Introduction

The Colour and Stereo Surface Imaging System (CaSSIS; Thomas et al., 2017) has been acquiring 4 m/pixel images of the martian surface since 2018, building a database of over 38,000 images in up to four spectral bands across the planet. CaSSIS NIR-PAN-BLU (NPB) and HiRISE IR-RED-BLUE (IRB) images reveal conspicuous, red-toned outcrops (RTO) at a range of scales that are distributed across the southern highlands. While visually striking, the composition, distribution, and origins of these outcrops remain unclear. Here, we present a global analysis of RTOs aimed at resolving this.

Methods

To investigate the RTO, we manually identified a selection of ~30 examples of RTO covering a range of sizes, morphologies, textures, colours, and lighting geometries in CaSSIS NPB images, and used these examples as a training dataset for a convolutional neural network (CNN), which is able to detect occurrences of RTO similar to those in the training dataset (see techniques in Bickel et al., 2024 and references therein).

The CNN assessed all >38,000 images in the CaSSIS database (as at 28/02/2024), and produced an output of 2232 detections at >60% CNN confidence level. These outputs were manually sorted to remove false positives and to assess RTO morphology/texture. True positive RTOs, as well as those from the training dataset, were compared with CRISM footprints, and those CRISM MTRDR cubes that overlapped were analysed following the standard ratioing method (e.g. McGuire et al., 2009; Murchie et al., 2007).

Results

We observe a total of 923 “true positive” RTO CaSSIS detections (e.g. Figure 1). RTOs are most common in the areas north of the Hellas and Argyre basins, in lower elevation regions of eastern Valles Marineris, and in the Nili Fossae region. These usually crop out in the ejecta of large (>10 km) craters in these areas but can also be observed in the walls of craters and on relatively flat-lying terrain. Most RTOs are associated with Noachian-aged terrains with 76% occurring within Noachian Units (Tanaka et al., 2014), 12% in Hesperian Units, 4% in Amazonian Units, and 8% in Hesperian/Amazonian Impact Units.

RTOs typically possess a blocky, massive appearance (Figure 1a), and occur as both discrete outcrops with well-defined margins (Figure 1b), interpreted as ejecta blocks, or as diffuse deposits (Figure 1c), interpreted as intermixing with other components within ejecta blankets.

CRISM spectra from RTOs reveal a consistent and broad, yet extremely weak and slightly long-shifted 1.25 μm absorption feature, consistent with partial transformation of Fe-plagioclase to maskelynite, a diaplectic amorphous glass associated with shock metamorphism from hypervelocity impact events (e.g. Jaret et al., 2015; Spudis et al., 1984).

Figure 1: False-color examples of Red-Toned Outcrops (RTOs) from across the Hellas region. a) Large blocky RTO in Terby Crater (CaSSIS NPB); b) Discrete fractured RTO north of Hellas (HiRISE IRB); c) Large diffuse RTO with some sharp boundaries NW of Hellas (CaSSIS NPB); d) RTO under younger dark material NE of Hellas (CaSSIS NPB).

Discussion

We infer RTOs to be the products of large basin-forming impacts, with their current distribution shaped by subsequent impact gardening. Their occurrence surrounding Hellas and Argyre suggests that these units are part of the original basin ejecta fields and therefore, at least in the case of Hellas, predate the Noachian. In these regions, RTOs likely derive from Fe-plagioclase-bearing massifs uplifted from depth during the impact events, now observed as degraded massifs along the basin rims (Phillips et al., 2022; Phillips and Viviano, 2025).

RTO exposures are commonly found within ejecta in impact-modified terrains superposed on the Hellas and Argyre ejecta blankets. The absence of similar features in Noachian-aged terrains outside of these ejecta fields suggests that large basin-forming impacts are a pre-requisite to exhume deeply buried plagioclase material, and that subsequent impact gardening of basin ejecta is a primary mechanism for their exposure.

Collectively, the observed distribution, morphology, and mineralogy of RTOs point to the presence of a plagioclase-rich lower crustal component that was widespread in the Pre-Noachian martian crust, likely explaining the lower-than-expected observed density of the martian crust (Knapmeyer-Endrun et al., 2021; Bouley et al., 2020; Baratoux et al., 2014). The evidence indicates that this plagioclase-rich material underwent shock metamorphism, excavation, and emplacement within the ejecta of early basin-forming events, providing a unique window into the composition and modification history of Mars’ ancient crust.

References

• Baratoux, D., et al. (2014) Journal of Geophysical Research: Planets, vol. 119, no. 7, pp. 1707–1727
• Bickel, V. T., et al. (2024) Scientific Data, vol. 11, no. 1, p. 845
• Bouley, S., et al. (2020) Nature Geoscience, vol. 13, no. 2, pp. 105–109
• Jaret, S. J., et al (2015) Journal of Geophysical Research: Planets, vol. 120, no. 3, pp. 570–587
• Knapmeyer-Endrun, B., et al. (2021) Science, vol. 373, no. 6553, pp. 438–443
• McGuire, P. C., et al. (2009) Planetary and Space Science, vol. 57, no. 7, pp. 809–815
• Murchie, S., et al. (2007) Journal of Geophysical Research E: Planets, vol. 112, no. 5, pp. 1–57
• Phillips, M. S. and Viviano, C. E. (2025) LPSC 56, Houston, Texas, abs#1653
• Phillips, M. S., et al. (2022) Geology, vol. 50, no. 10, pp. 1182–1186
• Spudis, P. D., et al. (1984) Journal of Geophysical Research, vol. 89
• Thomas, N., et al. (2017) Space Science Reviews, vol. 212, no. 3–4, pp. 1897–1944

How to cite: McNeil, J., Grindrod, P., Tornabene, L., Bickel, V., Stabbins, R., and Cuadros, J.: Seeing Red: Shocked Plagioclase as Pre-Noachian Stratigraphic Tracers, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-617, https://doi.org/10.5194/epsc-dps2025-617, 2025.

The Mawrth Vallis region of Mars features abundant phyllosilicate outcrops as well as smaller areas where sulfates are present. This study evaluates field sites where phyllosilicates and sulfates co-occur to assist in constraining the ancient geochemical environments on Mars. Mineral transitions at Mawrth Vallis indicate changing geochemical conditions over time - from the lower Fe-rich smectite horizon about 200 meters thick to thinner units of sulfates, Al-phyllosilicates including halloysite in some regions, then Si-rich phases at the top of the profile [1] (Fig. 1a-c). Smectites form through wet/dry cycling in generally arid environments, while halloysite requires more humid conditions. Ca-sulfates and Al-clays represent a decrease in pH from the environment supporting formation of Fe/Mg-smectite, and the jarosite outcrops indicate an even lower pH. Sulfuric gases released from Syrtis may have produced sulfates in the groundwater [2] that flowed downhill from Meridiani towards Mawrth Vallis (Fig. 1d). This could have produced acidic brines that altered the expansive Fe/Mg-smectites at Mawrth Vallis and formed pockets of sulfates.

Specific phyllosilicate and sulfate minerals are mapped using vibrational bands in CRISM images (Fig. 1a). Spectral features in the region ~1.4-2.6 µm are most useful for identifying and characterizing these minerals, including the H₂O combination band near 1.91-1.92 µm. The Fe-rich smectite outcrops also exhibit Fe-OH bands near 1.42 and 2.29-2.30 µm. The Al-smectite units include Al-OH bands at 1.41-1.42 and 2.20-2.21 µm, while small locations containing halloysite/kaolinite and alunite have additional bands near 1.39-1.47, 1.75, 2.17, and 2.32 µm (Fig. 2). Areas containing jarosite have spectral bands near 1.47, 1.85, 2.22, and 2.26 µm (Fig. 3). Sites including hydrated sulfates include a drop in reflectance near 2.4-2.5 µm and Ca sulfates have a band near 1.75-1.78 µm.

Phyllosilicate - sulfate assemblages were investigated at field sites to assist in constraining the environments where these minerals form. The Painted Desert in Arizona features expansive outcrops of clay-bearing horizons (Fig. 4a), similar to Mawrth Vallis. Coordinated analyses of spectra from the field, lab, and aerial instruments of the light-toned and reddish horizons show the presence of clays and carbonates [3] (Fig. 4b-d). Sulfates are present in regions with polygonally-cracked surfaces where combinations of gypsum, jarosite, and montmorillonite are observed [4] (Fig 4ef). The south sulfur bank inside the Kilauea caldera (Fig. 5) contains a mixture of nontronite, saponite, montmorillonite, opal-A, gypsum, jarosite, and ferrihydrite due to hydrothermal alteration of ash and basalt from volcanic gases [5]. Lighter-toned outcrops are dominated by opal with some gypsum, saponite and jarosite (Fig. 5d), while the darker orange-tan layers include nontronite, ferrihydrite, and jarosite in addition to opal and gypsum (Fig. 5e). Analogs from the rainy Waimea Canyon region of Kauai include goethite, halloysite, ferrihydrite, and allophane in altered rinds on the rocks (Fig. 6). Additional sites altered under lower pH conditions contain hematite and jarosite [6].

Pedogenic alteration at the Painted Desert produced wide horizons of clay-bearing units interspersed with units of iron oxides/hydroxides and carbonates. Sulfates are observed together with phyllosilicates in regions with polygonally-cracked terrain. Jarosite and gypsum are present in a hydrothermal setting at Kilauea, while halloysite and goethite or jarosite and hematite are observed in the rainy and highly leached environment of Kauai. Observations of alteration minerals at these field sites suggest the Mawrth Vallis region of Mars experienced a largely arid environment with wet/dry cycling to produce the thick smectite profiles, with short-term periods of acidic fluids to form sulfates and strong leaching to form halloysite. Allophane likely formed on Mars when water was less abundant or colder [7].

Acknowledgements: The authors are grateful for support from NASA MDAP # 80NSSC19K1230 and NASA SSW #80NSSC23K0032.

References: [1] Bishop et al. (2020) Multiple mineral horizons in layered outcrops at Mawrth Vallis, Mars, signify changing geochemical environments on early Mars, Icarus, 341, 113634. [2] Moore & Szynkiewicz (2023) Aqueous sulfate contributions in terrestrial basaltic catchments: Implications for understanding sulfate sources and transport in Meridiani Planum, Mars, Icarus, 391, 115342. [3] McKeown et al. (2009) Coordinated lab, field, and aerial study of the Painted Desert, AZ, as a potential analog site for phyllosilicates at Mawrth Vallis, Mars, 40th LPSC, #2509. [4] Perrin et al. (2018) Mars evaporite analog site containing jarosite and gypsum at Sulfate Hill, Painted Desert, AZ, 49th LPSC, #1801. [5] Bishop et al. (2024) Solfataric alteration at the South Sulfur Bank, Kilauea, Hawaii, as a mechanism for formation of sulfates, phyllosilicates, and silica on Mars American Miner., 109, 1871–1887. [6] Gruendler et al. (2023) Characterizing Altered Volcanic Rocks from Waimea Canyon, Kauai, 54th LPSC, #1892. [7] Bishop et al. (2018) Surface clay formation during short-term warmer and wetter conditions on a largely cold ancient Mars, Nature Astronomy, 2, 206-213.

Figures:

Fig. 1 a-c) Alteration at Mawrth Vallis, Mars [1]. a) CRISM spectra of 5 distinct units. b) Diagram of altered stratigraphy. c) View of CRISM over HRSC. d) Potential formation mechanism for sulfate formation in groundwater at Mawrth Vallis, after [2].

Fig. 2 a) HRSC view of light-toned phyllosilicate-rich units. b) CRISM image FRT0000B141. c) Mineral parameter maps for Fe-smectite, halloysite, Al-smectite. d) CRISM spectra of selected outcrops compared to spectra of minerals.

Fig. 3 a) HRSC view of light-toned phyllosilicate-rich units. b) CRISM image FRT0000A425 with region containing jarosite marked by blue oval. c) Mineral parameter maps including jarosite. d) CRISM spectra of selected outcrops compared to spectra of minerals.

