Keywords:

Eberswalde crater, aeolian bedforms, atmospheric circulation, environmental changes.

Introduction

Aeolian bedforms on Mars record past atmospheric circulation. Dune turnover times of tens to hundreds of thousands of years (Fenton and Richardson, 2001) mean that individual bedform generations can reflect the obliquity cycles that drove climate transitions during the Late Amazonian (Laskar et al., 2004). Where multiple generations are preserved and their relative ages established through stratigraphic superposition, successive wind regimes can be reconstructed. Eberswalde Crater (23.5°S, 326.5°E, ~65 km; fig. 1) contains a well-preserved Noachian fluvial delta (Malin and Edgett, 2003; Pondrelli et. al, 2008) whose complex topography interacts with atmospheric circulation, producing a diverse aeolian bedform record and making it a particularly informative site for studying regional wind regimes and local topographic effects.

Figure 1. Regional context of Eberswalde Crater (THEMIS infrared mosaic; inset: MOLA topography).

Data and Methods

Mapping was carried out in QGIS v3.40 using HiRISE images (~25 cm/px; McEwen et al., 2007), CTX mosaics (~6 m/px) as basemap (fig. 2), and DEMs from HiRISE stereo pairs (~1 m/px) for 8 areas (A–H); 7 areas (I–Q) used HiRISE 2D only. Each bedform crest was digitized manually; parameters include height, crest length, wavelength, sinuosity, wind direction, topographic influence, type, and generation. Four morphogenetic types (dunes, megaripples, barchan dunes, star dunes) and four generations (G1–G4, oldest to youngest) were identified through crosscutting relationships; 242 bedforms assignable by type but not by generation (ND category), due to absence of crosscutting relationships or multidirectional morphology. Wind directions were reconstructed from stoss–lee side asymmetry (certain) or crest orientation and context (probable); multidirectional bedforms excluded. Present-day winds were extracted from MCD v6.1 (Forget et al., 1999; Millour et al., 2018) at Eberswalde for four solar longitudes.

Figure 2. Locations of all 15 study areas on CTX mosaic. Purple: HiRISE stereo DEM images (A–H); pink: HiRISE 2D images (I–Q). Note: the same letters without subscripts correspond to the same area and morphological location (excluding Area G).

Results

1,923 bedforms were mapped across 15 study areas in five morphological depositional settings: delta, basin, drainage basin, source area, and crater plateau. G2 dominates (913, 58%), followed by G1 (618, 40%), G4 (85, 5%), and G3 (36, 2%). Nineteen stratigraphic relationships were identified. The G1→G2 transition is confirmed in 12 of 15 areas (fig. 3), demonstrating a regional atmospheric event. The full G1→G2→G3→G4 sequence is documented in Area F (fig. 3G); G3 also cuts G2 in Area M (fig. 3F); in Area E (fig. 3E), G3 cuts G1 without intervening G2. In Area H (fig. 3H), G4 probably overlies star dunes (ND), implying the multidirectional regime pre-dates the G4 easterly phase.

Inter-area temporal correlation relies on wind direction coherence rather than direct stratigraphic continuity, following standard practice in Martian aeolian stratigraphy (Silvestro et al., 2012). Wind directions reveal a systematic anticlockwise rotation (fig. 4, 5): G1 shows SE–S orientation (mean ~145–163°); G2 is bimodal SW to E (mean ~178°); G3 and G4 are dominated by easterly directions (~90°). The MCD annual mean (161° SSE) matches the G1 regime (fig. 6); the SSE/NW bimodal pattern provides a physical basis for star dune formation, locally amplified by delta lobe and crater rim topography (Edgett and Blumberg, 1994; Courrech du Pont et al., 2024). The G3/G4 easterly direction is absent from all MCD seasons, suggesting local topographic channelling or a circulation shift. Bedform size varies depending on location morphological position: delta areas yield the largest G1 bedforms (~252 m mean crest length), consistent with abundant reworked fluvio-lacustrine sediment; the source area (M) shows anomalously small G2 megaripples (23.2 m), reflecting high sediment flux; and crater plateau areas show reduced sizes consistent with lower sediment availability.

Figure 3. Stratigraphic superposition: A-B-C. G2 cuts G1; D. barchan dunes cut G2; E. G3 cuts G2; F. G3 cuts G1; G. full sequence G1→G2→G3→G4; H. G4 overlies star dunes. Yellow circle: key crosscutting contact..

Figure 4. Rose diagrams of transport directions (G1–G4). Anticlockwise rotation from SE/S (G1) through SW/E (G2) to E (G3/G4) is visible.

Figure 5. Comparative rose diagram showing the anticlockwise rotation.

Figure 6. MCD v6.1 seasonal winds (solid) vs. bedform generation means (dashed). G3/G4 easterly direction (~90°) is absent from all seasons.

Discussion and Conclusions

The anticlockwise rotation from SE/S (G1) through SW/E (G2) to E (G3/G4) is consistent with an obliquity-driven weakening of the meridional Hadley circulation and strengthening of the zonal easterly component. We tentatively correlate G1 with the pre-ice-age Late Amazonian (>2.1 Ma), when higher obliquity sustained vigorous meridional winds; G2 with the Martian ice age (~2.1–0.4 Ma), when a transitional wind regime prevailed; and G3/G4 with the post-ice-age interglacial (<0.4 Ma), when declining obliquity weakened the Hadley cell and easterly winds became dominant (Laskar et al., 2004; Head et al., 2003) This interpretation is analogous to aeolian sequences at Utopia Planitia (Liu et al., 2023) and supports obliquity variations as the primary driver of Late Amazonian atmospheric changes. The fossil delta adds topographic complexity and promotes bedform preservation, and Eberswalde preserves a wind record spanning ~2 Ma of Martian atmospheric circulation history.

References

Courrech du Pont et al. (2024), Earth-Sci. Rev. 255.

Edgett & Blumberg (1994), Icarus 112. https://doi.org/10.1006/icar.1994.1197

Fenton & Richardson (2001), JGR 106. https://doi.org/10.1029/2000JE001407

Forget et al. (1999), JGR 104, 24155–24175.

Head et al. (2003), Nature 426. https://doi.org/10.1038/nature02114

Laskar et al. (2004), Icarus 170. https://doi.org/10.1016/j.icarus.2004.04.005

Liu et al. (2023), Nature 620. https://doi.org/10.1038/s41586-023-06206-1.

Malin & Edgett (2003), Science 302. doi:10.1126/science.1090544.

McEwen et al. (2007), JGR 112. doi:10.1029/2005JE002605. E05S02.

Millour et al. (2018), ESAC Workshop.

Pondrelli et al. (2008), Icarus 197, 429-451.

Silvestro et al. (2020), JGR Planets. doi:10.1029/2020JE006446.

Silvestro et al. (2012), E.S.P.L.37, 1424–1436. https://doi.org/10.1002/esp.3286

Acknowledgements

This study was carried out within the Space It Up project funded by the Italian Space Agency, ASI, and the Ministry of University and Research, MUR, under contract n. 2024-5-E.0 - CUP n. I53D24000060005

How to cite: Piscopo, A., Pondrelli, M., Marinangeli, L., and Cavalazzi, B.: Analysis of aeolian bedforms at Eberswalde crater and preserved delta, Mars: a possible record of Late Amazonian wind regimes transition, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-254, https://doi.org/10.5194/epsc2026-254, 2026.

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Mars aeolian studies commonly compare mapped surface features such as dunes, ripples, and wind streaks with atmospheric model outputs in order to infer formative wind regimes. In practice, these comparisons are often based on only the strongest modelled winds, typically the upper 5% of wind speeds, under the assumption that sediment transport and streak formation are dominated by rare high-wind events. However, the extent to which this assumption is universally valid across different Martian environments remains poorly tested. Here, we investigate whether restricting analyses to the top 5% of modelled winds provides the most representative comparison with observed aeolian orientations across three contrasting regions on Mars: Mawrth Vallis, Ares Vallis, and Syrtis Major.

We use mesoscale simulations produced with the Laboratoire de Météorologie Dynamique Mars Mesoscale Model [1], forced using the Open access to Mars Assimilated Remote Soundings (OpenMARS) assimilated atmospheric boundary conditions [2], and compare modelled wind direction distributions against mapped dune slip faces and wind streaks derived from CTX imagery [3]. We quantify correspondence between observed and modelled directional distributions using Earth Mover’s Distance metrics [4]. Our results suggest that the common approach of focusing on the strongest modelled winds is broadly appropriate at two of the study sites, where the upper tail of the wind distribution provides the closest agreement with mapped aeolian orientations. However, results from the third site reveal a substantially more complex relationship between surface feature orientation and atmospheric circulation. The complexity of the local environment appears to exert a stronger control on the observed aeolian record, implying that site-specific atmospheric dynamics must be considered when interpreting surface wind indicators.

These findings suggest that while threshold-based approaches remain useful, applying a universal “fastest winds create the landforms” assumption across Mars may not always be appropriate, oversimplifying the relationship between atmospheric circulation and aeolian landscape evolution.

[1] Spiga, A. and Forget, F. (2009) JGR-Planets, 114(E2) [2] Holmes, J. A. et al. (2020) Planet. Space Sci., 188, 104962 [3] Dickson, J. L. et al. (2024) Earth and space Sci., 11(7) [4] Rubner, Y., Tomasi, C., and Guibas, L. J. (2000) Int. J. Comput. Vis., 40(2), 99–121.

How to cite: Patel, M. R., Favaro, E. A., Rajendran, K., and Holmes, J. A.: Are Mars Aeolian Features Controlled by the Strongest Winds? A Mesoscale Modelling Investigation, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-1134, https://doi.org/10.5194/epsc2026-1134, 2026.

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Introduction

Olympia Undae, in the north circumpolar region of Mars, is one of the largest dune fields on the planet and a key site for investigating the interaction between aeolian transport, sediment availability and local relief. Dune morphology in this region records both the regional circumpolar circulation and local perturbations caused by topographic obstacles [1,2]. In addition to its dune field, Olympia Undae contains non-impact landforms including Simple Domes (SD) and Irregular Structures (IS), which locally modify airflow and sediment redistribution [3–5] (Fig. 1). These edifices provide natural markers to analyse how topography controls dune distribution and inferred near-surface wind regime.

Data and methodology

This study focuses on the 6 Simple Domes and 5 Irregular Structures identified in Olympia Undae [3–5]. The analysis combines MOLA topography, HRSC/MOLA digital terrain models, orbital imagery, and GIS-based morphometric analysis using tools such as JMARS [3–5]. Dune distribution on and around each structure was compared with local altitude and slope in order to evaluate the topographic control on sediment accumulation and mobility.

The methodology is based on a structured analysis of elevation (h) and slope (S) derived from HRSC/MOLA DEM data, organised on a spatial grid (latitude–longitude) (Fig. 2), allowing the extraction of morphometric gradients and their relationship with dune occurrence.

Two diagnostic parameters are defined and applied: the critical altitude and the limiting slope. The critical altitude corresponds to the elevation above which dunes become scarce or absent and is computed from altitude gradients (dh/dx) using percentile thresholds (typically absent and identify significant topographic transitions associated with changes in wind behavior. The limiting slope represents the maximum terrain inclination allowing dune mobility and is derived from slope distributions using a similar percentile-based approach. This value is defined by identifying from which slope values of moving dunes surfaces are usually uncommon under normal conditions [5].

Both parameters are calibrated using dune distribution and morphology, including crest orientation and dune type, and their spatial relationship with HRSC/MOLA-derived elevation and slope data, allowing a direct link between topographic forcing and inferred wind regime.

Results

The results show that dune distribution around the SD and IS of Olympia Undae is markedly asymmetric and strongly controlled by local topography. As expected, dunes preferentially accumulate on low-slope flanks and sheltered sectors, whereas summit areas and more exposed sectors tend to be dune-free or to show reduced sediment cover. This confirms that the edifices locally modify near-surface airflow and sediment transport pathways [5].

IS-01 is one of the catalogued Irregular Structures shown in Fig. 1 [3,4]. With an overall relief of approximately 423 m, it clearly illustrates this pattern (Fig. 3). Above an altitude of –4727.8 m, the presence of dunes decreases sharply, defining a critical threshold. The same structure shows a limiting slope of about 1.021° [5]. However, summit slopes are below 1°, indicating that the lack of dunes cannot be explained by slope alone. Instead, this is interpreted as the effect of wind interaction and turbulence over the summit, which prevents sediment accumulation, whereas the flanks favour belts of linear dunes [5].

Other edifices confirm that the topographic effect is systematic, although expressed differently according to morphology. In IS-04, the calculated values are –4742.2 m for critical altitude and 1.485° for limiting slope [5]. Because of its irregular shape and internal slope variability, part of the structure remains covered by dunes. Its surface includes linear dunes aligned NW–SE, barchans in transition to barchanoids, and curved dune patterns that suggest local variations in wind intensity and direction superimposed on the dominant circumpolar flow [1,2,5] (Fig 4).

The SD also records this coupling between topography and wind. In SD-01, transverse dunes, barchanoids and barchans occur on different sectors of the edifice. The main inferred wind direction is NW–SE, in agreement with the regional circumpolar circulation, while a secondary NE–SW component is indicated by oblique crests in the eastern and southern sectors [1,2,5]. The relief appears to promote sectorial sediment trapping and differential erosion.

Summary and Conclusions

The simple domes and irregular structures of Olympia Undae act as local topographic obstacles capable of reorganising dune distribution and modifying the local expression of the regional wind regime. The combined use of critical altitude and limiting slope provides a useful framework to identify where dunes can form and where sediment transport is inhibited by wind–topography interaction [5].

