes will require crucial in-situ validation by the ESA Rosalind Franklin rover.
[1] Vago J. et al. (2017). Astrobiology, 17. [2] Quantin et al. (2021), Astrobiology, 21.
How to cite: Silvestro, S., Vaz, D. A., Grasso, F. M., Tirsch, D., Favaro, E. A., Rizza, U., Salese, F., Popa, C. I., Franzese, G., Mongelluzzo, G., Porto, C., Pajola, M., and Esposito, F.: Consolidated Aeolian Streaks in Oxia Planum: Evidence for Differential Erosion and Topographic Shielding, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11725, https://doi.org/10.5194/egusphere-egu26-11725, 2026.
The Olympia Undae Sand Sea of the North Polar region contains unique gypsum-rich dunes that provide insights into modern polar processes. Detailed characterization of gypsum and associated minerals is now feasible at the tens of meters scale due to advances in CRISM image processing and is revealing compositional variations across the dunes and interdune regions. Dunes with the strongest gypsum signatures are present in the eastern part of Olympia Undae and contain spectral features at 1.75, 1.94, 2.22, 2.27 and 2.48 μm as well as a triplet at 1.45, 1.49, and 1.54 μm. The bright interdune patches in the east are filled with ripples (as seen in HiRISE images) and have spectra consistent with gypsum but are brighter, indicating the presence of an additional spectrally bright material as well (likely a sulfate or chloride salt).
Traveling west, the dunes have slightly weaker gypsum-like spectral bands that are shifted slightly and could be resulting from dehydration of the gypsum or the presence of additional alteration minerals. Specifically, the band at 1.75 µm in the eastern dunes is shifted to 1.78 µm, which is observed in spectra of bassanite and some hydrated Ca chlorides. Continuing from central to western Olympia Undae the ~1.94 µm band becomes substantially weaker, indicating a much lower abundance of gypsum. Polygonal cracks can be seen in HiRISE images of the interdune regions that are reminiscent of evaporitic-type formations accompanied by secondary salt precipitation. The interdune regions also have weak spectral signatures consistent with a mixture of hydrated Ca and Mg sulfates and possibly hydrated Ca chlorides. These interdune regions in central to western Olympia Undae may be providing glimpses of the Planum Boreum basal unit below the dunes.
We are also investigating CRISM and HiRISE images bordering the Cavi region in order to gain insights into formation of the evaporitic-type salts under the Olympia Undae dunes. Surface materials at the Cavi region are hydrated but exhibit spectral properties different from those of gypsum and bassanite. Instead, spectra of dunes and regolith at the Cavi region have features similar to the spectra of hydrated ferric sulfates and perchlorates. Some hydrated chlorides may also be present. Ice and ice-regolith mixtures are also observed there.
MOLA maps reveal a lower elevation in eastern Olympia Undae where the gypsum is strongest. Thus, if more water pooled here at the time of alteration of the basal unit, then more gypsum may have formed in this depression. This area also contains the highest abundance of bright gypsum-bearing ripples, suggesting wind reworking of bright polygonal surfaces as a mechanism for extracting gypsum from the basal unit. Additionally, wind patterns from east to west could be spreading gypsum westward and at the same time dehydrating the gypsum. Additionally, frost is frequently observed on the dunes and interdune regions in winter and spring and could be altering the mineralogy and morphology.
How to cite: Bishop, J. L., Gruendler, M. R. D., Itoh, Y., Yanez, K. L., Parente, M., Szynkiewicz, A., Fenton, L. K., Saranathan, A. M., Zuschneid, W., Gross, C., and Gibson, T.: Advances in the Mineralogy and Potential Formation Processes of Sulfates and Cl-Salts in the North Polar Dunes at Olympia Undae on Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14981, https://doi.org/10.5194/egusphere-egu26-14981, 2026.
Fan-shaped deposits (FSDs) on Mars are key geomorphic indicators of past surface water activity and provide important constraints on sedimentary processes, hydrology, and paleoenvironments [1]. These landforms have been widely detected across the planet using orbital imagery, particularly at the margins of basins, craters, and valley networks, recording the sediment transport and water availability [2]. Within Coprates Chasma, fan-shaped deposits offer an opportunity to investigate localized depositional processes in Valles Marineris, where fluvial, lacustrine, and mass-wasting processes have been documented [3].
Using high-resolution imagery from the Colour and Stereo Surface Imaging System (CaSSIS) [4] aboard the ExoMars Trace Gas Orbiter, we identify two fan-shaped deposits in Southeast Coprates Chasma. In CTX basemap imagery, both deposits display similar geomorphic characteristics, including (1) branched channel networks in their source regions, (2) evidence for sediment transport along a ~35 km thalweg toward their apices, and (3) radially convex sedimentary bodies with comparable dimensions, approximately ~5 km in width and ~3 km in length at the downstream end of the source areas. Despite these geomorphic similarities, CaSSIS near-infrared, panchromatic, and blue (NPB) composites reveal distinct colour differences between the two FSDs. FSD A exhibits a light purple tone, whereas FSD B appears to be dark blue. Observations from Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité (OMEGA) [5] spectra hint that the light purple signature has an absorption band in 0.91 µm, while the dark blue signature in 1.04 µm.
We interpret these combined geomorphic and spectral observations as evidence for differing depositional environments. FSD A is interpreted as a fan-delta [6], formed where sediment-laden flows entered a standing body of water, promoting finer-grained deposition and the relative enrichment of Low-Calcium Pyroxene (LCP) bearing materials. In contrast, FSD B is interpreted as an alluvial fan, deposited under subaerial conditions dominated by episodic fluvial activity and limited aqueous alteration, preserving High-Calcium Pyroxene (HCP) rich compositions. These findings highlight the importance of integrating high-resolution morphology with spectral data to distinguish between superficially similar fan-shaped landforms and to better constrain the hydrological history of Coprates Chasma.
References:
- Morgan et al., (2022). Icarus 385, https://doi.org/10.1016/j.icarus.2022.115137
- Vaz et al., (2020). EPSL 533, https://doi.org/10.1016/j.epsl.2019.116049
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- Argadestya et al., (2026). Npj Space Exploration 2, https://doi.org/10.1038/s44453-025-00015-8
How to cite: Argadestya, I., Pommerol, A., Schlunegger, F., Anselmetti, F., and Thomas, N.: Mineralogical, Sedimentological, and Geomorphic Distinction of Fan-Delta and Alluvial Fan Deposits in Southeast Coprates Chasma: Observations from CaSSIS and OMEGA, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13609, https://doi.org/10.5194/egusphere-egu26-13609, 2026.
How to cite: Aye, M., Ihro, T., Portyankina, G., Michaels, T., Schwamb, M. E., and Hansen, C. J.: Planet Four: Inter- and Intra-annual Variability of Dark Regolith on Ice Coverage at the Martian South Polar Region, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20832, https://doi.org/10.5194/egusphere-egu26-20832, 2026.
Landslides on Mars are abundant and far more mobile than terrestrial landslides. Their exceptional scale and mobility provide key constraints on Martian surface processes, tectonic activity, and the environmental conditions that govern landslide mechanics. However, existing global inventories remain incomplete as small, overlapping, or morphologically ambiguous deposits are difficult to capture through manual mapping alone, leaving uncertainty in understanding their spatial distribution. Automated Martian landslide detection remains challenging due to the data scarcity with only a few thousand labeled samples and the natural morphological complexity of landslides. Therefore, we propose Mars-DiSVM, a landslide identification framework based on multi-modal imagery, which fuses features extracted from CTX, MOLA-HRSC DEM, and THEMIS night-time imagery using a DINOv2 backbone, followed by a downstream SVM classifier. The classification using fused feature representations achieves the top accuracy, up to 97.5%, with precision, recall, and MCC consistently exceeding 90%. Mars-DiSVM was further assessed within four areas of interest (AOIs), including the area with mapped landslides in the existing global inventory [1] and areas without mapped landslides in Noachian/Hesperian highlands.
Our framework identified 25 previously unmapped landslides across four AOIs, where the features are predominantly located on slopes within impact craters and along valley slopes, and are classified as rock avalanches and slump/flow types. These features are generally small, with approximately
half exhibiting runout lengths shorter than 5 km, sizes which are often underrepresented in manual mapping due to limited visibility or morphological degradation. The newly mapped landslides display diagnostic morphological characteristics, including lateral levees, tongue-shaped deposits, and longitudinal ridges within the deposits. Notably, three of the detected landslides occur adjacent to impact craters, implying impact events as the possible trigger. These findings highlight the importance of improving the completeness of global inventory, providing clues to their potential triggering mechanism.
Mars-DiSVM is implemented at the global scale to generate a preliminary expanded global inventory of Martian landslides. The resulting dataset will provide new constraints on the spatial distribution of landslides, thereby improving our understanding of their relationship with key controlling factors, such as the presence of ice or water and seismic activity [2]. In addition, we plan to monitor recent Martian landslide activity by incorporating newly acquired CTX imagery, thereby gaining insights into Martian recent geological activity and triggering mechanisms.
[1] Crosta, G. B., Frattini, P., Valbuzzi, E., & De Blasio, F. V. 2018, Earth and Space Science, 5, 89, doi: 10.1002/2017EA000324
[2] Roback, K. P., & Ehlmann, B. L. 2021, Journal of Geophysical Research: Planets, 126, e2020JE006675, doi: 10.1029/2020JE006675
How to cite: Tao, Y., Pan, L., and Liu, Z.: Expanding the Global Martian Landslide Inventory with Multi-modal DINOv2 Feature Fusion and SVM Classification, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6146, https://doi.org/10.5194/egusphere-egu26-6146, 2026.
Valley networks and wrinkle ridges are commonly observed in the Martian highlands. Geologic cross-cutting relationships between fluvial and tectonic features provide constraints on their formation sequences and the spatiotemporal evolution of these processes. For example, in central Terra Sabaea, a valley network appears to be affected by a wrinkle ridge. Tributaries are diverted along the ridge front and converge into a single, elevated channel across the ridge, suggesting coevolution between fluvial erosion and wrinkle ridge development. In this work, we systematically examine all intersections between valley networks and wrinkle ridges across the Martian highlands, assessing the relative timing and activity of tectonics and fluvial erosion. We identify 70 intersection sites from previously mapped valley networks and wrinkle ridges. Among them, ~60% exhibit syn- to post-fluvial tectonic modification, as indicated by drainage reorganization and valley profile changes; ~30% record pre-fluvial tectonic activity, and only ~7% show purely post-fluvial tectonic activity. Longitudinal profiles from six syn- to post-fluvial tectonic sites indicate that tectonic uplift produced comparable amounts of deformation during syn-fluvial and post-fluvial periods, with one exception. Erosion efficiency coefficients estimated from the incised valley profiles are similar to those observed in arid climates or in regions underlain by resistant bedrocks on Earth. Our results suggest that the widespread tectonic modification of existing valley networks in the intersection sites may reflect a dynamic coevolution of tectonic and fluvial systems during Mars’ hydrologically active past.
How to cite: Chen, H., Moon, S., Kim, E., and Paige, D.: Dynamic coevolution of valley networks and wrinkle ridges in the Martian highlands: Implications for geologic evolution and paleoclimate, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4576, https://doi.org/10.5194/egusphere-egu26-4576, 2026.
In its past, Mars experienced a warmer and wetter climate than on present days. Many uncertainties remain about the early climate of Mars, for instance on the nature of gas species included in the greenhouse warming or the duration of the warm episodes. Most existing reconstructions of Martian paleo-topography either rely on idealised assumptions, large-scale isostatic corrections, or limited regional reconstructions, and therefore do not explicitly integrate stratigraphic information on buried Noachian terrains. As a result, it is uncertain how paleo-topography impacted the early climate, and the development of the valley network.
For the first time, we present a global reconstruction of the Noachian paleo-surface using constraints from geological mapping, and craters central peaks mineralogy and morphology. Starting from the present-day Mars Orbiter Laser Altimeter topography, we removed all the terrains younger than Noachian, based on the geological map from Tanaka et al., 2014. That includes the large areas from the lowlands in the northern hemisphere, the Tharsis bulge, recent impact basins, craters with inner sedimentary deposits, and the Noachian surfaces extensively affected by post-Noachian tectonic activity such as Valles Marineris and outflow channels. We used the mineral detections in the central peaks of impact craters and the central peak morphologies to describe the buried terrains and find the boundary between Noachian (lowest layer) and post-Noachian terrains (shallower layer). Phyllosilicates-bearing central peaks and massive morphologies are considered as evidence for excavated Noachian material, while mafic detections without hydrated minerals associated to layers morphologies are interpreted as post-Noachian units. We estimated the stratigraphic uplift for each impact to infer the original depth of the excavation, allowing us to define upper and lower bounds of the Noachian surface. The points are interpolated using a kriging interpolation technique to produce global envelopes, and the Noachian paleo-surface is defined taking the spatial mean of the lower and upper envelopes.
Unlike previous products, this reconstruction directly links surface elevation to independently derived stratigraphic and mineralogical constraints, providing a physically grounded estimate of Noachian topography rather than a purely geometric or isostatic correction of present-day relief. Future refinements of the paleo-surface will include the effects of the true polar wander and lithospheric flexure effects due to the surface loading, particularly for the Tharsis region. This resulting dataset is designed to be used as a common boundary condition for climate, hydrological, erosional, and thermal models. We expect the paleo-surface to allow more realistic simulations of early Mars and a reassessment of the environmental conditions under which valley networks formed.
Tanaka, K. L. et al. (2014). The digital global geologic map of Mars: Chronostratigraphic ages, topographic and crater morphologic characteristics, and updated resurfacing history. Planetary and Space Science, 95, 11-24.
How to cite: Millot, C., Quantin-Nataf, C., and Salles, T.: Rebuilding the Noachian paleo-surface of Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7280, https://doi.org/10.5194/egusphere-egu26-7280, 2026.
Mars’ northern lowlands record some of the most extensive resurfacing events on the planet, yet the cumulative thickness and volume of their stratigraphic fill remain poorly constrained. This uncertainty directly affects estimates of volcanic resurfacing rates, the timing and magnitude of major emplacement phases, and the integrated volatile release potentially influencing Noachian–Hesperian environments. Here we reassess the minimum stratigraphic volume of the northern lowlands by combining crater-based reconstruction of buried topography with regional geologic constraints.
We quantify fill volumes through an approach that leverages crater size–frequency distributions and morphometric relationships calibrated on reference terrains, coupled with MOLA topography and CTX imagery to characterize present-day crater geometries and preservation states. Pristine crater shapes are reconstructed to approximate pre-burial morphologies, enabling estimation of the material volume required to bury crater interiors and to raise intercrater plains. We explore conservative end-member scenarios that explicitly bound uncertainty, including (i) present-day vs. reconstructed crater geometries and (ii) plausible intercrater-plain thickness ranges (1–2 km), consistent with independent stratigraphic and geologic considerations.
The resulting bounds indicate a substantially larger cumulative stratigraphic volume for the northern lowlands than many commonly adopted estimates, yielding ~0.8–1.7 × 10^8 km^3 of fill. When interpreted in terms of volcanic emplacement, this implies proportionally larger time-integrated volatile outgassing, with CO₂, H₂O, and SO₂ totals of order 10^21–10^20 g. These revised constraints provide a quantitative basis to (i) refine volcanic resurfacing histories of the northern plains, (ii) reassess the magnitude of volatile contributions to ancient atmospheric budgets, and (iii) improve the geological context for interpreting orbital observations and future exploration of lowland stratigraphy and its interfaces with highland terrains.
How to cite: Salese, F., Hiatt, E., Pondrelli, M., Hesse, M., Soldano, M., and Fairén, A.: Constraining the stratigraphic fill of Mars’ northern lowlands from buried-crater statistics: implications for resurfacing history and volatile budgets, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14203, https://doi.org/10.5194/egusphere-egu26-14203, 2026.
The Martian geologic record contains abundant evidence for the presence of surface liquid water in the past, however, the fate of this liquid water is not well constrained. One mechanism to sequester this water is within the crystal structure of minerals, such as gypsum (CaSO4*2H2O), which both contains structurally bound water and requires liquid water to form. Olympia Undae, also known as the North Polar Erg, is the largest dune field on Mars, and is known to contain gypsum sands. These gypsum dunes are a reservoir for water that has not been accounted for in Mars' water budget. As the amount of water stored in the gypsum dunes is currently unknown, the water budget for Mars' northern polar region is not well constrained.
Our study combines orbital data from several instruments onboard the Mars Reconnaissance Orbiter, specifically visible near-infrared (VNIR) data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), images from the Context Camera (CTX), and digital terrain models (DTMs) from the High-Resolution Imaging Science Experiment (HiRISE), to help constrain the amount of water bound in the Olympia Undae gypsum dunes. These remote-sensing data sets are supplemented by ground truth results from White Sands National Park, New Mexico, USA, which contains the largest gypsum dune field on Earth. By combining these different data sets and leveraging in-situ measurements from a terrestrial analog, the water content of the entire north polar erg will be quantitatively estimated and contextualized. This investigation will improve our constraints on the Martian volatile budget, and the processes that have contributed to the sequestration of water on Mars.
How to cite: Bretzfelder, J., Rivera-Hernandez, F., and Day, M.: Constraining Water Volume in the Gypsum Sands of the Martian North Polar Erg, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21944, https://doi.org/10.5194/egusphere-egu26-21944, 2026.
Understanding the Martian soil water budget is crucial not only for in situ resource utilization in future human missions to Mars, but also for reconstructing the geological and climatic history of the planet, as well as to assess the potential of ancient or even present microbial life. Here, we present a methodology to study near-surface water using albedo protons, based on measurements from the Radiation Assessment Detector (RAD) onboard the Mars Science Laboratory (MSL). With this approach, water can be investigated beneath dust layers at approximately 3–7 cm, representing a new observational depth range compared to existing methods. In combination with data from the Dynamic Albedo of Neutrons (DAN) experiment, also part of MSL, we show that MSL/RAD has so far been unable to resolve small variations in regolith water of 2–7 %. However, supporting simulations suggest that larger water reservoirs, such as those at higher latitudes or locally near the equator, may be detected by MSL/RAD with measurement times of approximately one to two months. We demonstrate that a future Mars detector, specifically redesigned to measure albedo protons, could detect changes in near-surface water content of about 20 % within roughly 5–17 days, and variations exceeding 40 % within only a few days, with statistical significance. We therefore propose including albedo proton measurements in future missions to Mars or other extraterrestrial bodies, as they represent a promising complement to existing methods for probing near-surface water.
How to cite: Löwe, J. L., Wimmer-Schweingruber, R., Khaksari, S., Löffler, S., Nikiforov, S., Guo, J., Charpentier, G., Ehresmann, B., Hassler, D., Matthiä, D., Berger, T., Reitz, G., and Zeitlin, C.: Martian Proton Albedo as Signature of Near-Surface Water, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10419, https://doi.org/10.5194/egusphere-egu26-10419, 2026.