Fig. 4   Painted Desert, Arizona. a) Phyllosilicate-rich horizons. b-c) Close-up views of changing mineralogy. d) Comparison of HyMap aerial spectra with field and lab spectra. e) Gypsum and jarosite outcrops under polygonally-cracked terrain. f) Spectra of Painted Desert materials and lab mixtures compared to CRISM spectrum.

Fig. 5  Kilauea south sulfur bank, Hawaii. a) LG with field spectrometer. b) View of light-toned material. c) JLB sampling orange layered material. d-e) VNIR spectra of light-toned material, orange layers, and minerals.

Fig. 6  a) Waimea Canyon, Kauai. b-c) Close-up views of altered rocks. d) Spectra of selected samples compared to spectra of minerals.

How to cite: Bishop, J., Gruendler, L., Gruendler, K., Parente, M., Gross, C., Saranath, A., Itoh, Y., Gruendler, M., McKeown, N., and Murchie, S.: Constraining the Ancient Geochemical Environments that formed the Complex Phyllosilicate and Sulfate Assemblages at Mawrth Vallis Through Comparison with Field Sites, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1957, https://doi.org/10.5194/epsc-dps2025-1957, 2025.

The study of Martian mineralogy provides valuable insights into its geological history and environmental conditions over time. One significant aspect of Martian mineralogy is the presence of Fe/Mg-phyllosilicates, also known as clay minerals. These phyllosilicates are important indicators of past aqueous activity on Mars, suggesting the presence of water in its early history. The formation of Fe/Mg-phyllosilicates typically occurs in environments with moderate to low temperatures and near-neutral pH conditions, where water interacts with volcanic rocks or crustal materials containing iron and magnesium. Phyllosilicates make up the majority of aqueously altered minerals on Mars and are widespread on its surface, preferably in ancient Noachian/Hesperian terrains.

Significant amounts of this mineral type have been detected from orbital measurements by the Mars Express/OMEGA and MRO/CRISM spectrometers and are recorded in the Mars Orbital Catalog of Aqueous Alteration Signatures (MOCAAS) [1]. This work concentrates on the substantial Fe/Mg-phyllosilicate deposits that were detected northwest of Argyre Planitia, one of the large impact basins in the ancient terrain of the southern hemisphere of Mars. Despite the wide-spread presence of alteration minerals in this region, no detailed studies have ever been conducted to characterize their geology and chronology.

We investigated the substantial Fe/Mg-phyllosilicate deposits that were detected northwest on Argyre Planitia to shed light on to what extent these hydrated minerals correlate with deposits and structures that were formed by the formation of the Argyre basin, such as impact-induced hydrothermal alteration processes and impact tectonics.

We used remote sensing data (HRSC [2], CTX [3], THEMIS [4], HiRISE [5], MGS MOLA - MEX HRSC Blended DEM Global [6], CaSSIS [7]) to produce a photogeological map with a mapping scale of 1:100,000 and boundaries of 41.5°S to 36.5°S and 298°E to 304°E. The mapping was accomplished on CTX whereas the other dataset were used to validate different surface units. In particular, we used multispectral colour data from HRSC and CaSSIS to discriminate candidate units in terms of their mineralogical composition.

Our region of interest features widespread fractured units that are embayed between two presumably tectonic, scarp-bounded blocks with an elongation approximately concentric around Argye, suggesting a impact-controlled structural history. The unit “fractures_light_tones_plains” and “smooth_light_toned_plain” are considered the main clay-bearing units of interest due to their spatial correspondence with the areas where MOCAAS detected Fe/Mg-phyllosilicates. The region also displays abundant fractures forming polygonal ground, a characteristic that is typically associated with phyllosilicates elsewhere on Mars. 

References

[1] Carter, J., Riu, L., Poulet, F., Bibring, J.-P., Langevin, Y., Gondet, B., 2023. A Mars orbital catalog of aqueous alteration signatures (MOCAAS). Icarus 389, 115164, https://doi.org/10.1016/j.icarus.2022.115164.

[2] Jaumann, R., Neukum, G., Behnke, T., Duxbury, T.C., Eichentopf, K., Flohrer, J., Gasselt, S.v., Giese, B., Gwinner, K., Hauber, E., Hoffmann, H., Hoffmeister, A., Köhler, U., Matz, K.-D., McCord, T.B., Mertens, V., Oberst, J., Pischel, R., Reiss, D., Ress, E., Roatsch, T., Saiger, P., Saiger, F., Scholten, F., Schwarz, G., Stephan, K., Wählisch, M., the HRSC Co-Investigator Team, 2007. The high-resolution stereo camera (HRSC) experiment on Mars Express: Instrument aspects and experiment conduct from interplanetary cruise through the nominal mission. Planetary and Space Science 55, 928-952[3] Malin, M. C., Bell, J. F., Cantor, B. A., Caplinger, M. A., Calvin, W. M., Clancy, R. T., et al. (2007). Context camera investigation on board the Mars Reconnaissance Orbiter. Journal of Geophysical Research, 112, E05S04. https://doi.org/10.1029/2006JE002808.

[3] Malin, M. C., Bell, J. F., Cantor, B. A., Caplinger, M. A., Calvin, W. M., Clancy, R. T., et al. (2007). Context camera investigation on board the Mars Reconnaissance Orbiter. Journal of Geophysical Research, 112, E05S04. https://doi.org/10.1029/2006JE002808

[4] Christensen, P.R., Jakosky, B.M., Kieffer, H.H. et al. The Thermal Emission Imaging System (THEMIS) for the Mars 2001 Odyssey Mission. Space Science Reviews 110, 85–130 (2004). https://doi.org/10.1023/B:SPAC.0000021008.16305.94.

[5] McEwen, A. S., Eliason, E. M., Bergstrom, J. W., Bridges, N. T., Hansen, C. J., Delamere, W. A., et al. (2007). Mars Reconnaissance Orbiter's High Resolution Imaging Science Experiment (HiRISE). Journal of Geophysical Research, 112(E5). https://doi.org/10.1029/2005JE002605.

[6] Smith, D., Zuber, M., Frey, H., Garvin, J., Head, J., Muhleman, D., . . . Banerdt, W. (2001). Mars Orbiter Laser Altimeter: Experiment summary after the first year of global mapping of Mars. Journal of Geophysical Research: Planets, 106(E10), 23689-23722. doi:10.1029/2000JE001364.

[7] Thomas, N., Cremonese, G., Ziethe, R. et al. The Colour and Stereo Surface Imaging System (CaSSIS) for the ExoMars Trace Gas Orbiter. Space Sci Rev 212, 1897–1944 (2017). https://doi.org/10.1007/s11214-017-0421-1.

How to cite: Da Silva Encarnacao, M., Tirsch, D., Hauber, E., Rangarajan, V., Machado, P., and Peixinho, N.: Mapping of phyllosilicates NW of Argyre basin (Mars) with Mars Express/HRSC colour data, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1729, https://doi.org/10.5194/epsc-dps2025-1729, 2025.

Introduction:

Iron plays a pivotal role in shaping Mars’ surface processes, influencing its climate evolution, and affecting its potential for habitability. Over the past decade, data from Mars exploration missions have significantly deepened our understanding of iron geochemical cycling -- the set of processes through which iron transitions between different oxidation states and mineral forms within the Martian surface environment. These transformations are closely linked to Martian hydrological activity, atmospheric changes, and redox conditions that may have supported life. This review synthesizes key advances in our knowledge of iron cycling on Mars from recent years. It examines the primary sources and mineral forms of iron, traces the temporal evolution of iron cycling across geological epochs, explores its environmental and climatic implications, and reviews mechanistic insights gained from experimental and modeling studies. The paper also discusses unresolved scientific debates and methodological challenges, providing perspectives to guide future study.

Sources and forms of Fe on Mars

Iron inventory on Mars primarily originates from mafic and ultramafic igneous rocks formed through planetary differentiation and volcanic activity. Over time, these iron-bearing silicates underwent aqueous alteration, giving rise to a diverse suite of secondary minerals. These include iron oxides (e.g., hematite, magnetite), hydroxides (e.g., goethite, ferrihydrite), sulfates (e.g., jarosite), carbonates (e.g., siderite), and iron-rich phyllosilicates (e.g., nontronite) [1,2]. Notable new discoveries from the rover missions include siderite-rich layers in Gale Crater, suggesting CO₂ sequestration in ancient Martian lakes [3] and at Jezero Crater, Perseverance identified coarse-grained olivine-rich igneous rocks and serpentinized fragments, indicative of hydrothermal activity [4]. Furthermore, spectral analyses now suggest that Martian dust is dominated not by crystalline hematite, but by ferrihydrite, an amorphous iron oxyhydroxide typically formed under low-temperature aqueous conditions [2].

Temporal evolution of Fe cycling

Iron cycling on Mars closely mirrors the planetary transition from early wet or icy conditions to the cold, arid environment observed today. During the Noachian period (4.1-3.7 Ga), iron was likely highly mobile in the form of Fe²⁺ within neutral to mildly acidic aqueous environments. Evidence from Gale Crater suggests the presence of redox-stratified lake systems, characterized by magnetite and ferrous phyllosilicates at depth, with more oxidized iron phases near the surface [5]. Ferrihydrite-rich sediments may also have formed under these conditions. In the Hesperian epoch (~3.7-3.0 Ga), increasingly oxidizing and acidic conditions favored the formation of iron sulfates, such as jarosite. The detection of high-Mn oxides by the Curiosity rover has been interpreted as evidence for transiently oxygen-rich episodes[6], though alternative oxidants, such as chlorates or UV-driven photochemical processes, remain plausible [7]. During the Amazonian period (~3.0 Ga to present), extreme cold and aridity severely limited aqueous alteration. Iron cycling during this time has been dominated by the oxidation of surface-exposed Fe²⁺ minerals and the wind-driven redistribution of iron-rich dust.

Climatic and habitability implications

Iron minerals function as valuable environmental proxies on Mars. For example, ferrihydrite is indicative of cold, aqueous conditions, while jarosite and other sulfates point to acidic, evaporative environments. The occurrence of siderite implies near-neutral pH and elevated CO₂ levels, suggesting a more temperate early climate [3]. Beyond environmental reconstruction, iron redox cycling may have supported microbial metabolisms. Nitrate-dependent Fe²⁺ oxidation has been proposed as an energetically favorable pathway in early Martian lakes, which likely contained both dissolved Fe²⁺ and nitrate [8]. Moreover, oxidized iron minerals may have served as long-term sinks for oxygen, helping to buffer the planetary atmospheric composition and influence climate evolution. In the present day, iron-bearing dust continues to affect Mars energy balance by modulating solar radiation and atmospheric dynamics.

Future directions

Iron cycling on Mars has not only recorded environmental transitions but has also actively shaped them. Processes such as serpentinization likely contributed to abiotic hydrogen production and may be linked to episodic methane detections. At the same time, extensive Fe oxidation may have consumed significant amounts of atmospheric O₂, hindering its long-term accumulation. Upcoming missions, including Mars sample return, will enable detailed laboratory analyses of iron speciation and isotopic composition, including isotopic signatures of other elements, critical for constraining the timing of redox transitions and evaluating potential biosignatures. Key open questions remain: When and how did the Fe oxidation occur on Mars? Did Mars undergo a global oxidation event? How deeply did oxidation penetrate the crust? Answering these questions will require integrated approaches that combine planetary missions, laboratory experiments, and advanced geochemical modeling.

Acknowledgements: This research was supported by the National Natural Science Foundation of China (Grant Nos. 42441803, 4237304).

References

[1] Fraeman, A. A. et al. (2020). J. Geophys. Res. Planets, 125, e2020JE006527.

[2] Valantinas, A. et al. (2025). Nat. Commun., 16, 1712.