The observed asymmetries in dune occurrence, the concentration of mobile dunes below critical thresholds, and the contrast between exposed summit areas and sediment-rich flanks indicate that local relief exerts a first-order control on aeolian redistribution at the scale of individual edifices. The results support the interpretation that dune patterns around the SD and IS of Olympia Undae can be used to infer local atmospheric circulation in the Martian polar environment [1,2,5].

References

[1] Ewing, R. C., Peyret, A. P. B., Kocurek, G., and Bourke, M.: Dune field pattern formation and recent transporting winds in the Olympia Undae dune field, north polar region of Mars, J. Geophys. Res. Planets, 115, E08005, 2010.

[2] Rubanenko, L., Gunn, A., Pérez-López, S., Fenton, L. K., Ewing, R. C., Soto, A., and Lapôtre, M. G. A.: Global surface winds and aeolian sediment pathways on Mars from the morphology of barchan dunes, Nat. Astron., 7, 1037–1047, 2023.

[3] Sánchez-Bayton, M., Herraiz, M., Martin, P., Sánchez-Cano, B., Tréguier, E., and Kereszturi, A.: Morphological analyses of small and medium size landforms in Scandia Cavi and Olympia Undae, Northern Circumpolar Region of Mars, Planet. Space Sci., 210, 105389, 2022.

[4] Sánchez-Bayton, M., Herraiz, M., Martin, P., Sánchez-Cano, B., Tréguier, E., and Kereszturi, A.: Morphometric and topographic data of small and medium size landforms in the Northern Circumpolar Region of Mars, Data in Brief, 43, 108417, 2022.

[5] Sánchez-Bayton Sánchez, M.: Zona Circumpolar Norte de Marte: Análisis Físico y Morfológico de Estructuras Pequeñas y Medianas en Scandia y Olympia Undae mediante Datos de Sensores Remotos de ESA Mars Express, Mars Global Surveyor y Mars Reconnaissance Orbiter, PhD thesis, Universidad Complutense de Madrid, Universidad Complutense de Madrid, 2025.

How to cite: Sánchez-Bayton, M., Herraiz, M., Martin, P., Sánchez-Cano, B., and Kereszturi, A.: Topographic forcing of dune distribution and local wind regime around simple domes and irregular structures in Olympia Undae, Mars, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-218, https://doi.org/10.5194/epsc2026-218, 2026.

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 Introduction:

The Hadriacus Cavi are an ~50km long chain of up to 700 m deep depressions, located near the northern rim of Hellas Basin in Mars’ southern highlands¹. They are set between high relief mountains to the south, and lower, low relief sedimentary plains to the north. The Cavi themselves record successions of alternating pale and dark layers, probably deposited during the early to middle Noachian, that together are 100s of meters thick², and generally dip ~1° north-northwest³. Previous work by Skinner et. al. (2021) identified a layer within a 20 km² region in the western extent of the Cavi containing bedforms which they interpreted to be buried fluvial channels². It is currently unknown how widespread these channels are throughout the Cavi, or whether they occur in layers other than the one identified by Skinner et al., (2021). Investigating these unknowns will inform our understanding of the fluvial history of early Mars and may reveal more information about the possibility of a past ocean in Hellas basin⁴.

Methods:

We have used CTX (6m/pixel), HiRISE (25-50 cm/pixel) and CaSSIS (colour; ~4m/pixel) orbital images and Digital Elevation Models (DEMs) in a GIS-based approach. Using ortho-rectified images draped over a series of 1m/pixel HiRISE DEMs we have analysed the regional geology in 3D, creating linework to mark unit boundaries, fluvial structures and other features in the GIS. The wider sedimentary succession in the Cavi was documented, covering an area of ~500 km², extending into areas beyond that where fluvial structures were first identified². We have identified multiple potential fluvial structures across the Cavi, based on their morphology, texture and setting and have also documented distinct stratal packages and repeating tonal and textural patterns of strata that extend across the region. The dimensions of the potential fluvial structures and the strata that host them were measured, and we documented any internal structures visible in HiRISE images. We have also begun to measure the dip directions of the strata using 3D GIS tools and to make stratigraphical columns of key areas across the Cavi that will allow us to contextualise the different exposures and channel bearing units.

Preliminary results and interpretation:

We have identified that the fluvial channel deposits postulated by Skinner et al. (2021) extend both laterally and vertically across the Cavi and sit within at least three distinct sedimentary packages. Stratigraphically, these new channels occur both above and below the layer identified by Skinner et al. (2021). The layers are separated by tens to hundreds of metres vertically, and crop out in a series of brighter, steeply dipping cliffs (~40° ³) separated by darker, gently sloping terraces. That they crop out so far from each other stratigraphically suggests that, rather than a single continuous period of fluvial activity, the region experienced multiple episodes of fluvial activity and deposition.

Figure 1: Map of Hadriacus Cavi with inset globe of Mars for context. Yellow polygons indicate possible channel features, blue lines indicate inverted channels. Locations of figures 2 and 3 marked.

Between the fluvial periods, other types of deposition might have dominated, although it is possible that there are other fluvial features which are not currently. We note at least two types of deposit: i) generally flat-topped, curved-bottom features which we interpret as channel deposits²; ii) several examples of a series of dipping layers truncated by flat surfaces that conform to regional bedding at the top and bottom which we interpret as lateral accretion surfaces recording channel migration.

Figure 2: An oblique view of a section of cliff within the Cavi. A) image. B) image and markup denoting fluvial features and sedimentary layers. C) markup only.

Figure 3: An oblique view of a section of cliff within the Cavi. A) image. B) image and markup denoting locations of fluvial features and sedimentary layers. C) markup only.

The fluvial features are found predominantly in brighter layers and are more common to the west of the study region, though this may be due to higher quality exposures with less overlying cover-material. For the same reason, most channel forms are found in cliffs in the south of the Cavi, those in the north are obscured, shadowed and generally of lower relief than the cliffs to the south. To the east, the bottom of the Cavi pits reveal layers from higher parts of the stratigraphy than seen in the pits to the west, so some of the channel bearing layers (if present) are below ground in the east. We also note the presence of inverted channels in the landscape which occur at the same stratigraphical level as some channels seen in cross section. These can be found across the Cavi and tend to crop out at the same stratigraphical level as the ‘fluvial layer’ first identified by Skinner et al. (2021), supporting the idea that the channel forms are deposits from ancient river systems.

Preliminary conclusions:

We have studied a region more than 500 km² searching for fluvial channel forms. The channels we have identified are much more laterally extensive and crop out in more strata than those identified previously, being found across the entire 50 km long southern extent of the Cavi. This indicates that the fluvial system or systems which formed these features was more laterally extensive than previously described. One or more larger meandering fluvial systems would explain the diversity in channel form and the range in orientations of various channel forms that we see in the Cavi. Our observations point to either multiple periods of fluvial activity in this region or a long period of fluvial activity. These deposits indicate sustained deposition prior to the more recent processes that have since led to excavation of the Cavi.

References: [1] Smith, D. E. et al. (1999) Science, 284, 1495–1503. [2] Skinner, J.A. et al. (2021) Icarus. 354, 114071. [3] Skinner, J.A. et al., (2017) 48^th LPSC, p.2694  [4] Wilson, S.A. et al. (2007) JGR, 112, E8

How to cite: Losekoot, A., Balme, M. R., Fawdon, P., and Coe, A. L.: The Fluvial History of Hadriacus Cavi, Mars, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-478, https://doi.org/10.5194/epsc2026-478, 2026.

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The Perseverance rover landed on Mars in 2021 in Jezero crater, which contains evidence of an ancient lake. Deltaic deposits are preserved at the inlet of this paleolake, and connected to an ancient fluvial network via a valley dissecting the crater rim, named “Neretva Vallis” (Figure 1a). Between sols (i.e., Martian days) 1169 and 1244 of the mission (June to August 2024), the rover explored light-toned deposits in Neretva Vallis, informally named the “Bright Angel formation” (Figure 1b). This formation attracted significant interest after the discovery of rocks interpreted as fluvio-lacustrine mudstones containing organic compounds, as well as reduction spots (mm-scale nodules and redox fronts enriched in Fe-phosphates and Fe-sulfides) interpreted as potential biosignatures (Hurowitz et al., 2025).

Figure 1. Context for the Bright Angel formation exposed at the Bright Angel and Masonic Temple localities. (a) Colour and Stereo Surface Imaging System (CaSSIS; Thomas et al., 2017), Context Camera (CTX; Malin et al., 2007) and (b) High Resolution Imaging Science Experiment (HiRISE; McEwen et al., 2007) enhanced-color composite basemaps over Western Jezero crater.

Here, we characterize the elemental and mineralogical composition of the Bright Angel formation using complementary datasets from Perseverance instruments to further constrain past water-rock interactions and diagenetic evolution. Our analysis integrates: elemental composition from SuperCam Laser-Induced Breakdown Spectroscopy (LIBS; Wiens et al., 2020; Maurice et al., 2021) and from the Planetary Instrument for X-Ray Lithochemistry (PIXL; Allwood et al., 2020), as well as mineralogy from SuperCam Visible and near-infrared reflectance, SuperCam Raman spectroscopy (Wiens et al., 2020; Maurice et al., 2021), and deep ultraviolet Raman spectroscopy using the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC; Bhartia et al., 2021) instrument.

We confirm that most of the stratigraphy of the exposed bedrock consists of mudstones with a composition distinct from previously investigated formations at Jezero crater, which exhibited mafic to ultramafic compositions. In contrast to other units, the Bright Angel formation is enriched in Al-silicates and Ca-sulfates, broadly lacks olivine and its alteration products, and exhibits high Al and very low Mg contents. Preliminary interpretation of the associated mineral assemblages suggest diverse and prolonged fluid activity, consistent with enhanced diagenesis and hydrothermal processes:

• Elevated Chemical Index of Alteration values (up to ~80) indicate open-system weathering, either acquired in situ or inherited from pre-deposition processes
• The co-occurrence of illite (and/or a mixed-layer illite/aluminous smectite phase) and fluorite suggests hydrothermal processes at moderately elevated temperatures (>~85°C), assuming that these minerals are not detrital. This warm-temperature scenario could favor an abiotic origin for sulfate reduction in the reduction spots; however, these temperatures may have occurred independently of sulfur reduction, leaving the biogenic hypothesis still possible
• Jarosite and akaganeite in the upper stratigraphy attest to episodic circulation of oxidizing and saline fluids

Overall, the degree of alteration and diagenesis recorded by the Bright Angel formation may be inconsistent with a late post-delta origin, leaving open the possibility that it represents one of the oldest sedimentary units explored by Perseverance, preserving key constraints on Noachian aqueous environments.

References

• Allwood, A.C. et al., 2020. PIXL: Planetary Instrument for X-Ray Lithochemistry. Space Science Reviews 216, 134. https://doi.org/10.1007/s11214-020-00767-7
• Bhartia, R. et al., 2021. Perseverance’s Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) Investigation. Space Science Review 217, 58. https://doi.org/10.1007/s11214-021-00812-z
• Hurowitz, J.A. et al., 2025. Redox-driven mineral and organic associations in Jezero Crater, Mars. Nature 645, 332–340. https://doi.org/10.1038/s41586-025-09413-0
• Malin, M.C. et al., 2007. Context Camera Investigation on board the Mars Reconnaissance Orbiter. Journal of Geophysical Research: Planets https://doi.org/10.1029/2006JE002808
• Maurice, S. et al., 2021. The SuperCam Instrument Suite on the Mars 2020 Rover: Science Objectives and Mast-Unit Description. Space Science Reviews 217, 47. https://doi.org/10.1007/s11214-021-00807-w
• McEwen, A.S. et al., 2007. Mars Reconnaissance Orbiter’s High Resolution Imaging Science Experiment (HiRISE). Journal of Geophysical Research: Planets https://doi.org/10.1029/2005JE002605
• Thomas, N. et al., 2017. The Colour and Stereo Surface Imaging System (CaSSIS) for the ExoMars Trace Gas Orbiter. Space Science Reviews 212, 1897–1944. https://doi.org/10.1007/s11214-017-0421-1
• Wiens, R.C. et al., 2020. The SuperCam Instrument Suite on the NASA Mars 2020 Rover: Body Unit and Combined System Tests. Space Science Reviews 217, 4. https://doi.org/10.1007/s11214-020-00777-5

How to cite: Mandon, L., Mangold, N., Forni, O., Dehouck, E., Beck, P., Beyssac, O., Schröder, S., Phua, Y. Y., Hurowitz, J., Jones, A., Moreland, E., Clavé, E., Johnson, J., Fouchet, T., Manelski, H., Simon, J., Siljeström, S., Broz, A., Cousin, A., and Wiens, R.: Complex diagenetic history of organic-bearing sedimentary rocks in Neretva Vallis, Mars, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-356, https://doi.org/10.5194/epsc2026-356, 2026.

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Introduction: The Martian surface hosts an extensive geologic record indicative of widespread surface water during the 'valley network-forming era' (~3.7–3.5 Ga [1]). However, the climatic conditions required to incise the eponymous valley networks (VNs) remain poorly constrained. Proposed end-member solutions range from a long-lived 'warm and wet' climate with regular rainfall [2,3] to a 'cold and dry' climate with episodic snowmelt events [4,5]. The primary reason for this uncertainty is the wide range of unconstrained model parameters, exacerbated by a lack of quantitative ground-truth observations for model validation. In an attempt to compare VN erosion and climate conditions, previous studies have performed simple comparisons between model precipitation maps and the location of VNs [6,7]. However, these approaches have thus far led to poor spatial correlations. 