The Curiosity rover recently discovered a deposit of native sulfur (S0) in Gediz Vallis, Gale crater, composed of decimetric light-toned blocks forming a 60 m wide talus. Such accumulations are rare on Earth and typically require volcanic, hydrothermal, or bio-mediated processes, yet the Martian deposit challenges direct terrestrial analogies. While previous studies proposed subsurface clathrate decomposition as a source, we propose an alternative scenario involving a sulfur flow produced by meteoritic impact melting of the light-toned yardangs unit upstream, hypothesized to be enriched in volcanic native sulfur. A 390 m-diameter, 80 m-deep breached crater is identified as the possible source of the melt flow that traveled 4 km down Gediz Vallis. Considering the low viscosity of sulfur, thermal modeling of the flow confirms that the travel time would be shorter than its crystallization time. The molten sulfur would then pool, crystallize, and exsolve the remaining gases, including H2S, forming subspherical cavities as observed in the blocks. The sulfur outcrop is also laterally wedged with a near-horizontal upper contact, consistent with a low viscosity melt filling the channel. The high purity and rhombic crystal habit of the sulfur blocks, along with an apparent increase of the number of gas bubbles from bottom to top, further support in-situ crystallization from a single melt pool. In-situ reflectance spectroscopy reveals that dust obscures the native sulfur signal on naturally exposed blocks, explaining why its presence could not be detected from the orbit.
This scenario implies that the light-toned yardangs unit, previously interpreted as eolian deposits and possibly linked to the Medusae Fossae formation, may represent a new type of distal volcanic deposit enriched in native sulfur. Such deposits could provide new insights into Hesperian atmospheric and volcanic processes, as well as Mars’ magmatic evolution. The Curiosity rover is planned to investigate this unit during its fifth extended mission, offering an opportunity to test this hypothesis and refine our understanding of sulfur cycling on early Mars.
How to cite: Rapin, W., Baratoux, D., Mangold, N., Maggioni, L., Dupuis, E., Forni, O., Beck, P., Gasnault, O., Le Deit, L., Le Mouélic, S., and Dromart, G.: An impact melt flow scenario to form the pure native sulfur deposit at Gale crater, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22162, https://doi.org/10.5194/egusphere-egu26-22162, 2026.
Jezero crater is a 45-km diameter impact crater, formed during the Early-Middle Noachian period, ~3.9 Ga, on the northwest rim of the Isidis Planitia within the highland crust of Mars of the Nili Fossae region. Rocks excavated by the impact, thus pre-dating Jezero crater, potentially >4.0Ga, were investigated by the Perseverance rover on the rim of the crater. The outer Jezero rim displays a light-toned, layered unit informally named Witch Hazel Hill, which has been analyzed by Perseverance in locations named Broom Point and Sallys Cove. There, the SuperCam Remote Micro-Imager (RMI) and Mastcam-Z cameras revealed rocks with spherical granules, which hereafter we refer to as “spherules”, a term used here as purely descriptive. At Broom Point, we analyzed the largest number of spherule-bearing targets, among which two clasts and two bedrock targets have been analyzed thoroughly. The spherules are ~2-mm of mean diameter in all targets, are closely packed, and represent >90% of the granules. In one of the targets, they are partly broken and piled up by an energetic process. The elemental composition derived SuperCam is basaltic, close to that of the surrounding bedrock. However, the featureless infrared reflectance spectra lack signatures of hydration, and are interpreted as glasses, in agreement with their shiny surface on images. In contrast, the surrounding rocks display hydration features linked to the presence of sulphates and phyllosilicates. At Sally’s Cove, 50 m away to the north, spherules are scattered along laminae of the bedrock. They display a mean diameter (<0.5 mm) too small for SuperCam individual analysis. While no proximity science was possible at Broom Point, Sallys Cove was favourable for a chemical analysis by the PIXL instrument. The composition of the eight spherules analysed there show rims distinct from the interior, and diverse compositions ranging from plagioclase-rich to pyroxene-rich. On Earth, spherule-bearing rocks can be found in impact, volcanic or sedimentary rocks. The chemical characteristics of Jezero rim’s spherules do not favour sedimentary concretions such as those observed at Meridiani Planum. A volcanic context would reasonably explain the presence of spherical clasts such as accretionary lapilli produced by explosive volcanism. Nevertheless, the homogeneity of the spherule size and their well-defined sphericity is frequent for impact spherules observed on Earth at the K-Pg boundary for which spherules were created by droplets of melt ejected to several thousands of km. The basaltic, anhydrous composition is consistent with such a hypothesis, although it does not fully rule out volcanic fire fountains. Yet, at Sallys Cove, the variable compositions of spherules measured by PIXL are difficult to explain in a volcanic context, which assumes homogeneous compositions. Hence, we currently favour the presence of these spherules from impact ejecta. If this hypothesis was confirmed, the sample collected at this location could represent a unique opportunity to analyse impact processes at the surface of a terrestrial planet in the early history of the solar system.
How to cite: Mangold, N. and the Mars 2020 Perseverance Crater Rim spherule beds analysis team: Four-billion years old spherule beds revealed by Perseverance on the outer rim of Jezero crater, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6455, https://doi.org/10.5194/egusphere-egu26-6455, 2026.
Multiple orbital studies have highlighted the importance of Fe/Mg phyllosilicate minerals on Mars, especially in Noachian terrains (e.g. Poulet et al., 2006; Mangold et al., 2007;), even showing that they are the dominant hydrous mineral family on Mars (Carter et al., 2013). Although widespread in exposures of the oldest terrains on Mars, it is hard to constrain either their composition or formation process based on orbital data only (Ehlmann et al., 2011; Carter et al., 2015). The best matches for the orbital spectra were proposed to be smectite (nontronite, saponite) and/or vermiculite (Carter et al., 2013). In the Nili Fossae region specifically, the Noachian basement was shown to be bear widespread signatures of Fe/Mg smectites (Goudge et al., 2015).
After exploring diverse geological units inside Jezero Crater (Nili Fossae, Mars), and going over the rim of the crater, the Perseverance rover has reached a unit informally called Krokodillen, at the base of the outer part of the rim. It is thought to be part of the Noachian crust that was locally uplifted by the emplacement of Jezero Crater (Sun & Stack et al., 2020). Dark looking from orbit, it is surrounded on the North, West and South by ridges and an exposure of the regional olivine-rich unit, understood to be younger.
We will present the data acquired on rocks of the Krokodillen area with the SuperCam instrument (ref Maurice et al., SSR 2021; Wiens et al., SSR 2021). Overall structureless, the rocks of Krokodillen are generally fine grained, with locally some millimetric granules. The chemical composition characterized with LIBS shows a relatively homogeneous composition intermediate between the average basaltic crust of Mars and orthopyroxene. This is likely an average, close to the bulk composition, due to the mixing of multiple fine-grain mineral phases within the footprint of the LIBS analysis. Visible and near infrared (VISIR) reflectance spectroscopy data show strong and ubiquitous signatures of Fe-Mg phyllosilicates, closely matching those observed from orbit in the broader Nili Fossae region.
We propose that the rocks of Krokodillen are representative of the Noachian clay-bearing rocks characterized from orbit, specifically the (ridged) Altered Basement mapped by Goudge et al., (2015) in the Jezero watershed. In that case, the in situ measurements from the Mars 2020 mission provide the first in situ constraints on the composition, aqueous alteration and emplacement mechanism of these rocks.
How to cite: Clavé, E., Dehouck, E., Quantin-Nataf, C., Mandon, L., Mangold, N., Gasnault, O., Beck, P., Bedford, C., Johnson, J., Klidaras, A., Simon, J., Wiens, R., and Cousin, A.: Perseverance at Krokodillen: first in situ observations of the clay-bearing Noachian basement of the Nili Fossae region, Mars. , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9472, https://doi.org/10.5194/egusphere-egu26-9472, 2026.
From the first 1700+ sols and over 40 km of total odometry of the NASA Mars 2020 mission’s Perseverance Rover traverse, many Mastcam-Z observations exist for rocks that have been scuffed/broken by the rover wheels. Broken/scuffed rock surfaces provide clearer insight into rock interior mineralogies compared to natural surfaces, which are often further eroded or covered with a layer of dust that can mask many spectroscopic signatures (Rice et al., JGR–P, 128, 2023). Broken surfaces provide a look into the deeper interiors of rocks compared to abrasion patches, and could reveal mineral heterogeneity of the whole rock for cleaved massive rock types. In addition to broken rocks, we are investigating subsurface regolith overturned by Perseverance’s wheels via Mastcam-Z and SuperCam. Disturbed regolith in particular provides an opportunity to investigate material that contains significantly less airfall dust and could have undergone less recent transport than the surface layer from saltation creep (e.g., Sullivan & Kok, JGR–P, 122, 2017), allowing more reliable investigations into long-term historical sediment sources.
Here, we present a Mastcam-Z multispectral analysis of multiple cleaved rock interiors and crushed rocks spanning Jezero crater floor to the crater rim. We compare broken rock interiors with dusty surfaces and verify the effectiveness of previous studies in creating a ‘dust metric’ to evaluate the extensiveness of Martian dust on a surface using Mastcam-Z. Within a potential crater rim impact ejecta ‘megablock’ observed from mission Sol 1624, we identify differing mineral classes, some of which are consistent with laboratory spectra of serpentinized minerals. We also observe mineral heterogeneity on the cm- to dm-scale within this megablock. Many rock interior multispectral observations across the rover traverse are consistent with low-calcium pyroxene spectral signatures based on band ratio metrics and laboratory comparisons, with some crushed rocks (e.g., Sol 1238 in the crater rim) showing a strong agreement with crystalline iron oxide lab spectra, suggesting regional alteration. These interpretations reflect local rock units where observations occurred, and provide supportive results for inferring the origin and evolution of rock units throughout Jezero crater.
How to cite: Robbins, G., Bell, J., Johnson, J., Rice, M., and Gasnault, O.: Perseverance-Exposed Broken Rock Interiors and Subsurface Regolith in Jezero Crater, Mars., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14982, https://doi.org/10.5194/egusphere-egu26-14982, 2026.
Multispectral imaging from the Mars 2020 Perseverance rover provides key constraints on how dust cover and small-scale surface texture influence the photometric behavior of Martian materials. During Sols 63–65, the Mastcam-Z camera acquired multispectral stereo mosaics from Van Zyl Overlook in Jezero crater at five wavelengths between 442 and 1022 nm. These observations span phase angles from near opposition to ~150°, allowing detailed characterization of surface scattering properties across a diverse set of geological units near the landing site.
Radiance and reflectance products were derived using onboard calibration targets. Stereo disparity maps were used to compute incidence, emission, and phase angles at the pixel scale and to incorporate topographic information into the analysis. Regions of interest were selected for seven surface units, including dark and dusty soils, regolith, dust-poor “blue” rocks, dustier “red” rocks, intermediate-toned rocks, and rover wheel tracks. Hapke photometric models employing both one-term and two-term Henyey–Greenstein phase functions were applied to retrieve single-scattering albedo, macroscopic roughness, and phase-function parameters describing the angular distribution of scattered light.
The modeling results show that rocks and soils at Van Zyl Overlook are variably modified by differences in dust coverage and surface texture. Blue rocks are consistently the darkest and most strongly backscattering units across wavelengths, with relatively low single-scattering albedos (w ≈ 0.30–0.40), consistent with minimally dust-coated, rough surfaces. Red rocks are brighter, less backscattering, and exhibit trends toward more forward scattering, particularly at shorter wavelengths, with w values approaching ~0.8 at longer wavelengths. Their photometric behavior, together with their visual appearance, is consistent with relatively thick dust mantles that brighten and smooth the surface at small scales. Intermediate rocks follow the scattering behavior of blue rocks but at slightly higher albedo, suggesting similar substrates with modest additional dust contributions.
Regolith and soils span a continuum of scattering behaviors that broadly track their spectral appearance. Regolith tends to be more backscattering, while red soils show more forward-scattering trends, with blue soils occupying an intermediate regime. Rover wheel tracks represent the most atypical unit: despite relatively flat bidirectional reflectance curves, two-term phase-function solutions indicate backscattering trends. Tracks also exhibit the lowest macroscopic roughness values among all units, consistent with surface compaction and smoothing caused by wheel interaction. This behavior differs from some previous rover track observations, suggesting that wheel-induced modification of porosity or grain arrangement may vary between sites.
Overall, variations in single-scattering albedo, phase-function shape, and macroscopic roughness indicate that dust cover and small-scale surface texture play key roles in controlling photometric differences at Jezero crater. While the observed trends are broadly consistent with early Gale crater results, contrasts with Mars Exploration Rover findings highlight the influence of local surface conditions. Extending similar analyses to additional Mars 2020 and Mars Science Laboratory observations will help further isolate the roles of dust, texture, and physical modification in shaping Martian surface scattering properties.
How to cite: Margara, B., Johnson, J., Hayes, A., Lemmon, M., Grundy, W., Bell, J., and Barrington, M.: Mastcam-Z Spectrophotometric Properties of Materials at the Van Zyl Overlook, Jezero Crater, Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15557, https://doi.org/10.5194/egusphere-egu26-15557, 2026.
The SuperCam instrument onboard the Mars2020 Perseverance rover is a suite of remote sensing instruments that is operating on the Martian surface since February 2021 (Maurice et al., 2021 ; Wiens et al., 2021). It notably includes a Visible-InfraRed (VISIR) spectrometer covering the 385–465 nm, 536–853 nm, and 1.3–2.6 μm spectral ranges (Fouchet et al., 2022), which regularly performs observations of the Martian atmosphere using the passive sky geometry (Bertrand et al., 2022). At these wavelengths, scattering by aerosols is strongly sensitive to the particle size. The ability of the passive sky technique to retrieve the atmospheric dust content has been demonstrated in the VIS spectral range with MSL/ChemCam (McConnochie et al., 2018), and SuperCam is now able to probe for the first time the Martian atmosphere from the ground for both the VIS and near-IR domains, which provides further information on the aerosol properties.
Dust and water ice aerosols play an important role in the current Martian climate: they affect the thermal structure of the atmosphere as they absorb and scatter the incoming sunlight, and contribute to the global water cycle of the planet (Haberle et al., 2017). Thus, monitoring the properties of these aerosols is of importance to better understand and model the current Martian climate. On Perseverance, the optical depth of the aerosols above the rover is monitored on a seasonal and local time basis by the MEDA and ZCAM instruments (Toledo et al., 2024 ; Smith et al., 2025 ; Moya-Blanco et al., this conference).
By measuring the spectra of the sky luminosity at two different elevation angles, and by comparing the measurement with the results of a multiple scattering radiative transfer model, we are able to retrieve the aerosol properties for both the dust and water ice. Here we use the DIScrete Ordinate Radiative Transfer (DISORT) code in version 4 (Stamnes et al., 2017) through the pyRT_DISORT (Connour & Wolff, 2024) Python module to retrieve the respective optical depth of dust and water ice from the VISIR passive sky measurements of SuperCam performed since the beginning of the mission in 2021, and constrain their particle size. We assume asymmetric hexahydra dust particles and droxtals shapes for the water ice crystals, and we use vertical atmospheric profile from the Mars Climate Database version 6.1 (Forget et al., 1999 ; Millour et al., 2024). These retrievals complement the ones performed by the rover’s other instruments, notably ZCAM. While it is highly challenging with their measurements to distinguish between dust and water ice contributions in the total optical depth, their results can be directly compared with those from SuperCam, as the wavelength ranges of the two instruments overlap in the visible.
How to cite: Stcherbinine, A., Bertrand, T., Wolff, M., Lasue, J., McConnochie, T., Montmessin, F., Fouchet, T., Knutsen, E., Lacombe, G., Cousin, A., Gasnault, O., Maurice, S., and Wiens, R.: Retrieving the Properties of Martian Aerosols at Jezero Crater using SuperCam PassiveSky Observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6805, https://doi.org/10.5194/egusphere-egu26-6805, 2026.
We present a standalone and fast algorithm for retrieving aerosol optical depth using data from the Mars Environmental Dynamics Analyzer Thermal-InfraRed Sensor (MEDA-TIRS) onboard NASA’s Mars 2020 Perseverance rover. MEDA-TIRS provides thermal infrared measurements during both daytime and nighttime, supplying a continuous and comprehensive dataset that captures variability across diurnal, seasonal and inter-annual timescales. This capability enables the retrieval of a nearly complete record of aerosol optical depth at the rover’s location since the beginning of the mission. Aerosol optical depth at the Perseverance site has previously been reported using onboard instruments, including MEDA, ZCAM and SCAM (Smith et al., 2024; Lemmon et al. 2025; Stcherbinine et al., this conference).
The algorithm operates independently of external datasets and is designed to be integrated directly into the MEDA data processing pipeline, allowing for systematic and autonomous retrievals. We describe the algorithm in detail and present results covering two full Martian years (MY 36 and MY 37) and the first half of MY 38. This temporal coverage allows for inter-annual and seasonal comparisons, the identification of local atmospheric events such as dust storms and the analysis of diurnal variability. The results also distinguish between two major periods: the aphelion season, dominated by water ice clouds, and the perihelion season, where dust is the dominant aerosol. In addition, the algorithm provides opacity data in near real time, enabling the early detection of dust events, which is of vital importance for the human exploration of Mars.
How to cite: Moya-Blanco, T., Sebastián, E., Vicente-Retortillo, Á., Smith, M. D., Martínez, G., Mora, L., and Rodríguez-Manfredi, J. A.: A Standalone MEDA-TIRS Algorithm for Continuous Aerosol Optical Depth Retrieval on Jezero Crater, Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8137, https://doi.org/10.5194/egusphere-egu26-8137, 2026.
The ExoMars Trace Gas Orbiter (TGO) has characterised trace gases in the Martian atmosphere over several Mars years, improving the accuracy of species concentration measurements and observing temporal, vertical and spatial variations. Hydrogen chloride—detected for the first time with TGO [1,2]—has been investigated recently using the mid-infrared channel on the Atmospheric Chemistry Suite (ACS MIR). HCl observations show a strong seasonal variation, with almost all of the detections occurring during the latter half of the year (solar longitudes 180-360°) in the dusty season, when water vapour is present in the Martian atmosphere and ozone concentrations are low. Chlorine-bearing species such as HCl are important to understand in Mars’ atmosphere because on Earth they are involved in numerous processes throughout the planetary system, including volcanism, and they play a key role in atmospheric chemistry, e.g., by influencing concentrations of oxidative species such as oxygen (O2) and ozone (O3).
Here, we use the Mars Planetary Climate Model—a 3-D global climate model that includes a photochemical network—to explore the atmospheric HCl observations. We build on existing chlorine photochemical networks [3,4] to investigate potential source and sink mechanisms, focusing in particular on heterogeneous chemistry involving ice aerosols, and exploring the possibility of its role in direct release of HCl to the atmosphere. We also explore how chlorine species are affected indirectly by changes in the abundances of oxidative species (e.g., OH and HO2,and by extension, O and O3),driven by heterogeneous chemistry. Understanding the role of oxidative chemistry on HCl and other trace gases is key to achieving a more complete picture of processes occurring in the present-day Mars atmosphere, as well as processes that have shaped its evolution and habitability.
[1] Korablev O. I. et al. (2021). Sci. Adv., 7, eabe4386. [2] Olsen K. S. et al. (2021). Astron. Astrophys., 647, A161. [3] Rajendran, K. et al. (2025). JGR: Planets 130(3), p.e2024JE008537. [4] Streeter, P. M. et al. (2025). GRL 52(6), p.e2024GL111059.