[3] Tutolo, B. M. et al. (2025). Science, 370, 270-274.

[4] Farley, K. A. et al. (2022). Science, 377, 1321-1327.

[5] Hurowitz, J. A. et al. (2017). Science, 356, eaah6849.

[6] Lanza, N. L. et al. (2016). Geophys. Res. Lett., 43, 7398-7407.

[7] Mitra, K. et al. (2022). J. Geophys. Res. Planets, 127, e2021JE007067.

[8] Bryce, C. et al. (2018). Front. Microbiol., 9, 513.

How to cite: Zhao, Y.: Iron Geochemical Cycling on Mars: A Temporal and Planetary Perspective, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1488, https://doi.org/10.5194/epsc-dps2025-1488, 2025.

Introduction: Martian meteorites are currently the only samples on Earth available to study Mars. These samples comprise mainly (>80% by number) shergottite-type rocks, which are basaltic to lherzolitic [1]. Shergottites provide valuable information regarding the conditions of the martian interior, including its chemical composition and redox state. The redox state of shergottites of various petrologic types has been estimated (Fig. 1), and there appears to be a correlation between oxidation state and relative enrichment/depletion of incompatible trace elements (ITEs), with rocks that are enriched in ITEs also being more oxidized. An additional observation is that shergottites undergo extensive oxidation during their formation [2-4], with an increase in fO₂ of 1-3 log units. Auto-oxidation can increase fO₂ by a maximum of ~0.5 log units [3, 5] and thus cannot solely explain this change. Degassing of volatiles had been suggested as an alternative mechanism to oxidize these rocks [2-6]. Recent studies on the solubility of C, S, and H species in martian compositions [7-12], have allowed for Mars-appropriate degassing models to be developed, like Magma and Gas Equilibrium Calculation (MAGEC) [13]. MAGEC allows a user to specify the melt composition, pressure, temperature, and starting fO₂ and calculates the proportion of volatile species that would exsolve from the melt, and the fO₂ of the remaining melt. This study uses the program MAGEC to evaluate the effect of volatile degassing on the redox evolution of shergottites.

Methods: Various shergottite compositions were tested to capture the diversity within the group. The bulk compositions of olivine-phyric shergottites Northwest Africa (NWA) 5789 [14], NWA 6234 [15], and Larkman Nunatak (LAR) 06319 [16] were used, as these samples represent a mantle melt or closely approximate one, and thus, serve as representations of the martian interior. Additionally, the parental melt compositions of poikilitic shergottites NWA 7755, NWA 10169, NWA 11065, and Allan Hills (ALHA) 77005, estimated from their melt inclusions [6, 17], were used. Poikilitic shergottites were included in this study as they display some of the largest fO₂ variations. To evaluate how changing melt composition can affect volatile degassing, all compositions were crystallized at 1 kbar at an fO₂ of QFM-4, QFM-3, or QFM-2, using rhyolite-MELTS [18, 19]. The melt composition was recorded for every 10% of crystals formed, from 10%-99% crystals. Degassing models were run for every 10% increase in crystals/decrease in melt, with degassing from decompression occurring from 1000-1 bar at a temperature of 1100°C, 1050°C, 1000°C, or 950°C, and degassing from cooling occurring at 1 bar from the initial temperature down to 900°C. These models were run at an fO₂ of QFM-4, QFM-3, or QFM-2, with 0.3 wt.% H₂O, 0.08 wt.% CO₂, and 0.5 wt.% S added. The volatile abundances used in this study are based on H, C, and S abundances estimated for the martian mantle and crust [7, 11, 20-24].

Results and Discussion: All models displayed oxidation through degassing from decompression (Figs. 2-3). However, the extent of oxidation depends on the composition of the melt and the initial fO₂ of the melt before any degassing. While degassing from decompression consistently increased fO₂, degassing during cooling generally decreased fO₂, unless the melt was highly evolved (90-99% crystals)(Figs. 2-3). The composition of the vapor as the sample degassed during decompression was similar for all model runs. Initially, the vapor consisted of C-species (Fig. 4), which did not lead to significant changes in fO₂ (Fig. 1); however, at pressures <100 bar, H-species become dominant, which is when the largest oxidative increases occur. For NWA 5789, the maximum oxidative increase (Δ+1.5) occurred when the melt had only crystallized 10-20%. Generally, however, the runs that showed the largest oxidative increases were those where the melt had crystallized 90-99% (Figs. 2-4). The largest increase in fO₂ occurred in models run at QFM-4, with a Δ+1.5-2.75 log unit change seen. The smallest redox change occurred in models run at QFM-2, with a Δ+0.5-1 log unit change. This may explain why depleted and intermediate shergottites (Fig. 1) show the largest fO₂ changes – they have magmatic fO₂s of QFM-3 to QFM-4. The oxidative changes reported in the poikilitic shergottites studied could be replicated with the degassing models (Fig. 2). However, samples that had the greatest increase in fO₂ required extensive crystallization (90-99%) to have occurred before degassing. This work suggests that the large fO₂ changes seen in shergottites do not require martian magmas to be particularly hydrous to degas or require extensive auto-oxidation to occur. Additional models attempting to replicate the redox changes of other poikilitic, olivine-phyric, and basaltic/gabbroic shergottites are ongoing.

References: [1] Herd C.D.K., and Benaroya S. (submitted). [2] Castle N. and Herd C.D.K. 2017. MaPS 52, 125–146. [3] Peslier A.H. et al. 2010. GCA 74, 4543–4576. [4] Rahib R.R. et al. 2019. GCA 266, 463–496. [5] Shearer C.K. et al. 2013. GCA 120, 17–38. [6] Combs, L.M. et al 2019. GCA 266, 435–462. [7] Ardia P. et al. 2013. GCA 114, 52–71. [8] Armstrong L.S. et al. 2015. GCA 171, 283–302. [9] Ding, S. et al. 2014. GCA 131, 227–246. [10] Iacono-Marziano G. et al. 2012. GCA 97, 1–23. [11] Li Y. et al. 2017. JGR: Planets 122, 1300–1320. [12] Stanley B.D. et al. 2014. GCA 129, 54–76. [13] Sun C. and Lee C-T. 2022. GCA 338, 302–321. [14] Gross J. et al. 2011. MaPS 46, 116–133. [15] Filiberto J. et al. 2012. MaPS 47, 1256–1273. [16] Basu Sarbadhikari A. et al. 2009. GCA 73, 2190–2214. [17] O’Neal E.W. et al. 2024. GCA 373, 122–135. [18] Ghiorso M.S. and Gualda G.A.R. 2015. Cont. Min. & Petro. 169, 53. [19] Gualda, G.A.R. et al. 2012. J. of Petro. 53, 875–890. [20] Gaillard F. et al. 2013. Space Sci. Rev. 174, 251–300. [21] McCubbin F.M. et al. 2012. Geology 40, 683–686. [22] Paquet M. et al. 2021. GCA 293, 379–398. [23] Righter K. et al. 2009. EPSL 288, 235–243. [24] Stanley B.D. et al. 2011. GCA 75, 5987–6003.

How to cite: Benaroya Fucile, S. and Herd, C. D. K.: Degassing as the cause of the large redox variations seen in shergottites, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-873, https://doi.org/10.5194/epsc-dps2025-873, 2025.

During >17 years observing Mars from orbit, the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) collected 2 main types of spectral images, targeted images at 18 or 36 m/pixel that utilized the instrument's full 544-wavelength hyperspectral capability, and mapping image strips that returned fewer channels at reduced spatial resolution. Targeted images cover ~3% of Mars at very high resolution, focusing on key exposures that reveal primary and secondary mineral assemblages and their geologic relations. Mapping image strips cover intervening areas to provide spatial continuity in mineral mapping, find new sites for targeted observations, and allow geologic relations to be extrapolated over the Martian surface [1].

Two primary mapping modes were used. (A) VNIR+IR multispectral mapping was CRISM’s original mapping mode. CRISM spent most of its observing time in this mode or its derivatives for as long as cryocoolers for the IR detector remained functional. 73 wavelengths of returned data were selected to characterize depths of atmospheric gas and mineral absorptions known to be present from OMEGA data including olivine, pyroxene, hematite, smectite clay, and hydrated sulfate [2]. Spatial sampling at 10x pixel binning yielded a pixel scale of 180 m, covering ~86% of Mars. A subset of the data covering 39% of Mars had extended 262-channel coverage to more accurately measure subtly different absorptions due to newly discovered carbonates, hydroxysulfates, hydrated silica, and higher metamorphic grade hydrous silicates. (B) VNIR-only hyperspectral mapping was performed whenever cryocoolers were off, to map Fe-bearing silicates, oxides and sulfates. Most areas are covered by data using 5x pixel binning, yielding 90-m effective pixels including 90 VNIR channels with useful signals. Gaps are filled by VNIR mapping using 10x pixel binning, yielding 180-m effective pixels. Together, VNIR hyperspectral mapping modes cover >99% of Mars.

VNIR+IR multispectral data were assembled into a near-global mosaic of mapping strips divided into 1764 ~5°x5° tiles with a sampling of 327 pixels per degree (ppd), Multispectral Reduced Data Records or MRDRs; VNIR hyperspectral data were assembled into a parallel set of tiles with twice the spatial resolution (654 ppd), VNIR Hyperspectral Data Records or VRDRs. Both data sets are available in the PDS (https://pds-geosciences.wustl.edu/missions/mro/crism.htm). Using procedures described in detail by Seelos et al. [3] reflectance data have been processed to remove optical and instrument artifacts, correct photometric effects of illumination to a normal solar incidence, and normalize atmospheric opacities to parts of the dataset collected under clearest atmospheric conditions. Both data sets include spectral reflectance as well as derived spectral indices that serve as mineral indicators, plus pixel-by-pixel information that relates mosaicked data back to source mapping strips.

Figure 1 compares MRDR and VRDR data sets, over the first 8 Mars charts (out of 28, excluding polar regions) of VRDR tiles released to the PDS as of 7 May 2025 (494 of 1764 tiles). The "browse products" shown are combinations of spectral reflectances and/or spectral indices as defined by Viviano et al. [4]. In MRDR IR "false color" (upper left), most areas appear in shades of gray due to the relatively "flat" spectral reflectance at IR wavelengths, with the exception of pale blue and green tones in areas of hydrated mineralogy. In contrast, VNIR enhanced "true color" (lower left) varies from dark reddish gray to bright red, due to differences in coverage of gray mafic sand and rock by dust having a red visible spectral slope due to nanophase ferric oxides (npFeOx). The VRDRs have superior spatial continuity and 2x-higher spatial resolution. MRDR coverage of IR wavelengths (upper right) measures centers and shapes of broad absorption centered near 1 and 2 µm in the spectral indices BD1300, LCPINDEX2, and HCPINDEX2. The combinations of values distinguish low- and high-Ca pyroxenes, olivine, and Fe-bearing glass (in green, blue, red, and orange tones respectively). VRDR coverage of Fe2+ and Fe3+ absorptions at 0.4-1.02 µm (lower right), measured in the spectral indices BD920_2 and BDI1000VIS, discriminates low- and high-Ca pyroxene (in cyan and blue tones respectively) but does not uniquely discriminate olivine or glass. The BD530_2 and BD860_2 or BD920_2 spectral indices in the VRDRs indicate locations rich in crystalline hematite. Additional VRDR spectral indices including RBR–in concert with IR indices – can together indicate other ferric phases such as the oxyhydroxide goethite and the ferric sulfate copiapite where they occur. More than two dozen additional spectral indices in the MRDR data discriminate the wide variety of hydrated and hydroxylated silicates, oxides, and sulfates, and hydrated silica and carbonate phases detected in CRISM data [4].

SUMMARY: Over 17 years operating in Mars orbit, CRISM collected two major global spectral maps of Mars. The image strips forming each map were corrected for artifacts and normalized to clear atmospheric conditions with atmospheric gas absorptions removed. The data are available to the community as corrected spectral reflectance as well as derived spectral indices that serve as indicators of various minerals, plus pixel-by-pixel information that relates mosaicked data back to source mapping strips.