On Earth, the relationship between erosion and precipitation is well documented [8,9], albeit complex. However, quantitative precipitation-discharge-erosion models have seen limited application in deciphering the climate history of Mars. Here, we bridge the gap between climate simulations and geomorphic observations by integrating a mechanistic understanding of precipitation, runoff, and erosion. 

Methods: We use the hydrological toolbox WhiteboxTools [10] to run flow accumulation analysis: a simulation of the flow at each elevation grid cell to its steepest downslope neighbor. We use the digital elevation model (DEM) from the Mars Orbiter Laser Altimeter (MOLA; ~463 m/pixel [11]) to simulate flow directions. In the resultant flow accumulation map, each pixel represents the number of cells (or area) upstream of that point. Standard flow accumulation methods assume that precipitation is spatially constant. We refine this by using global precipitation maps from existing Mars climate model outputs [6,7,12,13] as weights (Fig. 1a-d). In the resulting 'precipitation-weighted' flow accumulation map (Fig. 1e), each pixel represents the cumulative precipitation rates of the upstream pixels, i.e., the discharge, Q, at each point, assuming no losses in conversion between precipitation and discharge. 

The relationship between erosion and precipitation on Earth is generally quantified through the stream power law [14], which states that the erosion rate is nonlinearly proportional to channel slope, S, and precipitation-sourced discharge Q, given a constant rock erodibility. Applying this to the Martian context, we compare our modeled global discharge maps to observed erosion, assuming steady erosion rates. We first measure channel slope, S, as the mean channel gradient between the second point upstream and second point downstream of each pixel, based on the MOLA DEM. Using a global map of eroded depths of VNs [15], we generate a planetwide, pixel-wise comparison of model discharge and channel slope, Q × S, to measured VN depth, d, along mapped stream lines (e.g., Fig. 2). Using this framework, we test the question: which climate models yield a good fit to the geomorphic record, as evidenced by positive correlations between observed eroded depths and a model's flow map (i.e., large valley depths, d, occur in areas of high model discharge, Q)? Through this intercomparison, we determine which climate scenarios within the explored parameter space (n = 91) yield the best fit. 

Results and Discussion: We find that the best-performing climate scenario [13] uses a pre-Tharsis paleotopography [16] and a global water inventory of 500 m global equivalent layer (GEL), achieving a Spearman’s rank correlation of ρ = 0.325 (Fig. 2). In climate model outputs, the Tharsis plateau typically causes westerly surface winds to be orographically lifted, leading to a 'rain shadow' east of Tharsis. Previous studies have speculated that poor agreement between precipitation from climate models and the surface record could be a result of Tharsis' rain shadow [6,13].  The growth of Tharsis likely induced a reorientation of Mars with respect to its spin axis, known as TPW. However, the timing of Tharsis' emplacement [17] and associated TPW (e.g., [18,19]) remains under debate. We find that 9 of the top 10 best-performing climate scenarios use a putative pre-Tharsis paleotopography. Our results thus suggest that the erosional record is most compatible with global VN incision prior to, or contemporaneous with, Tharsis' emplacement and associated TPW. 

References: [1] Fassett, C. I. et al. (2008) Icarus 195, 61–89. [2] Craddock, R. A. et al. (2002) JGR: Planets 107, 21-1-21–36. [3] Pollack, J. B., et al. (1987) Icarus 71, 203–224. [4] Wordsworth, R. et al. (2013) Icarus 222, 1–19. [5] Squyres, S. W. et al. (1994) Science 265, 744–749. [6] Wordsworth, R. D., et al. (2015) JGR: Planets 120, 1201–1219. [7] Steakley, K., et al. (2019) Icarus 330, 169–188. [8] Ferrier, K. L., et al. (2013) Nature 496, 206–209. [9] Marder, E. et al. (2023) Geology 51, 424–427. [10] Lindsay, J. B. (2016) Comp. & Geosci. 95, 75–84. [11] Smith, D. E. et al. (2001) JGR: Planets 106, 23689–23722. [12] Kamada, A. et al. (2020) Icarus 338, 113567. [13] Guzewich, S. D. et al. JGR: Planets 126, e2021JE006825. [14] Leonard, J. S. et al. (2021) JGR: Earth Surface 126, e2021JF006183. [15] Goudge, T. A., et al. (2021) Nature 597, 645–649. [16] Bouley, S. et al. (2016) Nature 531, 344–347. [17] Anderson, R. C. et al. (2001) JGR: Planets 106, 20563–20585. [18] Roberts, J. H. et al. (2007) Icarus 190, 24–31. [19] Matsuyama, I. et al. (2010) JGR: Planets 115, 2156-2202. 

Fig. 1(a)-(d) Global precipitation maps showing representative examples from [6,7,12,13]. (e) Modeled discharge map for a single Martian basin given the climate scenario in (d), overlaid on MOLA DEM. Blue outline shows a closed-basin lake which the VNs drain into. 

Fig. 2: Global comparison of observed valley erosion depth, d, against modeled discharge, Q, and channel slope, S, for the best-performing climate scenario [13]. Dashed line indicates line of best fit.

How to cite: Koh, Z.-W., Mitchell, W. H., Goudge, T. A., and Stucky de Quay, G.: Deciphering Early Mars Climate Conditions from Valley Network Erosion, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-608, https://doi.org/10.5194/epsc2026-608, 2026.

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Introduction: Extensive valley networks on Mars record some of the strongest evidence for ancient, sustained water flow on the surface [1]. Encoded in the morphology of these valley networks are quantitative constraints on paleohydrology and, by extension, habitable atmospheric conditions on early Mars [2]. These constraints include key metrics such as the volume of water required to carve them [3-5] and the aridity of the climate in which they formed [6,7]. Estimates of these values made in previous studies [3-5] rely on current valley morphology. However, valley morphologies are likely to have been altered since their formation (>3.5 Ga). In particular, impacts are destructive geomorphic events that can reshape landscapes [8]. Given the ubiquity and destructive nature of impacts, we hypothesize that: (i) the global record of valley networks is incomplete to a non-negligible extent, (ii) larger fluvial features (e.g., flood canyons) are preferentially preserved over smaller features (e.g., higher-order tributaries), and (iii) drainage densities on Mars may be reduced relative to their initial values.

These hypotheses are motivated by several observations. First, impacts can remove portions of valley networks and have the potential to erase extensive global features such as the ancient Martian shoreline [8]. Second, flood canyons represent 24% of the eroded volume on Mars, but only 3% of the valley length [9]. The disparity between spatial extent and total eroded volume suggests that large features could be more resistant to destruction than their shallower counterparts. Third, drainage densities of Martian valley networks resemble those formed in terrestrial arid climates [6]. Impact events may have reduced drainage density, influencing how we interpret the Martian paleoclimate.

We test these hypotheses by modeling the effects of impact events on valleys, reconstructing the pre-impact distribution of valley depths on Mars, and assessing alterations to eroded volume and drainage density. In addition to shedding light on how craters act as geomorphic agents, our results provide an improved understanding of the relative importance of catastrophic fluvial events, and how valley geometries reflect paleo-climate metrics.

Methods: To quantify the preservation of valley networks on Mars, we create a cratering model to simulate 3.5 billion years of impacts at Mars-like impact rates [10]. We begin with un-cratered (pre-impact) terrain that represents the Martian surface at the end of the valley forming era. We use terrain from an analog site on the Kohala Peninsula, in Hawaiʻi, which contains a wide variety of valley depths, ranging from meters up to a kilometer in depth.

For study site, we calculate the size distribution of impact craters expected on Mars since 3.5 Ga and randomly place them on the terrain. Impactors that form small craters compared to the valley they strike do less damage than a comparatively larger impact. For this reason, our model compares the relative size of the impact crater to the valley to determine whether the valley survives impacting.

We quantify how valley depths are modified in the cratering simulation and apply these results to the measured Martian valley depth frequency distribution to reconstruct the pre-impact frequency distribution. This distribution can then be used to reconstruct the total eroded volume at the end of the valley forming era.

Results: Our model placed ~2.510⁶ craters ranging from ~10 m to ~3,000 m on sample topography representing Mars. By comparing the topography of emplaced impact craters and valley depths, the model removed portions of the valley networks (Figure 1). In total, ~90% of valley pixels were classified as “destroyed” by the model. In particular, shallower portions of valleys were preferentially removed, supporting Hypothesis ii. For example, the presence of valleys in the western portion of the depth map in Figure 1d is reduced compared to the original depth map in Figure 1b, while the large canyons in the east are almost entirely preserved.

After reconstructing the pre-impact frequency distribution of valley depths, we calculate the global eroded volume of the valley networks to be ~19.5% greater than today’s measured eroded volume. While this is an increase in volume, compared to the overall scale of valley formation, it does not substantially alter our understanding of the extent of the valleys, contrary to Hypothesis i.

Finally, we found an overall decrease in drainage density. Tributaries are the primary drivers of drainage density but they are often shallower than the main trunk. If shallower features are indeed more vulnerable to destruction from impacts, it makes physical sense that drainage density would be reduced. This result supports Hypothesis iii.

Figure 1: Terrain before and after cratering simulation. (a) Kohala topography hillshade (DEM obtained from USGS); (b) Kohala pre-impact depth map; (c) impact craters (> 0.1 km); (d) Kohala post-impact depth map.  

Conclusion: Impact cratering modifies the preservation of Martian valley networks. This result modeled and used to reconstruct their pre-impact eroded volume. Our results show that preservation is depth dependent, with valleys deeper than ~200 m surviving billions of years of impacts, while shallower valleys are preferentially filled in or destroyed.

References:

[1] Hoke, M. R. T. et al. (2011), Earth and Planetary Science Letters, doi:10.1016/j.epsl.2011.09.053.
[2] Kite, E. S., and Conway, S. (2024), Nature Geoscience, doi:10.1038/s41561-023-01349-2.
[3] Rosenberg, E. N. et al. (2019), Icarus, doi:10.1016/j.icarus.2018.07.017.
[4] Rosenberg, E. N., and Head, J. W. (2015), Planetary and Space Science, doi:10.1016/j.pss.2015.08.015.
[5] Luo, W. et al. (2017), Nature Communications, doi:10.1038/ncomms15766.
[6] Carr, M. H., and Chuang, F. C. (1997), Journal of Geophysical Research: Planets, doi:10.1029/97JE00113.
[7] Seybold, H. J. et al. (2018), Science Advances, doi:10.1126/sciadv.aar6692.
[8] Baum, M. et al. (2022), Icarus, doi:10.1016/j.icarus.2022.115178.
[9] Goudge, T. A. et al. (2021), Nature, doi:10.1038/s41586-021-03860-1.
[10] Michael, G. G. (2013), Icarus, doi:10.1016/j.icarus.2013.07.004.

How to cite: Fanson, G., Morgan, A., and Stucky de Quay, G.: Quantifying the Effects of Impact Cratering on the Preservation of Martian Valley Networks, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-750, https://doi.org/10.5194/epsc2026-750, 2026.

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Studying Noachian times on Mars from both climate and geological evolution is crucial to characterize the habitable conditions of early terrestrial planets. To understand global planet dynamics in its earliest times, assessment of the ancient topography of Mars is required. However, current paleo-topography models are mostly based on idealized assumptions, large-scale isostatic corrections, or limited regional reconstructions, and do not rely on geological analyses to integrate stratigraphic information from buried Noachian terrains. Therefore, the impact of paleo-topography on the early climate and the formation of valley network remains poorly constrained.

For the first time, we present a global reconstruction of the Noachian paleo-surface using constraints from geological mapping (Tanaka et al., 2014), and craters central peaks mineralogy and morphology. First, we removed all the post-Noachian terrains from the Mars Obriter Laser Altimeter topography, including the lowlands from the north hemisphere, the Tharsis province, and post-Noachian impact craters with their inner sedimentary deposits. We also excluded Noachian surfaces extensively reworked by younger tectonic or volcanic events, like Valles Marineris, and the 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 lowest Noachian terrains and shallower post-Noachian deposits. We interpret phyllosilicates detections and massive morphologies as part of the Noachian excavated material, and mafic detections without hydrated minerals associated to layering as post-Noachian samples. By inferring the stratigraphic uplift for each Noachian impact, we provided constraints on the upper and lower bounds of the Noachian surface. The points are interpolated using spherical harmonics to produce smooth global envelopes, and the Noachian paleo-surface is defined by the spatial mean located between the lower and upper envelopes. We accounted for True Polar Wander caused by the formation of the Tharsis bulge, and included isostatic corrections.

Unlike previous products, the reconstructed Noachian paleo-surface links the surface with stratigraphic and mineralogical constraints. This provides a physically grounded estimate of Noachian topography rather than pure corrections of the current topography. Future work will bring new improvements by including the effect of the lithospheric flexure due to the surface loading. The final dataset is designed to be used as an input for modelling climate, hydrology, bathymetry, and landscape evolution through time. We expect our Noachian paleo-surface to allow even more realistic models of early Mars, and a robust reassessment of the environmental conditions during the formation of valley networks.

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., Salles, T., and Arnould, M.: Reconstructing the Noachian paleo-surface of Mars, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-990, https://doi.org/10.5194/epsc2026-990, 2026.

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Abstract

Understanding the hydrological evolution of early Mars is essential for interpreting geomorphological evidence of past liquid water, including valley networks, paleolakes, sedimentary deposits and possible northern oceans (for a review see Carr and Head, 2010). While Global Climate Models (GCM) can simulate atmospheric circulation and precipitation/evaporation patterns, they remain computationally limited to study climatic timescales. On the other hand, hydrological models generally rely on prescribed climatic conditions or are applied at regional scale. Because of this, the coupled long-term evolution of Martian climate and hydrology remains poorly understood.