How to cite: Gregory, B., Olsen, K., Millour, E., Brown, M., Streeter, P., Rajendran, K., and Patel, M.: Modelling the Variation of HCl in the Martian Atmosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18786, https://doi.org/10.5194/egusphere-egu26-18786, 2026.
The Visual Monitoring Camera on board Mars Express provides images of varied resolutions, covering a wide range of locations and seasons, and has been taking images for several Martian Years. Some of these images show clear instances of aerosols layers in the limb of the planet, which allow studying their height and extension. Images close to pericenter display varying morphologies, and the extensive coverage by VMC allows determining inter-annual and areographicaI variations in occurrence.
The first years of the database were explored in Sánchez-Lavega (2018a), but this study was conditioned by the fact that there was no scientific programming of the observations until 2016. Nowadays, after several years of planning, a much more complete set of observations is available, covering four Martian years, with the added interest that a global dust storm developed in one of them (Sanchez-Lavega et al, 2018b). In this work, we will present results of a systematic analysis that aims to extend this study to MYs 33-37, measuring the extension and height of aerosols, their aerographic distribution and dependence on season and local time. We also contextualize our results using values of dust and water opacity retrieved by the Mars Climate Sounder onboard the Mars Reconnaissnce Orbiter and the estimates of the Mars Climate Database of the Laboratoire de Météorologie Dynamique.
References:
- Sánchez-Lavega, A. et al. “Limb clouds and dust on Mars from images obtained by the Visual Monitoring Camera (VMC) onboard Mars Express” ICARUS 299, 194-205 (2018a)
- Sánchez-Lavega, et al. “The Onset and Growth of the 2018 Martian Global Dust Storm” Geophysical Research Letters, 46, 6101-6108 (2018b)
How to cite: del Río-Gaztelurrutia, T., Sanz Hernández, T., Sánchez-Lavega, A., and Hernandez-Bernal, J.: Aerosols and clouds in the limb of Mars: A study with the VMC camera onboard Mars Express, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4041, https://doi.org/10.5194/egusphere-egu26-4041, 2026.
We present a study of singular systems of clouds seen as single “dot” clouds, clusters of dot clouds and ring-shaped clouds that form every Martian Year (MY) around solstice and aphelion period (from solar longitudes Ls ~ 40° to ~ 120°) in the Southern Hemisphere of Mars. The study is based on images taken with the VMC and HRSC cameras onboard Mars Express from 2008 (MY29) to 2025 (MY38). These clouds mainly concentrate in a sector between longitudes ~ 120°E to 180°E and latitudes ~ 35°S to 50°S in Terra Cimmeria (around Kepler and Cruls craters), with a second much less dense concentration west of the Argyre basin (280°E - 310°E). The isolated bright and compact clouds (dot-shaped clouds) occur in early morning hours (~ 8-11 hr LTST) and have sizes of ~ 100 km. An analysis of their projected shadows indicates cloud bases at heights of ~ 49 km and tops at ~ 55 km. The spots have maximum optical depths of ~ 0.5 (at visual wavelengths) and lifetimes of ~ 1 hr. At the same location and season, but a few hours earlier (LTST ~ 6-7 hr), clusters of bright dots are observed at dawn in twilight, and in some cases projected onto the sky above the Martian limb. They consist of ~ 15 bright spots each with a size of ~ 125 km, separated by ~ 200 km and tops at 65-70 km height. On some cases, the clusters appear to be organized in a ring-like morphology, with projected size of ~ 700-1000 km and tops in twilight at ~ 75-80 km. These clouds are most likely made of H2O ice and probably form when the dominant eastward winds flow on the craters walls and force a vigorous ascent. However, the mechanism leading to the formation of clusters and the ring-like organization, and the possible role of the magnetic crust anomaly at the region of their occurrence, remain to be explored.
How to cite: Sanchez-Lavega, A., Larsen, E., del Río-Gaztelurrutia, T., Hernández-Bernal, J., Tirsch, D., Maätänen, A., Spiga, A., and Sánchez-Cano, B.: Singular Clouds in Mars Southern Hemisphere around solstice and aphelion season , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10017, https://doi.org/10.5194/egusphere-egu26-10017, 2026.
Geological evidence indicates that Mars experienced multiple lake-forming climates lasting longer than 100 years around 3–4 billion years ago. These early warm climates cannot be explained solely by the greenhouse effect of carbon dioxide and water vapor. Recently, a warming mechanism driven by high-altitude water-ice clouds has been proposed for early Mars under surface water-limited climatic conditions. Here, we develop a general circulation model for terrestrial planetary atmospheres capable of simulating both early and modern climates of Earth and Mars. Simulation results show that the radiative effect of clouds can lead to two distinct climate states: when low-latitude surface regions are relatively arid, cloud radiative effects are dominated by warming, which can sustain dry–wet cycles in early Mars climate; however, when surface meltwater in low-latitude regions exceeds a critical threshold, cloud radiative effects shift to cooling, maintaining the climate in a cold, stable state. This work provides a new perspective for studying the climate evolution of early Mars.
How to cite: Ding, F., Wan, Z., and Wordsworth, R.: Can High-altitude Water-ice Clouds Sustain Dry–wet Cycles in Early Mars Climate?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10203, https://doi.org/10.5194/egusphere-egu26-10203, 2026.
The presence of carbon dioxide (CO₂) clouds in the Martian atmosphere requires extremely low temperatures for their formation. These clouds were first observed at low altitudes during the polar night. Subsequent observations identified similar clouds at higher altitudes near the equator, especially during spring and summer [1]. Further evidence has shown their occurrence at northern mid-latitudes and in the southern hemisphere during late autumn. Unlike water vapour clouds, which form from a minor atmospheric component, CO₂ clouds are composed of a major atmospheric constituent. The polar CO₂ clouds are convective in nature. Data from multiple missions indicate that the temperature profiles in the polar regions often align with the CO₂ saturation curve up to 30 km, implying that CO₂ condensation helps regulate these temperatures. Significant cloud opacity between 0 and 25 km altitude also supports the presence of CO₂ clouds.
Figure 1: Formation of CO2 clouds in the Martian atmosphere [2].
Data from the Pathfinder mission indicate that CO₂ exceeded saturation levels during equatorial descent phases at altitudes near 80 km, implying that CO₂ cloud formation in equatorial regions may occur at significantly higher altitudes compared to polar regions [3]. The genesis of these high-altitude equatorial CO₂ clouds is modulated by conditions in the Martian mesosphere. Notably, mesospheric temperatures can drop well below the CO₂ condensation threshold, particularly near aphelion, when diurnal atmospheric tides promote additional cooling conducive to cloud formation. Furthermore, high-altitude CO₂ cloud formations were detected at solar longitudes between 264° and 330°, located above 90 km in altitude [4]. These clouds exhibit limited horizontal extent, spanning approximately 500 to 700 km.
In this study, we investigate the formation and persistence of Martian CO2 clouds during the Northern Hemisphere winter and dust season. Open – access observations from the Mars Climate Sounder (MCS) on board the Mars Reconnaissance Orbiter (MRO) are used to identify atmospheric cloud occurrences. In addition, inter-annual variability is analysed to assess the influence of dust storms on CO2 cloud formation.
Figure 2: Examples of MCS temperature profiles (blue) with the CO2 saturation curve [5].
References:
[1] Määttänen A. et al. (2010), Icarus, 209(2) :452–469.
[2] Mars Climate Modeling Center. GCM overview: Lecture, November 2021.
[3] Schofield J. T. et al. (1997), Science, 278(5344) :1752–1758.
[4] Jiang F. Y. et al. (2019), GRL, 46(14) :7962–7971.
[5] Mathilde V. (2024), Master Thesis, Université Catholique de Louvain, Belgium.
How to cite: Krishnan, A. and Karatekin, Ö.: Martian CO2 cloud formation as observed by MCS , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19032, https://doi.org/10.5194/egusphere-egu26-19032, 2026.
Martian dust can be lifted to about 100 kilometres by known processes such as dust storms (e.g. Heavens et al, J. Atmos. Sci. 76, 2019). Dust has been observed at higher altitudes, but this is attributed to capture of interplanetary dust (Andersson et al, Science 250, 2015).
During its flight from Earth to Jupiter, a star camera on the Juno spacecraft observed dust in the size range of 1-100 um, contributing to the Zodiacal light and sharing orbital elements with Mars (Jørgensen et al, JGR: Planets 126, 2020). The origin of this dust was speculated to be Mars itself but a mechanism that allows the dust to reach escape velocity (~5 km/s) has not yet been identified. While dust can theoretically be lofted to hundreds of kilometres by electric forces on, for instance, the Moon (Wang et al, Planet. Space Sci. 184, 2020), the Martian atmosphere (thin as it is) makes this more difficult.
In this work we investigate the possibility of dust escaping Mars by electric forces. In order to reach the escape velocity a dust particle must overcome the forces of gravity and atmospheric drag. Beyond altitudes reached by meteorological phenomena, only electric forces can accelerate the particles. Recently observations by the Perseverance rover (Chide et al, Nature 647, 2025) showed discharges during dust events, indicating that the Martian atmosphere can have breakdown fields (about 15 kV/m at ground level).
In our model a dust particle of a prescribed size, charge, and updraft velocity is released at a given altitude into an atmosphere with an altitude dependent electric field. The resulting electric, drag, and gravity forces are calculated to find the particle’s velocity and altitude as a function of time. We test limit cases of electric charge and fields for relevant particle sizes to see what velocity is reached and how far a particle can be lifted.
How to cite: Enghoff, M. B. B., Jørgensen, P. S., Benn, M., Jørgensen, J. L., and Connerney, J. E. P.: Dust escape from Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10624, https://doi.org/10.5194/egusphere-egu26-10624, 2026.
Dust, composed of mineral micrometre-size particles, is omnipresent on Mars and has its own cycle: uplift from the surface and injection into the atmosphere, transport and formation of dust storms, and dissipation (grain sedimentation). Atmospheric dust, and thus dust storms, absorbs and diffuses incoming sunlight, strongly affecting the atmosphere by modifying its thermal structure [1] and enhancing global atmospheric circulation [2]. The intensity of these impacts depends on storm sizes, which are usually classified as local or regional storms (≥ 1.6×106 km2, [3]). Regional storms have been well studied (e.g., [4,5,6]) and characterised in opposition to local ones. This work focuses on local dust storms to better understand the storm evolution mechanisms (local to regional) that are still not well constrained.
We developed a method to detect dust storms [a] in the OMEGA IR dataset (2004-2010, Martian Years 26-30), the visible and near-IR imaging spectrometer of Mars Express (ESA). This method is based on a pixel clustering algorithm that is applied to the dust optical depth map [7] of each OMEGA observation. Then, we generate a mask that corresponds to the storm, from which we extract information, after confirming the presence of the storm, such as its size, position, local time, etc. We compiled about 440 new detections into the OMEGA/Mars Express Dust Storm Catalogue (ODSC), mainly composed of local storms (~81%).
We identified a peak of local storms, notably in MY 27, during the northern “solstitial pause” (solar longitude, Ls~240-270°), which corresponds to a period of lower regional storm activity due to lower wave activity (e.g., [8,9]). Therefore, this decrease in regional storm detections is not due to a strong decrease in local storm formation, but to a decrease in the growth process efficiency to regional size [a]. Local storms are also very active during the “C-regional storm season” (Ls~305-330°) and widespread on Mars. We found some privileged areas: high southern latitudes (polar cap edges) and close to strong topographic gradients, as inside topographic channels (e.g., Chryse, Acidalia, Arcadia; [4]), Hellas, Valles Marineris, Olympus and Elysium Mons [a]. This suggests that topographic winds contribute to the formation of dust storms during this period. We also noticed a similar diurnal pattern between local storms detected with OMEGA (MY 26-30) and regional ones detected with EXI/EMM (MY 36, [5]).
References:
[a] Leseigneur, Y., et al. (in revision), JGR:Planets, “OMEGA/MEx Dust Storm Catalogue”.
[1] Kass, D. M., et al. (2016), GRL, 43, 6111-6118.
[2] Barnes, J. R., et al. (2017), Cambridge Univ. Press, The atmosphere and Climate of Mars, 229-294.
[3] Cantor, B. A., et al. (2001), JGR:Planets, 106, 23653-23687.
[4] Battalio, M. J., Wang., H. (2021), Icarus, 354, 114059.
[5] Guha, B. K., et al. (2024), JGR:Planets, 129, e2023JE008156.
[6] Lombard, T., Montabone, L. (2024), EPSC2024, abs.#1334.
[7] Leseigneur, Y., Vincendon, M. (2023), Icarus, 392, 115366.
[8] Lewis, S. R., et al. (2016), Icarus, 264, 456-464.
[9] Battalio, M. J. (2022), JAS, 79, 361-382.
How to cite: Leseigneur, Y., Gautier, T., Bertrand, T., Spiga, A., Battalio, M., Lombard, T., and Montabone, L.: Shedding Light on Local Martian Dust Storms with OMEGA/Mars Express, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9515, https://doi.org/10.5194/egusphere-egu26-9515, 2026.
Owing to gravitational perturbations from the giant planets, the absence of a large stabilizing moon, and its non-spherical shape, Mars could have experienced large obliquity variations over its history. Numerical simulations suggest that over the past 10 Myr, Mars’s obliquity has spanned a range of ~30°, varying between ~15° and ~45°, with the long-term mean shifting from ~35° to ~25° around 5 Myr ago and superimposed rapid oscillations of up to ~20° on ~100-kyr timescales.
High obliquity increases polar insolation, accelerating the sublimation of surface ice and thereby raising atmospheric water vapor, whereas low obliquity favors cold trapping at the poles and a much drier atmosphere. Because the photolysis products of water vapor act as key catalysts in Martian photochemistry, variations in Mars’s obliquity can strongly influence atmospheric chemistry by modulating the atmospheric water content.
We use a fully coupled 3D photochemistry–radiation–dynamics model, the Mars Planetary Climate Model (PCM), to test this hypothesis and to quantify how Martian atmospheric composition and chemistry respond to obliquity variations over the recent past. A key strength of this class of models is its ability to self-consistently simulate the spatiotemporal distribution of atmospheric water vapor through polar sublimation–condensation and 3D atmospheric transport, as well as the atmospheric CO2 abundance through the seasonal exchange of CO2 with the polar caps.
We first evaluate the capability of the model to reproduce the present-day composition of the Martian atmosphere. One-dimensional photochemical models underestimated CO by up to ~85%, a discrepancy that has persisted for more than three decades. The Mars PCM reproduces a much more realistic CO abundance, yielding a global annual mean of ~750 ppmv, close to observed values of 800–960 ppmv. We find that tuning key reaction rates or including heterogeneous chemistry on airborne dust particles can further improve agreement with observations. However, the model simultaneously predicts H2 abundances more than an order of magnitude higher than observed, transforming the long-standing CO deficit problem into an H2 surplus problem.
We then simulate the Martian atmosphere across obliquities from 5° to 45°. The results confirm the expected obliquity control on atmospheric water vapor. Near the present-day obliquity, increasing obliquity—and hence atmospheric water vapor—enhances the production of OH, a photolytic product of water vapor and a key atmospheric oxidant, thereby increasing the oxidizing capacity of the atmosphere and reducing the abundance of reduced species such as CO.
At obliquities below ~15°, extremely low polar temperatures lead to the formation of a massive CO2 polar ice cap, substantially reducing the atmospheric CO2 column. The weakened UV shielding enhances H2O photolysis, resulting in a further decline in CO as obliquity decreases.
At high obliquity, rapid H2O photolysis increases odd-hydrogen radicals by orders of magnitude, but the abundance of H2O2, which is derived from odd-hydrogen radicals, remains relatively stable, only modestly higher than present-day levels. This limits the likelihood that extremely elevated H2O2 concentrations at high obliquity would have sterilized organic matter produced by ancient life at the surface or in the shallow subsurface.
How to cite: Luo, Y., Lefèvre, F., and Forget, F.: Oscillations in the Composition and Oxidizing Capacity of the Martian Atmosphere Driven by Obliquity Variations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19483, https://doi.org/10.5194/egusphere-egu26-19483, 2026.
Before NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft entered Mars’ orbit in 2014, meteoric metals had not been directly measured in a planetary atmosphere beyond Earth. MAVEN’s Imaging Ultraviolet Spectrograph (IUVS) has since measured a persistent layer of Mg+ in the Martian upper atmosphere. Metal species are injected into the atmosphere via ablation at altitudes where the pressure is ~1 μbar; the peak of the Mg+ layer varies over the Martian year due to changes in atmospheric density caused by the deposition and sublimation of CO2 at the poles. During Mars’ close encounter with the Oort cloud comet, Siding Spring, in October 2014, the IUVS instrument could also observe Mg, Fe, and Fe+. Neutral Mg was observed to decay at rates much faster than predicted and global models simulate nominal densities above the detection limit of the IUVS instrument, suggesting an incomplete understanding of Mg chemistry. The MAVEN mission included nine ‘Deep Dip’ campaigns, during which the nominal altitude range of the spacecraft was extended to include altitudes as low as 125 km. These week-long campaigns were designed to sample a variety of locations, local times, and solar longitudes, and offered the unique opportunity to measure Mg+, Fe+, and Na+ in-situ with the Neutral Gas and Ion Mass Spectrometer (NGIMS).
This study investigates the variability of Mars’ meteoric metal layers by comparing MAVEN IUVS and NGIMS observations with PCM-Mars simulations of the deep dip campaigns and the passing of Siding Spring. The PCM-Mars is a 3D numerical model of the Martian atmosphere, simulating atmospheric chemistry, circulation, temperature, and dust from the surface to the exobase. For the deep dip simulations, the Leeds Chemical Ablation Model (CABMOD) and the Meteoric Input Function (MIF) of Carrillo-Sánchez et al. (2022) were used to model the injection of MgO, Mg+, Fe, Fe+, Na, Na+, SiO, and Si+; we implemented a Siding Spring MIF to investigate the missing neutral Mg. For all simulations we have implemented a 4-metal chemistry scheme modelling Mg, Fe, Na, and Si reactions. This intercomparison of MAVEN observations and PCM-Mars simulations is vital to constraining global models and understanding the key drivers controlling the variability of Mars’ metal layers.
References
Crismani, M.M.J., Schneider, N.M., Plane, J.M.C., Evans, J.S., Jain, S.K., Chaffin, M.S., Carrillo- Sánchez, J. D., Deighan, J.I., Yelle, R.V., Stewart, A.I.F., McClintock, W., Clarke, J., Holsclaw, G.M., Stiepen, A., Montmessin, F., and Jakosky, B.M. Detection of a persistent meteoric metal layer in the Martian atmosphere, Nat. Geosci., 10(6): 401-405, doi:10.1038/ngeo2958, 2017.
Crismani, M.M.J., Schneider, N.M., Evans, J.S., Plane, J.M.C, Carrillo-Sánchez, J. D, Jain, S.K., Deighan, J.I., and Yelle, R.V. The Impact of Comet Siding Spring’s Meteors on the Martian Atmosphere and Ionosphere, JGR. Planets., 123(10): 2613-2627, doi:10.1029/2018JE005750, 2018.
Carrillo-Sánchez, J. D., Janches, D., Plane, J.M.C., Pokorný, P., Sarantos, M., Crismani, M.M.J., Feng, W., and Marsh, D.R. A Modeling Study of the Seasonal, Latitudinal, and Temporal Distribution of the Meteoroid Mass Input at Mars: Constraining the Deposition of Meteoric Ablated Metals in the Upper Atmosphere, Planet. Sci. J., 3(10), art. no. 239, doi:10.3847/PSJ/ac8540, 2022.