Figure 1. IR false color (upper left) and VNIR enhanced true color (lower left) browse product maps covering the first eight Mars charts of VRDR deliveries. IR (upper right) and VNIR (lower right) browse products show spectral indicators of Fe mineralogy. Spectral absorptions at IR wavelengths distinguish primary mafic mineralogies. VNIR wavelengths distinguish low- and high-Ca pyroxene as well as a number of ferric minerals including crystalline hematite.

References: [1] Murchie, S.  et al. (2009) J. Geophys. Res., 114, E00D07. [2] Bibring, J.-P. et al. (2005) Science, 307, 1576-1581. [3] Seelos, F. et al. (2024) Icarus, 419, 115612. [4] Viviano, C. et al. (2014) J. Geophys. Res., 119, 1403-1431.

How to cite: Murchie, S., Seelos, F., Hancock, K., Stephens, D., Poffenbarger, R., Romeo, G., Viviano, C., Frizzell, K., and Packer, L.: CRISM Global Visible/Infrared Spectral Maps of Mars, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-136, https://doi.org/10.5194/epsc-dps2025-136, 2025.

Introduction

Earth's prebiotic chemistry is based on water and thermal sources (internal or external to the Earth)^1,2. In contrast, the prebiotic chemistry of extraterrestrial systems (Mars, Europa, Titan, Enceladus, etc.) is primarily driven by radiation sources^3–5. Recent work leveraging Martian and ocean world natural and synthetic analog materials was used to classify biotic and abiotic organics in the context of multiple planetary missions (with Curiosity, Perseverance, Rosalind Franklin, and Dragonfly)^6–9. Our experiments yielded a chemical network that abiotically produced building blocks of life (e.g., amino acids up to small-peptides and thiamine and nucleobases up to nucleotides) when synthetic analogs were hydrolyzed in contact with salts and/or exposed to X-/Ɣ-rays and proton irradiation^7,10. The different irradiation simulations on natural and synthetic analog materials analyzed by spaceflight instruments and/or high-resolution mass spectrometry assessed the question: How fast may the transition from prebiotic abiotic chemistry to biotic chemistry take place? A “primitive biochemistry transition” would occur and contradicts the expectation of a clear biotic-abiotic boundary between the production of polymers abiotically and biologically in a primitive environment. Indeed, our experiments and some meteoritic data revealed the production of small biopolymers abiotically from a few hundred to tens of thousands of years^10–12.

Materials and Methods

To address the influence of different radiation sources on organic matter transformation as a pure standard or in a matrix/medium analog to extraterrestrial surfaces, we got access to multiple radiation facilities (SOLEIL-France and CLS-Canada synchrotron for X-rays, GSFC-NASA-USA for Ɣ-ray and protons radiations) and analyzed with X-ray, infrared spectroscopy and GC-MS/orbitrap.

To simulate Mars near surface environment, we first studied soft/mid X-rays that could be indirectly produced by the main elements in the Martian regolith (secondary X-rays by carbon (0.28 keV), silica (1.74 keV), sulfur (2.31 keV), chlorine (2.62 keV), or iron (6.40 keV)). Those experiments focused on amino acids (L-Ala, L or D/L-Phe), peptides (Ala-Gly), carboxylic acids (trimesic, lignoceric, and benzoic acids), nucleobases (adenine and uracil), and organics detected by the Sample Analysis at Mars (SAM) at Gale crater (chlorobenzene and thiophene).

We then simulated the radiative conditions at higher energies for Mars and ocean worlds (using γ-rays at 1-300 krad equivalent to 6 months-1000 Titan years’ simulation, for instance, and protons at 200 MeV – e.g., a few Titan months) and chemical environment that tropospheric aerosols or surface deposits may undergo on Titan to forecast Dragonfly operations, analysis, and interpretations.

Results

Low radiation energies enhance the production of building blocks of life (e.g., nucleobases, amino acids, sugars) (Fig. 1).

Low eradiation energies induce interactions between organic matter and inorganic soluble or solid material (bond and/or form organo-mineral/salt products).

While low energy radiation enhanced the production of building blocks of life (BBLs), high energy radiation degraded faster the prebiotic precursors than  produced the BBLs (Fig. 2). High radiation energies (photons and particles) benefit to the polymerization.

Conclusions

Within protected environments (e.g., Mars subsurface environments – below 10 cm – from SAM-MSL data and investigation for MOMA-ExoMars), biosignatures may be preserved for at least 100 million years thanks to salts.

A “primitive biochemistry transition” may have occurred in crater impacts few billion years ago (e.g., at Gale and Jezero craters) and contradicts the expectation of a clear biotic-abiotic boundary between the production of polymers abiotically and biologically in a primitive environment. Indeed, our experiments and some meteoritic data revealed the abiotic production of small biopolymers from a few hundred to tens of thousands of years driven by radiation and a catalytic substrate.

References

• Westall, F. et al. A Hydrothermal-Sedimentary Context for the Origin of Life. Astrobiology 18, 259–293 (2018).
• Westall, F., Brack, A., Fairén, A. G. & Schulte, M. D. Setting the geological scene for the origin of life and continuing open questions about its emergence. Frontiers in Astronomy and Space Sciences 9, (2023).
• Cooper, J. F., Johnson, R. E., Mauk, B. H., Garrett, H. B. & Gehrels, N. Energetic Ion and Electron Irradiation of the Icy Galilean Satellites. Icarus 149, 133–159 (2001).
• Cockell, C. S. & Andrady, A. L. The Martian and extraterrestrial UV radiation environment--1. Biological and closed-loop ecosystem considerations. Acta Astronaut 44, 53–62 (1999).
• Dartnell, L. R., Desorgher, L., Ward, J. M. & Coates, A. J. Modelling the surface and subsurface Martian radiation environment: Implications for astrobiology. Geophysical Research Letters 34, (2007).
• Boulesteix, D. et al. Geochemical and Metabolomic study of few Yellowstone spring systems over a range of pH. in Life in the Sub Surface: Habitats, Species, Metabolism and Survival Strategies (Angra do Heroismo, Portugal, 2023).
• Buch, A. et al. Influence of the secondary X-Rays on the organic matter at Mars’ near-surface. in AGU Fall Meeting 2022 P12A-08 (Chicago, United States, 2022).
• Boulesteix, D. et al. Extremophile Metabolite Study to Detect Potential Biosignatures and Interpret Future Gas Chromatography-Mass spectrometry Ocean Worlds in situ analysis (e.g. Dragonfly mission with its DraMS instrument and EuropaLander with its EMILI instrument). in AGU Fall Meeting Abstracts vol. 2022 P55G-1650 (2022).
• Millan, M. et al. Sedimentary Organics in Glen Torridon, Gale Crater, Mars: Results From the SAM Instrument Suite and Supporting Laboratory Analyses. Journal of Geophysical Research: Planets 127, e2021JE007107 (2022).
• Boulesteix, D. et al. Titan Simulation for DraMS Analysis and Prebiotic Chemistry Interpretation Using Analog Materials Exposed to Gamma-rays and Protons. AGU24 (2024).
• Schmitt-Kopplin, P. et al. High molecular diversity of extraterrestrial organic matter in Murchison meteorite revealed 40 years after its fall. Proceedings of the National Academy of Sciences 107, 2763–2768 (2010).
• Barks, H. L. et al. Guanine, adenine, and hypoxanthine production in UV-irradiated formamide solutions: relaxation of the requirements for prebiotic purine nucleobase formation. ChemBioChem 11, 1240–1243 (2010).

How to cite: Boulesteix, D., Buch, A., Masson, G., Szopa, C., Freissinet, C., Trainer, M., Eigenbrode, J., and Chou, L.: Radiation-driven Prebiotic Chemistry and Biosignatures Detection, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-411, https://doi.org/10.5194/epsc-dps2025-411, 2025.

Keywords: Polygon, Qaidam Basin, Subsurface fluid, Halite crust, Gypsum raised rim, Mars

Abstract:

Polygonal landforms ranging in size from a few meters to several hundred meters are present in ancient salt playas on Earth and Mars (Anglés and Li, 2017). The formation of these landforms may provide information about the paleoclimate of Mars. The Qaidam Basin is one of the highest, largest, and driest deserts on Earth, located in a dry, cold, and high ultraviolet environment similar to the surface of Mars (Xiao et al., 2017). The historically hyperarid climate of the Qaidam Basin has allowed the development of extensive polygonal landforms with diverse geometric and genetic types. Here we report a terrain characterized by polygons with raised rims, ranging in size from approximately 60 to 120 meters, and exhibiting spatial variation in mineral composition and geometry from the Dalangtan area of the western Qaidam Basin on the Tibetan Plateau.

An unmanned aerial vehicle (UAV) was used to capture high-resolution aerial imagery and generate a high-resolution digital elevation model (DEM) through photogrammetric software (Li et al., 2022). Spatially, the polygons in the northeastern part of the study area have complete rims, while the polygons in the southwest have incomplete rims (Fig .1). Surface and subsurface samples were collected at 6-meter intervals from the center to the rim of the polygons and analyzed for mineral composition and content by X-ray diffraction (chung et al., 1974). These polygons consist of a halite crust in the subsurface and raised rims formed mainly of gypsum. In some areas, the polygonal rims are broadened and form boundary belts that are up to ~30 m wide and about 1.2 m high.

Through spatial and mineral analysis, we propose a formation mechanism for polygonal landforms: the formation of the halite crust in the subsurface re-directs upward migration of evaporitic pore fluids that accumulate gypsum deposits to form the wide polygonal boundary belts (Lasser et al., 2023; Fig. 2). We suggest that the similarly sized polygons with raised rims on Mars have similar lateral and vertical structures caused successively by the strong evaporation of lacustrine brines and subsurface pore fluids (Zhu et al., 2023).

Figure 1. Digital elevation model (DEM) of the study area generated by an unmanned aerial vehicle survey.

Figure 2. Schematic representations of the formation of the raised rims/boundary belts of the pan-like polygons in the Qaidam Basin. The early stage is characterized by the drying of lacustrine (left column). Continued evaporation causes the surface to dry out and form polygonal cracks. In the middle stage, the halite crust begins to form and diverts the evaporative fluids, and gypsum begins to accumulate at the rim (middle column). In the development stage, the halite crust thickens, and more gypsum is deposited to widen the polygonal rims into wide belts (right column).

References

Anglés, A., Li, Y. (2017). The western Qaidam Basin as a potential Martian environmental analogue: An overview[J]. Journal of Geophysical Research: Planets, 122(5), 856-888.

Xiao, L., Wang, J., Dang, Y., Cheng, Z., Huang, T., Zhao, J., Xu, Y., Huang, J., Xiao, Z., Komatsu, G. (2017). A new terrestrial analogue site for Mars research: the Qaidam Basin, Tibetan Plateau (NW China)[J]. Earth-Science Reviews, 164, 84-101.

Dang, Y., Xiao, L., Xu, Y., Zhang, F., Huang, J., Wang, J., Zhao, J., Komatsu, G., Yue, Z. (2018). The polygonal surface structures in the Dalangtan Playa, Qaidam Basin, NW China: controlling factors for their formation and implications for analogous Martian landforms[J]. Journal of Geophysical Research: Planets, 123(7), 1910-1933.

Li, Z., Wu, B., Liu, W. C., Chen, Z. (2022). Integrated photogrammetric and photoclinometric processing of multiple HRSC images for pixelwise 3-D mapping on Mars[J]. In IEEE Transactions on Geoscience and Remote Sensing, 60, 1-13.

Chung, F. H. (1974). Quantitative interpretation of X-ray diffraction patterns of mixtures. II. Adiabatic principle of X-ray diffraction analysis of mixtures[J]. Journal of Applied Crystallography, 7(6), 526-531.