Here we present a coupled climate-hydrology framework based on the Generic Planetary Climate Model (PCM; see the wiki in the references) and the Planetary Evolution Model (PEM, Clément et al., 2026). The PEM is designed to simulate the long-term evolution of surface reservoirs by asynchronous coupling with the PCM. The PEM evolves the long-term climate state from annual tendencies periodically provided by the PCM which computes the full climate physics. New PCM integrations are triggered when the evolving state deviates significantly from the climatic conditions under which the tendencies were derived. This strategy reduces computational cost and bridges the gap between detailed short-term climate simulations and planetary-scale long-term evolution.

The PEM includes a global high-resolution hydrology model (Gauvin et al., 2026) that evolves perennial liquid water reservoirs on the surface (e.g., lakes and oceans). This module computes the formation, disappearance, overflow and merging of lakes according to topography and PCM precipitation/evaporation tendencies. The resulting perennial water distribution is given back to the PCM to update the tendencies, allowing climate and hydrology to interact iteratively.

This work aims to explore how climatic forcing controls the spatial organization and hydrological connectivity of perennial surface water reservoirs on early Mars. As a first application, we consider idealized simulations using prescribed climate scenarios to analyze how precipitation/evaporation patterns influence the redistribution, persistence and connectivity of lakes and runoff systems. We investigate the role of topography in the stability of precipiation-fed reservoirs and runoff-fed reservoirs as well as the transition between isolated lacustrine systems and regionally connected drainage networks. Our results provide key insights into the climate scenarios required to reproduce the fluvial features observed on Mars (e.g., Barnhart et al., 2009; Carr and Head, 2010; Hoke et al., 2011).

This study represents a first demonstration of the PCM-PEM hydrology coupling strategy. Ultimately, this framework will provide a new tool to investigate the co-evolution of climate, hydrology and geomorphology on Mars over geological timescales.

References

Barnhart, C. J., Howard, A. D., and Moore, J. M. (2009). Long‐term precipitation and late‐stage valley network formation: Landform simulations of Parana Basin, Mars. Journal of Geophysical Research: Planets, 114(E1). https://doi.org/10.1029/2008JE003122.

Carr, M. H., and Head, J. W. (2010). Geologic history of Mars. Earth and Planetary Science Letters, 294(3–4), 185–203. https://doi.org/10.1016/j.epsl.2009.06.042.

Clément, J.-B., Forget, F., Vos, E., Lange, L., and Millour, E. (2025). Mars Through Time International Conference, 40.

Gauvain, A., Forget, F., Turbet, M., Clément, J.-B., Lange, L., and Vandemeulebrouck, R. (2025). A Global High-Resolution Hydrological Model to Simulate the Dynamics of Surface Liquid Reservoirs: Application on Mars, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2025-4992.

Hoke, M. R. T., Hynek, B. M., and Tucker, G. E. (2011). Formation timescales of large Martian valley networks. Earth and Planetary Science Letters, 312(1-2), 1-12. https://doi.org/10.1016/j.epsl.2011.09.053.

Wiki of the Generic Planetary Climate Model (PCM) online at https://lmdz-forge.lmd.jussieu.fr/mediawiki/Planets/index.php/Main_Page.

How to cite: Clément, J.-B., Gauvain, A., Metz, C., Forget, F., and Turbet, M.: A coupled climate-hydrology model for the long-term planetary evolution of surface water reservoirs on early Mars, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-1071, https://doi.org/10.5194/epsc2026-1071, 2026.

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Introduction

Mars’ Amazonian period (3 Gyr to present) is thought to have been cold and hyperarid, with a limited role of liquid water in modifying the surface. Mars’ mid-latitude regions host thousands of buried glaciers (termed ‘viscous flow features’), which formed within the last 10s-100s Myr, during the mid-to-late Amazonian period [e.g., 1]. These glaciers are thought to have been deposited by snowfall during Martian ‘ice ages’ driven by cyclical variations in Mars’ orbital obliquity. It has long been assumed that the glaciers have remained predominantly cold-based under cold Amazonian climate conditions. A small number of eskers (ridges of glaciofluvial sediment deposited in ice-confined meltwater tunnels) extending from glaciers in the Phlegra Montes and Tempe Terra regions [e.g., 2-4] have been attributed to rare, spatially restricted subglacial melting of their parent glaciers, driven by transient, localized geothermal heating events. This is consistent with their locations within glaciated tectonic grabens in major volcano-tectonic provinces.

Observations and interpretations

Here, we present two key advances based on observations from orbital image and elevation datasets [5]. First, we identify three additional eskers associated with glaciers in Tempe Terra, which, when combined with three identified by previous studies [3,4], indicate regionally widespread occurrences of Amazonian subglacial melting distributed along a 650 km long mountain chain in Mars’ northern mid-latitudes.

Second, two of the newly identified eskers in Tempe Terra are associated with a landsystem consistent with meltwater drainage into a subglacial palaeolake (37.44°N, 86.42°W). The landsystem comprises two major viscous flow features (debris-covered glaciers), two landforms interpreted as eskers, an esker-terminal fan, subglacial channels, a medial moraine, and a quasi-flat-topped deposit interpreted as glaciofluvial sediments deposited in the subglacial lake cavity [5]. It also contains landforms consistent with postglacial erosion and slumping. Impact crater size-frequency distributions on the surfaces of the two major debris-covered glaciers return a minimum age of 130 Myr (late Amazonian). Considering uncertainties, and that the glaciers have retreated to expose the eskers and subglacial palaeolake deposits, we cautiously estimate that esker formation and meltwater drainage into the palaeolake occurred ~130 Myr to 1 Ga (mid-to-late Amazonian) [5].

Implications

The implications of our observations are twofold. First, evidence for at least six occurrences of subglacial melting evidenced by eskers distributed along a 650 km-long mountain chain in Tempe Terra [3-5] likely necessitates a much more spatially extensive heat source than previously expected (e.g., a geothermal hotspot and/or regional climate change), within the last 100s Myr to 1 Gyr.

Second, the landsystem of which two of these eskers are a part implies that formerly thicker and more extensive Amazonian mid-latitude ice masses on Mars were capable of supporting subglacial lakes. Glaciers in Mars’ mid latitudes are prime targets for next-generation missions aiming to search for life [e.g. 6]. Subglacial palaeolake deposits proximal to these glaciers, which have been exposed by ice retreat, would represent high-priority science targets for such missions. Subglacial lakes on Earth support microbial ecosystems under extreme conditions [7], and palaeolake deposits have high potential for preserving biosignatures in the geologic record [8]. Hence, our discovery should motivate an extensive search for glacial palaeolake deposits across Mars’ mid latitudes as an important new class of exploration targets.

References

[1] Levy et al. 2014. Geophys. Res. Lett

[2] Gallagher and Balme 2015 Earth Planet Sci. Lett.

[3] Butcher et al. 2017 JGR Planets.

[4] Woodley et al. 2022 Icarus.

[5] Butcher et al. 2026 In Review.

[6] National Academies of Science Engineering and Medicine 2023 Origins, Worlds, and Life: Planetary Science and Astrobiology in the Next Decade

[7] Christner et al. 2014 Nature

[8] Summons et al. 2017 Astrobiology

How to cite: Butcher, F. E. G., Arnold, N. S., Johnsson, A., Davis, J. M., Woodley, S. Z., Clark, C. D., Ely, J. C., Gallagher, C., Balme, M. R., Lewis, S. R., Livingstone, S. J., and Storrar, R. D.: Candidate subglacial palaeolake deposits associated with Amazonian-aged debris-covered glaciers and eskers in the mid-latitudes of Mars, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-232, https://doi.org/10.5194/epsc2026-232, 2026.

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How to cite: Acharya, P. (. and Calvin, W.: Mapping Albedo Change Across the South Polar Perennial Cap: A Multi-Year MARCI Analysis , Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-600, https://doi.org/10.5194/epsc2026-600, 2026.

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Introduction: On Mars, various geomorphological and geological processes leave behind distinct morphological evidence on the surface, providing insights into Mars's history (Carr and Head, 2010). However, the understanding of the origin of such features is often perplexing and challenging, especially when different geological processes are interlinked, reinforced, or modified through interactions over time. Various hypotheses and studies exist connecting lava/magma interactions with water and subsurface ice to the origins of volcanic features in general, such as Volcanic Rootless Cones (VRCs) (Edwards et al., 2012; Hamilton et al., 2011; Marcucci et al., 2017; Pieterek and Jones, 2026). Though connecting lava cum impact crater ejecta materials with surface ice melting for the formation of sinuous discontinuous morphological features remains unexplored and not characterised properly on the surface of Mars. This study identifies such features to the south of Daedalia Planum and involves 1) the geomorphic mapping, 2) regional geomorphic characterisation of the landforms, 3) the chronology of geomorphic units and age dating of rampart craters, 4) Mineralogical analysis of CRISM tiles, and 5) Interconnecting inferences of the morphological features with various geomorphic processes observed.

Data and Methods: In this study, the global high-resolution MRO-CTX mosaic (V01 release) images (Dickson et al., 2024), HiRISE (McEwen et al., 2007), ExoMars TGO-CaSSIS color cubes (Thomas et al., 2017), and MO-THEMIS Day/Night images (Christensen et al., 2004) were used for morphological analysis. The MRO-CRISM Hyperspectral TRDRs tiles (Murchie et al., 2007) were utilized for mineralogical analysis, while the MGS-MOLA (Smith et al., 2001), MEX-HRSC (Jaumann et al., 2007), and CaSSIS DTMs (Thomas et al., 2017) were used for topographical analysis.

Results and discussions: Daedalia Planum, predominantly known for its lava flows (Giacomini et al., 2012), also preserves well-documented glacial deposits (Schon and Head, 2012). We observed the presence of layer ejecta or Rampart craters, and the glacial evidence, such as Lineated Valley Fills (LVFs), Ring Mold craters (RMCs), Pitted terrain patterns, ice-sublimation scarps within them, provides substantial evidence for subsurface ice presence in the region, along with other surface processes (Mangold, 2011). Interestingly, such sinuous features are more often found in the proximity of layered ejecta craters and short-lived wide fluvial channels within the region of interest encompassing three volcanic Mons and episodes of lava flows. Among those features within the same volcanic ice interactions mapped unit, we observe the presence of possible Volcanic Rootless Cones (Pieterek and Jones, 2026) in the southern extent of the study area, emphasizing more the role of lava and subsurface ice interactions. A localised presence of an inverted fluvial channel gives more clues on the past water activity (Liu et al., 2021), and the role of differential erosion processes of the indurated channel material owing to the lava-filled induration mechanism (Burr et al., 2010), provided its proximity to the Mons. The Chronology of volcanic ice interaction units indicates a Late Noachian to Early Hesperian period, possibly linking either to ancient (sub)surface ice most likely to have been present at high altitudes during high obliquity cycles (Wordsworth et al., 2013), and age dating of rampart craters reveals 3.4 Gya, further supporting the evidence of potential buried ice layers (Boyce and Mouginis-Mark, 2025). In addition to these, the CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) mineralogical analysis of the rampart crater wall shows an active H₂0 ice spectral signature as per spectral parameters of (Viviano et al., 2014; Harish et al., 2020), emphasizing the ice/frost activity in the region. Further extended CRISM mineralogical analysis in the intra-crater deposits reveals the presence of phyllosilicates, precisely the hydrous mineral Mg-smectite spectral signature, which substantiates strong aqueous activity.

Conclusion: The morphological record of these interactions preserved in various morphological processes, glacio-volcanic landforms, lava-filled plains, and intra-crater deposits offers a critical understanding of Early Mars to the present. Thus, delivering new insights on interactions of Ice, lava, or impact ejecta-driven surface morphology on Mars.

Acknowledgement: This work has been developed under the ASI-INAF agreement n. 2024-40-HH.0

References:

Boyce, J. M. and Mouginis-Mark, P. J.: Icarus, 425, 116336, doi:10.1016/j.icarus.2024.116336, 2025.

Carr, M. H. and Head, J. W.: Earth Planet. Sc. Lett., 294, 185–203, doi:10.1016/j.epsl.2009.06.042, 2010.

Christensen, P. R., et al.: Space Sci. Rev., 110, 85–130, doi:10.1023/B:SPAC.0000021008.16309.94, 2004.

Dickson, J. L., et al.: Earth Space Sci., 11, e2024EA003555, doi:10.1029/2024EA003555, 2024.

Edwards, B., et al.: J. Geophys. Res., 117, 2011JB008985, doi:10.1029/2011JB008985, 2012.

Giacomini, L., et al.: Icarus, 220, 679–693, doi:10.1016/j.icarus.2012.06.010, 2012.

Hamilton, C. W., et al.: J. Geophys. Res., 116, E03004, doi:10.1029/2010JE003657, 2011.

Jaumann, R., et al.: Planet. Space Sci., 55, 928–952, doi:10.1016/j.pss.2006.12.003, 2007.

Liu, Z., et al.: Earth Planet. Sc. Lett., 562, 116854, doi:10.1016/j.epsl.2021.116854, 2021.

Mangold, N.: Geomorphology, 126, 1–17, doi:10.1016/j.geomorph.2010.11.009, 2011.

Marcucci, E. C., et al.: Bull. Volcanol., 79, 89, doi:10.1007/s00445-017-1176-y, 2017.

McEwen, A. S., et al.: J. Geophys. Res., 112, E05S02, doi:10.1029/2005JE002605, 2007.

Mouginis‐Mark, P. J. and Baloga, S. M.: Meteorit. Planet. Sci., 41, 1469–1482, doi:10.1111/j.1945-5100.2006.tb00430.x, 2006.

Murchie, S., et al.: J. Geophys. Res., 112, E05S03, doi:10.1029/2006JE002682, 2007. [1]

Pieterek, B. and Jones, T. J.: npj Space Explor., 2, 15, doi:10.1038/s44453-026-00031-2, 2026.