How to cite: Gough, C., Marsh, D., Plane, J., Feng, W., Carrillo-Sánchez, J. D., Janches, D., Crismani, M., Poppe, A., Schneider, N., Benna, M., González-Galindo, F., Chaufray, J.-Y., and Forget, F.: Martian Meteoric Metals: An intercomparison of MAVEN Observations and PCM-Mars Simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-912, https://doi.org/10.5194/egusphere-egu26-912, 2026.
Rio Tinto and Odiel are part of the fluvial system of the Iberian Pyritic Belt (IPB), so far the largest massive sulfide deposits found on continental crust on Earth. The extreme geochemical characteristics of Rio Tinto revealed this area as one of the most important geochemical Mars analogues on Earth. Its exotic mineralogy provides a good environmental analog for Hesperian/Teiikian mineral deposits on Mars, [1, 2, 3], and thanks to that, it is a unique place for developing and testing instruments for future planetary missions. Robotic vehicles and the recent technological demonstration of Ingenuity on Mars open up the possibility of using the powerful and non-destructive geophysical tool of magnetic surveys at different heights, for the investigation of surfaces and subsurfaces of planetary bodies. We explore IPB area Odiel-San Platón, were both jarosite (a key mineral from the Teiikian era of Mars) and important outcrops of Manganiferous Formation of the IPB are accessible. Manganese is a key element to support a putative microbial metabolism on Mars, but both acidic alteration of the rocks in this area and the low magnetic signal of manganese rich minerals, make the magnetic signature of the rocks, a challenge to be detected. We identify manganese-rich areas and minerals thanks to its magnetic signal, both in the field and with a detailed magnetic characterization of rock samples using a Vibrating Sample Magnetometer. In this research, we have done a magnetic survey and taken geological samples in field campaigns in 2018 and 2025. We propose a methodology which comprises an analysis of the morphology using images, magnetic field surveys, rock sample magnetic characterization, and simplified models for the interpretation of geological structures on the field. This methodology is applied successfully to the study of different areas of the Iberian Pyritic Belt, representative of the Martian landing sites mineralogy, as a preparatory action prior to the exploration of the planetary bodies’ surfaces.
How to cite: Díaz-Michelena, M., Velasco Domínguez, E., Melguizo Baena, Á., Cortés Mañanes, A., Rivero Rodríguez, M. Á., López Escolano, A., and Fernández Romero, S.: Magnetic survey in Rio Tinto area: a Mars analogue., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1716, https://doi.org/10.5194/egusphere-egu26-1716, 2026.
Perchlorate and chloride brines, while capable of transient liquid stability on Mars, rapidly lose their aqueous component under Martian pressure. Ionic liquids' negligible vapor pressures enable indefinite persistence, and they function without water activity constraints or chaotropic stress. Here we present the novel concept of iron-based ionic liquids as a complementary class of Mars-relevant solvent systems.
We synthesized iron-based imidazolium ionic liquids and we showed that (i) month-long exposure to simulated Mars surface conditions (600 Pa, CO₂) produces negligible mass loss (<0.1%), and (ii) they exhibit glass transitions near −65°C, bulk melting points of 7–19°C, and thermal stability exceeding 300°C. Notably, both CO₂ dissolution and confinement within nanoporous matrices, conditions directly relevant to Mars, are known to substantially depress melting points in imidazolium-based ionic liquids. We will present results from ongoing experiments examining how these factors influence the phase behavior of our iron-based compounds, with implications for their liquid stability range under Martian surface conditions. We performed Raman spectroscopy at 532 nm and confirmed tetrahedral iron-halide anion formation. Based on Raman data, we established diagnostic fingerprints for in situ detection.
The geochemical precursors required for iron-based ionic liquid formation (i.e., iron oxides, chlorides, bromides, sulfates, and organic molecules including chloromethane) have all been detected on Mars. Whether iron-based ionic liquids can support biochemical processes or preserve biosignatures remains unexplored, but their capacity for solvating polar molecules, negligible volatility, and potentially extended liquid range under Mars-relevant conditions motivate systematic investigation. We propose that ionic liquids represent an underexplored component of Mars solvent chemistry detectable by current instrumentation (i.e., SuperCam instrument aboard Perseverance).
How to cite: Iakubivskyi, I., Seager, S., and Pętkowski, J.: Beyond Brines: Iron-Based Ionic Liquids as Persistent Non-Aqueous Solvents on Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15625, https://doi.org/10.5194/egusphere-egu26-15625, 2026.
Here we synthesize work conducted at Lehigh University and the Pheasant Memorial Laboratory in Misasa, Japan (Institute for Planetary Materials, Okayama University), focusing on nitrogen (N) behavior in altered basaltic glasses and related secondary minerals that serve as terrestrial analogs for Martian surface/subsurface alteration. Initial proof of concept work demonstrated N enrichment in aqueously altered seafloor volcanic glasses with biotic influence suggested by δ15N signatures and microtubular textures (Bebout et al., 2018). Recently, this approach has been applied to study of hyaloclastites from Antarctica and Iceland that serve as better analogs for Martian hydrothermal alteration processes. This pursuit, employing advanced microanalytical and microscopic techniques, has extended knowledge of the modes of incorporation and isotopic signatures of N as a valuable tracer of biogeochemical processes in such materials (Nikitczuk et al., 2022a,b).
In new studies, we have investigated Icelandic amygdules in altered basalts that are mineralogical and geochemical analogs for those on the Noachian Mars surface (Ehlmann et al., 2012; Weisenberger and Selbekk, 2009). In addition, we examined erupted basaltic tephra from Surtsey Island, Iceland which, together with the amygdules, provide records of the alteration of very young erupted mafic volcanics (for Surtsey, <50 years; Jackson et al., 2019). These studies combine N concentrations and isotope compositions with microscopic and microanalytical techniques (SEM, SIMS, XRD, XRF), other isotopic tracers (δ13C, δD, δ18O) and organic geochemistry (GC-MS and Orbitrap work ongoing).
Collectively, our work demonstrates ubiquitous N enrichment of one to two orders of magnitude beyond initial concentrations of unaltered equivalents (MORB and OIB), during aqueous alteration of basaltic glass and associated secondary phases. Alteration phases include palagonite and clay, composed mainly of phyllosilicates (e.g., celadonite, illite, chlorite, smectite, saponite, nontronite among others) and zeolites (e.g., analcime, phillipsite, mesolite/scolecite, heulandite, stilbite, thomsonite and chabazite), amorphous silica (e.g., opal) and sulfates (e.g., jarosite and alunite), with enrichment most likely occurring during very early stages of aqueous alteration. Furthermore, their textural features (granular and tubular), trace element abundance, isotopic signatures (δ15N and δ13C) and organic chemistry (presence of n-alkanes and fatty acids with short C chains) indicate the likelihood of past microbial activity and incorporation of bioprocessed N.
Through this comprehensive approach, we highlight aqueously altered basaltic rocks and their associated phases, as high-priority targets for biosignature exploration, with a specific focus on N, in alignment with Mars Exploration Program Analysis Group (MEPAG) science goals.
References: Bebout et al. (2018) Astrobiology; Nikitczuk et al. (2022a) Astrobiology; Nikitczuk et al. (2022b) Journal of Geophysical Research: Planets; Ehlmann et al. (2012) Journal of Geophysical Research: Planets; Weisenberger and Selbekk (2009) International Journal of Earth Sciences; Jackson et al. (2019) Scientific Drilling.
How to cite: Bustos-Moreno, J. F., Bebout, G. E., Weisenberger, T. B., Kobayashi, K., Potiszil, C., Tanaka, R., Ota, T., Nikitczuk, M. P., Kunihiro, T., Kitagawa, H., Mustard, J. F., and Nakamura, E.: Biosignatures in Terrestrial Altered Volcanic Rocks — Focus on Nitrogen as a Key Biogeochemical Tracer, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10871, https://doi.org/10.5194/egusphere-egu26-10871, 2026.
Terrestrial microbial life is documented in micrometer-scale rock pores in boreholes and mines as deep as 5 km. If life ever emerged in Mars, it may still survive actively at similar depths in the Martian crust, where temperatures are above zero Celsius. Since such Martian depths are out of reach for present technology, we set off to conceive Martian settings where putative life could be active closer to the surface.
One possible way for microbial life to approach the Martian surface is by using the warmth of eruptions to migrate parallel to magma vents, at distances where temperature is above 0 C. Magmatic activity creates dikes and surface lava flows with basalt at about 1250 C, transitorily increasing the temperature of the surrounding crust. We hypothesize that the cooling rates may be slow enough for Earth-like microbial-life to migrate through these warm corridors and approach the surface.
Bacteria and Archea swim at velocities faster than 250 m/yr and migrate through rock pores with highly variable motilities of 28 m/yr and higher (Horvath et al., 2021; Jin and Sengupta, 2024; Nishiyama and Kojima, 2012), depending on porosity types and fracturing. InSight data suggests a weakened Martian crust compatible with intense fracturing and high porosity infilled with water (Li et al., 2023), probably caused by the multi-billion-year long exposure to meteoritic impacts. Open fractures are hypothesized to be particularly prominent around and above magmatic dikes in Martian conditions due to stresses related to magma injection and later cooling (Rivas-Dorado et al., 2023). The lower Martian gravity should minimize mechanical and chemical pore compaction, contributing to make the Martian underground more passable than in Earth’s. We therefore test whether bacterial-like migration velocities can defeat post-magmatic underground cooling in Mars following a magmatic event and actively approach the surface.
To this purpose, we perform diffusive thermal relaxation modeling of the subsurface inspired by the Elysium and Cerberus Fossae region, where 53,000 to 210,000 years old eruptions have been identified (Horvath et al., 2021). We constrain the magmatic intrusion’s geometry based on dike modeling (Rivas-Dorado et al., 2022) and on observed lava flows (Cataldo et al., 2015), supported by published interpretations of InSight seismic data. The results suggest that dike sizes are consistent with a passable pathway above freezing temperature propagating slower than Earth-like microbial motility. We constrain minimum depths reachable by hypothetical bacterial-like underground organisms as a function of realistic Martian magmatic intrusion parameters.
How to cite: Garcia-Castellanos, D., Butturini, A., Rivas-Dorado, S., Palomino, S., Schimmel, M., Jiménez-Munt, I., and Esteban, M.: Magmatic pathways for subsurface habitability on Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5787, https://doi.org/10.5194/egusphere-egu26-5787, 2026.
To reconstruct the past climate and assess the potential habitability of Mars, it is essential to understand its geological processes and environmental evolution. Till now, observations from orbital spectroscopy and in-situ rover missions have revealed the widespread presence of phyllosilicates, such as smectites, on the martian surface, indicating extensive past water-rock interactions and a prolonged aqueous history (Ehlmann & Edwards, 2014; Sheppard et al, 2021). Therefore, understanding basalt weathering processes is essential for constraining the formation history of these minerals and the climate evolution of Mars. However, given the limited direct access to Martian samples, geochemical modeling has become an essential tool for reconstructing these ancient processes. In our study, we apply such an approach to investigate basaltic weathering conditions and the formation of secondary alteration minerals within Lyot Crater, located in the northern lowlands of Mars. Lyot Crater formed during the Amazonian period and previous observations indicate the presence of significant amounts of Fe/Mg Phyllosilicates, chlorite, illite/ muscovite, prehnite and some other unidentified hydrated minerals within the region (Pan & Ehlmann, 2018). Because the Amazonian period is considered a dry phase in Martian history (Kolkas, 2026), investigating the origin of secondary minerals in Lyot Crater can provide important insights into the possibility of aqueous activity during this arid period. To examine this, geochemical simulations were performed using the REACT Module of Geochemist’s Workbench (GWB) software, adopting initial basaltic rock compositions derived from in situ analyses at the Zhurong rover landing site (Zhao et al, 2023) and a groundwater composition representative of the Gale Crater region (Kikuchi & Shibuya, 2021). The simulations are performed under closed system condition, which means the system is unbuffered and does not remain in constant equilibrium with the atmosphere. The modeling results reproduce secondary mineral assemblages observed in Lyot Crater, supporting previously proposed hydrothermal formation scenarios for the region (Pan & Ehlmann, 2018). These results constrain Amazonian-age aqueous alteration processes and highlight Lyot Crater as a potential target for future habitability-focused exploration.
References:
Ehlmann, B.L. and Edwards, C.S., 2014. Annual Review of Earth and Planetary Sciences, 42(1), pp.291-315.
Kikuchi, S. and Shibuya, T., 2021. Minerals, 11(4), p.341.
Kolkas, M.M., 2026. The Professional Geologist (TPG), Jan–Feb–Mar, pp. 7–15.
Pan, L. and Ehlmann, B.L., 2018. Journal of Geophysical Research: Planets, 123(7), pp.1618-1648.
Sheppard, R.Y., Thorpe, M.T., Fraeman, A.A., Fox, V.K. and Milliken, R.E., 2021. Minerals, 11(9), p.986.
Zhao, Y.Y.S., Yu, J., Wei, G., Pan, L., Liu, X., Lin, Y., Liu, Y., Sun, C., Wang, X., Wang, J. and Xu, W., 2023. National Science Review, 10(6), p.nwad056.
How to cite: Bhowmik, S., Mukherjee, A., and Gupta, S.: A Glimpse into Basalt Weathering on Mars: Geochemical Modeling Study of Lyot Crater, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12820, https://doi.org/10.5194/egusphere-egu26-12820, 2026.
The presence of sedimentary volcanism on Mars has been proposed as an explanation for many characteristic features in areas such as Chryse, Acidalia, and Utopia Planitia. Orbital investigations and rovers have identified the presence of clay minerals including smectite, kaolinite, and chlorite on the Martian surface. However, the specific composition (lava vs. mud) of most flow deposits cannot be confidently described due to the scarcity of data. Interpreting the past behaviour of flow deposits on terrestrial or planetary bodies requires a comprehensive knowledge of the flow rheology. As such, constraining the composition of remotely observed flows relies on the use of rheological models. However, the rheological behaviour of sedimentary flows is not well constrained, especially under Martian conditions. The lower pressure, temperature, and gravity on Mars have been shown to produce different propagation conditions of sediment-water mixtures compared with those on Earth, highlighting the importance of investigating mudflow behaviour under Martian conditions through analogue experiments. Here, we choose a non-swelling kaolinite clay to firstly investigate the rheological behaviour of a clay-water suspension under different shear-rates and solid volume fractions. We analyse the relationship between yield stress, τy , and solid volume fraction, φ, to select realistic input values for modelling remote sedimentary flows on both Earth and Mars. We find the Herschel-Bulkley model provides the best fit to laboratory rheological data, but the Bingham model provides more utility with remotely sensed datasets. We then investigate the effects of simultaneous external cooling and internal frictional heating of our kaolinite clay-water mixtures, assessing the balance between the two processes. We find that the control of these disequilibrium conditions varies with both φ and the shear-rate, γ̇, (i.e., the flow velocity). For all values of φ, at high γ̇, we find that complete freezing/jamming is delayed compared with lower values of γ̇. We assess the morphology of inferred sedimentary flow deposits in Chryse Planitia by quantifying their flow length, local slope angle, flow thickness, and surface textures. Alongside our experimental data, these remotely sensed parameters serve as inputs for a non-Newtonian plug model designed to estimate realistic flow properties. This integrated approach allows us to better constrain the origin and composition of the Martian deposits.
How to cite: Whorton, J., Jones, T. J., Wilson, L., and Pieterek, B.: Mudflow rheology under disequilibrium conditions: implications for the interpretation of Martian flow deposits, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-656, https://doi.org/10.5194/egusphere-egu26-656, 2026.
The exploration of Mars and the Moon has been a primary focus of planetary science for decades. The prospects of resource surveying and extraction, searching for water ice, and finding potential evidence of past life have resulted in multiple missions being sent to uncover what lies within the Martian and Lunar subsurfaces. Ground Penetrating Radar (GPR) is a critical, non-destructive instrument for planetary subsurface exploration, emitting electromagnetic waves to study and reveal structures in the subsurface. The RIMFAX (Radar Imager for Mars' Subsurface Experiment) GPR antenna, aboard the NASA 2020 mission Perseverance rover, has generated approximately 40km of data since February 2021, mapping the complex sedimentary history of the Jezero crater subsurface. The Jezero crater has been an area of fervent study as it preserves a clear paleolake and river delta system. This has also made it a high-priority target for detecting biosignatures within the ancient sedimentary deposits. RIMFAX has been instrumental in this effort, mapping the dielectric properties of the crater floor to depths of tens of meters.
However, interpreting this data is challenged by an absence of readily available, high-fidelity 3D numerical models of the RIMFAX antenna and its interaction with the rover structure. Accurately modelling the geometry and properties of RIMFAX and the local Perseverance rover structure better simulates how the antenna pulse interacts with its complex environment. Approximating RIMFAX to a simple point-source can cause deviations in the waveforms, as well as fail to model the electromagnetic coupling with the rover structure; leading to flawed interpretations of the subsurface.
To address this problem, we present robust and geometrically accurate numerical models of the RIMFAX antenna and the Perseverance rover for use in gprMax, an open source finite-difference time domain (FDTD) solver. Our workflow adapts existing surface mesh models, voxelating them so that they are compatible in an FDTD environment. Material properties and excitation sources are derived from available technical specifications, or constrained through optimization processes, where proprietary data is unavailable. Validation of the models show highly consistent results with both laboratory measurements and in-situ planetary data. These freely available models enable the community to produce more realistic radargrams, leading to more accurate characterisations of the mechanical and mineralogical properties of the Martian subsurface. Furthermore, this modelling workflow provides a scalable framework for future rover-mounted GPR systems across the solar system.
How to cite: Wilson, Z., Warren, C., Hamran, S.-E., Giannakis, I., and Giannopoulos, A.: Beyond a Point Source: Realistic Modelling of the RIMFAX Ground Penetrating Radar at Jezero Crater, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11217, https://doi.org/10.5194/egusphere-egu26-11217, 2026.
Recent remote sensing studies of Mars have revealed an exceptionally large (~4,000 km diameter) regional domal uplift in the Eastern hemisphere near Elysium Planitia, which is hypothesized to be supported by an actively upwelling giant mantle plume. Given its size, that plume head appears to be nearly three times larger than the Afar superplume on Earth, despite Mars' small size (i.e., Mars’ diameter is smaller than Earth’s core). The Elysium dome is intersected by a rift zone through which very young lavas (~2 Myrs to ~60 Kyrs old) erupted in large volumes and traveled long distances, indicating that the dome is an active geodynamic feature. Another recent discovery about Mars, based on data from NASA’s InSight lander, is an exceptionally thick (~400 km) Mantle Transition Zone (MTZ) located 1100 km below the surface, in direct contact with the core at a depth of ~1500 km. Therefore, Mars likely lacks a refractory and dense lower mantle, unlike Earth. This suggests that the 400 km thick Martian MTZ is the only zone from which mantle plumes can originate.