Lasser, J., Nield, J. M., Ernst, M., Karius, V., Wiggs, G. F., Threadgold, M. R., Beaume, C., Goehring, L. (2023). Salt polygons and porous media convection. Physical Review X, 13(1), 011025.Salt polygons and porous media convection[J]. Physical Review X, 13(1), 011025.

Zhu, J., Wu, B., Zhao, T., Li, Y. (2023). Polygons with halite-crusted floors and gypsum-raised rims in western Qaidam Basin and implications for polygonal landforms on Mars. Geomorphology, 443, 108934.

How to cite: Zhu, J., Wu, B., and Li, Y.: A study of polygonal landforms in the western Qaidam Basin and implications for polygonal landforms on Mars, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-244, https://doi.org/10.5194/epsc-dps2025-244, 2025.

Introduction:

Understanding the relationship between the western and northern deltas in the Jezero crater on Mars is crucial for the reconstruction of the water history in this region. The northern delta appears to be more eroded and older than the western delta; however, contemporaneous northern and western fan building was also recently proposed ([1], [2]). In our study, we explore the origin of the LCP (low-calcium pyroxene)/smectite and olivine/carbonate spectral units, which were found in both deltas and which may record the interaction between them in the past [2] (Fig. 1). We use topographic and compositional data to model potential deposition of the sediments from the western inlet on the northern delta. Our results shed light on the interconnection between the western and northern deltas, establish their relative age and suggest that Neretva Vallis (western inlet) could be the source of the LCP/smectite unit on both deltas in Jezero.

Fig. 1. CRISM Mafic map, adapted from [1]; Green – LCP/smectite; red – olivine/carbonate; blue – High-calcium pyroxene. CC’ profile is shown in Fig.2.

Fig. 2. Example of the topographic-compositional profile (profile line is on Fig. 1).

Data:

CRISM spectral data [2] and the Mars 2020 Science Investigation CTX DEM Mosaic (20 m/pixel) and its corresponding ortho-mosaic (5 m/pixel, [3], [4]) were used.

Methodology:

Based on topographic and compositional data we plotted topographic-compositional profiles that show changes in topography and composition simultaneously (Fig. 2).

To model the hypothesized deposition of the sediments coming from the western inlet through the northernmost channel located within the western delta (Fig.3a), we combined two equations: 1) sediment settling velocity [5] – for the vertical movement of sediment particles and 2) conservation of volumetric flow rate before and after the river enters the lake – for the horizontal movement of the sediment particles. Using the sediment transport equations of [6], we determined that particles up to 5 mm in size are transported in suspension through the above-mentioned channel. Therefore, we used a grain size range from 5 mm (small pebble) to 0.0039 mm (clay) for our model calculating the distance at which sediments transported by the northernmost channel of the western delta can be deposited on the northern delta.

Results:

Topographic-compositional profiles show that the LCP/smectite unit is stratigraphically higher than the olivine/carbonate unit, but does not reveal prominent correlations between separate delta outcrops that would represent the parallel layering typical of Gilbert-type deltas. Therefore, the LCP/smectite unit had to overlie the olivine/carbonate unit when the northern delta was already eroded to its present topography. According to the CRISM data, the closest possible source of the LCP/smectite unit is the western delta and the watershed of the western inlet. At the same time, the CTX DTM shows that a scenario where the northernmost channel of the western delta is subaerial (above the shoreline), while the northern delta is subaqueous could be possible (Fig.3a). Therefore, we hypothesize that the LCP/smectite unit consists of material transported by the northernmost channel of the western delta which is connected to the western inlet. Our model shows that fine silt can be deposited at a distance of 5,000 – 10,000 m from the end of the channel – at this distance the LCP/smectite unit is indeed found on the northern delta (Fig. 3b).

Fig. 3. a) Overview map with studied features; b) Results of modeling, showing that fine silt will be deposited on the southern part of the northern delta, which coincides with the appearance of the LCP/Smectite units.

Discussion:

We validated the model using information about the minimum grain size of the western delta provided by the Perseverance rover results (in bottomsets – “<0.02 mm” for M2020-575-16 Shuyak sample [7]) and RIMFAX data, which show that the length (projected to the crater floor) of the one “topset-foreset-bottomset” sequence is approximately 135-200 m [8]. We modeled the case of deposition of western delta material only and found that sediments with the grain size “0.02 mm” form bottomsets at a distance of 192 m, agreeing with the RIMFAX data.  In addition, THEMIS data [9] show low thermal inertia in the southern part of the northern delta (where LCP/smectite is located) consistent with loose fine-grained material (such as silt). 

Conclusion:

We interpret the uppermost LCP/smectite unit within the northern delta as material from the western inlet deposited over already existing topography of the northern delta. This implies that there was a period when the active western inlet provided sediment to cover the already eroded northern delta. We therefore conclude that the main body of Jezero Crater's northern delta is older than the western delta but covered with the relatively thin and younger layer of silt deposits from the western inlet.

References:

[1] M. J. Jodhpurkar, et al., J. Geophys. Res. Planets, 129 (2024)

[2] B. H. N. Horgan, R. B. Anderson, G. Dromart, E. S. Amador, and M. S. Rice, Icarus, 339 (2020)

[3] F. Calef, Planetary Data System, USGS Astrogeology Science Center (2021) https://astrogeology.usgs.gov/search/map/mars_2020_science_investigation_ctx_dem_mosaic

[4] M. C. Malin, et al., J. Geophys. Res. Planets, 112(5) (2007)

[5] R. I. Ferguson, and M. Church, Journal of Sedimentary Research, 74(6), 933–937 (2004)

[6] M. G. Kleinhans, J. Geophys. Res. Planets, 110(12), 1–23 (2005)

[7] K. Farley, and K. Stack, Mars 2020 reports, Volume 2, Delta Front Campaign (2023) https://mars.nasa.gov/internal_resources/1656/

[8] S.-E. Hamran, D. Paige, F. Andersson, T. Berger, E. Cardarelli, L. Carter, H. Dypvik, P. Russell, M. Mellon, D. Nunes, and D. Plettemeier, Europlanet Science Congress 2024, EPSC2024-403 (2024). https://doi.org/10.5194/epsc2024-403

[9] C. S. Edwards, K. J. Nowicki, P. R. Christensen, J. Hill, N. Gorelick, and K. Murray, J. Geophys. Res. Planets, 116(10) (2011). https://doi.org/10.1029/2010JE003755

How to cite: Ovchinnikova, A., Jaumann, R., Walter, S. H. G., Gross, C., Zuschneid, W., and Postberg, F.: Exploring the connection of the Northern and the Western Deltas in Jezero Crater on Mars, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-795, https://doi.org/10.5194/epsc-dps2025-795, 2025.

Introduction

Floor-Fractured Craters (FFCs) are a class of impact craters characterized by fractured and hummocky crater floors, often displaying features such as concentric or radial fractures, mesas, tilted blocks, and irregular topographies. These morphologies suggest post-impact modification processes that have been extensively studied across the Solar System. On Mars, the origin of FFCs is still debated, with several hypotheses proposed, including intrusive magmatism and associated doming, tectonic deformation, glacial or periglacial activity, and the migration or discharge of pressurized groundwater [1–4]. This study presents preliminary results from a detailed geological and geomorphological analysis of a small (~18 km diameter) floor-fractured crater located in the Noachian-aged terrain of Terra Sirenum (37°S, 190°E), within the broader Gorgonium Chaos basin (~240 km wide [5]).  The study aims to investigate the origin of the fractures and the geological evolution of the crater, and to assess the potential roles of tectonic, magmatic, and periglacial processes [6] in shaping its morphology.

Methodology

A detailed geomorphological and stratigraphic analysis was performed by integrating high-resolution datasets, including HiRISE (25 cm/px) [7], CaSSIS (4.5 m/px) [8], CTX (6 m/px), and topographic data from MOLA [9]. Crater counting was performed on the continuous ejecta blanket using CraterTools [10] and Craterstats2 [11], applying the Hartmann and Neukum chronology system [12] and Ivanov's production function [13] to constrain the formation age of the impact. A preliminary evalution of the mineralogical composition of the crater was performed using spectral data from CRISM [14]. As a first step, we used the RGB color composites (browse products) of CRISM [15], which enable a rapid, visual and qualitative multiparametric evaluation of the spectral characteristics of the surface.

Preliminary Results and Interpretation

The interior displays typical FFC features, including a polygonal fracture network, tilted blocks, and mesas of varying elevation and morphology. These morphologies are particularly developed in the southern and central portions of the floor, which appear topographically elevated compared to the northern and eastern parts. This doming-like structure, may indicate the emplacement of a shallow magmatic intrusion beneath the crater floor, causing uplift and fracturing [3]. At the same time, several indicators point toward the involvement of cryospheric processes. The crater ejecta blanket shows a double-layered morphology, a characteristic feature of many Martian craters formed in ice-rich or volatile-rich targets [16-17]. The inner ejecta lobe is more continuous and lobate, while the outer lobe is discontinuous and thinner, consistent with ballistic deposition over an icy or volatile-rich regolith. Within the crater, some mesas appear mantled or smoothed, possibly due to deposition of later ice-related material or sublimation lag deposits. The crater size-frequency distribution (SFD) suggests an early Hesperian to late Noachian formation age (3.4 ± 0.09 Ga, Fig. 1).

Fig. 1 –On the left the image shows the extent of the ejecta in red and the counting crater in yellow. The white arrows highlight the interaction of the Sirenum Fossae fractures with the crater ejecta. On the right, the plot shows the calculated age for the ejecta.

The fracture geometry and spatial distribution within the crater floor suggest at least two deformational phases: an (i) early tectonic control linked to the broader Sirenum Fossae system, and (ii) a later local doming and fracturing episode possibly due to magmatic intrusion. The CRISM-FAL (false color), MAF (mafic mineralogy), PHY (phyllosilicates), PFM (Fe/Mg-phyllo-silicates), PAL (Al-phyllosilicates) and ICE (carbon dioxide frost or ice) browse products were used to investigate the mineralogical composition of the crater and its infilling. These mineralogical maps indicate that the central/southern mesas are characterized by the presence of pyroxene, while the rim and the inner wall of the crater show signs of Fe/Mg Phyllosilicates.

Future Work

The integration of geomorphology, stratigraphy, and composition seems to support a complex interplay of tectonic, magmatic, and later cryospheric processes in the evolution of the crater. Further analysis will include (i) quantitative analysis of spectra derived from CRISM, to constrain the composition of floor and ejecta materials, and to test the possible emplacement of magmatic material and ii) the radar data from SHARAD and MARSIS, in order to assess the presence of present subsurface ice.

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

References

[1] Schumacher S. and Zegers T. E. (2011) Icarus, V. 211, pp 305-315. [2] Sato H. et al. (2010), Icarus 207 pp. 248-264. [3] Bamberg M. et al. (2014) PSS, V. 98, pp.146-162. [4] Hanna J. C. and Phillips R. J. (2006) JGR, V. 111. [5] Wendt L. et al. (2013) Icarus 225, pp 200-215. [6] Bertoli et al. (2025), submitted to GFT&M [7]. McEwen et al. A. S (2007), JGR:Planets, V. 112. [8] Thomas et al. (2017) Space Sci. Rev. 212 (3–4), 1897–1944. [9] Smith D. E. et al. (2001), JGR:Planets, V. 106, pp. 23689 – 23722. [10] Kneissl T. et al. (2011) PSS, V. 59, pp. 1243–1254. [11] Michael G. G., and Neukum G. (2010) -EPSL, V. 294, pp. 223–229. [12] Hartmann W. K. and Neukum G. (2001) Space Science Reviews, V. 96, pp. 165 – 194. [13] Ivanov B. A. (2001), Space Science Reviews, V. 96, pp. 87–104. [14] Murchie S. et al. (2007), JGR:Planets, V. 112. [15] Viviano-Beck et al. (2014) J. Geophys. Res., V. 119, pp. 1403-143. [16] Barlow et al. (2000), JGR:Planets, V. 105, pp. 26733 – 26738. [17] Weiss D. K. and Head J. W. (2013), Geophys. Res. Lett., V. 40, pp. 3819 – 3824.