Schon, S. C. and Head, J. W.: Earth Planet. Sc. Lett., 317–318, 68–75, doi:10.1016/j.epsl.2011.09.005, 2012.

Smith, D. E., et al.: J. Geophys. Res., 106, 23689–23722, doi:10.1029/2000JE001464, 2001.

Thomas, N., et al.: Space Sci. Rev., 212, 1897–1944, doi:10.1007/s11214-017-0421-1, 2017.

Viviano, C. E., et al.: J. Geophys. Res.-Planets, 119, 1403–1431, doi:10.1002/2014JE004627, 2014.

Weiss, D. K. and Head, J. W.: Icarus, 233, 131–146, doi:10.1016/j.icarus.2014.01.038, 2014.

Wordsworth, R., et al.: Icarus, 222, 1–19, doi:10.1016/j.icarus.2012.09.036, 2013.

Fig 1: The Geomorphic Map of the study area, Daedalia Planum, Mars.

Fig 2: The possible morphological evidence of Ice, lava, and impact ejecta interactions

Fig 3: Some of the glacial evidence observed: Ring Mold Craters (RMCs) on Lineated Valley Fill (LVF) within a crater in the study area.

Fig 4: H₂O ice spectra observed on a rampart crater ejecta

How to cite: Umar Baig, T., Bertoli, S., Re, C., Tullo, A., Cremonese, G., Baschetti, B., and Costa, N.: New insights on interactions with Ice, lava, and impact ejecta in Daedalia Planum, Mars, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-1236, https://doi.org/10.5194/epsc2026-1236, 2026.

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References:  [1] Thiessen F. et. al. (2024) Met. Soc. 2024, Abstract #6173 [2] Thiessen F. et. al. (2024) 55^th LPSC, #1208 [3] Thorpe M. T. et al. (2025), 56th LPSC, #2109 [4] Velbel et al. (2026), 57^th LPSC, #1751 [5] Ciocco et al. (2025), EPSC-DPS, #1445, [6] Willcocks et al. (2026), 57^th LPSC, #1428.

How to cite: Thiessen, F., Sefton-Nash, E., Ciocco, M., Krzesinska, A., Werner, S., Mueller, A., Harrington, A., Thorpe, M., Velbel, M., Griffiths, L., Mikesell, D., Smith, A., Hays, L., and Kminek, G.: Updates on the Mars Missions Analogue Sample Library, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-502, https://doi.org/10.5194/epsc2026-502, 2026.

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Introduction: The MGS/MOLA topography data of Mars shows a dichotomy between the highly craterised and elevated southern hemisphere compared to the northern smoother and low-altitude terrains¹ (Fig. 1A). Many morphological and mineralogical clues today support the existence of a past liquid water ocean in the northern hemisphere of Mars, such as a large sedimentary formation in the North^2-3; possible paleo-shorelines following the topographic dichotomy between the two hemispheres^4-5; a network of fluvial valleys oriented northward^6-7; deposits of an ancient tsunami caused by an impact⁸ as well as hydrated mineralogy^9-12. However, the spatio-temporal extent of this ocean remains poorly constrained. It is argued that such an ocean could have existed until at least 3 Gyr in Mars’ history¹³. A recent study highlights the morphological resemblance between Olympus Mons, the largest volcano of the solar system on Mars located at the dichotomy, and terrestrial volcanic islands (Canary, Azores, Cape Verde, Hawaii…) today still surrounded by the ocean, which display a 15° basal scarp average slope break¹⁴. Could Olympus Mons once have been a volcanic island? Here we further explore this hypothesis by studying the mineralogy and morphology of Olympus Mons using hyperspectral and high resolution imagery data.

Methodology: Here we aim to determine if hydrated minerals can be found around the edifice of Olympus Mons, and thus imply a past interaction of volcanic rocks with water. We used hyperspectral data from the MRO/CRISM spectrometer¹⁵ to get insights on the mineralogy of Olympus Mons’ basal scarp (Fig. 1B). Pre-processing¹⁶ was followed by a photometric and atmospheric correction, a smoothing pipeline¹⁷ and the calculation of spectral parameter maps¹⁸ to localize potential hydrated minerals which typically absorb in the near infrared 1.0-2.6 µm range. To better constrain the precise geomorphology of a putative water-volcano contact where hydrated mineralogy is suspected, we also studied the morphology of the basal scarp using MRO/HiRISE images at a resolution of up to 30 cm/pixel¹⁹ (Fig. 1B).

Results & Discussion: The flanks and summit caldera of Olympus Mons, above 6 km of altitude and therefore supposedly never in contact with an ocean, spectrally show a highly widespread signal with no remarquable absorption bands on the range of 1.0 to 2.6 µm, interpreted as the iron-rich basaltic primary composition of rocks covered in a high amount of dust at the surface of the volcano. We also find dominant signatures of water ice with strong features at 1.5 and 2.0 µm, in several locations of the volcano flanks and basal scarp. However, we also find spectral signatures that we interpret as signs of hydrated mineralogy in several locations around the volcano. These spectra either show an absorption band around 2.1 µm, similarly to mono-hydrated sulfates, or bands at 2.2 and 2.3 µm, typically found for hydrated phyllosilicates (Fig. 1D). These features occur in the basal scarp (Fig. 1C), precisely where the rock is expected to outcrop under a lower dust cover in steep slope ravines. The scarcity of detections either suggests that the volcano’s mineralogy is barely hydrated, or that the hydrated spectral signatures are mainly hidden by the dust cover even in most places of the basal scarp. In any case, if these detections are not yet a confirmed evidence of an ancient volcano-ocean contact, they could be a sign of volcanic interaction with liquid water in the past of Mars in the region of Olympus Mons.

Conclusions & Perspectives: No in-situ data is today available in the area of Olympus Mons. Hence, to further test if Olympus Mons could have been an ancient volcanic island, we presently analyze a terrestrial volcanic analog that could inform on alteration conditions and processes of volcanic rock in contact with a liquid water ocean. We expect this comparative study to better constrain the observed spectral signatures around Olympus Mons.

Acknowledgments: This work has been financially supported by the National Planetology Program (PNP) of the National Institute of Universe Sciences (INSU-CNRS) and benefited from financial support from the CNES Research Proposal Call (APR).

References: [1] Smith, D. E. et al. (1998) Science 279 (5357): 1686–92. [2] Tanaka K. L. and Scott D. H. (1987) USGS IMAP 1802-C. [3] Carr M. H. and Head J. W. (2003) JGR: Planets 108 (5). [4] Parker J. T. et al. (1993) JGR 98 (E6). [5] Sholes S. F. et al. (2021) JGR : Planets 126 (5). [6] Carr M. H. and Clow G. D. (1981) Icarus, Vol. 4. [7] Baker et al. (1982) Reports of Planetary Geology Program. [8] Costard F. et al. (2017) JGR: Planets 122 (3): 633–49. [9] Poulet F. et al. (2005) Nature 438 (7068): 623–27. [10] Fueten F. et al. (2014) JGR: Planets119 (2): 331–54. [11] Flahaut J. et al. (2015) Icarus 248 (March):269–88. [12] Brossier J. et al. (2024) ResearchGate conference paper. [13] Schmidt F. et al. (2022) PNAS, Vol. 119, No. 4. [14] Hildenbrand A. et al. (2023) EPSL 619. [15] Murchie S. et al. (2007) JGR, 112. [16] Quantin-Nataf C. et al. (2018) Planetary and Space Science 150, 157-170. [17] Bultel B. et al. (2015) IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 8.6, 3039-3049. [18] Viviano-Beck C. E. et al. (2014) JGR: Planets 119 (6): 1403–31. [19] McEwen A. et al. (2007) JGR, 112.

How to cite: Cornillon, A., Bultel, B., and Hildenbrand, A.: Hydrated mineral features suggested around Olympus Mons on Mars using CRISM and HiRISE: implications on water-volcano interactions , Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-56, https://doi.org/10.5194/epsc2026-56, 2026.

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   Valles Marineris is a natural cross-section exposing rocks from the ancient Martian crust. The mineralogical composition of these rocks has been studied at the 18 m/pixel spatial scale from orbit using Visible to Short-Wave Infrared (VSWIR) spectroscopy with the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM, MRO, [1]). The oldest Martian crustal blocks are light-toned and associated with spectral absorptions indicative of Low-Calcium Pyroxene (LCP) [2, 3]. Nearby, plagioclase feldspar rich layers have also recently been detected, suggesting the ancient Martian crust may have had a more felsic composition than the basalts found on the surface [4, 5]. In situ data from the rocks exposed in Valles Marineris’ walls would improve our ability to characterize the geologic setting and composition of these ancient terrains and address key questions about the formation of the early Martian crust such as whether the light-toned rocks containing LCP and plagioclase are related to alkaline magmatism, and which formation processes could explain the juxtaposition of both mafic and felsic crustal materials [6].

   The study presented below is funded through NASA’s Planetary Science Technology and Analog Research program and aims to advance the scientific and technical basis for a future in situ mission to access the ancient terrains exposed in the walls of Valles Marineris. Specifically, a helicopter equipped with a VSWIR imaging spectrometer could investigate the mineralogical composition of the rocks at a much higher spatial resolution than is currently possible from orbit, resolving key information about their texture and mineralogy which is necessary to distinguish between crustal formation models. Of great interest is the abilities of a helicopter-mounted spectrometer to detect the 1.3 µm spectral absorption associated with plagioclase feldspars [7], which can only be detected if ferrous iron is incorporated in its chemical lattice [8], which can be quickly obscured by darker, mafic minerals [9]. Within whole rocks, plagioclase crystal size [10, 11, 12] and the degree of weathering [12, 13] have been identified as key parameters that affect the detectability of plagioclase absorptions.

   In this study, we use spectral datasets collected at multiple spatial resolutions to determine how plagioclase crystal size, distribution, weathering state, and transparency affect the detectability of the 1.3 µm plagioclase absorption at different spatial scales. These results will inform requirements for VSWIR spectral data acquired by future Mars helicopter payloads and help interpret the data they collect. We analyzed hyperspectral datasets of whole plagioclase-phyric basalts from outcrops of the Steens basalt unit collected at several locations in southeast Oregon, including Steens Mountain and Hart Mountain.  The Steens basalt unit is part of the Columbia River Basalt Group (CRBG) and is the oldest (~17 Ma) and most mafic member of this Large Igneous Province [14]. Alongside olivine and pyroxene contained in this basalt, it is notable for its dominant microlithic porphyritic texture characterized by centimeter-scale plagioclase phenocrysts [15]. The plagioclase phenocrysts share a similar chemistry (An_57–74) throughout the section [15], but they remain diverse in size, shape, and abundance, providing an ideal location to explore how these physical properties affect bulk spectral properties. These basaltic samples were also selected as potential analogs for Martian rocks. Indeed, a plagioclase-phyric basalt has been proposed as one possible lithology for the plagioclase rich layer in Valles Marineris [5].

   Rock samples were first imaged as cut slabs and rough surfaces at JPL using the Ultra-Compact Imaging Spectrometer for the Moon (UCIS-Moon) hyperspectral camera that operates between 0.6 and 3.6 µm [16]. The high spatial resolution, of about 80 µm/pixel, allowed identification and spectral characterization of individual plagioclase crystals. To complement laboratory analyses, outcrops at Steens Mountain and Hart Mountain were imaged at the landscape scale using a Headwall SWIR hyperspectral camera operating between 0.9 and 2.6 µm, with a spatial resolution on the order of centimeters per pixel under our acquisition conditions [17].

   Here we will present preliminary results from this investigation (Figure 1). At the 80 µm/pixel scale, large plagioclase crystals (ranging from the millimeter scale up to several centimeters >> 80 microns) in these rocks are readily identified by a ~1.3 µm absorption, even in weathered surfaces. The depth and shape of the plagioclase absorption is dependent on surface texture (fresh rough surface vs. saw cut face) and crystal transparency. Spectra are averaged over several pixels, simulating lower spatial resolution data, and the absorption is less readily detected in samples with very small plagioclase crystals than large ones, even if plagioclase on average takes up the same surface abundance within an averaged region. Plagioclase absorptions are also mappable in the outcrop-scale hyperspectral images, and their shape and depth vary throughout the outcrop. These first results demonstrate that airborne sensors operating at tens of centimeter spatial resolutions on Mars could reliably detect plagioclase phenocrysts in steep, natural outcrops. Natural rock textures will generally favor detection relative to cut samples, and large phenocrysts rather than microlites is the dominant control spectral detectability, rather than volumetric abundance. The persistence of plagioclase signatures under weathering is also encouraging for the detection of plagioclase in Valles Marineris using VSWIR spectro-imaging datasets.

References:

[1] Murchie, S., et al. (2007), J. Geophys. Res., 112, E05S03.

[2] Flahaut, J., et al. (2012), Icarus, 221(1).

[3] Quantin, C., et al. (2012, Icarus, 221(1).

[4] Viviano-Beck, C.E., et al. (2017), Icarus, 284.

[5] Flahaut, J., et al. (2023), Geophys. Res. Lett., 50, e2022GL100772.

[6] Payré, V., et al. (2024), Minerals, 14, 452.

[7] Adams, J.B., and Goullaud, L.H. (1978), Lunar Planet. Sci. Conf. 9^th.

[8] Hafner, S.S., et al. (1971), Earth Planet. Sci. Lett., 12.

[9] Crown, D.A., and Pieters, C.M. (1987), Icarus, 72.

[10] Rogers, A.D., and Nekvasil, H. (2015), Geophys. Res. Lett., 42.

[11] Barthez, M., et al. (2023), J. Geophys. Res.: Planets, 128, e2022JE007680.