Along with majorite and pyroxenes, the MTZ contains wadsleyite and ringwoodite (i.e., high-pressure polymorphs of olivine), which have unique crystallographic and compositional features because their crystal structures can potentially trap water up to 2 to 3 wt.% and halogens, as well as some noble gases (e.g., neon). Although present in small amounts, these volatile elements may impart unusual flow properties to the MTZ by significantly reducing its viscosity and density, promoting upwelling. Once a part of the Martian MTZ begins to upwell, it is theoretically subjected to mineral phase transformations: ringwoodite and wadsleyite convert into wet olivine at depths shallower than about 1000 km, and wet olivine transforms into two hydrous minerals—amphibole and phlogopite—which are stable at pressures shallower than approximately 300 km in Mars.
Petrological evaluation of meteorite and Rover data compiled from the literature in this study indicates the presence of amphibole and phlogopite in the source of nearly half of Martian lavas, thereby confirming theoretical considerations presented above. Results from petrological melting models in this study indicate that primitive Martian lavas may have formed through the mixing of magmas with contrasting compositions from two sources: (i) a depleted mantle, possibly representing plume material from the MTZ, and (ii) a metasomatized lithosphere highly enriched in incompatible elements. Both sources contain hydrous minerals such as phlogopite and amphibole, as well as anhydrous minerals like olivine, pyroxenes, garnet, and spinel. These findings suggest the volatile-rich nature of this small planet's mantle. The higher halogen levels in Martian lavas relative to terrestrial lavas support this interpretation. In summary, the rheological, mineralogical, and compositional characteristics of the Martian mantle explain why plumes rising within Mars’ mantle are rich in volatiles and why they can grow much larger than those on Earth, disproportionate to Mars’ size. Based on these findings, this study proposes that Martian mega-mantle plumes may be low-viscosity, hydrous upwellings originating from its MTZ, driven by heat from the underlying core, which increases their fluidity.
How to cite: Keskin, M.: Insights into the Martian Interior: Geochemical Constraints on Mantle Dynamics and Magma Source Compositions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15132, https://doi.org/10.5194/egusphere-egu26-15132, 2026.
Recent Mars orbiters and landers have yielded valuable insights into the planet’s surface and interior. Radio tracking of Mars Global Surveyor, Mars Reconnaissance Orbiter, and Mars Odyssey has provided detailed knowledge on Mars’ gravity field, revealing subsurface structure in the crust and mantle. Seismic observations from the InSight mission indicate that marsquakes occur more frequently than previously expected, implying ongoing interior activity. InSight data also constrain the viscosity and density structure of the interior. New interpretations of the static gravity field and seismic observations suggest large negative mass anomalies in the mantle that may be associated with a mantle plume beneath the Tharsis Rise or Elysium Region.
In this study, we investigate whether mantle flow related to such a plume produces a detectable gravity-rate signal. Using currently available viscosity and density models of Mars’ interior, we perform a parameter search over plume depth, radius, thickness, and viscosity and density contrasts relative to the surrounding mantle. For each configuration, we compute the induced long-term gravity field variations and compare them with observed static and time-varying gravity models and surface topography. We use a fast axi-symmetric Stokes mantle flow code, coupled with a Spherical Harmonics code (GSH package) that can model 3D density distributions.
Plumes with low viscosity (1021 Pa s), deeper presence (1300 km), and high-density contrast with the surrounding mantle (-150 kg/m3) provide the highest gravity anomaly rate (of around 20 nGal/year). Furthermore, we see that smaller mass anomalies can in certain circumstances produce stronger gravity-rate signals than large anomalies. This is contrary to the static geoid signals. Our results assess the detectability of active mantle flow with present-day data and place constraints on the physical properties of possible Martian mantle plumes. These findings provide new insight into the thermal and geodynamic evolution of Mars and other terrestrial planets.
How to cite: Alkahal, R., Root, B., Thieulot, C., Dirkx, D., Fayolle, S., and Goossens, S.: Gravity-rate signature of mantle flow on Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18403, https://doi.org/10.5194/egusphere-egu26-18403, 2026.
In our studies, we deal with the numerical modelling of the trajectories of planetary balloons on Mars and the optimisation of the balloon parameters using different machine learning approaches. The balloon’s horizontal and vertical motion is computed by solving a system of differential equations (Palumbo, 2008) numerically. In an earlier study (Nöding et al., 2025), we used atmospheric data (temperature, wind speed) from the Mars Climate Database (Millour et al., 2022) and computed the balloon’s path for several starting points and start dates. In our current studies, two types of balloons, zero-pressure and super-pressure balloons, are tested with different envelope materials, carrier gases, and payload configurations. We use atmospheric data provided by two different data sets, the Mars Climate Database and EMARS (Greybush et al., 2019). Our aim is to model the balloon’s properties and dynamic behaviour as physically accurately as possible. We discuss the permeability of the balloon envelope, the effects of temperature fluctuations on the carrier gas, the air resistance of the balloon and different payload masses. Moreover, we work on optimising those parameters for various missions by using different machine learning approaches.
References:
Greybush, S. J., Kalnay, E., Wilson, R. J. et al. (2019). The ensemble Mars atmosphere reanalysis system (EMARS) version 1.0. Geoscience Data Journal, 6(2), 137-150. https://doi.org/10.18113/D3W375
Millour, E., Forget, F., Spiga et al. & MCD Team. (2022, September 23). The Mars Climate Database (Version 6.1). https://doi.org/10.5194/epsc2022-786
Nöding, F., Ziese, R., & Oberst, J. (2025, März 18). Analysis of Balloon Missions and Flight Trajectories on Mars.
https://doi.org/10.5194/egusphere-egu25-17677
Palumbo, R. (2008). A simulation model for trajectory forecast, performance analysis and aerospace mission planning with high altitude zero pressure balloons [Doctoral dissertation, Università Degli Studi di Napoli]. https://doi.org/10.6092/UNINA/FEDOA/1839
How to cite: Nöding, F., Ziese, R., and Oberst, J.: Modelling and Parameter Optimization for Balloon Missions on Mars , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18589, https://doi.org/10.5194/egusphere-egu26-18589, 2026.
Oxia Planum, the landing site for ESA’s ExoMars Rover, Rosalind Franklin, hosts widespread layered Fe/Mg phyllosilicate-bearing deposits of Noachian age, evidence of a potentially long-lived aqueous paleoenvironment in a deltaic to fluvio-lacustrine setting. Fluvio-lacustrine environments have moderate to high preservation potential for organic matter, due to rapid sedimentation and subsequent burial. As a result, these are also some of the environments that, over the course of Earth history, have preserved biosignatures on billion-year timescales. Microbial activity and capture within sediments can result in geochemical and mineralogical anomalies, including localised elemental enrichments. These provide a means of detecting evidence of past life in concert with molecular biosignatures. Microbial mats especially can alter the geochemistry of surrounding sediments, producing spatially constrained variations that persist over geological timescales. Investigating such biosignatures in sedimentary environments analogous to those recorded at Oxia Planum is essential for informing future rover observations and measurement strategies.
We examine clay-bearing sedimentary facies with well-preserved microbially induced sedimentary structures (MISS), including (1) the 1.0 - 1.1 Ga Clachtoll and Diabaig formations in northwest Scotland— a package of fluviolacustrine and estuarine sedimentary rocks deposited under fluctuating redox conditions; and (2) the 2.7 Ga Tumbiana Formation (Pilbara Craton, Western Australia), which records deposition in a shallow lacustrine environment that received input from basaltic volcanism. We present elemental distributions, redox sensitive trace element behaviour, and mineralogical variations in preserved microbial mat structures and compare these to neighbouring sediments with no microbial influence. Using a combination of raman spectroscopy and elemental mapping, we show elemental enrichments linked to biology, such as iron, manganese, and potassium, coincide with clay-rich organic matter bearing areas within the sediment, indicating that ~1 – 2.7 Ga microbial mats can preserve distinct geochemical biosignatures in association with clay-bearing lithologies. The spatial association between centimetre-millimetre sized sedimentary structures observable at outcrop scale and sub-millimetre geochemical anomalies highlights the importance of integrating imaging and geochemical datasets to support biosignature interpretations.
How to cite: Nielson, G. C., Cousins, C. R., Stüeken, E. E., and Law, S.: Preservation of clay-bearing geochemical biosignatures in Mars analogue sedimentary rocks over billion-year timescales , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5974, https://doi.org/10.5194/egusphere-egu26-5974, 2026.
Surface and subsurface ice in the mid-latitudes of Mars is a vital water reservoir, and its distribution and volume are controlled by obliquity-driven climate change. Periglacial landforms, formed in areas where ice thaws on a seasonal timescale, can indicate the distribution and evolution of ice on Mars. Among these landforms, scalloped depressions, which are characterized by rimless, shallow depressions with asymmetric shape, have attracted high attention owing to their thermokarst-like origin and asymmetric morphology. This study mapped scalloped terrain in the Martian northern lowlands at meter scale and explored its implications for Amazonian climate and habitability. We used CTX mosaics to generate a meter-scale map of scalloped terrain, and found that scalloped depressions are mainly distributed in the Utopia Planitia. These depressions in Utopia Planitia exhibit unique stepped lineae within the depressions compared to those in the southern hemisphere. Detailed geological investigation of 926 large depressions (>20 km²) revealed that 218 contain stepped lineae, forming staircase profiles that point to multiple episodes of equatorward degradation. Bisides, expanded craters with thermokarst modifications were also observed, providing another trigger for the formation of scalloped depressions and supporting sublimation-driven ice degradation. These landforms are sensitive records of recent high-obliquity events on Mars and provide crucial clues to the planet’s climatic changes, water resource distribution, and potential habitability during the Amazonian period.
How to cite: Xia, M., Zhao, J., Wang, Y., Zhao, Y., and Xiao, L.: Mapping Stepped Scalloped Terrain in the Utopia Planitia at Meter Scale: Implications for Amazonian Climate and Habitability of the Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17268, https://doi.org/10.5194/egusphere-egu26-17268, 2026.
The astrobiological exploration of Mars is ongoing, with multiple missions investigating whether ancient environments could have supported life (Grotzinger et al., 2012) and whether traces of that life could still be preserved in the geological record (Farley et al., 2020). Clay-bearing terrains are regarded as prime targets for these missions because of the strong capacity of some phyllosilicates to adsorb, concentrate, and preserve organic carbon (Hedges and Keil, 1995; Kennedy et al., 2002). Early Earth clay-rich mudstones are also well known for exquisitely preserving delicate morphologies, including cells, filaments and microbial mats (Javaux, 2019). However, Martian surface radiation and oxidizing processes may alter such materials (cf. Fornaro et al., 2018). ESA’s ExoMars mission will therefore extend the search to the subsurface to access materials expected to be less altered (Vago et al., 2017). The selected landing site, Oxia Planum, is a Noachian region dominated by Fe/Mg phyllosilicates (Mandon et al., 2021) that has experienced at least two aqueous episodes, as evidenced by a clay-bearing unit overlain by fan-shaped sedimentary deposits (Quantin-Nataf et al., 2021).
If life ever existed on Mars, potential biomass sources at Oxia Planum could include (i) subsurface communities associated with clay-rich regolith, as observed in hyperarid Earth analogues (e.g., Azua-Bustos et al., 2020), later exhumed and physically reworked, and/or (ii) organisms living in surface or near-surface aqueous settings and locally incorporated into basin-floor clay-rich muds. On Earth, clay-rich sediments can physically shield labile organic matter, reducing its accessibility to microbial degradation within micro- to nano-porosity (McMahon et al., 2016), and low-oxygen bottom waters can further enhance organic carbon preservation in fine-grained deposits (Ritzer et al., 2024). Assuming anoxic conditions in Noachian depositional settings, biosignatures could be well preserved at Oxia. Yet, Oxia’s contrasting sedimentary contexts raise the following question: at constant bulk organic content and under identical diagenetic conditions, to what extent can different pre-diagenetic textures and microstructures bias the morphological and chemical signals, and thus the detectability of fossil biosignatures by vibrational spectroscopy and mass spectrometry in clay-rich sediments?
Here, we investigate this question by conducting laboratory fossilization experiments using saponite (a Mg-rich smectite, synthesized following the protocol of Criouet et al., 2023) and cells from the cyanobacterial strain Synechocystis sp. (PCC6803). Samples were prepared to represent two experimental end-members that differ in their initial texture (wet embedding within a clay-rich mud versus dry physical reworking) while maintaining the same organic content (TOC= 5 wt.%). All samples were then remoistened at the same water-to-rock ratio (W:R=3) and subsequently subjected to accelerated early diagenesis (100 °C, autogenous pressure ~2 bar, 30 days) in a closed system under an early Mars-like (CO2-rich) atmosphere.
Experimental residues were characterized by SEM-EDS to document fossil morphologies and organo-mineral interactions from micro- to nano-scale, and by complementary spectroscopic (i.e., µRaman, FTIR) and mass spectrometric (i.e., GC-Orbitrap, EA-IRMS) analyses to evaluate associated chemical signals. Altogether, this work aims to provide well-constrained analogs for anticipating how biosignatures may be expressed across Oxia’s contrasting sedimentary contexts and to help validate space instrumentation and protocols.
How to cite: Criouet, I., Demaret, L., Boulesteix, D., Fadel, A., Buch, A., Lara, Y., Malherbe, C., Vertruyen, B., Lambion, A., and Javaux, E.: Effect of depositional mode on the detectability of microbial fossils in Mars-analog clay-rich sediments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5731, https://doi.org/10.5194/egusphere-egu26-5731, 2026.
This study developed and applied an integrated framework to analyse surface mineralogical variability and radar backscatter response in Mawrth Vallis, Mars. The primary goals were to evaluate the lateral extent and potential subsurface continuity of phyllosilicate-bearing layers, and discussing the benefits, limitations and improvements for this approach. The methodology combined HRSC imagery, both color mosaics and digital terrain models to map four distinct surface units (S1, S2, S3, and DT) based on hue, brightness patterns, and topographic context. This was complemented by OMEGA and CRISM HSP hyperspectral data to characterize the regional distribution and composition of hydrated mineral phases, specifically Fe/Mg- and Al-phyllosilicates. Finally, SHARAD radargrams were used to identify clutter patterns, possible subsurface reflectors, and to analyse radar backscatter variations across the mapped surface units.
Spectral analysis confirmed that surface units mostly but not completely match the compositional boundaries, with S2 consistently shows dominant Fe/Mg-smectite absorptions, S1 exhibits Al-smectite features in a mixed spectrum, and S3 is characterized by dominant kaolinite absorptions. While these mineralogical variations generally align with the mapped surface units, small-scale heterogeneities suggest a finer stratification that is not fully resolved at the current data resolution.
SHARAD radargrams revealed variations in radar backscatter that are dependent on surface unit type. The DT unit consistently produces strong surface echoes, even in areas with similar terrain characteristics, which points to variations in the dielectric properties of the materials. In contrast, S2 returns weaker radar signals, consistent with the relatively lower dielectric constant of Fe-smectite. S1 exhibit intermediate radar responses. Additionally, potential subsurface reflectors were identified beneath the DT-S3 interface along Mawrth Vallis' southern flank, which may represent preserved stratigraphic interfaces, likely due to dielectric contrasts between the regolith-like DT material and the kaolinite-rich S3 unit.
This integrated approach highlights both the synergies and challenges of using multiple datasets for interpretation. Spectral data are effective for constraining surface composition but lack the ability to probe depth, while radar instruments can detect subsurface structures but struggle with thin layering and strong clutter patterns.
How to cite: Larrota, D., Bakker, W., and van Ruitenbeek, F.: Integration of Spectral Datasets and Radargrams in Mawrth Vallis, Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-311, https://doi.org/10.5194/egusphere-egu26-311, 2026.
Early Mars exhibited terrestrial-like hydrologic activity, with extensive fluvial networks and lacustrine deposits preserved due to the lack of plate tectonism. Ma’adim Vallis (≈22°S, 177.3°E) in Terra Cimmeria extends ~900 km, is 10–15 km in width, and reaches depths of ~2 km, linking the Eridania basin system to Gusev crater on the northern plain. The competing formation hypothesis involves surface runoff, paleolake overflow, and dry volcanic megafloods. This work employs high-resolution orbital imageries like CTX, HiRISE, CRISM, and Digital Elevation Models to quantify more than 50 morphometric parameters, including length-area scaling, sinuosity indices, dissection indices, and junction angles for channels, etc. Mineralogical mapping identifies key minerals, including Mg-smectite, Fe/Mg phyllosilicates, and olivine from the study area. Even though the integrated morphometric and mineralogical evidence points to a dominantly catastrophic water outflow event that carved the valley, implying a transient but intense hydrologic regime in Mars’ early climate history; evidence suggests that the evolution of Ma’adim Vallis may not be derived from a single process, indicating the involvement of multiple, distinct formative mechanisms.
How to cite: Ebrahim, S., Porwal, A., and Mullassery, N.: A comprehensive morphometric and mineralogical assessment of Ma’adim Vallis, Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1024, https://doi.org/10.5194/egusphere-egu26-1024, 2026.
Sinuous rilles observed on Venus, the Moon, and Mars, with lengths ranging from 10s to 1000s of kilometers, have been interpreted as either erosional or constructional features formed by flowing lava. Exotic lava compositions and high effusion rates have been proposed to explain these landforms. On Mars, the spatial distribution, morphology, and emplacement conditions of these channels are key to understanding its volcanic history, interior and surface evolution. The Tharsis volcanic province covers approximately a third of the planet’s surface and presents the largest volcanic region. Numerous sinuous rilles are observed in the flanks of the Tharsis Montes, three large shield volcanoes trending NE-SW. Specifically, each volcano displays a rift apron, a large wedge of effusive deposits postdating the formation of the main shield edifice. The aprons represent an understudied region with relatively young deposits. We mapped and characterized sinuous rilles on the Tharsis Montes (Arsia, Pavonis, and Ascraeus) rift aprons.
We delineated rift apron subregions using previously published geologic maps and boundaries (e.g. Plescia 2004, Skinner et al. 2006). Using the Thermal Emission Imaging System (THEMIS) infrared [100m/px] and the Context Camera (CTX) a [~6 m/px], we have identified, to date, 162 sinuous rilles on the 6 rift aprons of the Tharsis Montes. On the Arsia Mons rift apron, we have identified 74 sinuous rilles, with lengths ranging from ~2 - 90 km with a mean length of ~19 km and a median length of ~13 km. On Pavonis Mons, we have identified 27 sinuous rilles. Channels range in length from ~3 - 72 km with a mean and median of ~16 km and ~9 km, respectively. On Ascraeus Mons, we have identified 76 sinuous rilles, with lengths ranging from ~2 - 235 km, a with a mean length of ~27 km, and a median length of ~17 km. The rilles are emplaced on regional slopes ranging from ~0.1 – 3°. To date, we have calculated 76 of 169 (45%) rille widths with a mean width of 0.21 km.
These preliminary observations suggest that long-lived effusive eruptions capable of eroding the substrate were part of the later evolution of the Tharsis Montes. Furthermore, the sinuous rilles formed contemporaneous with widespread tectonic and collapse features evident in crosscutting relationships. Measured rille depths and sinuosity will provide further constraints on their formation.
How to cite: Peters, S. and Derenoncourt, K.: A Catalog of Sinuous Rilles on the Tharsis Montes Rift Aprons, Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14066, https://doi.org/10.5194/egusphere-egu26-14066, 2026.