How to cite: Bertoli, S., Massironi, M., Salvatore, M. C., Baroni, C., Baschetti, B., Tullo, A., Munaretto, G., Martellato, E., Cremonese, G., Pajola, M., Hauber, E., and Faletti, M.: Geological history of a Floor-Fractured Crater in Gorgonum Chaos, Terra Sirenum, Mars, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1494, https://doi.org/10.5194/epsc-dps2025-1494, 2025.

Introduction

Noachis Terra, in Mars’ southern highlands, is a region which is poorly dissected by erosional fluvial landforms^[1,2] but which warm/wet climate models of the early Martian climate predict should have experienced high rates of precipitation^[3]. A recent study in Arabia Terra^[4], another poorly dissected region of the highlands, found a network of distributed sinuous ridges. These were interpreted as fluvial sinuous ridges (FSRs), topographically inverted fluvial channel belts that are at least as old as the Noachian-Hesperian transition and interpreted to be evidence for ancient river systems with high depositional rates. Noachis is similarly aged, but has a distinctly different geological history^[5], so finding FSRs here would provide evidence both for widespread ancient rivers in another part of Mars, and also suggest this style of fluvial activity was common across Mars’ highlands at this time.

Methods

We used ArcGIS Pro software to conduct a survey of a > ten million km² study area (-35°E, -12°N; 45°E, -55°N). We used the Context Camera (CTX^[6]) online global mosaic (5-6 m/pixel^[7]), supplementing this with High Resolution Science Experiment (HiRISE; 25-50 cm/pixel^[8]) data. We digitized FSRs at a scale of 1:50,000 and measured, calculated, and classified key features relating to each ridge segment, assigning each ridge to one of four morphotypes. We categorised ridges as either ‘certain’ or ‘confident’ based on exposure and image quality; if ridges did not meet these criteria, they were excluded.

Results/Discussion

Morphology:

‘Certain’ ridges have a combined length of more than 8,000 km. This increases to 15,000 km if including the ‘confident’ class. Here we discuss only the ridges classified as certain.

 Figure 1: FSR types. Black arrows denote FSRs, white arrows denote downslope topographic trends. A) Type A: rare. B) Type B: most common, 84% of the total length for ‘Certain’ FSRs. C) Type C: narrow, pointed. D) Type D: heavily degraded chains of mounds.

Individual FSR segments are a few kilometres to tens of kilometres long. All four types are sinuous to sub-sinuous: the 30 longest segments (>20 km each) have an average sinuosity of 1.2. The ridges all appear to conform to local topographic trends, exhibit various degrees of preservation, range in width from <100 m to >3 km and exhibit 2-21 m of vertical relief. The shortest segment digitised is 200 m long and the longest is more than 78 km. Visible internal layering or structure is rare and offers little additional information. FSRs commonly record curving plan-view shapes that we interpret as meanders, branching, anastomosing, and smaller ridges connecting at oblique angles to a central wider ridge, which we interpret as tributaries joining a main channel. Ridges with branches may record avulsions or anabranching, or might represent different generations of fluvial activity stacked vertically^[9].

Distribution:

The FSRs are widely distributed across Noachis Terra. They are predominantly found in local depressions, and more than 91% (in length) occur in the intercrater plains. Many distinct FSR segments can reasonably be linked to one another, suggesting that river systems many tens or even hundreds of kilometres long were present. However, there are other examples of isolated FSRs or multiple FSRs that do not align with one another, demonstrating that either shorter systems were common or that erosion has removed the evidence for longer rivers. There is little variation in distribution for type B, C, and D, though there is a significant concentration of all FSRs in and west of Greeley Crater (4°E, -37°N); this is also where most type A FSRs occur. We find few FSRs at latitudes higher than 47°S. This indicates a true absence of ridges here, but also shows that we were more conservative in identification due to icy mantling and poorer data quality this far south. The broad distribution of FSRs suggests that the water source must also have been widely distributed (e.g. precipitation). The most likely explanation for the distribution of FSRs is a protracted period (or periods) during which the regional climate was able to sustain precipitation and allow stable surface water long enough to form river systems.

Almost a quarter of FSRs can be found within, or connected to, valleys. Many of these FSRs are in the lower reaches of individual fluvial systems but in other cases FSRs transition to and from valleys. The FSRs occur as narrow, sometimes isolated sections, and are not amenable to accurate age determination using crater counting. Nevertheless, the FSRs are all on Noachian Basement units^[10]. The oldest crater they are present in is Dollfus (-4.2°E, -21.4°N; ~4.08-4.013 Ga^[11]), and the youngest is Bakhuysen (15.7°E, -22.7°N; ~ 3.49-3.73 Ga^[11]). The maximum age of the FSRs is likely to be Noachian or Early Hesperian.

Conclusion

More than 15,000 km of FSRs occur across Noachis Terra, a region of Mars’ southern highlands that is poorly dissected by valleys. These record evidence of sustained fluvial processes, and deposition of fluvial sediment, in a region that was previously thought to lack them. They are likely to have formed during the late Noachian or Early Hesperian, suggesting an at least transiently warm and wet early Mars. These observations provide an important input into future climate models for this period, especially into those that use a lack of valleys in this region to argue against a warm, wet climate^[3]. We suggest that having found FSRs in two geologically and geographically diverse, but similarly-aged highland regions on Mars^[4], FSRs are likely to be present throughout many Noachian/Hesperian highland regions. Similar survey projects examining CTX data in other regions will test this hypothesis.

 References

¹ Alemanno et al., Earth and Space Science (2018)

² Hynek et al., JGR: Planets (2010)

³ Wordsworth et al., JGR: Planets (2015)

⁴ Davis et al., Geology (2016)

⁵ Fassett and Head, JGR: Planets (2007)

⁶ Malin et al., JGR: Planets (2007)

⁷ Dickson et al., Earth and Space Science (2024)

⁸ McEwen et al., JGR: Planets (2007)

⁹ Hayden et al., Icarus (2019)

¹⁰ Tanaka et al., USGS (2014)

¹¹ Robbins et al., Icarus (2013)

How to cite: Losekoot, A., Balme, M. R., Coe, A. L., and Fawdon, P.: The Fluvial History of Noachis Terra, Mars, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1751, https://doi.org/10.5194/epsc-dps2025-1751, 2025.

Introduction

The ESA ExoMars Rosalind Franklin (EMRF) rover will launch in 2028, and land in the Oxia Planum region of Mars. The main target is Noachian phyllosilicate-rich deposits [1,2]. This region probably represents the oldest aqueous environments to be explored in situ on Mars. In this study we have investigated extensive secondary craters within the EMRF landing ellipse, to place absolute age markers in the stratigraphic framework of Oxia Planum, and identify the likely primary source crater(s). We pay particular attention to possible secondary craters from Mojave crater, due to its likely recent formation age [3] and importance as a potential source crater for martian meteorites [4].

Method

We first used the recent Mars catalogue of small impact craters [5, 6] in a small (1 x 10⁵ km²) ‘Oxia Planum study region’. We refined the crater identification through manual crater addition, deletion, movement, and scaling. We produced a final catalogue with an extra 22,209 craters, totalling 381,584 impact craters. We applied the ‘Algorithm for the Secondary Crater Identification’(ASCI) [3] to identify possible primary and secondary impact craters. We then produced a crater size density map of possible secondary craters for the Oxia Planum study region, from which we identified acute triangle-shaped clusters (or ‘cones’) of craters. We carried out crater size-frequency distribution (CSFD) studies of previously-identified units in Oxia Planum [1] to determine model surface ages, both with and without secondary craters removed. We then merged the original catalogue of small impact craters [5, 6], with craters with diameters >1 km [7] in a larger (1.2 x10⁶ km²) ‘context study region’. We used the same methods to identify possible primary and secondary craters, and produced a crater size density map of possible secondary craters.

Results

We separate our results into (1) the identification and analysis of secondary craters, and (2) the implications for model ages in Oxia Planum.

Secondary Craters. Of the impact craters in the smaller Oxia Planum study region, we classified 176,927 (46.4%) as primary craters, with 204,657 (53.6%) classified as secondary craters. The number of possible secondary craters has been revised down from our previous results [8]. We identified at least 13 separate clusters of craters that occur in cone shapes, with each cluster typically up to 40 km long and 20 km wide at the distal ends. These cones are oriented radially away from Mojave crater, with the median direction being 225°, similar to the median direction (222°) to Mojave crater. The cones show a distinctive size distribution of craters, with larger craters limited to the proximal (apex) region, with a gradual transition to smaller craters in the distal zone. The cones in our Oxia Planum study region are located at distances of ~700 to 930 km from Mojave. The larger, context study region contains 2,877,811 impact craters, ranging in size from 29 m to 54.4 km [5-7]. We classified 1,356,995 (47.2%) as primary craters, with 1,520,816 (52.8%) classified as secondary craters. We identify a further 13 cone-shaped clusters of secondary craters in the context study region, with ranges ~275 – 500 km from Mojave.

Figure 1. (A) Possible primary (red) and secondary (green) impact craters in our Oxia Planum study region. (B) Secondary crater size density map of same region. EMRF 1s  (grey) and 3s (black) ellipse ranges are shown.

Model Surface Ages. The removal of secondary craters from CSFD studies does not affect the model surface age of the phyllosilicate units in Oxia Planum. We derive a model surface age of 3.9 Ga for the Noachian layered clay-bearing unit (lNc) of [1] using all our craters, and an identical age when using just our primary craters. This similarity is due to the lack of secondary craters at larger diameters.

Implications

Our results suggest that there are extensive secondary impact craters in Oxia Planum, with ~4000 secondaries within the EMRF 3s ellipse pattern. It is therefore likely that EMRF will encounter secondary craters during surface operations. The orientation of cone-shaped clusters of small craters indicates that the majority of secondaries are sourced from the Mojave impact crater, although larger, older secondary craters from other sources are also present. Given that the Mojave impact is estimated to have occurred 10.1 Ma [3], these secondaries can be used as absolute stratigraphic markers throughout Oxia Planum, particularly in quantifying the rate of recent and active surface processes. These secondary craters will also be important for target prioritization during in situ studies.

References: [1] Quantin-Nataf C. et al. (2021) Astrobiol. 21, 345-366. [2] Mandon L. et al. (2021) Astrobiol. 21, 464-480. [3] Lagain A. et al. (2021) Earth Space Sci. 8, e2020EA001598. [4] Werner S.C. (2014) Science, 343, 1343-1346. [5] Lagain A. et al. (2021) in GSA Spec. Paper 550, 629-644. [6] Lagain A. et al. (2021) Nature Comms. 12, 6352. [7] Robbins S.J. & B.M. Hynek (2012) JGR 117, E05004. [8] Grindrod, P.M. et al. (2023) LPSC 54, #1113.

How to cite: Grindrod, P., Collins, G., Magnarini, G., Davis, J., Fawdon, P., Favaro, E. A., Tornabene, L., Sokołowska, A., Martin-Wells, K., and Balme, M.: Extensive Secondary Impact Cratering in the ExoMars Rosalind Franklin Landing Site at Oxia Planum, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-157, https://doi.org/10.5194/epsc-dps2025-157, 2025.