[12] Barthez, M., et al. (2026), Icarus, 453, 117027.

[13] Mandon, L., et al. (2022), Earth Space Sci., 9, e2021EA001871.

[14] Moore, N.E., et al. (2020), Geochem. Geophys. Geosyst., 21, e2020GC008910.

[15] Moore, N.E., et al. (2018), Geosphere, 14(6).

[16] Haag, J.M., et al. (2020), Proc. of SPIE, 11504(03).

[17] Greenberger, R.N., et al. (2020), J. Geophys. Res.: Planets, 125, e2019JE006218.   

How to cite: Barthez, M., Fraeman, A. A., Liu, Y., Ehlmann, B. L., Kamps, O., Levy, J., and Brockers, R.: Constraining plagioclase detectability in potential Martian crust analogs for future helicopter-based imaging spectroscopy, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-657, https://doi.org/10.5194/epsc2026-657, 2026.

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Mapping the global distribution of carbonate minerals on the Martian surface is a prerequisite for understanding the aqueous and atmospheric evolution of Mars, as these minerals represent a principal sink for atmospheric CO₂ and direct tracers of past liquid water activity. To date, the orbital data from CRISM offers our best opportunity for detecting the diagnostic vibrational signatures of these minerals; however, studies have focused almost entirely on the weak short-wave infrared (SWIR) overtone and combination bands near 2.3 and 2.5 µm [1,2]. These features can be spectrally degenerate with co-occurring phyllosilicates and are not always strong enough to reveal smaller or less exposed deposits, leaving a significant fraction of the carbonates undetected.

The strongest spectroscopic signatures of carbonates lie in the mid-wave infrared (MWIR): the fundamental absorptions at 3.4 and 3.9 µm [2]. These features remain largely unexploited in CRISM data, due to the limited spectral range of the instrument, which does not fully cover the 3.9 µm band, and to the superposition of reflected solar radiance and planetary thermal emission in the 3–4 µm window, which renders band depth estimation challenging.

To overcome this issue, we developed a dual-band detection framework based on two independent pipelines processing the SWIR and MWIR parts of the spectrum. While the SWIR pipeline works similarly to conventional detection methods, refining the 2.5 µm overtone absorption, the MWIR pipeline has to deal with the presence of thermal emission. Each pipeline produces a spatially filtered detection map with fully propagated, SNR-anchored uncertainties.

In particular, the MWIR pipeline operates on the atmospherically corrected datacube and treats the observed signal as the sum of a reflected solar continuum, a surface thermal contribution, and channel noise. The solar continuum is estimated using an iteratively reweighted least-squares (IRLS) fit to a band-masked window between 1.8–2.6 µm, which serves as a robust estimator with a well-defined per-pixel noise level, avoiding the limitations that affect classical shoulder-based approaches. Using these residuals, the thermal contribution is estimated by a constrained Planck greybody fit in the 3–4 µm window, with temperature values restricted to a realistic Martian daytime range. Instrumental artifacts are subsequently identified and filtered both at the channel level and in map space before proceeding with the final detection step.

The SWIR pipeline uses a pre-processed atmospherically corrected and denoised datacube, where thermal emission is absent. The 2.5 µm overtone is isolated with an iterative continuum fit and sub-pixel band-centre localisation, while band absorption is quantified via a Gaussian-kernel-weighted band-depth integration. SNR, band-centre location, and amplitude of the detected absorption serve as criteria for distinguishing carbonates from overlapping phyllosilicates and sulphates [3].

As a first demonstration, the framework is applied to a single CRISM observation, FRT000186FA at Nili Fossae, a scene chosen for its close proximity to Jezero Crater, where carbonate presence has been independently established both from orbit [4] and in situ by the Perseverance rover [5,6]. Both pipelines detect a spatially coherent area of elevated absorption,with detection maps consistent in spatial extent and structure. 

Figure 1: Band depth integral at 2.5 µm (SWIR pipeline) for CRISM observation FRT000186FA (Nili Fossae). 

Figure 2: Band depth integral at 3.9 µm (MWIR pipeline, thermal-corrected) for CRISM observation FRT000186FA (Nili Fossae). 

Nili Fossae serves here as a validation benchmark, with the framework designed for systematic application across a geologically diverse sample of CRISM observations, moving toward a more complete carbonate inventory of Mars. 

This work is funded by the Italian Space Agency (ASI) [ASI-INAF n.23-3-HH.0]

[1] Harner, P.L., & Gilmore, M.S. (2015). Visible–near infrared spectra of hydrous carbonates, with implications for the detection of carbonates in hyperspectral data of Mars. Icarus 250, 204-214. http://dx.doi.org/10.1016/j.icarus.2014.11.037 

[2] Bishop, J.L., et al. (2021). Spectral properties of anhydrous carbonates and nitrates. Earth and Space Science, 8, e2021EA001844. https://doi.org/10.1029/2021EA001844 

[3] Plebani, E.,  et al. (2022). A machine learning toolkit for CRISM image analysis. Icarus 376, 114849. https://doi.org/10.1016/j.icarus.2021.114849 

[4] Ehlmann, B.L., et al. (2008). Orbital Identification of Carbonate-Bearing Rocks on Mars. Science 322, 1828-1832. https://doi.org/10.1126/science.1164759 

[5] Clavé, E., et al. (2023). Carbonate detection with SuperCam in igneous rocks on the floor of Jezero Crater, Mars. JGR Planets 128, e2022JE007463. https://doi.org/10.1029/2022JE007463

[6] Clavé, E., et al. (2026). In Situ Carbonation of Sedimentary and Igneous Rocks of Ultramafic Composition in Jezero Crater, Mars. JGR Planets 131, e2025JE009107. https://doi.org/10.1029/2025JE009107

How to cite: Saggese, V., Altieri, F., Brossier, J., De Sanctis, M. C., Frigeri, A., and Raponi, A.: Improved Detection of Martian Carbonates from CRISM, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-819, https://doi.org/10.5194/epsc2026-819, 2026.

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Introduction

Oxia Planum (Fig. 1) is a region of Mars located on the margin between the old, heavily cratered highlands of Arabia Terra (Noachian-aged) and the younger, smoother lowlands of Chryse Planitia (Hesperian-aged). From orbit it shows several geomorphological records of past widespread water–rock interactions, including fractured, layered, clay-bearing deposits with high astrobiological potential [1, 2, 3]. For this reason, Oxia Planum has been selected as the landing site for the ESA Rosalind Franklin Mission (RFM). The main goal of the RFM is to search for past (and/or present) traces of life, particularly in the Martian shallow subsurface where material of astrobiological interest is better preserved. To achieve this, the RFM rover is equipped with a drill capable of collecting, for the first time for a mission on Mars, samples down to a depth of 2 meters, and with a suite of instruments designed to discriminate biosignatures in the samples, gathering supporting geological context information [4]. 

Figure 1: Oxia Planum, Mars with CTX basemap colored by elevation. The white ellipses represent the current landing ellipses, and the orange polygon in center represents the outline of the geologic map of the region [5], with the map’s cross-section added in orange. Note that two cubes selected for study overlap with the geologic map while one cube for study is towards the delta and outside the previously mapped area.

Here, we focus on selected regions of interest (ROIs) within the Oxia Planum landing area (Fig. 2) to investigate how clay distribution relates to other geologic features. We incorporate an Oxia Planum survey of fractures mapped at 1:1250 scale in spaced windows (e.g., blue squares in Fig. 2) which provides the general fracture characteristics of multiple units. Within ROIs, we repeat this fracture mapping to connect the geomorphological and spectral analysis with bedrock fracture behavior to more fully characterize the rocks, and contribute to strategies for guiding the selection of drilling sites.

Figure 2: CRISM spectral maps of the 2.3 micron band depth [3] where yellow tones represent high Fe,Mg-phyllosilicate signatures, with CTX basemap as background and the geologic cross-section [5] overlain in orange. The ROIs are shown and labeled in white. Dark blue squares represent areas where regional fracture analysis has been performed to aid in extending the geologic mapping to unmapped areas. Inset of ROI 10 shows the fractures which have been mapped (blue) on HiRISE imagery (shown), and exhibit a strong correlation with clay-rich areas. 

Data and Methods

ROIs were chosen based on (1) mapped contacts between bedrock units [5], (2) stratigraphic exposures within mounds and/or crater walls, (3) association with the geologic cross-section [5], and/or (4) high likelihood of encountering phyllosilicates (Fe,Mg-rich clays), based on CRISM cube analysis [3]. The southernmost CRISM cube of interest, FRT09A16 (Fig. 1), is located near the delta containing sediments derived from the highlands, thus providing a key insight into the stratigraphic relationships and depositional modes of the units farther downslope. Within ROIs, we created meter-scale resolution digital terrain models (DTMs) using the NASA Ames Stereo Pipeline and HiRISE stereopairs, tied to MOLA elevations.

Fracture mapping was performed on HiRISE images which were manually georeferenced to improve their correlation with CRISM data. Mapping at 1:2000 scale (minimum resolvable fracture size approximately 10m) provides comparable data to the fracture survey, providing a dataset that aids in expanding geologic units beyond the current bounds of the map [5]. Detailed mapping at 1:1000 scale, following [8], has sufficient detail to analyze fracture topology, improving unit characterization and providing insight into fracture formation mechanisms [e.g., 9].

Preliminary results and Discussion 

Figure 3 compares the DTM created from HiRISE using the NASA Ames Stereo Pipeline [6] with the MADNET DTM [7] created through machine learning, both of which are based on HiRISE images. The example shows the subdued elevation changes of the MADNET DTM, where the elevation decrease from west to east is partially inherited within the crater rim elevations. The Ames Stereo Pipeline DTM shows a more accurate crater depth-to-width ratio of approximately 0.1, with the crater rim maintaining a realistic cross-sectional shape and the elevation change mostly impacting the surrounding landforms.

Figure 3: Example DTM quality comparison at a crater near transect 9 (Fig. 2), with the MADNET DTM [7] shown in red and the DTM from Ames Stereo Pipeline [6] shown in purple (this work).

Fracture mapping performed across the broader area shows that the phyllosilicate clays exhibit a higher number (fracture density) and sum length (fracture intensity) of fractures per area, relative to low-clay areas that are also mapped as bedrock units. Preliminary results suggest that this trend is consistent within the ROIs. In the southernmost ROIs which the geologic map does not cover, CTX brightness and CRISM clay signatures are used to identify the clay-rich bedrock groups. We then manually assign unit designations based on comparison with the stratigraphic relationships, fracture characteristics, and geomorphological behavior of the units in mapped regions, leveraging the fracture survey to inform unit extents.

By combining multiple datasets (CTX, CRISM, HiRISE) with different scientific approaches (spectral, fracture, and geomorphological analysis) we provide further context for RFM. Although orbital data only provides information on the surface and limited subsurface exposures, using a combination of geologic approaches allows us to propose realistic subsurface scenarios, critical for mission success in drilling the near subsurface.

Acknowledgements: This work is supported by the ASI-INAF Mars Exploration agreement 2023-3-HH 0 and the European Space Agency (ESA) SKP IDS, F.O.1.05.04.33.13.

References

[1] Mandon L. et al., 2021, Astrobiology, 21(4), 464–480. https://doi.org/10.1089/ast.2020.2292. 

[2] Quantin‐Nataf, C., et al., 2021, Astrobiology, 21(3), 345–366. https://doi.org/10.1089/ast.2019.2191.

[3] Brossier, J., et al., 2022, Icarus, 386, 115114. https://doi.org/10.1016/j.icarus.2022.115114. 

[4] Vago, J., et al., 2017, Astrobiology, 17(6–7), 471–510. https://doi.org/10.1089/ast.2016.1533  

[5] Fawdon, P., et al., 2024, Maps 20 (1), 2302361, https://doi.org/10.1080/17445647.2024.2302361

[6] Beyer, R. A., et al., 2018, Earth and Space Science, 5, 537–548. https://doi.org/10.1029/2018EA000409

[7] Tao, Y., et al., 2021, Remote Sensing, 13(21), 4220, https://doi.org/10.3390/rs13214220 

[8] Apuzzo A. et al., 2025, Planetary and Space Science, Volume 267, 2025, 106169, https://doi.org/10.1016/j.pss.2025.106169

[9] Peacock, D., et al., 2026, Earth-Science Reviews, 277, 105461, doi: https://doi.org/10.1016/j.earscirev.2026.105461

How to cite: Rasmussen, M., Altieri, F., Frigeri, A., Brossier, J., Trisic Ponce, J., Saggese, V., and De Sanctis, M. C.: Characterizing clay-rich regions of Oxia Planum, Mars, through geomorphological and fracture analysis, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-829, https://doi.org/10.5194/epsc2026-829, 2026.

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We are conducting a coordinated effort to investigate the sulfate-bearing deposits within Aram and Aureum Chaos where three types of sulfates have previously been identified. Using improved Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) image processing to produce Map-Projected Targeted Reduced Data Record (MTRDR) images, we have mapped out the occurrences of polyhydrated sulfates (PHS), monohydrated sulfates (MHS), and ferric hydroxysulfate outcrops (FHS; Fe³⁺SO₄OH) beyond what was mapped previously. High Resolution Imaging Science Experiment (HiRISE), Context Camera (CTX), High Resolution Science Camera (HRSC), and Colour and Stereo Surface Imaging System (CaSSIS) images were used to map and characterize the morphologies and locations of sulfates within these two chaos regions. We then used these morphologic characteristics for each type of sulfate where CRISM targeted coverage existed to extrapolate the sulfate occurrences within both chaos regions outside of the CRISM images. Digital Terrain Models (DTMs) made from HRSC, HiRISE, and CTX stereo pairs were used to establish stratigraphic relationships between the different sulfates and determine thicknesses of deposits. We also mapped out the distribution of a spectrally bland, crenulated, layered, light-toned caprock unit within both chaos regions because it is found in association with the sulfates. 