Fretted terrains are among the most striking geomorphological features on Mars. Predominantly developed in a 500-km-wide zone located along the dichotomy boundary especially between 270°W and 360°W in regions such as Deuteronilus Mensae, these landscapes are characterized by parallel ridges, troughs, and mesas separated by broad valleys. Understanding their formation provides critic insights into the geological and climatic evolution of Mars. Here we suggest that the development of fretted terrains occurred in several major stages, beginning with tectonic activity in relation with the formation of Tharsis, contemporaneous with fluvial erosion, and ending with glacial processes that further modified the landscape.
During the Late Noachian to Early Hesperian periods, Mars experienced significant crustal stress associated with the formation of Tharsis and the resulting true polar wander, leading to regional uplift along the fretted terrains. This stress generated extensional fractures and fault systems with the formation of kilometer scale U-shaped valleys. The resulting landscape consisted of plateaus and isolated mesas delineated by steep scarps.
The Mars’s climate is thought to have undergone a period of relative warm and wetter regime during the Hesperian period. During this time, heavy rainfall or snowmelt events likely led to widespread fluvial erosion. Water flowed through the pre-existing tectonic valleys, widening them into large troughs or “fretted” corridors. Fluvial processes removed material from the highlands and transported sediments northward, to the low-lying basins of the northern plains with the formation of a large sedimentary accumulation north of the fretted terrains.
The final phase in the evolution of fretted terrains was dominated by recent glacial activity. As Mars cooled during the Late Hesperian to Amazonian periods, the climate became colder and drier, leading to the accumulation of ice within the valleys.
Evidence for this glacial phase mostly includes lineated valley fills. The glaciers likely originated from snow accumulation on the plateau surfaces, which then flowed down into the valley postdating the fluvial episod.
How to cite: Costard, F., Séjourné, A., Bouley, S., and Schmidt, F.: A revised chronological formation of fretted terrains on Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6618, https://doi.org/10.5194/egusphere-egu26-6618, 2026.
The ratio of effusive to explosive volcanism from the late Noachian to the early Amazonian remains a knowledge gap in understanding the volcanic evolution of Mars. Valles Marineris, a 4000 km canyon system in the Tharsis region, exposes up to 7 km of stratigraphy that records billions of years of geologic history, allowing for the investigation of the changes in volcanic styles over a large swath of martian geologic history. In this work, we performed a morphologic investigation to identify and characterize stacks of exposed lava flows in order to quantify the relative contribution of effusive volcanism.
We initially selected four sites across Valles Marineris: Candor, Ophir, West Ius, and East Melas ta, located at [-5.95679, 282.70], [-3.00, -287.50], [-7.34, 273.11], and [-10.98, 293.63], respectively. All sites exhibited clear exposures of at least 1 - 2 km of stratigraphic section and sufficient data coverage. We performed analysis using high resolution visible image data from the High-Resolution Imaging Science Experiment (HiRISE) (~0.3 m/px) and the Context Camera (CTX) (~6 m/px); moderate and high-resolution digital terrain models High Resolution Stereo Camera (HRSC) DTM (~60 m/px) and CTX DTM (~15 m/px). Data analysis was conducted in the Java Mission-planning and Remote Sensing (JMARS) GIS. To quantitatively assess morphology, we measured the lateral extent of exposed marker beds and estimated bed thickness by measuring the distance between marker beds. We also measured cliff slopes by producing transects at multiple locations within each study site.
Preliminary observations in Candor Chasma show a clearly defined transition between upper competent units and the lower talus-rich zone. In Ophir Chasma, we observed deposits consistent with mass-wasting events that have exposed lower competent and layered units. Whereas in Ius and Melas , while exposed competent rock is present, the competent cliffs are mostly obscured by talus. In West Candor Chasma, marker beds (i.e., competent rock layers) exhibit a mean vertical spacing of 8.4 m and a mean lateral extent of 22.3 m, in Northern Ophir Chasma (Site 2) layers show a mean vertical spacing of 5.81 m and a mean lateral extent of 15.8 m, while in West Ius Chasma the mean vertical spacing is 6 m. Assuming the distance between marker beds represent individual flow units, we interpret this sequence of layers as massive thick (~6 – 8 m) lava flows.
Our preliminary results are consistent with previous literature that the upper and middle walls of Valles Marineris preserve horizontal lava stacks, which suggests that effusive volcanism has dominated in the region in recent martian geologic history. Deeper layered deposits observed in Ophir Chasma may belong to magmatic intrusions, consistent with previous literature that subsurface magmatism occurs under extensional tectonic regimes and has played an active role either before or during the formation of Valles Marineris.
How to cite: Xanthoudakis, A., Peters, S., Meyer, H., Matiella Novak, A., Whelley, P., and Richardson, J.: Investigation of Ancient Volcanism in Valles Marineris: Evidence for Effusive Activity and Possible Plutonic Intrusions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14022, https://doi.org/10.5194/egusphere-egu26-14022, 2026.
Lyot (50.8°N, 330.7°W), the largest and deepest impact structure on the northern plains of Mars, with an approximate diameter of 220 km, is a prominent peak-ring crater situated near the hemispheric dichotomy within the Vastitas Borealis region. This Amazonian-aged crater has long fascinated due to its potential association with past hydrologic activity. Previous studies have suggested that the Lyot impact may have breached the cryosphere, enabling the release or exposure of subsurface groundwater. As a result, the crater interior and its surroundings preserve geomorphic signatures of both ancient and relatively recent water-related processes, including groundwater upwelling as well as atmospheric precipitation.
The primary objective of this study is to systematically map and characterize the major morphological features and mineral assemblages within Lyot Crater to better understand its hydrologic and climatic evolution. For this purpose, we employ a multi-instrument dataset comprising MOLA blended DEM for topographic analysis, Context Camera (CTX) imagery (5–6 m/pixel) for regional geomorphologic mapping, and select high-resolution HiRISE images (25–30 cm/pixel) for detailed surface feature interpretation. Mineralogical information is derived from CRISM observations (18 m/pixel), enabling the detection of key alteration minerals. Our geomorphic analysis identifies a diverse suite of features including fluvial channels, distal ridges, glacial and periglacial landforms, and multiple dune fields. Spectral analysis reveals the presence of Fe/Mg-smectites, chlorites, illite/muscovite, prehnite, and other hydrated minerals distributed across the central peak ring, crater floor, and rim. Together, these features and mineral signatures highlight the complex interplay of fluvial, glacial-periglacial, and aeolian processes that have shaped Lyot over time. While hydrous minerals and water-related landforms provide important clues to subsurface water activity and Mars’ broader hydrologic evolution, the aeolian deposits record more recent atmospheric dynamics and ongoing topographic changes. Overall, this integrated investigation enhances our understanding of Lyot Crater as a key site for reconstructing Amazonian-era water activity and climate transitions on Mars.
How to cite: Mullassery, N. and Ebrahim, S.: Deciphering Water and Climate History in Lyot Crater, Mars: A Morphological and Mineralogical Perspective, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1160, https://doi.org/10.5194/egusphere-egu26-1160, 2026.
Geological investigations of planetary surfaces require combination of orbital datasets. Multiple-instruments platforms operated by space agencies made the quantity of data available increase quickly. MarsSI [1] is a platform to facilitate exploring and processing those datasets.
As of 2026, MarsSI indexes and provide access to optical data (visible, multi and hyper-spectral) and derived products from the most recent missions. Our emphasis was to provide ”ready-to-use” products. MarsSI do not provide analysis or visualization tool, users will be able to use GIS or remote sensing software to run the analysis suited to their research.
MarsSI provides access to multiple optical datasets for visible, multi/hyper-spectral data. Optical imagery will follow a correction & projection piprline using ISIS (https://isis.astrogeology.usgs.gov/). Post-calibration, hyperspectral data is corrected with the volcano-scan method [2] and spectral parameter maps are produced.
MarsSI produces Digital Elevation Model (DEM) products from the CTX and HiRISE datasets (finding image pairs with a 60% minimum overlapping and 10° deviation in emission angle). DEM generation workflow was updated in 2020 with a completely new version[3].
MarsSI is accessed through a web browser portal. As shown on figure 1, the user can explore the datasets using a map interface. Data can be selected and sent to a workspace. The workspace view, shown on figure 2, allow to review products in detail, and request data processing. More Workspaces can be created to organize datasets.
When processing are finished, the user can order a copy operation, that make the requested data available in a SFTP directory. The platform now aims to complete its datasets, expanding on radar data (observation and simulation). Expanding non-martian datasets is also in our targets.
MarsSI offers the scientific communities a way to explore space agencies catalogs and automatically process them to high value products.
Acknowledgments
MarsSI is part of national Research Infrastructure PSUP, recognized as such by the French Ministry of Higher Education and Research under the ANO5 label. It was supported by the Programme National de Planétologie (PNP) of CNRS/INSU, co-funded by CNES. This application is part of the ERC project OCEANID funded by the Horizon Europe Program (ERC Grant Agreement No. 101045260).
References
[1] C. Quantin-Nataf et al. In: Planetary and Space Science 150 (2018).
[2] P. C. McGuire et al. In: Planetary and Space Science 57.7 (2009).
[3] M. Volat, C. Quantin-Nataf, and A. Dehecq. In: Planetary and Space Science 222 (2022).
How to cite: Volat, M., Quantin-Nataf, C., Brighi, E., Dehouck, E., Millot, C., Pineau, M., Torres, I., Rogez, Y., Herique, A., and Zine, S.: MarsSI: Martian surface data processing service, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4855, https://doi.org/10.5194/egusphere-egu26-4855, 2026.
A main goal of the ExoMars Rosalind Franklin Rover (EMRF) mission is to search for past life on Mars, preserved within phyllosilicate-bearing geological deposits at its landing site in Oxia Planum. Enfys is a new infrared spectrometer added to the mission payload in 2023 and is currently under development for Flight Model delivery in 2026 and launch in 2028 for landing in 2030. Enfys will provide remote sensing spectroscopic capabilities for exploration, target selection, and geological contextualisation through the measurement of point infrared reflectance spectra. Enfys will play a major role not only in mission operations, but also in linking orbital and in situ spectroscopic observations and mineralogical interpretations. As a replacement for the former Roscosmos ISEM instrument, Enfys has been developed at pace to meet the revised mission schedule, drawing heritage from the Panoramic Camera (PanCam), an instrument Enfys will work in concert with. In a little under 3 years since inception, the first Enfys prototype has now been assembled, characterised and calibrated, for installation on the Amalia Ground Test Model rover.
Enfys utilises two near-infrared Linear Variable Filters (LVFs), each with a dedicated InGaAs detector. Together, these cover the wavelength range 0.9 – 2.5 mm. Both LVFs are translated simultaneously on a mechanical stage. Enfys sits on top of the EMRF mast, co-aligned with and directly underneath the High Resolution Camera (HRC) element of the PanCam instrument. Embedded within the design is an overlap in wavelength range with PanCam covering 0.9 and 1 mm, allowing spectral continuity between VIS-NIR multispectral imaging and point IR spectroscopy. Enfys data will also be complementary to the other near-infrared spectrometers on EMRF, including Ma-MISS, which will collect data from within the drill hole, and MicrOmega, which will analyze the drill core once collected, prepared and delivered into the analytical suite inside EMRF. To maximise the scientific return from Enfys, a variety of geological analogue testing is currently underway with Enfys emulators. This has focused on sedimentary deposits, ranging from mudstones to sandstones of compositions ranging from mafic to felsic, and ages from 2.7Ga to 10Ka. An overview of the Enfys project will be presented, along with instrument design and performance figures and analogue study results.
How to cite: Cousins, C. R., Gunn, M., Grindrod, P., Nielson, G., Marsh, H., and Langston, J.: The Enfys Spectrometer for the ExoMars Rosalind Franklin rover, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11920, https://doi.org/10.5194/egusphere-egu26-11920, 2026.
In 2030, the ExoMars Rosalind Franklin Mission Rover (RFM) is scheduled to land at Oxia Planum, Mars, to search for the chemical building blocks of life [1]. The mission’s success depends not only on the rover’s scientific payload, but also on RFM’s ability to safely and efficiently traverse the Martian terrain: what terrains are safe to drive across; what terrains or features on the landscape are potential mobility hazards; and how efficiently can the rover make it from one point to another?
Extensive work has gone into characterizing the landing site at Oxia Planum including the creation of high-resolution digital elevation models [DEMs; e.g. 2], high fidelity geologic [3] and mineralogic mapping [e.g. 4], and machine-learning assisted landscape classifications [5,6]. Additionally, many studies have characterized the wider Oxia region, identifying widespread evidence for ancient fluvial [e.g. 7, 8] alteration, as well as modern aeolian reworking of the surface [9]. RFM engineers and mission scientists will use this scholarship, as well as in situ images and DEMs to get the rover from one location in Oxia Planum to another.
During this pre-launch phase of the mission, we were curious to test whether we could automate the creation of rover traversability paths between two arbitrary points at Oxia Planum in a geographic information system (GIS). Specifically, we wanted to answer three simple questions: (1) what is the safest path from point A to point B, (2) how quickly can we traverse that distance, and (3) therefore, how many driving sols are needed?
First, we compared NOAH-H (The Novelty and Anomaly Hunter – HiRISE [5]) deep learning terrain classifications at Jezero Crater [10] to Oxia Planum [5, 6] with in situ images from NASA’s Perseverance rover. We then developed Python-based algorithms in a GIS environment which considered factors such as topography (derived from HiRISE DEMs), geomorphology (from NOAH-H), and solar radiation balances at a test site within the nominal landing area. These data, and combinations thereof, were assigned weighting values that were passed to the algorithm and then used to compute individually optimized drive paths for different objective prioritizations.
Using multivariate terrain analysis, our route-generation algorithms produced over thirty possible drive paths with associated statistics. The algorithm’s adjustable weighting parameters allow prioritization of variables, which will be critical when in situ data becomes available. We continue to iterate on our approach and will present current findings at this conference. Our work demonstrates that lightweight, flexible Python-based drive paths can be generated from existing data, supporting strategic planning and operational readiness across mission phases.
[1] Vago et al. (2017), Astrobiology, 17(6-7); [2] Volat et al. (2022), PSS, 222; [3] Fawdon et al. (2024), Journal of Maps, 20(1); [4] Bowen et al. (2022), PSS, 214; [5] Barrett et al. (2022), Icarus, 371; [6] Barrett et al. (2023), Journal of Maps, 19(1); [7] Fawdon et al. (2021), Journal of Maps, 17(2); [8] Davis et al. (2023), EPSL, 601; [9] Favaro et al. (2021), JGR:P, 126(4); [10] Wright et al. (2022), Journal of Maps, 18(2).
How to cite: Favaro, E. A., Fernandez, L., Fayolle, S., Barrett, A., Balme, M. R., Fawdon, P., Wright, J., and Joudrier, L.: Developing Flexible Algorithms to Optimize Drive Paths for the ExoMars Rosalind Franklin Rover, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12037, https://doi.org/10.5194/egusphere-egu26-12037, 2026.
The European Space Agency (ESA) Rosalind Franklin rover Mission (RFM) is expected to land at Oxia Planum, Mars in 2030. Orbital spectral data and imagery reveal layered, clay-rich sedimentary deposits, often overlain by or interbedded with a dark, more resistant rock rich in mafic minerals [e.g., 1, 2]. The 1:30k scale geologic map of the landing site [1] associates two geologic units to their VNIR color and fracture spacing; Apuzzo et al. [3] studied directional statistics of fractures in selected regions of interest. However, complete quantitative fracture metrics over the RFM landing area are not yet available. Since at least 35% of the landing site is covered by fractures [3], a comprehensive study of fractures, and the composition of their hosting bedrock, is critical for elucidating whether formation mechanism, alteration history, and/or mineralogy vary across the Oxia Planum site.
Here, we present fracture density (number of fractures/m^2) and topological connectivity of fractures within an unbiased collection of 33 approximately 500x500 m square windows spaced along transects over the center of the predicted landing footprint of the RFM. Multiple windows overlap with Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) spectral cubes for which Fe,Mg-clay abundance has been qualitatively estimated [2]. Fractures are mapped manually as linear segments in QGIS software, using visual interpretation of High Resolution Imaging Science Experiment (HiRISE) images (0.3 m/px) in the red spectral range. We map at 1:1250 scale resulting in a minimum resolvable fracture length of about five pixels, or 1.5 m. The NetworkGT QGIS software plugin [4] is used to extract node connectivity, fracture orientations, and fracture lengths.
Topological analysis of node types and fracture-bounded polygon shapes is then leveraged to aid in interpreting (1) changes in fracture behavior across previously mapped unit boundaries, and (2) formation mechanisms of the fracture networks, following [5]. We also compare fracture mapping within and outside specific clay-rich areas of interest [2, 6] to determine if they have unique mechanical or formation characteristics. Preliminary analysis
indicates that fracture density is often higher within more clay-rich areas, and that the majority of mapped fractures are “I-node”, meaning they terminate without connecting to another fracture. Where fractures do connect, three- and four-sided polygon shapes dominate. We compare these findings with previous topological network characterization [e.g., 5] to enhance our interpretation of the possible scenarios of formation and current unit composition at Oxia Planum, considering topological characteristics will better constrain our understanding of past aqueous activity. Our results will support the better selection of analog materials for terrestrial drill testing before mission launch, and help inform drill site selection when the rover reaches Mars’ surface.
References: [1] Fawdon et al. (2024) Journal of Maps 20, 2302361. [2] Brossier et al. (2022) Icarus 386, 115114. [3] Apuzzo et al. (2025) PSS 267, 106169. [4] Nyberg et al. (2018) Geosphere 14(4) 10.1130/GES01595.1. [5] Silver et al. (2025) PNAS 22 (10) e2411738122. [6] Altieri et al. (2026), this conference.
Acknowledgements: This work is funded by the Italian Space Agency (ASI) [Grant ASI-INAF n. 2023–3–HH.0].
How to cite: Rasmussen, M., Altieri, F., Frigeri, A., Brossier, J., Trisic Ponce, J., Silver, S., Jerolmack, D. J., Rossi, L., and De Sanctis, M. C.: Fracture geometry and topology and their spectral signatures at OxiaPlanum, Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12476, https://doi.org/10.5194/egusphere-egu26-12476, 2026.
The Makgadikgadi Salt Pans (MSPs) in northern Botswana offer to study the mineralogy of evaporates and clays derived from fluvio-lacustrine sediments in their geological context. A field campaign taking place in August 2022, funded by Europlanet 2024 RI (grant agreement No 871149) was performed to investigate variations in the mineralogical composition of the pan materials with respect to neighboring and/or underlying (bedrock) units. Spectral measurements were performed directly in the field with a portable spectroradiometer (PSR) that samples the surface in the visible and near-infrared (VNIR) wavelength range between 0.35 and 2.5µm. In addition to VNIR spectroscopy, samples collected in the field were analyzed in the laboratory using laser-induced breakdown spectroscopy (LIBS) and Raman spectroscopy, a triple combination, which has proven to significantly enhance the scientific potential for studying the mineralogy of planetary analog materials (Stephan et al., 2025). Even more, VNIR spectra acquired in the field provide spectral endmembers, which are now used to classify the currently available data of the MSPs provided by the Environmental Mapping and Analysis Program (EnMAP) of the German hyperspectral satellite mission. EnMAP data cover the same wavelength range in the VNIR as the field instrument and covered major portions of the pans at the same seasonal period of the year.