Capri Chasma is a canyon located at the exit of Valles Marineris. Its flanks are piled with lava flows. It also contains in places, bright Interior Layered Deposit (ILD) revealing a complex geological history. Some slopes are also the site of a phenomenon known as RSL (recurrent slope lineae). In the northern part of the Chasma, within the thickest portion of the Interior Layered Deposit (ILD), rock units are exposed along some walls, that are part of a ∼30-km circular depression. A well-preserved stratigraphy in the northwest-facing slope reveals several sulfate-rich units, including kieserite and poly-hydrated sulfates, some of which are associated with red and gray hematite [1,2]. A presumed impact has disrupted the southern stratigraphy, redistributing these mineral layers and contributing to a jumbled geological structure. The presence of sulfates and hematite suggests initial ILD deposition by evaporation of magnesium and sulfur-rich brines, followed by groundwater upwelling events that penetrated the ILD, allowed gray hematite precipitation, and induced diagenetic alteration. Alternative explanations involve atmospheric deposition of sulfur-rich aerosols and dust particles within the ice deposits followed by weathering and formation of the sulfates during Martian climatic cycles. As a result, the origin of the Capri Chasma ILDs is still rather vague, and more information needs to be gathered on the stratigraphy, morphology, and color of the deposits, as well as on the microtexture of the materials that make them up. In order to better understand the nature of the deposits and the conditions of their formation, our investigation is based on three types of data: (i) CTX and HiRISE digital terrain models refined by photoclinometry (ii) a multi-angle sequence of hyperspectral images acquired by the CRISM spectro-imager on which we invert Hapke's photometric model after atmospheric correction (iii) a series of images from the CaSSIS multispectral sensor on which photometric and atmospheric correction is performed to extract the intrinsic surface reflectance in four spectral bands, resulting in true color images.

First, we analyze the spectrophotometric data generated from the fusion of the sequence FRTB385 of 11 hyperspectral CRISM images, estimating both atmospheric optical thickness and surface reflectance at a 200 m resolution using the MARS-Reco tool [3]. An unsupervised k-means classification clusters the reflectance data into five photometric classes(fig.1), and Hapke photometric model parameters are computed using the GLLiM algorithm [4] to interpret surface microtexture properties. These parameter maps are overlaid on geological images, and mean volume phase function parameters (b, c) are compared with laboratory data to infer material textures (fig.2). The analysis shows that bright sulfate deposits (cyan class) have translucent grains throughout the wavelength range with high surface roughness, consistent with crystals formed by evaporation of brines. Hematite-bearing materials (blue class) are strongly backscattering at visible wavelengths, where internal absorption is high, and become significantly forward scattering in the shortwave infrared, suggesting round, clear grains, similar to textures observed by the Opportunity rover at Meridiani. This likely indicates very similar conditions of formation.

Fig.1 False color CRISM image (left) and classification map (right) superimposed on a context CTX image of a semi-circular depression in the Eos Chasma, Mars. The classification of the terrains is based on a kmeans clustering of their CRISM photometric curves at a wavelength of 755m.

Fig.2 Qualitative interpretation of the microtexture of the different terrain classes based on a comparison of the spectral behavior of the phase function with laboratory measurements in the Hapke (b, c) parameter space.

Second we use a CTX DTM and its associated CTX orthoimage D07_029766_1668_XN_13S047W, both products generated by a photogrammetric processing of an image pair. The goal is to remove artifacts from the initial CTX DTM at 18m.pixel-1 and to densify it to 6m.pixel-1 using the ortho-image, which exploits intensity variations associated with slopes. To do this, we use the HDEM photoclinometric method [5] based on the CRISM reflectance model previously established for the scene. Prior to this, the initial DTM is filtered to an effective resolution of 288 m.pixel-1 after being decomposed on a spatial wavelet basis using the 2D Isotropic Undecimated Wavelet Transform algorithm, followed by the elimination of high frequencies. The result is highly satisfactory, allowing a much finer, less error-prone topographic characterization of the terrain (fig.3). A similar process was applied to a HiRISE DTM and its associated PSP_008958_1665 orthoimage, resulting in a resolution of 25 cm.pixel-1. In this case, morphometric terrain analysis is possible with a relative vertical resolution estimated at 15-20 cm, giving access to the details of aeolian figures, for example.

Fig 3. Topographic profiles extracted for a mound in the Capri Chasma circular depression.

Thanks to the use of novel CTX, HiRISE and CaSSIS image processing methods, we are carrying out a detailed morphological, stratigraphic and textural characterization of the sulfate- and hematite-rich units over an interesting part of the Capri Chasma. Valuable information has already been obtained that complements the spectroscopic studies to understand the origin and evolution of these formations, as well as the surface phenomena that are currently shaping these landscapes.

[1] Roach, L.H., Mustard, J.F., Lane, M.D., Bishop, J.L., Murchie, S.L., 2010. Icarus 207, 659–674.

[2] Weitz, C.M., Noe Dobrea, E.Z., Lane, M.D., Knudson, A.T., 2012. Journal of Geophysical Research (Planets) 117, E00J09.

[3] Ceamanos, X., Douté, S., Fernando, J., Schmidt, F., Pinet, P., Lyapustin, A., 2013. Journal of Geophysical Research (Planets) 118, 514–533.

[4] Kugler, B., Forbes, F., Douté, S., 2022. Statistics and Computing 32, 31.

[5] Douté, S., Jiang, C., 2019. IEEE Transactions on Geoscience and Remote Sensing 1–14.

Acknowledgment : S.D. is grateful to the Centre National d’Etudes Spatiales (CNES) for supporting his CaSSIS and HiRISE related work through the Program “Exobiologie, protection planétaire et exoplanètes”.

How to cite: Douté, S.: Stratigraphy, morphology, microtexture of the ILDs in Capri Chasma: insights into their formation., EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1724, https://doi.org/10.5194/epsc-dps2025-1724, 2025.

Introduction

Sulfates are abundant at the Martian surface, incorporating sulfur delivered by volcanic eruptions and degassing [1,2]. The thickest sulfate accumulations are found in the interior layered deposits (ILDs) of Valles Marineris. We have studied them in Ophir Chasma (Figures 1 and 2). They have been interpreted as either purely sedimentary deposits (e.g., [3]) or weathered volcanic products (e.g., [4, 5]).

Spectral analysis

We performed nonlinear spectral unmixing of CRISM data [6] located in the lower, massive member of the ILD pile in Ophir Chasma. The best spectral fit is obtained when primary igneous minerals (orthopyroxene, plagioclase) and coquimbite were present (Figure 3), alongside kieserite and szomolnokite. The latter are thought to be the main mineral constituents of the ILDs [7-11]. Coquimbite is necessary in the spectral mixture to obtain a good spectral fit. Copiapite is possibly present as well.

Analysis of wind patterns and geomorphology

Wind patterns (Figure 4) and geomorphological evidence show that the igneous minerals are from a local source [14, 15] within the ILDs, rather than from wind transportation from neighbouring volcanic plateaus [16].

Results and discussion

Our findings suggest that the deposition of the lower member of the ILDs was influenced by Tharsis-related syntectonic and synvolcanic activity within the subsided Valles Marineris plateau, and by the redox state of an overlying Valles Marineris sea in a geologic context akin to volcanogenic massive sulfide deposition on Earth. Subsequent climate cooling, potentially related to Tharsis activity waning, would have led to gradual sea freezing, resulting in further alteration in acid-cold environment, and precipitation of the polyhydrated sulfates that compose the upper, layered ILD member. ILD erosion by glacial flows down to the currently exposed chasma floor level and aeolian erosion have shaped the current ILD morphology (Figures 5-6). In summary, the comprehensive ILD pile formed by in-situ weathering of volcanic products, redox state instabilities, and water level fluctuations in a warming and cooling Valles Marineris sea [17].

Figure 1. Main ILD mounds in Valles Marineris.

Figure 2. CRISM and HiRISE views of the ILD region of interest (ROI) studied in this work. (a) Unprojected CRISM cube frt00018b55, also analyzed in another work [6]. The interpretation of geological units is from that work. (b) location of the ILD ROI; (c) Three-dimensional view of part of HiRISE image ESP_017754_1755 (50 cm/pixel), showing ILDs in the South and the approximate location of the ILD ROI. The HiRISE DTM was generated using the HiRISE images ESP_016053_1755 (0.25 m/pixel) and ESP_017754_1755 (0.5 m/pixel).

Figure 3. Outputs of 4 nonlinear spectral unmixing runs. The list of minerals included in the spectral library is given for each run. Runs 2 and 4 share the library used in Runs 1 and 3, respectively, with mafic minerals added. The overall spectral fit is good in all the runs, suggesting that the selected mineral libraries are overall satisfying. The presence of mafic minerals significantly improve the RMS. The red areas illustrate the fit discrepancies in the same representative wavelength ranges for comparison. Minerals in green are considered "detected". In yellow, they are considered "questionable". The value of the mixing coefficients X are given in both cases. The minerals which have a "negligible" or "null" contribution are in black. The value of the mixing coefficient of the atmosphere is indicated in gray.

Figure 4. Speed and direction of horizontal wind at its peak 10 m above the topographic surface. (a) At 20:00 (at longitude 0°), the only fall winds originating from bedrock exposures are located south of the ILD ROI. They do not propagate to the ROI. (b) At 4:00, fall winds originate from the northern chasma slopes. However, fall winds from the ILD slope above the ROI control the wind patterns and the ILDs in the ROI only face fall wind coming from the ILDs upslope. Data are from the Mars Climate Model [12, 13], using the Climatology scenario and solar longitude 180. The latitude and longitude ranges of the covered area are 4°S-5°S and 69.5°W-71.5°W. The width of the displayed area is 175 km.

Figure 5. Mechanisms of ILD deposition and erosion that satisfy the mineralogy interpreted from this and earlier works, stages a-c. Abbreviations: Coq: Coquimbite; Cpi: Copiapite; IO: Iron oxides; Ksr: Kieserite; MHS: Monohydrated sulfates; PHS: Polyhydrated sulfates; Szo: Szomolnokite.

Figure 6. Stages d-e and stratigraphic column.

Cited references

[1] Bibring, J.-P., et al. (2006) Science 312, 400–404. https://doi.org/10.1126/science.1122659

[2] King, P. L., & McLennan, S. M. (2010). Elements 6, 107-112. https://doi.org/10.2113/gselements.6.2.107

[3] Grotzinger, J. P., & Milliken, R. E. (2012). In J.P. Grotzinger & R.E. Milliken (Eds.), Sedimentary Geology of Mars, pp. 1–48. https://doi.org/10.2110/pec.12.102.0001

[4] Komatsu, G., et al. (2004) Planetary and Space Science 52, 167–187. https://doi.org/10.1016/j.pss.2003.08.003

[5] Niles, P. B., & Michalski, J. (2009) Nature Geoscience 2, 215–220. https://doi.org/10.1038/NGEO438

[6] Gurgurewicz, J., et al. (2022) Communications Earth & Environment 3, 282. https://doi.org/10.1038/s43247-022-00612-5

[7] Noel, A., et al. (2015) Icarus 251, 315–331. https://doi.org/10.1016/j.icarus.2014.09.033

[8] Wendt, L., et al. (2011) Icarus 213, 86–103. https://doi.org/10.1016/j.icarus.2011.02.013

[9] Murchie, S. L., et al. (2009) JGR: Planets 114, E00D05. https://doi.org/10.1029/2009JE003343

[9] Roach, L.H., et al. (2010) Icarus 207, 659–674. https://doi.org/10.1016/j.icarus.2009.11.029

[10] Weitz, C.M., et al. (2012) JGR: Planets 117, E00J09. https://doi.org/10.1029/2012JE004092

[11] Weitz, C.M., et al. (2015) Icarus, 251, 291–314. https://doi.org/10.1016/j.icarus.2014.04.009

[12] Forget, F., et al. (1999) JGR 104, 24155–24175. https://doi.org/10.1029/1999JE001025

[13] Millour, E., et al. (2018) Scientific Workshop From Mars Express to ExoMars, ESA-ESAC and IAA-CSIC, Madrid, Spain.