Our results for both chaos regions reveal that the PHS-rich units are always stratigraphically above the MHS-rich units where they occur together. We found that the PHS unit is typically smooth, darker-toned, and contains several layers of meter-scale thickness forming broad plateaus that are commonly covered by ripples and debris. Steeper cliffs along specific layers within the PHS unit correlate to brighter, jagged, and heavily fractured outcrops. Spectra of the PHS unit have bands near 1.44 and 1.93-1.95 µm and a drop in reflectance near 2.42 µm, similar to spectra of rozenite (Fe²⁺SO₄•4H₂O) and starkeyite (MgSO₄•4H₂O). In contrast, the MHS is brighter and rougher with scalloped fracturing, and can be either massive or very finely layered, with the finely layered material typically exposed beneath the overlying crenulated caprock. The MHS spectra are consistent with szomolnokite (FeSO₄•H₂O) and kieserite (MgSO₄•H₂O). We also detected kieserite in dark-toned talus and eolian ripples adjacent to or mantling MHS outcrops, indicating erosion of the outcrops produces finer-grained kieserite-bearing debris, but why the debris is darker than the outcrops from which it is derived is unknown. Interestingly, some of the brightest and clearest outcrops within both chaos regions had some of the weakest sulfate signatures in CRISM images, suggesting other factors are influencing brightness besides the presence of sulfates. The FHS, which is spectrally characterized by a strong absorption at 2.236 µm, occurs in smaller, patchy outcrops along the lower-lying floors of both chaos regions and it generally appears dark-toned and heavily fractured with ridges sometimes present. The FHS is always adjacent to or directly beneath the MHS, and is also associated with chaos terrain where it typically occurs along the chaos block edges.

Recent laboratory studies indicate that the FHS can only form by heating hydrated ferrous sulfates above 100°C [Bishop et al., 2025]. We find that the FHS is only associated with Mg-bearing MHS, perhaps because the Fe-bearing MHS was transformed to FHS due to heating, leaving behind the Mg-bearing MHS that is now seen from orbit. Moreover, the correlation between upturned and tilted chaos blocks and FHS is consistent with heating in the subsurface that caused conversion of the MHS to FHS, as well as the tectonic disruption that created and uplifted the chaos blocks. The geothermal heating could have arisen from intrusion of magma that never reached the surface but caused heating along the chaos floors due to their deeper depths. We did not find any FHS within Iani Chaos even though there are MHS in Iani that are much closer to Aram than those at Aureum. These observations suggest the subsurface heat source extended from Aram to the southwest where it reached northeastern Aureum rather than towards the southeast to reach Iani. Alternatively, heating could have reached portions of northwestern Iani Chaos but there were no hydrated ferrous sulfates present for conversion to FHS. Deposition of the sulfates within these chaos regions occurred in the Late Hesperian to Early Amazonian, implying the magmatic heating event that altered the MHS to FHS also took place relatively recently in martian history (<3 billion years ago). 

References: 

Bishop, J.L., Meusburger, J.M., Weitz, C.M. et al. Characterization of ferric hydroxysulfate on Mars and implications of the geochemical environment supporting its formation. Nat Commun 16, 7020 (2025). https://doi.org/10.1038/s41467-025-61801-2

How to cite: Weitz, C., Bishop, J., and Sheppard, R.: A Geologic Study of Three Types of Sulfates within Aram and Aureum Chaos, Mars, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-277, https://doi.org/10.5194/epsc2026-277, 2026.

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Hydrated sulfate minerals on Mars are of critical importance to understand the ancient climates of the planet, as they can form through multiple processes involving water-rock interaction. Particularly, they can form as evaporitic deposits ^[1], when bodies of liquid water containing dissolved salts slowly evaporate, transitioning to brine-like environments and finally leaving behind the crystallized salts they once contained. This makes them ideal to trace ancient aqueous environments. These salts have been detected in several places on Mars ^[2,3,4], but are not as widespread as initially expected. Additionally, they are rarely seen alongside the other phases they have been modelled to form alteration sequences with, namely the clay minerals dominating the Southern Noachian terrains ^[5]. This could be explained by some geological processes, but also by incomplete detections and/or observational biases.

To identify mono- and poly-hydrated sulfates (MHS and PHS respectively), one technique available both orbitally and in-situ is Visible and Near-Infrared (VISIR) reflectance spectroscopy. But even though hydrated sulfate minerals present distinctive spectral signatures, their identification is rarely straightforward. Indeed, other families of alteration minerals also detected on Mars ^[2,3,4] (such as phyllosilicates, carbonates, amorphous hydrated silica, …) bear spectral signatures in the wavelength ranges available in current Martian data (typically from 1.3 to 2.6 µm) ^[6,7] that can overlap with sulfate spectral features. This problem becomes exacerbated in the case of mineral mixtures, where spectral contributions from several phases make clear identification challenging ^[8,9]. Other studies have come up with spectral parameters capable of detecting hydrated sulfates ^[10], and while they can work well in some conditions, they can also mix them up with other mineralogical families.

Here, we develop a new suite of spectral parameters capable of confidently identifying MHS and PHS using VISIR data. The objective is to automatically detect hydrated sulfate-bearing outcrops with minimal ambiguity, even when mixed with other phases. To do so, we base our study on 2 key absorption features in hydrated sulfate spectra: (1) an important drop in reflectance near 2.4 µm (S-O overtone) ^[11], present in other hydrated minerals but usually weaker in intensity; and (2) for most sulfates, a spectral plateau lacking any absorption feature in the 2.2-2.3 µm range. Features in that range may be linked to combinations/overtones of Al-, Fe- and Mg-OH for phyllosilicates ^[12], Si-OH for hydrated silica ^[13], and C-O for carbonate ^[12]. Exceptions to this second rule are some Ca-sulfates, which do present a large triple absorption between 2.1 and 2.3 µm (S-O or OH/H₂O combinations/overtones) ^[11].

We begin by investigating the 2.4 µm drop slope of sulfates in contrast to the slope of their 2.2-2.3 µm plateau. To avoid contributions from absorption bands when computing the slopes, we use the upper part of a convex hull from 2.05 to 2.40 µm to represent the spectrum as if no absorptions features were present there. From this convex hull, we compute two slopes, one between 2.22 and 2.24 µm (“Plateau slope”, green line on Figure 1), and the other between 2.36 and 2.39 µm (“Drop slope”, blue line on Figure 1). We then subtract the drop slope to the plateau slope, obtaining our first parameter named “DIFFSLOPE”. We correlate this value to the depth of a potential absorption band in the 2.2-2.3 µm range, lacking for most sulfate species. For this, we divide our original spectrum by the same convex hull, and measure the depth of an eventual feature as our second parameter (“Band depth”, red dotted line on Figure 1).

These parameters are applied on lab spectra, and preliminary results are shown in Figure 2. Gypsum and anhydrite (blue circle) plot higher than other sulfates (green circle), due to their absorption in the 2.2-2.3 µm range. However, because of their strong drop slope, they still plot away from other hydrated phases. Overall, we obtain a clear separation between sulfates and other hydrated minerals, which is a promising first step before applying this method to Mars data.

We then plan to apply our method to the VISIR data from the SuperCam ^[14,15] instrument onboard the Perseverance rover. By combining improved VISIR spectral parameters and results from SuperCam’s other analytical techniques (mainly LIBS and Raman), we aim to revisit the in-situ detections of hydrated sulfates in Jezero crater ^[16], in order to better understand the aqueous history of the site.

Aknowledgments: This work is supported by the ERC OCEANID project (Grant agreement ID: 101045260) funded by the Horizon programme from the European Research Council.

References: ^[1]Bąbel and Schreiber (2014), Elsevier, ^[2]Murchie et al. (2009), J. Geophys. Res., ^[3]Carter et al. (2013), J. Geophys. Res., ^[4]Ehlmann and Edwards (2014), Annu. Rev. Earth Planet. Sci., ^[5]Milliken et al. (2009), Geophys. Res. Lett., ^[6]Cloutis et al. (2008), Icarus, ^[7]Poitras et al. (2018), Icarus, ^[8]Stack and Milliken (2015), Icarus, ^[9]Baschetti et al. (2026), Icarus, ^[10]Viviano-Beck et al. (2014), JGR Planets, ^[11]Cloutis et al. (2006), Icarus, ^[12]Clark et al. (1990), J. Geophys. Res., ^[13]Goryniuk et al. (2004), Geophys. Res. Lett, ^[14]Wiens et al. (2020), Space Sci. Rev., ^[15]Maurice et al. (2021), Space Sci. Rev., ^[16]Mandon et al. (2023), JGR Planets.

Figure 1 : Illustration of parameters computed in this study on example gypsum and epsomite lab spectra.

Figure 2 : Scatter plot representing the 2 parameters mentionned in the text against each other, for different mineralogical families.

How to cite: Tricaud, V., Dehouck, E., Carter, J., Pineau, M., Clavé, E., and Quantin-Nataf, C.: Towards new methods for identifying hydrated sulfates on Mars using Visible-Infrared (VISIR) spectroscopy, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-330, https://doi.org/10.5194/epsc2026-330, 2026.

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The Perseverance rover landed in Jezero Crater in February 2021 as part of the Mars 2020 mission, with objectives that include geological characterization of the landing site, detection of potential biosignatures, and collection of samples for future return to Earth [1,2]. To achieve these goals, the SuperCam instrument has been extensively used, integrating Laser-Induced Breakdown Spectroscopy (LIBS) among other spectroscopic and imaging techniques to investigate the elemental, geochemical, and mineralogical composition of the Martian surface [3]. The reliability of LIBS measurements is ensured by an onboard calibration system comprising multiple reference targets [4].

Since the rover began its traverse on Mars, its scientific exploration has been organized into a series of Scientific Campaigns analyzing distinct geological units within Jezero Crater. The first campaign, the Crater Floor Campaign, focused on the Máaz, Artuby, Content, and Séítah formations. It was followed by the Rapid Traverse Campaign, whose primary objective was to reach the Delta region, resulting in limited scientific measurements. The third campaign, the Delta Front Campaign, and the fourth, the Delta Top Campaign, provided detailed investigations of the deltaic deposits. Subsequently, the Margin Unit Campaign distinguished between the Western and Eastern Margin Unit formations, with a focus on carbonate-bearing lithologies. The most recent phase corresponds to the Crater Rim Campaign, which is currently ongoing and targets the rim structures of Jezero Crater.

In this study, LIBS data collected by the SuperCam instrument during the first five scientific campaigns (until Sol 1280) were analyzed using Principal Component Analysis (PCA), to develop a model that can serve as a basis for comparing and predicting the composition of new targets from other geological formations investigated by the rover.

The full LIBS spectra measured by the Perseverance rover from the Máaz, Artuby, Content, Séítah, Delta Front, Delta Top, Eastern Margin Unit, and Western Margin Unit regions were used. Only targets measured on rocks or floats were selected, while those acquired on regolith or heavily dust-covered rocks were excluded to avoid misinterpretations, since regolith material can be transported across different regions of Mars by wind activity. For each target, the median LIBS spectrum was computed, followed by Norm-2 normalization and mean-centering. The PCA model was then developed using the PLS_Toolbox (Eigenvector Research, WA, USA) working under Matlab environment (The Mathworks, MA, USA).

The resulting PCA was robust and effectively captured compositional differences among the geological formations. The PCA results reveal clear geochemical differences among the Martian formations. Séítah is characterized by higher Mg contents and local olivine enrichment, while Máaz is enriched in Si, Fe, Al, and alkali elements, consistent with a feldspar- and pyroxene-rich composition. Artuby shows intermediate compositions between Séítah and Máaz formations and Content has a similar composition than Máaz. In contrast, Delta Front, Delta Top, Eastern Margin Unit and Western Margin Unit exhibit more homogeneous signatures dominated by Fe- and Mg-rich phases.

In conclusion, PCA based solely on LIBS spectra provides a rapid and robust framework for comparing and interpreting the mineralogical composition of new targets, enabling their integration into existing compositional models even when other SuperCam datasets are unavailable or incomplete. Furthermore, this approach facilitates the comparison of geological compositions across different formations within a consistent multivariate framework. 

References

[1] Mars 2020: Perseverance Rover, (n.d.). https://science.nasa.gov/mission/mars-2020-perseverance/  (accessed April 27, 2026).

[2] K.A. Farley, K.H. Williford, K.M. Stack, R. Bhartia, A. Chen, M. de la Torre, K. Hand, Y. Goreva, C.D.K. Herd, R. Hueso, Y. Liu, J.N. Maki, G. Martinez, R.C. Moeller, A. Nelessen, C.E. Newman, D. Nunes, A. Ponce, N. Spanovich, P.A. Willis, L.W. Beegle, J.F. Bell, A.J. Brown, S.-E. Hamran, J.A. Hurowitz, S. Maurice, D.A. Paige, J.A. Rodriguez-Manfredi, M. Schulte, R.C. Wiens, Mars 2020 Mission Overview, Space Sci Rev 216 (2020) 142. https://doi.org/10.1007/s11214-020-00762-y.

[3] S. Maurice et al., The SuperCam Instrument Suite on the Mars 2020 Rover: Science Objectives and Mast-Unit Description, Space Sci Rev 217 (2021) 47. https://doi.org/10.1007/s11214-021-00807-w.