The acquired spectral data reveal that salts dominate a more or less fresh, white to light brown, several mm-thick uppermost crust throughout the pans. They are particularly prominent where the salts themselves or at least the clays underneath this layer are still wet from the rainy season. The special shape of the water-related feature at 2 µm implies that sodium hydrogen carbonates such as trona dominate the salt layer. Although halite should be also present, its spectral signature might be masked by the signature of trona. In the wettest location, a thin greenish layer of organic material has been found, which causes a characteristic feature near 0.7 µm. In regions that have been dry for a prolonged period, clays such as montmorillonite dominate over salts. Bed rocks that are in direct contact with the pan deposits often show a distinct greenish color. Spectra of these rocks are dominated by glauconite (sometimes in combination with illite), which are known to develop as a consequence of slow sedimentation in a marine environment associated with low-oxygen conditions.
Intriguingly, lacustrine glauconitic clays could also be confirmed to exist in an ancient lake on Mars (Losa-Adams et al., 2021). Therefore, the collected spectra in combination with the knowledge of their geologic context will be extremely useful for identifying similar environments on Mars by spectrometers working in the visible-near infrared (VNIR) wavelength range (Mars Express OMEGA, MRO CRISM) and providing key parameters for characterizing aqueous Martian palaeoenvironments.
References:
Stephan et al. (2025). Multi-spectral field study of planetary analog material in extreme environments—alteration products of volcanic deposits of Vulcano/Italy. Earth and Space Science, 12, e2024EA004036. https://doi.org/10.1029/2024EA004036.
Losa-Adams et al. Long-lasting habitable periods in Gale crater constrained by glauconitic clays. Nat Astron 5, 936–942 (2021). https://doi.org/10.1038/s41550-021-01397-x.
How to cite: Stephan, K., Hauber, E., Meyers, J., Rammelkamp, K., Baque, M., Baroni, M., Fernandes, M., Franchi, F., and Motlhasedi, A. J.: Mineralogical characterization of the Makgadikgadi Salt Pans in Botswana as a Martian analog for ancient lacustrine environments , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20861, https://doi.org/10.5194/egusphere-egu26-20861, 2026.
We report on the first known ground-based observations of a relatively recently discovered feature on Mars: the Arsia Mons Elongated Cloud (AMEC). This is the longest such structure in the Solar System, and it was first reported in 2020 using spacecraft data (J. Hernández-Bernal et al.). It was also found in archive images from different space probes, but not detected in Earth based images.
During the 2020 Mars Opposition, we obtain ground-based data at the Institute of Space Science in Romania, using a 35 cm telescope. The images clearly show this feature during two different nights, and the evolution of the feature could be observed for several hours.
We present the results that include an analysis of the images using specialized software, including position on the Martian globe and measurements of the cloud structure.
- Hernández-Bernal, A. Sánchez-Lavega, T. del Río-Gaztelurrutia, et al. (2020), JGR Planets, Volume126, 3, https://doi.org/10.1029/2022JE007352.
How to cite: Teodorescu, M.: First Earth-based observations of the Arsia Mons Elongated Cloud (AMEC) on Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19523, https://doi.org/10.5194/egusphere-egu26-19523, 2026.
The SO channel of the NOMAD instrument on board ESA’s Trace Gas Orbiter (TGO) has a spectral range extending from 2.2 to 4.2 µm (2400 cm-1 to 4600 cm-1). By solar occultation, the intense ν1+ν3 band of CO2 (around 2.7 µm or 3710 cm-1) is suitable for deriving CO2 density and temperature in the upper thermosphere of Mars at altitudes around 140 to 190 km. The lower altitude limit is due to the saturation of the CO2 molecular lines in that band. The retrieval algorithm is identical to the one described in Trompet et al. (2023) and relies on the calibration method outlined in Liuzzi et al. (2019), which was further improved in Villanueva et al. (2022). The CO2 density profiles are regularized using a Tikhonov method, and the temperature profiles are derived assuming hydrostatic equilibrium. A total of 5700 profiles were derived from April 21, 2018 (MY 34, LS 163°) to June 30, 2025 (MY 38, LS 104°).
Datasets of the Martian upper thermosphere at the terminator are rather sparse, being limited to observations from the Extreme UV monitor (EUVM - Thiemann et al., 2018) on board NASA’s MAVEN orbiter and the MIR channel of the Atmospheric Chemistry Suite (ACS-Belyaev et al., 2022) also on board TGO, which uses the same CO2 band at 2.7 µm. Despite this limited coverage, some collocated profiles suitable for comparisons are found amongst the datasets of EUVM, ACS-MIR, and NOMAD-SO.
Kumar et al. (2024) already derived characteristics of thermal tides for six sets of EUVM measurements. However, extending those measurements helps to confirm those characteristics and infer further information on thermal tides through comparison with the Mars Climate Database (MCD - Gonzalez-Galindo et al., 2015). The tides simulated by the MCD are in good agreement with those derived from TGO and MAVEN, with a still weaker amplitude likely due to the averaging performed within the MCD dataset. The datasets of both EUVM and NOMAD show the presence of a thermospheric polar warming at aphelion (Thiemann et al., 2024). In addition, the averaged profiles of NOMAD are compared to those of the Venus thermosphere derived from the SOIR instrument (Mahieux et al., 2023).
References:
Belyaev et al. (2022), JGR: Planets, 127 (10), https://doi.org/10.1029/2022JE007286
Gonzalez-Galindo et al. (2015), 120 (11), https://doi.org/10.1002/2015JE004925
Kumar et al. (2024), JGR: Planets, 129 (4), https://doi.org/10.1029/2023JE007887
Liuzzi et al. (2019), Icarus (321), https://doi.org/10.1016/j.icarus.2018.09.021
Mahieux et al. (2023), Icarus, 405, https://doi.org/10.1016/j.icarus.2023.115713
Thiemann et al. (2018), JGR: Planets, 123 (9), https://doi.org/10.1029/ 2018JE005550
Thiemann et al. (2024), GRL, 51 (5), https://doi.org/10.1029/2023GL107140
Trompet et al. (2023), JGR: Planets, 128 (3), https://doi. org/10.1029/2022JE007277
Villanueva et al. (2022), JRL, 49 (12), https://doi. org/10.1029/2022GL098161
How to cite: Trompet, L., Neary, L., Thomas, I., Mahieux, A., Robert, S., Aoki, S., Brines, A., López-Valverde, M. Á., Patel, M., Bellucci, G., and Vandaele, A. C.: CO2 density and temperature derived from NOMAD/TGO in the upper thermosphere of Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18692, https://doi.org/10.5194/egusphere-egu26-18692, 2026.
Gravity waves in the Martian atmosphere are generated by wind flow over topography, convection or shear instabilities. They propagate upward, transporting momentum and energy from the lower atmosphere into the mesosphere and thermosphere. While the waves are relatively small, ranging in wavelength from tens to hundreds of kilometres, their impact through thermal and dynamical forcing on the climate can be quite large.
The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission started operations in 2014 and was joined in orbit by the ExoMars Trace Gas Orbiter (TGO) in 2018. Together, they have been observing the Martian atmosphere contemporaneously, allowing for an unprecedented opportunity to produce a global view of gravity wave activity over several Mars years.
For this work, we use temperatures derived from the Nadir Occultation for MArs Discovery (NOMAD) Solar Occultation (SO) channel (Trompet et al., 2023), the Middle IR (MIR) channel of the Atmospheric Chemistry Suite (ACS) experiment (Belyaev et al., 2022), both onboard TGO, along with temperature retrievals from stellar occultation measurements from the Imaging UltraViolet Spectrograph (IUVS) (Gupta et al., 2022) on the MAVEN spacecraft.
The NOMAD/SO and ACS/MIR observations are performed using solar occultation, so they are limited in local time to the morning and evening terminators, with the majority of observations taking place around mid-latitudes (between 50-75° N/S) due to the orbit of TGO. The addition to the study of stellar occultation observations from MAVEN/IUVS fills in some of the gaps in terms of local time and latitude. Figure 1 provides a comparison of coverage by the three instruments in terms of Mars years, season, latitude and local time.
In altitude, the ACS/MIR profiles range from ~20 km to 150 km. For NOMAD, we use two different wavelength regions (diffraction orders 132 and 148) to view the atmosphere from ~20 km to 100 km. The MAVEN/IUVS stellar occultations provide temperature profiles between ~100 km to 150 km. This provides some overlap between the three instruments to compare temperature profiles, their perturbations and potential gravity wave activity.
We build on the work of Starichenko et al. (2021; 2024; 2025),who performed an analysis of gravity waves using ACS observations.
Figure 1: Data coverage for the three instruments used in this study, number of profiles per Mars Year (top left), Solar Longitude (top right), latitude (bottom left), and local time (bottom right). ACS/MIR profiles in blue, IUVS/stellar occultation in orange, and NOMAD in green.
References :
Belyaev et al. (2022), JGR: Planets, 127 (10), https://doi.org/10.1029/2022JE007286
Gupta et al. (2022), JGR: Planets, 127 (11), https://doi.org/10.1029/2022JE007534
Trompet et al. (2023), JGR: Planets, 128 (3), https://doi. org/10.1029/2022JE007277
Starichenko et al. (2021), JGR: Planets, 126 (8), https://doi.org/10.1029/2021JE006899
Starichenko et al. (2024), A&A, 683, A206, https://doi.org/10.1051/0004-6361/202348685
Starichenko et al. (2025), Front. Astron. Space Sci., 12:1672283, https://doi.org/10.3389/fspas.2025.1672283
How to cite: Neary, L., Trompet, L., Starichenko, E., Gupta, S., Belyaev, D., Thiemann, E., and Daerden, F.: A multi-mission climatology of gravity waves in the Martian mesosphere and thermosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18187, https://doi.org/10.5194/egusphere-egu26-18187, 2026.
The Mars Global Ionosphere-Thermosphere Model (M-GITM) (Bougher et al., 2015) has typically been used to perform shorter term simulations (~2 hours - 1 month) of the Mars upper atmosphere. Given that recent studies have demonstrated broad understanding of the longer term variability of the upper atmosphere (e.g. Jain et al., 2023, Gonzalez-Galindo et al., 2015), we have been working on using the model to perform annual simulations in order to 1) see how the model reproduces long-term variability and 2) provide a set of upper atmospheric data products for use in an updated version of Mars-GRAM (Justh et al., 2011). We present results from this suite of 4 annual simulations that span a range of solar and dust conditions and identify conditions and regions when the model compares well with previous studies and observations as well as conditions when the model demonstrates missing physics. For example, M-GITM is able to capture observed average long term seasonal variability in the middle and upper thermopshere. However, the model struggles to capture similar trends near the mesopause.
How to cite: Pawlowski, D., Bougher, S., and Kahre, M.: Mars climate trends simulated by M-GITM during MY24, 25, and 30, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8238, https://doi.org/10.5194/egusphere-egu26-8238, 2026.
In the framework of the project “Earth Moon Mars” (EMM)†, we present a novel forward model designed for the fast and accurate production of Martian radiance spectra in the longwave infrared region (100-3000 cm-1) under nadir geometry. Building upon the flexibility and capabilities of the recently developed forward model σ-FORUM (also referred to as σ-IASI/F2N), this project seeks to extend its application, by now limited to Earth study, to the Martian atmosphere. The new model, σ4Mars, generates high-resolution spectra (with a default spectral resolution of 10-2 cm-1) while maintaining computational efficiency through the use of precomputed lookup tables for the computation of gas and clouds/aerosol optical depths. Multiple scattering effects are treated using scaling methods, specifically the Chou scaling approximation and the Chou adjustment (Tang correction). In addition, the code allows the computation of fast analytical derivatives of the radiance with respect to atmospheric and cloud properties, thus being suitable for the application in fast retrieval of spectrally resolved infrared observations.
We present the choices made for the parametrization of the optical depths tailored to Martian atmosphere conditions. Gas optical depths parametrizations are obtained employing the Planetary Spectrum Generator (PSG) line-by-line radiative transfer suite by NASA, using HITRAN2020 as spectroscopic database for line parameters and the Martian Climate Database version 5.3 as atmospheric database. Clouds and aerosol optical depths are parametrized as a function of the particle size distribution effective radii. The performance of the model has been evaluated using PSG as reference code by comparing gas transmittances and high-resolution radiance spectra. Preliminary tests were conducted to compare the forward model results with observed spectral radiances from the ACS TIRVIM instrument on board the ExoMars TGO, and from EMIRS on board the Emirate Mars Mission.
† Part of the research activities described in this paper were carried out with contribution of the Next Generation EU funds within the National Recovery and Resilience Plan (PNRR), Mission 4 - Education and Research, Component 2 - From Research to Business (M4C2), Investment Line 3.1 - Strengthening and creation of Research Infrastructures, Project IR0000038 – “Earth Moon Mars (EMM)”. EMM is led by INAF in partnership with ASI and CNR.
How to cite: Buriola, L., Papandrea, E., Maestri, T., and Liuzzi, G.: σ4Mars, a new fast radiative transfer code for the analysis of the Martian atmosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18861, https://doi.org/10.5194/egusphere-egu26-18861, 2026.
The present study employs self-consistent three-dimensional global hybrid simulations of Mars–solar wind interactions to investigate how intrinsic magnetic fields regulate the escape of planetary ions with different masses, with escaping ion trajectories traced. Present-day Martian crustal magnetic fields modify ionospheric ion escape primarily by restructuring local electric and magnetic field configurations. First, they alter the magnetic topology (closed, open, or draped), inclination and intensity of magnetic field lines, thereby increasing local ion density and facilitating outward transport along open field channels. Second, they reduce the radial component of the local electric field, which directly influences ion acceleration.
The combined effects preferentially enhance the escape of heavy oxygen ions while suppressing the escape of light hydrogen ions, mainly because light ions are more effectively trapped within strong closed crustal magnetic loops. Finally, we extend our investigation to ancient Mars conditions and compare how intrinsic magnetic fields in early and present epochs differently regulate planetary ion escape, providing insight into the long-term evolution of the Martian atmosphere.
How to cite: Zhou, J., Su, Z., and Liu, K.: Hybrid Simulations of the Intrinsic Magnetic Fields Effect on Planetary Oxygen and Hydrogen Ion Escape at Mars: Ancient-to-Present Evolution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16831, https://doi.org/10.5194/egusphere-egu26-16831, 2026.
The Neutral Gas and Ion Mass Spectrometer (NGIMS) onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission has measured ions with mass-to-charge ratios between 2 and 150 in the Martian ionosphere. Among these observations, protonated species at 31, 33, and 41 atomic mass units (amu) exhibit densities substantially higher than those predicted by existing photochemical models. In this study, we investigate these model-observation discrepancies using a combination of photochemical modeling and NGIMS measurements from the dayside ionosphere.
Photochemical models predict ArH+ densities at 41 amu that are more than an order of magnitude lower than NGIMS observations, while modeled densities of HNO+ and HO2+ at 31 and 33 amu are underestimated by approximately three orders of magnitude. Analysis of vertical density profiles reveals strong similarities among the 31, 32, and 33 amu channels, as well as among the 41, 42, 43, and 44 amu channels. These similarities cannot be fully accounted for by known chemical pathways or contributions from oxygen isotopes. Instead, our results indicate that instrumental effects, specifically mass channel cross-talk from the dominant 32 and 44 amu species, provide a plausible explanation for the anomalously high densities reported at 31, 33, and 41 amu. These findings highlight the importance of carefully accounting for instrumental artifacts when interpreting ion composition measurements in the Martian ionosphere.
How to cite: Cheng, L. and Vigren, E.: Model-observation discrepancies in protonated species in Mars’ ionosphere from MAVEN/NGIMS, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7319, https://doi.org/10.5194/egusphere-egu26-7319, 2026.
Mars exhibits strongly magnetized crust, interpreted as a remanent signature acquired during the operation of the ancient martian dynamo. Several mechanisms can produce crustal magnetization, including thermal, shock, and chemical remanent processes. Thermal remanent magnetization can produce relatively clear and coherent signatures, shock-related magnetization associated with impact craters often yields more ambiguous or spatially complex magnetic patterns.Chemical remanent magnetization (CRM) can be acquired when water interacts with specific rock types, particularly olivine-rich lithologies, leading to the formation of secondary magnetic minerals such as magnetite. Geological and mineralogical evidence for past water activity on Mars, together with the widespread presence of suitable precursor minerals, suggests that this process may have been an important contributor to the martian crustal magnetic field.
Here, we evaluate magnetic field signatures in regions where water was likely present, at or beneath the surface. In areas where hydrothermal circulation is thought to have been active, such as impact-related hydrothermal systems, we identify magnetization signatures in regions that were active early in Mars’ history, including areas surrounding Ladon crater. In contrast, other regions such as Eridania basin, exhibit distinct demagnetization signatures, which may indicate that hydrothermal circulation persisted beyond the cessation of the martian dynamo. By further comparing magnetic anomalies with morphological indicators of aqueous alteration on the surface, we assess whether chemical remanent magnetization associated with water–rock interactions can explain observed crustal magnetic signatures and contribute significantly to the magnetization of the martian crust.
How to cite: Mittelholz, A., Stucky de Quay, G., Broquet, A., Delcourt, T., Johnson, C., Moorkamp, M., and Ojha, L.: Assessing the Role of Water–Rock Interactions in Martian Crustal Magnetization, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10791, https://doi.org/10.5194/egusphere-egu26-10791, 2026.
Mars lacks a global dipole magnetic field but hosts localized magnetic anomalies from magnetized crustal rocks. Accurate descriptions of the crustal magnetic field are crucial for understanding the magnetic environment and geology of Mars. In this study, We construct a Martian crustal magnetic field model using the Equivalent Source Dipole (ESD) approach, integrating data from three missions: Mars Global Surveyor (MGS), Mars Atmosphere and Volatile EvolutioN (MAVEN), and Tianwen-1. To mitigate contamination from solar wind-ionosphere interactions, we use satellite-measured upstream solar wind parameters, including the average values of IMF strength, IMF fluctuation levels, solar wind pressure, and electron density, as indicators of external field interference. The resulting model is then converted to a spherical harmonic (SH) model up to degree 130, achieving a spatial resolution of approximately 165 km at the Martian surface. Compared to previous studies, it exhibits reduced fitting residuals for the horizontal components of MAVEN dataset, confirming the effectiveness of our data selection methodology. Validation with rover measurements reveals that while the model’s predictions are significantly weaker at the InSight landing site, they show better agreement with observations at the Zhurong site than those of previous models. This work could assist in further research on the Martian magnetic environment and its interaction with the solar wind.
How to cite: Wanqiu, F., Long, C., Yuming, W., Zhenguang, H., and Rentong, L.: A Model of the Martian Crustal Magnetic Field Using Data from MGS, MAVEN, and Tianwen-1, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3633, https://doi.org/10.5194/egusphere-egu26-3633, 2026.
Impact-generated marsquakes with accurate positions are important to Mars seismic investigations. To better constrain the Martian crustal velocity structure, we repicked first-arrival P- and S-wave of three impacts (S0981c, S0986c and S1034a) near InSight lander and analyzed their possible ray paths. We significantly reduced body-wave arrival uncertainties by applying polarization filters and filter-bank methods. To verify that the detected energy originates from the corresponding events, the azimuth of each candidate arrival was calculated and compared with the true event azimuth. Then we derived the incidence angles from particle motion to constrain the ray path.