[4] A. Cousin, V. Sautter, C. Fabre, G. Dromart, G. Montagnac, C. Drouet, P.Y. Meslin, O. Gasnault, O. Beyssac, S. Bernard, E. Cloutis, O. Forni, P. Beck, T. Fouchet, J.R. Johnson, J. Lasue, A.M. Ollila, P. De Parseval, S. Gouy, B. Caron, J.M. Madariaga, G. Arana, M.B. Madsen, J. Laserna, J. Moros, J.A. Manrique, G. Lopez-Reyes, F. Rull, S. Maurice, R.C. Wiens, SuperCam calibration targets on board the perseverance rover: Fabrication and quantitative characterization, Spectrochim Acta Part B At Spectrosc 188 (2022) 106341. https://doi.org/10.1016/J.SAB.2021.106341.   

Acknowledgements

We are grateful to the many engineers and scientists who have supported the Perseverance mission. We acknowledge the support of Spanish Agency for Research (AEI), NASA’s Mars Exploration Program, CNES, CNRS and other supporting organizations. SuperCam data are archived in the PDS. This work is supported by the PAMMAT project “Alteration processes in Mars and Moon Meteorites, and Terrestrial Analogues at different environments: Mars2020, Rosalind Franklin and Returned Samples from Mars and Moon” (Grant No. PID2022-142750OB-I00), funded by the Spanish Agency for Research (through the Spanish Ministry of Science and Innovation, MCIN, and the European Regional Development Fund, FEDER, MCIN/AEI/10.13039/501100011033/FEDER,UE), the Strategic Project “Study of Alteration Processes in Terrestrial and Planetary Materials” (Grant No. UPV/EHU PES21/88), funded by the UPV/EHU, and the Italian Space Agency (ASI) through the ASI/INAF agreement no. 2025-12-HH.0.

How to cite: Coloma, L. and the SuperCam team: PCA-based modeling of SuperCam LIBS data for comparing geological composition across Martian formations, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-1027, https://doi.org/10.5194/epsc2026-1027, 2026.

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Introduction:  Martian regolith [1] is constituted with different mineral phases of various grain sizes that could originate from local, regional or global sources [2,3]. It corresponds to the ultimate stage of various erosion and weathering processes. Dust (<3microns) also constitutes the regolith and comes from a more global source. Understanding the different mineralogies with their associated grain sizes and shapes can help investigate the past conditions, as the regolith can record different aqueous alteration processes that Mars’ surface has undergone. This is also useful to decipher the different sources, from local to more regional or global, and therefore understand better the different physical processes forming the soils. Last, the study of the regolith can also help constrain some modern processes, such as the exchange between the surface and the atmosphere.

The MSL/Curiosity rover has been exploring Gale crater since 2012 [4], investigating first the crater floor (Aeolis Palus) and now climbing the central sedimentary mound, informally named Mount Sharp. Its traverse is documenting the climate evolution of early Mars. Indeed, the lower section of Mt Sharp stratigraphy corresponds mainly to ancient aqueous deposits, with abundant smectite signatures, whereas higher strata are dominated by sulfate-bearing rocks, representing a major environmental transition, probably with wet-dry cycles [5].  The SAM and CheMin instruments have analyzed a sieved regolith sampled (<150 microns), showing that the regolith was principally composed of primary igneous phases (40.8 wt% plagioclase, 22.4 wt% olivine, 14.6 wt% augite and 13.8 wt% pigeonite), along with some secondary phases (<10 %, no claysx) and around 30% of X-ray amorphous materials [6,7]. The ChemCam instrument also analyzed some regolith recurrently along the traverse. [8,9] have shown that the coarser grains (>500 microns) were felsic in composition and likely derived from the felsic rocks encountered early in the traverse. The active dunes were also slightly different in composition compared to the regolith, being depleted in the finest particles and in volatile elements [10,11]. [12] investigated the fine-grained regolith (<500 microns) during the first 200 sols of the traverse by ChemCam and found that the main carrier of the hydration in the regolith was related to the presence of Mg-rich sulfates in the amorphous component, probably derived from the weathering of olivine in water-limited acidic conditions.

The objective of this study is to better understand the volatile-element sources in the fine-grained regolith. In particular, we would like to explore the hypothesis that the amorphous sulfates found in Gale soils are derived from local inputs, more specifically the sulfate unit of Mt Sharp. Now that Curiosity has reached this unit, we would expect a higher abundance of sulfates in the regolith if the hypothesis is correct. On the other hand, we would like to explore the possible source of H and Cl in the fine-grained regolith at Jezero.

Method: ChemCam [13,14] uses the LIBS technique to retrieve the chemical composition of major elements and of some minor elements [15].

Results: The S signal has been monitored along the Curiosity traverse in the fine-grained regolith (<500 microns) analyzed by ChemCam up to sol 4160. One important thing to note is that most of the fine-grained regolith has been acquired with ChemCam during the first 60 meters of elevation, which correspond to the first 5 km of drive distance, in Aeolis Palus. Figure 1 shows some gaps in the data, with several intervals in the stratigraphy without any fine-grained regolith observations, such as between -4405 and -4285m. This is probably related to an observation bias.

Starting at elevation > -3845m, the median of the S signal is systematically higher than that found during the beginning of the traverse, in Aeolis Palus (the average of this region is shown with the red dashed line). Not only is the median overall higher, but the third quartile of the distribution is also overall higher than previous locations encountered. Moreover, the highest detections within the Mount Sharp observations do not correspond to outliers (but are included in the 3^rd quartile), in contrast to the Aeolis Palus and the VRR and Glen Torridon observations (around -4185 to -4085m).

Discussion: These preliminary results suggest that there is a slight enrichment in sulfur in the fine-grained regolith that have been analyzed in the Mount Sharp terrains compared to those analyzed in Aeolis Palus, VRR or Glen Torridon. Sulfur (along with Cl and H) in soils is mostly carried by the finest particles, as seen in Bagnold Dunes observations [11]. These finest particles are known to be transported by wind and therefore are considered to represent a global component. However, the bedrock encountered in the sulfate-bearing unit are fine-grained [29] and therefore their erosion would generate fine-grained particles more easily, that could contribute directly to the formation of local soils, which can explain the enrichment in the regolith in this unit. This would explain the difference of the S signal between the Gale and Jezero regoliths.

More work needs to be done with the ChemCam data, such as also investigating the H signal and the trends of major elements in regolith along the traverse, in order to understand if this increase in S is correlated to the presence of Mg sulfates in the bedrock, or even to search for mixtures of Mg-Na sulfates as found by [30] in some bedrock.

Figure 1: Boxplot representing the S signal in fine-grained ChemCam regolith as a function of the rover elevation (binned every 20m). Outliers are represented as stars. Red dashed line represents the average Aeolis Palus S signal.

[1] Certini et al., (2020) [2] McSween et al.,  (2010) [3] Yen et al., (2005) [4] Vasavada et al., Space Sci. Rev. 218 (2022) [5] Rapin et al.,  (2023) [6] Blake et al., (2013) [7] Rampe et al., (2018) [8] Meslin et al., (2013) [9] Cousin et al., (2015) [10] Cousin et al., (2017) [11] Ehlmann et al., (2017)  [12] David et al ,(2022) [13] Maurice et al., (2012) [14] Wiens et al., (2012) [15] Clegg et al., 2017)) [16] Rudolph et al., (2024) [17] Hughes et al, (2024).

How to cite: Cousin, A., Rapin, W., Meslin, P.-Y., Dehouck, E., Forni, O., David, G., Pilleri, P., Wiens, R. C., and Gasnault, O.: Investigation of the sources of volatile elements in fine-grained regolith on Mars   , Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-99, https://doi.org/10.5194/epsc2026-99, 2026.

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Seasonal CO₂ jet activity is one of the most dynamic surface processes currently observed on Mars [1, 2, 3, 4]. During spring, a solid-state greenhouse effect occurs due to the translucent seasonal CO₂ ice and generates pressurized gas pockets beneath the ice layer. This eventually leads to jet-like eruptions that transport dust and regolith from the substrate onto the ice surface. These events produce characteristic dark fans and blotches observed in high-resolution imagery. Their morphology and evolution provide direct information about near-surface winds, ice properties, and present-day surface–atmosphere interactions.

Repeated observations by HiRISE (High Resolution Imaging Science Experiment) onboard the Mars Reconnaissance Orbiter [5] have documented seasonal activity across large parts of the south polar regions over ten Mars years, from MY28 to MY38. The Planet Four citizen-science project was set up to outline dark seasonal deposits and has produced a large catalog of manually identified fans and blotches within selected regions of interest (ROIs). This dataset enabled the first statistical analyses of seasonal activity [6, 7], including studies of seasonal timing, regional distributions, and interannual variability [8]. However, existing analyses remain incomplete because a) they are limited to selected ROIs, b) rely on the narrow central color swath of HiRISE images, and c) do not cover the most recent years of HiRISE observations. As a result, the large-scale distribution and variability of seasonal activity across the south polar region remain poorly constrained.

This work focusses on the first application of machine learning (ML) techniques to the full record of seasonal HiRISE observations of these dark fans and blotches. Expanding on a baseline study [9] for automatic feature detection for citizen-science labelled data in selected regions for two MY, ML models are being trained and validated using the existing Planet Four catalog and will then be applied to all relevant HiRISE observations in the southern polar regions, including the full red-channel width as well as images outside of the current Planet Four ROIs. The resulting dataset will provide large-scale fan and blotch distributions over the full extent of HiRISE observations. This expanded activity catalog will be used to address several key scientific questions. First, the project will investigate how seasonal activity is distributed across the south polar cap and whether currently-known active regions are representative of broader seasonal processes. Second, repeated observations will be used to determine whether CO₂ jet activity recurs at stable locations over time, potentially implicating persistent local conditions. Third, the project will examine the interannual variability of activity patterns and fan orientations and compare these observations with atmospheric circulation predicted by higher-resolution atmospheric models (expanding the study in [7] to additional years and locations). Fan orientations derived from machine-learning detections will be used as proxies for near-surface winds and compared with modeled wind fields to assess the relationship between observed activity and atmospheric dynamics.

Fig 1. Example comparison of detection of fans and blotches by Planet Four citizen science project (on the left) and ML model YOLO11 trained on Planet Four labeled dataset [10] (on the right).

References:

[1] Kieffer, H. H. 2007, Journal of Geophysical Research, 112, E08005

[2] Hansen, C. J., Thomas, N., Portyankina, G., et al. 2010, Icarus 205, 283

[3] Thomas, N., Pommerol, A., Hauber, E., Portyankina. G. et al. 2025, SSR 221, 3

[4] Hansen, C. J., Byrne, S., Calvin, W. M. et al. 2024, Icarus 419, 115801

[5] McEwen, A. S., Byrne, S., Hansen, C. J. et al. 2024, Icarus 419, 115795

[6] Aye, K. M., Schwamb, M. E., Portyankina, G., et al. 2019, Icarus, 319, 558

[7] Portyankina, G., Michaels, T. I., Aye, K.-M., et al. 2022, Planetary Science Journal, 3, 31

[8] Hansen, C. J., Aye, K.-M., et al. 2023, LPI Contribution No. 2806, id.2315

[9] McDonnell, M. D., Jones, E., Schwamb, M. E., et al. 2023, Icarus, 391, 115308

[10] Jocher, G. and Qiu, J., 2024, https://github.com/ultralytics/ultralytics 

How to cite: Portyankina, G., Aye, K.-M., Marktstein, T., Fitoz, B., Pelivan, I., Schwamb, M., and Michaels, T.: Extending Planet Four: machine learning applied to seasonal CO2 jet activity on Mars, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-904, https://doi.org/10.5194/epsc2026-904, 2026.

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The volcanic complex Tharsis Region on Mars is known for its numerous volcanoes on top of the crust, elevated topography (doming), and a long-wavelength gravity anomaly correlated with the region. Flexural modeling of the lithosphere has commonly been used to understand the relationship between observed topography, crustal structure, and gravity, but no conclusive answers have been obtained due to the ambiguity of these models. NASA’s InSight mission has brought new information about the Martian lithosphere, which warrants a reanalysis of the support of the Tharsis Region.

Analyzing the topography and gravity data, we found that a thin shell model of can model the lithosphere of Mars that matches both the observed gravity field for spherical harmonic degrees higher than 8 and the crustal thickness at Elysium determined by the InSight mission. Our thin shell flexure model predicts an average crustal thickness of 55 km, crustal density of 3050 kg/m³, average mantle density of 3750 kg/m³, and an elastic thickness (T_e) of 100 km.

The remaining mismatch between modeled and observed gravity field for the long-wavelengths (between n=2-8 degrees) correlates with the Tharsis Region, suggesting active large-scale dynamic support of the volcanic region. We devise a fast, parameterised modelling approach to calculate the mantle flow and resulting gravity effect of such a mass anomaly. We have explored the multi-variable parameters space and run approximately 500.000 models in which we compare to the geophysical parameters.The optimal models show that there is a substantial negative mass anomaly (hot buoyant mantle material) in the mid mantle underneath the Tharsis Rise. The anomaly seems to have a flat disk shape, with a flatness of 0.2 (thickness over radius). Due to the ambiguity of the gravity data, we computed different sets of depth, size, and anomalous mass (all lighter density) for the mass anomaly underneath Mars.

We used remaining short-scale gravity residuals to derive an 3D Martian crustal density distribution. We are currently correlating these density distribution with geological events in Mars histiory. Buried mass anomalies in the subsurface of the northern polar plains seem not to be related to any geological or surface expressions, suggesting a more complex geology of the northern Martian crust than is suggested by the surface topography.

How to cite: Root, B., Qin, W., van der Tang, Y., and Thieulot, C.: Describing the Martian gravity field through lithospheric flexure and deep mantle flow modelling, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-827, https://doi.org/10.5194/epsc2026-827, 2026.

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