We find that for events at shorter epicentral distances (S0986c and S1034a), the first-arrival ray paths are typically confined to the uppermost crust. In contrast, first-arrival ray path from more distant event (S0981c) usually sample the mid-lower crust or the crust-mantle boundary. Furthermore, we detected later-arrival P-waves from S0981c. By combining these body-wave arrivals with incidence angles from three impacts, we inverted for the one-dimensional Martian crustal velocity structure beneath the InSight lander using a Markov Chain Monte Carlo (MCMC) method.
More refined processing techniques enable us to extract more information from marsquake signals, helping us understand Martian inner velocity structure better. In this study, we simultaneously incorporated body-wave travel times and incident angles into the inversion. This approach can lead to better constraints on the Martian crustal velocity structure and even constrict the Vp/Vs ratio at each crustal layer.
How to cite: Tian, L. and Yao, H.: Improved Constraints on Martian Crustal Velocity Structure of InSight lander, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6830, https://doi.org/10.5194/egusphere-egu26-6830, 2026.
Studying the geomorphology of crater ejecta at Martian mid- to high-latitudes is essential for understanding how impact-generated flows and debris patterns indicate subsurface ice or water at the time of impact. By analyzing ejecta morphologies, such as rampart structures, lobate flows, and layered deposits, we can reconstruct the distribution and abundance of volatiles in the Martian subsurface. These morphological observations provide the basis for stratigraphic correlations and spectroscopic analyses, enabling more precise quantification of past and present water-ice concentrations in the upper crust. Our study focuses on a fresh crater (43.81N, 301.53E) located roughly 225km NE of Timoshenko crater, in Tempe Terra. By using Digital Terrain Models (DTMs) at different scales (CTX at 6m ppx and HiRISE at 0.3m ppx) we map the different ejecta blankets that comprise this crater and classify it based on their topography and shape.
We created DTMs using the Ames Stereo Pipeline (ASP, [1]) and two stereopairs per instrument (CTX J14_050126_2236_XN_43N058W and P12_005807_2238_XI_43N058W, HiRISE ESP_059370_22401 and ESP_077029_2240), aligned to overlying MOLA data from PDS ([2]), and then projected within a GIS software (QGIS, v3.40.5), which helps in DTM manipulation, visualization, and topographic studies of the ejecta layers and their subsequent plotting, while using different data formats.
From CTX imagery, we recognize 2 ejecta layers: one proximal to the crater (500m from crater rim), with a slope of 20˚ and smoother topography, which ends in a small (~10m) edge step; and a second more distal, showing a radial lobate pattern exuding from the crater, composed of rougher materials, with little to no slope (~3˚).
Following [3]’s classification, we classify this as a type 2 (double ejecta facies) or type 3 (multiple facies) crater. This uncertainty is related to the resolution limits of CTX; it is difficult to determine whether the second ejecta layer is further subdivided into more layers, as the contacts become diffuse, and the more distal parts of it appear as isolated ejecta clusters, disconnected from the main facies, especially in the NW and SE margins.
Our multi-scale morphological analysis of the crater will place it into context with its surroundings [4] and prepare for specific studies, such as the spectroscopic analysis of specific areas [5]. Using CTX DTMs as a basemap will provide a robust and smooth topography, which can be better interpreted and used for mapping; HiRISE will offer very high resolution, allowing a more robust identification of smaller features. The accurate development of DTMs at appropriate resolution is key and we will concentrate efforts on uncertainty analyses of these higher-level data products. We are applying these techniques into operational mission-driven scenarios like the Oxia Planum landing site of the ESA/ExoMars Rosalind Franklin Rover [5].
This work is funded by the Italian Space Agency (ASI) [Grant ASI-INAF n. 2023–3–HH.0].
References: [1] Beyer et al. (2018) ESS 5(9), 537-548; [2] Smith et al. (2001) JGR Journal of Geophysical Research: Planets 106.(E10); 2156-2202. [3] Mouginis-Mark (1979) JGR Solid Earth 84(B14), 8011-8022. [4] Rasmussen et al., (2025) GSA A&Ps 57(6), p. 4976. [5] Altieri et al. (2026), this conference.
How to cite: Trisic Ponce, J., Frigeri, A., Rasmussen, M., Brossier, J., Altieri, F., and De Sanctis, M. C.: Multi-scale Morphology of Fluidized Ejecta Blankets and their Spectral Counterpart, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12307, https://doi.org/10.5194/egusphere-egu26-12307, 2026.
Superficial processes on Mars are responsible for the erosion and degradation of impact craters Primary crater morphologies are generally not preserved and affected by a complex and multi-stage degradation history. Under present cold and dry climate, Moste cent Martian impact craters offer valuable insights into impact processes and emplacement of various impact-related units. 19 recent craters younger than ~10 Ma old were identified by Lagain et al. (2021) and are considered as potential sources of Martian meteorites recovered on Earth. Among this particular set, the Mojave crater stands out due to its complex morphology and large diameter (D~58 km). Mojave is located in Xanthe Terra (7°N, 33°W), a Noachian-aged region, between Simud Vallis and Tiu Vallis (Williams & Malin, 2008). It lies within highly dissected plateaus shaped by catastrophic flood events associated with outflow channels mainly sourced from Valles Marineris and draining toward Chryse Planitia during the early Hesperian (Nelson & Greeley, 1999).
This study has combined very high-resolution imagery data (e.g., HiRISE images (≈ 0.25–0.5 m/pixel) and CTX images (≈ 6 m/pixel) to analyze fine morphological details. In addition, digital elevation models derived from MOLA (≈ 463 m/pixel) and CTX data were used to establish a detailed geological map of Mojave crater. Our preliminary map reveals several original features, that open new perspectives for understanding impact-related processes. These include the spatial distribution of secondary craters associated with Mojave, a discontinuous and asymmetric rim, and the presence of two superposed lobate ejecta layers (Williams & Malin, 2008) terminating in distal ramparts. The ejecta blanket displays a significant asymmetry, showing a typical long run-out in the northern and northeastern sectors, but appearing more chaotic in the southern region. One proposed explanation for this asymmetry is the presence of topographic obstacles in the southern part of the crater, modifying ground-hugging ejecta trajectories leading to localized accumulation of ejected material and therefore higher ejecta thicknesses. Our mapping also revealed a significant offset in the northwest direction of the central peak with respect to the center of the crater. Such an offset may result from an oblique impact and/or pre-existing structures and may be also enhanced by post-impact erosion (Wulf et al., 2011). To elucidate the cause of this offset, we plan to achieve a new survey of central peak offsets in recent impact craters
These observations highlight the complexity of the formation a complex crater in a target with pre-existing structural heterogeneities, with consequences on both the crater morphology and structure and on the ejecta deposits
How to cite: daldoul, M., bouley, S., baratoux, D., lagain, A., and Srarfi, F.: High-Resolution Geological Mapping of the Mojave Crater: A Window into Martian Impact and post-impact Processes., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7467, https://doi.org/10.5194/egusphere-egu26-7467, 2026.
NASA’s Curiosity rover recently discovered decimeter-sized clasts of nearly pure native sulfur within the Gediz Vallis channel in Gale crater, representing the first detection of elemental sulfur on Mars. The origin of this material remains uncertain, as native sulfur on Earth typically forms in volcanic, hydrothermal, or evaporitic environments. Here, we investigate a formation mechanism in which sulfur-rich material is melted by a meteoritic impact, producing molten sulfur that subsequently flows and solidifies at the surface. Geological mapping of the Gediz Vallis region reveals a partially breached crater (~390 m in diameter) located upstream of the sulfur-bearing deposits, within a light-toned yardangs unit. We interpret this structure as a candidate source crater, where impact-generated melt may have escaped through the breach and flowed a few kilometers downslope before solidifying. Production of melt in the context of such a small impact crater is qualitatively supported by the observations of impact melt pools associated with small craters on Lunar basaltic surfaces.
To assess whether the volume of melt produced could be comparable to the native sulfur deposit at Geidz Vallis, we performed numerical simulations using the iSALE shock-physics code. We modeled vertical impacts of dunite projectiles into a basaltic target at velocities of 5, 7, 10 km/s, the size of the asteroid being empirically adjusted to reproduce the observed crater size. Because a dedicated high-pressure equation of state for sulfur is unavailable, sulfur was treated as a minor component of the target, and shock propagation was assumed to be controlled by the basaltic matrix. Sulfur melting was then evaluated a posteriori using reconstructed thermodynamic properties derived from experimental shock data and melting curves.
From tracer-based shock pressure histories, we estimated the total mass of sulfur melted (liquid plus vapor), the fraction retained within the crater as a melt pool, and the amount potentially lost to vaporization. Our results show that total melt production increases with impact velocity, while only about 20–25% of the melted sulfur is retained within the crater after excavation. For sulfur concentrations typical of minor components, the retained melt mass is insufficient to explain the volume inferred from Curiosity observations. However, extrapolation to sulfur-rich substrates (≥ 50% sulfur fraction) would yield melt pool masses comparable in order of magnitude to Curiosity’s inferred mass, even under conservative assumptions regarding vaporization and ejected melt.
These results suggest that impact-induced melting of sulfur-rich materials is a possible mechanism for producing native sulfur deposits on Mars, provided that the light-toned yardangs unit is significantly enriched in sulfur. However, a model incorporating a dedicated sulfur equation of state is critical to further test this hypothesis, whereas in situ rover observations as Curiosity approaches the yardangs unit shall reveal its nature and composition.
How to cite: Maggioni, L., Rapin, W., Forni, O., Baratoux, D., Formisano, M., De Sanctis, M. C., Magni, G., and Altieri, F.: Impact-Induced Sulfur Melting on Mars: A Potential Source of Native Sulfur Detected by the NASA’s Curiosity Rover, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12327, https://doi.org/10.5194/egusphere-egu26-12327, 2026.
During the Late Noachian-Early Hesperian, geological evidence shows that the Mars surface had shallow seas, lakes, and possibly a northern ocean. This transition period, around 3.8 - 3.0 Ga, is characterised by a high rate of asteroid impacts, following which Mars gradually became colder and arid as surface water was lost. However, the relative importance of different mechanisms responsible for the loss of liquid surface water remains unclear. Here we investigate the role of asteroid impacts in vaporising and removing shallow surface-water layers on Early Mars. Using iSALE-2D shock physics code, we quantify water vaporisation, escape-capable vapour production, and liquid water survival for a range of impactor sizes, water depths, and projectile-target compositions. The results provide constraints on impact-generated hydrological loss mechanisms and inform scenarios for Early Mars climate evolution and surface habitability.
How to cite: Senel, C. B., Luther, R., Karatekin, Ö., Tang, Y., Dai, K., Collins, G. S., Goderis, S., Wünnemann, K., and Claeys, P.: The Role of Asteroid Impacts in Surface-Water Loss on Early Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12417, https://doi.org/10.5194/egusphere-egu26-12417, 2026.
The increasing availability of high-resolution orbital imagery, particularly from the Context Camera (CTX), provides the potential to resolve Martian surface features with unprecedented detail. However, existing crater catalogs are predominantly complete only for diameters larger than 1 km, leaving a critical knowledge gap regarding the distribution of sub-kilometer craters. This study addresses the challenge of mapping these small-scale features (down to ~50 m) by introducing a semi-automated framework that synergizes Generative AI benchmarks with feature space cleaning.
To establish a robust methodology, we systematically benchmarked various automated annotation strategies. We compared emerging unsupervised Foundation Models (including pure vision segmentation models like SAM and Multimodal Large Language Models like Gemini 3, GPT-5, and Qwen-Image) against traditional transfer learning baselines pre-trained on existing Lunar or large-scale Martian catalogs. Our analysis reveals that while transfer learning suffers from domain shifts and resolution mismatches when applied to fine-grained CTX targets, multimodal models demonstrate superior zero-shot generalization capabilities. Through extensive prompt engineering experiments, we found that identifying 50m-scale targets requires geologically contextualized prompts rather than simple geometric descriptions, although this comes with increased label noise.
To mitigate this noise, we developed a "Feature Prototype" cleaning mechanism. Utilizing a self-supervised vision transformer (DINOv2), we mapped candidate detections into a feature space defined by positive prototypes of diverse small-scale crater morphologies and negative prototypes of typical generative errors. By filtering samples based on feature distance, we achieved robust noise reduction.
The resulting dataset comprises 16,000 image tiles sampled from the Mars equatorial region (±30°). Notably, this workflow extends reliable detection capabilities down to the ~50-meter scale, demonstrating a distinct advantage over transfer learning baselines and traditional unsupervised methods in resolving fine-grained topography. This study not only fills a significant gap in small-scale crater records but also establishes a rigorous benchmark for leveraging foundation model knowledge in precision planetary cartography.
How to cite: He, F., Liu, S., and Tong, X.: Generative Paradigms in Planetary Cartography: Benchmarking Foundation Models and Feature Prototype Filtering for Detecting 50m-Scale Martian Craters, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21347, https://doi.org/10.5194/egusphere-egu26-21347, 2026.
Posters virtual: Mon, 4 May, 14:00–18:00 | vPoster spot 4
EGU26-8953 | ECS | Posters virtual | VPS27
Exploring Martian Auroras Using EMM/EMUS and MAVEN/MAG: Insights into Ultraviolet Emissions and Crustal Magnetic Field InteractionsMon, 04 May, 14:06–14:09 (CEST) vPoster spot 4
Auroras are the result of charged particles interacting with a planetary atmosphere, driving several processes involving the excitation and ionization of molecules and atoms, leading to spectacular emissions. This study investigates Martian auroral emissions using observations from the Emirates Ultraviolet Spectrometer (EMUS) onboard the Emirates Mars Mission (EMM) Hope Probe. The analysis focuses on the oxygen emission lines at 130.4 nm and 135.6 nm, which are key diagnostics of electron precipitation. EMUS emission images are processed to compute brightness maps and intensity ratios, identify energetic regions using thresholding techniques, and generate histograms that characterize the spatial distribution and statistical properties of auroral energy across different regions of Mars.
In addition, data from the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, particularly magnetic field measurements from the MAG instrument, are used to correlate auroral observations with the Martian crustal magnetic field. By combining EMM ultraviolet observations with MAVEN magnetic field measurements, the study explores the relationship between auroral morphology, energy deposition, and underlying magnetic field topology.The goal is to assess how magnetic field geometry influences the localization and structure of auroral emissions and to better constrain the coupling between the solar wind, the Martian magnetosphere, and the upper atmosphere.
The combined analysis demonstates the potential of how combined EMM and MAVEN observations improves our understaing of of auroral processes on Mars and their implications for planetary atmosphere studies and space weather interactions.
How to cite: Alblooki, S. and Atri, D.: Exploring Martian Auroras Using EMM/EMUS and MAVEN/MAG: Insights into Ultraviolet Emissions and Crustal Magnetic Field Interactions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8953, https://doi.org/10.5194/egusphere-egu26-8953, 2026.
EGU26-12992 | ECS | Posters virtual | VPS27
Integrated Micro to Nano-Scale Characterization of Hydrous Sulphate Mineral-Jarosite in Kachchh, Gujarat, India: Implication for MarsMon, 04 May, 14:09–14:12 (CEST) vPoster spot 4
The recent Martian exploration mission has provided substantial evidence for the presence of hydrous sulphate minerals, especially in the Gale Crater and Meridiani Planum. These findings are crucial for understanding the past climate, water activity, and geological history of early Mars. Studying the sulphate formation process, particularly jarosite, has become increasingly important. In this context, terrestrial analog sites with similar mineral deposits can serve as effective models for exploring and analyzing sulphate deposits in detail. The Matanomadh and Harudi formations of Kachchh, Gujarat, India, were chosen as Martian analog sites because they expose well-preserved, clay-rich jarosite layers that may help better understand paleo-environmental conditions during Martian alteration. Here, jarosite is found alongside grey carbonaceous shale, weathered basalt, and gypsum, typically appearing as lenses of variable width, interconnected veins, or veinlets. Pure jarosite samples were collected after detailed field studies from the Matanomadh and Harudi formations of Kachchh. Powdered samples were characterized using X-Ray Diffraction (XRD), High-Resolution Transmission Electron Microscopy (HR-TEM), Field Emission Scanning Electron Microscopy (FE-SEM), X-Ray Photoelectron Spectroscopy (XPS), and Elemental Analyzer-Isotope Ratio Mass Spectrometry (EA-IRMS) for sulfur isotope analysis. All XRD patterns were analyzed with the FullProf program using Rietveld refinement, employing the R-3m space group. The average a- and c-cell dimensions for jarosite were calculated as a = 7.3028 Å and c = 16.6376 Å. The XRD diffractogram displays a distinct peak at (006) at 2θ = 32.29°. FE-SEM images show that jarosite crystals have well-formed pseudohexagonal shapes with defined faces and edges. HR-TEM analysis indicates the dominance of sodium (Na), and elemental mapping confirms homogeneous grains. XPS analysis of jarosite revealed prominent peaks for Fe2p3/2 and S2p at approximately 713.4 eV and 169.9 eV, respectively. S2p peaks were also observed in the host shale rock. δ34S values for jarosite (-8.4 to -16‰) are close to values typical of supergene or steam-heated hydrous sulphates derived from pyrite or H2S oxidation. The cell dimensions obtained from XRD data agree with literature values, confirming the mineral as Natrojarosite. The peak position of the (006) reflection in natrojarosite differs from that of jarosite. In this sample group, iron (Fe) exists in the +3 oxidation state, as confirmed by XPS. Based on the presence of sulfur (S -1) peaks in the associated shale, it is inferred that shale may serve as a sulfur source for natrojarosite formation in the current study area under acidic, oxidizing conditions.
How to cite: Saha, N. and Majumdar, A. S.: Integrated Micro to Nano-Scale Characterization of Hydrous Sulphate Mineral-Jarosite in Kachchh, Gujarat, India: Implication for Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12992, https://doi.org/10.5194/egusphere-egu26-12992, 2026.
EGU26-14494 | Posters virtual | VPS27
Radical Terraforming of Mars and Planetary EngineeringMon, 04 May, 14:12–14:15 (CEST) vPoster spot 4
The radical terraforming of Mars was proposed in 2025 (LPSC2025, 1558.pdf) envisions bringing volatiles with a total mass of approximately 1019 kg from the Kuiper Belt to Mars. This would amount to approximately 1000 asteroids. Upon reaching Mars, these bodies will have velocities ranging from a few to a dozen or so km/s relative to the planet. The impact sites and their parameters will be controlled to some extent. This would be a unique opportunity to use these bodies to modify the surface of Mars. The goal of radical terraforming is also to create open water reservoirs and rivers. The planet's current topography makes these plans very difficult. Large elevation differences would lead to rapid concentration of water in a few low-lying areas. We show examples of possible stable zones that would provide habitable conditions for ecosystems from Earth. Another possibility of using impacts is the targeted transformation of minerals. Asteroids themselves contain not only water and volatile substances but also other compounds. Placing them in appropriate places can make the economy easier for future residents.
How to cite: Czechowski, L.: Radical Terraforming of Mars and Planetary Engineering, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14494, https://doi.org/10.5194/egusphere-egu26-14494, 2026.