[14] Chojnacki, M., et al. (2014) Icarus 230, 96–142. https://doi.org/10.1016/j.icarus.2013.08.018

[15] Chojnacki, M., et al. (2020) JGR: Planet 125, e2020JE006510. https://doi.org/10.1029/2020JE006510

[16] Liu, Y., et al. (2016) JGR: Planets 121, 2004–2036. https://doi.org/10.1002/2016JE005028

[17] Mège, D., Gurgurewicz, J., & Schmidt, F., submitted.

How to cite: Mège, D., Gurgurewicz, J., and Schmidt, F.: Altered lava flows and sulfide controls on the formation of layered deposits in Valles Marineris, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-191, https://doi.org/10.5194/epsc-dps2025-191, 2025.

The Argyre basin, located on the southern highlands, spans over 1500 km wide and is one of the largest impact basins on Mars. Three large valleys drain into Argyre from the southern circumpolar region, whereas the basin is breached at the north and perhaps connected to the Ladon-Morava-Ares outflow system draining into Chryse Planitia. Given its volume and valley connections, this basin played a key role in the global hydrology of early Mars (e.g., Clifford and Parker, 2001; Phillips et al., 2001). Several morphological features indicate that the basin may have contained a lake and/or ice sheet in the past, which could have been fed with meltwater from an ancient south polar ice sheet through three main inlet valleys (e.g., Hiesinger and Head, 2002; Ghatan and Head, 2004). A suite of sinuous ridges in the southern Argyre basin (ASRs)—commonly regarded as eskers—has been interpreted as evidence that an ice sheet once occupied the basin (e.g., Banks et al., 2009; Bernhardt et al., 2013). However, new morphological observations focusing on the context and stratigraphy raise discrepancies with the conventional esker interpretation, leading us to revisit their origin.

To assess the origin of these ridges, we first have undertaken detailed morphometric measurements of ASRs and compared them to other glacial and fluvial ridge features on Earth and Mars. We mapped cross-sectional profiles at 1 km intervals along crestlines of ASRs using Context Camera (CTX) images and digital elevation models (DEM). We fitted power-law relationships to those ridge geometries, including width (W) and cross-sectional area (A_CS). A power law is expected here because differing scaling relationships exist between channel width and bank-full discharge in fluvial (e.g., Parker et al., 2007) and subglacial systems (e.g., Ng, 1998, Hewitt and Cretys, 2019). We use A_CS as a proxy for bank-full discharge (e.g., Ruso et al., 2024). Next, we carefully considered the stratigraphy of the ridges as well as the context where they are found, characterized by laterally extensive layered terrains. We measured dip and azimuths of individual layers observed within the ridge stratigraphy and compared them to those in the surrounding terrains. Then, we worked to understand the stratigraphic relationships between ASRs and surrounding layered terrains. Last, we performed crater counts using the buffer crater counting technique on the ASR to determine their ages (e.g., Kneissl et al., 2011).

Two distinct populations of ASRs can be distinguished stratigraphically: NE-oriented ridges in the eastern population (upper) and NW-oriented ridges in the western population (lower). The power-law relationship for ASRs geometry, shown in Figure 1, shows a strong correlation between log-width and log-cross-sectional area, which is consistent with martian inverted fluvial channels in Aeolis Dorsa region, though the power-law exponents for ASRs are smaller than, yet still comparable to, the subglacial range. The measurement of layering structures revealed that the layers in ASRs are extremely horizontal (~0.07–<0.3°; Figure 2a). These values of dip and azimuth are consistently observed both in ASRs and the surrounding terrains, suggesting a shared sedimentological history, consistent with inverted fluvial channels where the former protective cap rocks have been eroded—manifesting as ridges composed of underlying shale bedrock extending from adjacent lacustrine or floodplain units (e.g., in Utah - Figure 2b). The lateral continuity of layers between ridges and surrounding terrain is entirely inconsistent with the hypothesis of eskers previously proposed (Banks et al., 2009). Whereas eskers may be layered, they are confined structures, preventing them to deposit simultaneously with the surrounding terrain, as subglacial conduits tend to draw water from the surrounding water-distributed regions because the water pressure in a conduit is less than in the adjacent bed. Thus, we conclude that the origin of ASRs is inverted fluvial channels, and the surrounding layered terrains are lacustrine deposits. We have dated ASRs to ~3.6 Ga as exhumed age. Given that the Argyre impact age is ~3.9 Ga, the basin may have hosted a lake at approximately the same time as ASRs (~3.8–3.6 Ga).

Furthermore, we also identified similarly layered terrains in other regions of the Agyre basin, justifying an extrapolation of the horizontal layers to the entire basin. The elevation of the ASRs and their layers ranges from approximately −2633 to −2734 m, and the layers extend to even lower elevations. This elevation indicates the minimum lake level of the putative paleo-Argyre lake, which remains below the hypothesized breach point at the northern end for an Argyre–Uzboi Vallis flood. The two distinct populations of ASRs could provide possible evidence for multi-fluvial periods driven by meltwater from an ancient southern polar ice sheet (e.g., Ghatan and Head, 2004), with the Argyre basin serving as an impoundment for the meltwater (lake volume: ~1.2 × 10⁵ km³).

Figure 1: Comparative geometry for ridge features. (a) ASR compared with martian inverted fluvial channels in Aeolis Dorsa region. (b) ASR compared with martian eskers in Dorsa Argentea Formation.

Figure 2: 3D view of layering structures. Black arrows indicate ridge landforms. (a) ASRs and surrounding layered terrains. CTX_669660_1229 and CTX_067573_1245. Colored lines indicate layers which appear both ASRs and surrounding layered terrains. (b) analogous terrestrial inverted fluvial channels where the cap rocks have been eroded, Utah, US (38.393565°N, 110.788020°W).

How to cite: Shozaki, H., Conway, S., Grau Galofre, A., Mangold, N., and Sekine, Y.: The origin of sinuous ridges in Argyre Planitia: Insights from terrestrial analogues and implications for its hydrology, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-205, https://doi.org/10.5194/epsc-dps2025-205, 2025.

Mars is a hyperarid, global cryosphere, and likely has been for over 3 Gyr. Contrastingly, during the so-called early Mars period 4-3.5 Gyr go, water flowed within thousands of valleys, in crater lakes, producing ancient deltas, building ice sheets, and possibly ponding in oceans [1]. However, this early benign climate collapsed with the continued loss of Mars’ atmosphere in the Hesperian period, ~3.5-3 Gyr ago.  Activity in most outflow channels has been dated from this period [1-3], with some channels displaying younger [2] and/or later [3] erosive episodes. Within the channels there are landforms indicative of the flow of massive amounts of fluid, including streamlined islands and longitudinal grooves and ridges, often seen diverging around obstacles. Among the outflow channels, Kasei Valles is of particular interest because of its large size, as the volume of water involved in its formation could have contributed substantially to the existence of a northern ocean [2-3] (figure 1c).

 Owing to the similar landforms carved by the Missoula megafloods observed in the Channeled Scablands on Earth [1,4] (figure 2, c and f), Kasei Valles along with other martian outflow channels is analogously interpreted to be the result of ancient massive outburst floods [1-4]. Support for this hypothesis includes the presence and morphology of streamlined islands, the presence of regularly spaced longitudinal ridges, and the presence of hanging valleys and U-shaped valleys [1,4,5]. Debate ensues, however, regarding the near surface stability and availability of liquid water during the Hesperian period required to produce repeated erosion at the scales of observed in Kasei Valles. Alternative hypotheses that could explain outflow channel formation include ice streaming [5-6] or regional construction and local erosion by turbulent lava flows [7].

Figure 1. (a) Global topography of Mars with outflow channel distribution. (b) Timeline of Earth (top) and Mars (bottom) highlighting the origin of life on Earth (green star) and the evolution of Mars’ climate and hydrology through time, and the moment of outflow channel incision coinciding the collapse of the early water-bearing climate. (c) Kasei Valles, the largest outflow channel. (d) Hesperian outflow channels, marking the landing site of ESA’s ExoMars Rosalind Franklin Rover, which will search of evidences of life (red circle on Oxia Planum).

This project aims to explore the contrasting hypothesis that Kasei Valles was eroded by an ice stream [5-7], a region of channelized, fast-flowing ice within an ice sheet, and reinvestigate the origin of other outflow channels under this perspective. Drawing from fluid dynamic simulations, analogue field work, geological mapping, and climate modelling, the objective is to test the ice sculpture hypothesis first raised by Baerbel Lucchitta (1982) [5-6], which if correct, would substantially impact our understanding of Mars’ transitional Hesperian climate, the nature of its hydrological cycle, and the possibility of a Hesperian ocean.

Our preliminary observations and results tentatively support this hypothesis [8]. In terms of geomorphology, we show that bedforms such as grooves and streamlined islands, spatial scales, cross-section geometry, and planform morphology all are consistent with terrestrial ice streams, even more so than with the classical analogue of the Channeled Scablands (figure 2, compare a&d with b&e and c&f). Moreover, Kasei Valles demonstrates a lack of significant landforms associated with turbulent flow, such as kolks, turbulent eddie marks, or labyrinthine terrain, which are well visible and reported for the Channeled Scablands as well as other megaflood-type landscapes [4].

Fig 2. Overview and comparative of Kasei Valles and analogue sites and processes. (a) Kasei Valles (MOLA elevation on hillshade). (b) Graphic outline of the northeast Greenland ice stream. (c) Outline of the Channeled Scablands (US) adapted from the USGS. (d) Longitudinal grooves in Kasei Valles (CTX mosaic). (e) Megascale glacial lineations and megagrooves, Dubawnt Lake ice stream bed (ArcticDEM hillshade). (f) Grooves carved by Missoula megaflood, Channeled Scablands (Maxar, Google Earth, contrast-stretched).

 We use fluid dynamic simulations to analyze, explain, and interpret the scale and bedforms that are observable within and around Kasei Valles, and then consider comparisons with relevant terrestrial analogues beyond the classic Channeled Scablands site as well as geomorphological characteristics of fast-flowing glacial bodies, to draw conclusions regarding the origin of Kasei Valles, and implications for other outflow channels [8]. Finally, we will contextualize its climatic implications during the time of climate collapse (figure 1) at the end of the Hesperian period, following previous work [10].

Acknowledgements. This project has received funding from the European Research Council (ERC) under the European Union’s Horizon Europe research and innovation programme (Grant agreement No. 101165197 - ICEFLOODS).

References: [1] Carr M.H. (2007) C.U.P (Vol.6). [2] Chapman M.G. et al. (2010a) EPSL, 294 (3-4). [3] Chapman M.G., et al. (2010b). [4] Baker, V.R. and Milton, D.J., (1974) Icarus, 23(1), 27-41. [5] Lucchitta B.K. (1982) JGR: Solid Earth 87(B12). [6] Lucchitta B. K. (2001) GRL, 28(3), 403-406. [7] Leverington D.W. (2011) Geomorphology 132(3-4) [8] Grau Galofre et al., 2023, LPSC. [9] Stokes C.R. and Clark, C.D. (2001) Quaternary Sci. Rev. 20(13). [10] Turbet et al., 2017 Icarus 288, 10–36.

How to cite: Grau Galofre, A.:  Glacial Sculpture on Mars’ Ancient Megacanyons : A Presentation of Project ‘Icefloods’, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-504, https://doi.org/10.5194/epsc-dps2025-504, 2025.

The dynamics of granular particles on Mars are influenced by environmental factors that are very different from those on Earth. While the low ambient pressure of 6 mbar makes movement by wind significantly more difficult, it is helpful and even necessary for another process that favors the slipping of particles on slopes.

In so-called thermal creep, gas flows from colder, deeper soil layers to layers near the surface, which are heated by solar insolation. This uncommon process does not occur on Earth at 1000 mbar, but it works efficient in the low mbar range of Mars (Bila et al. 2023). The gas flow creates an overpressure under the surface, which can loosen particles and if the whole process takes place on a slope, this leads to a reduction in the slope angle, way below the typical angle of repose (Bila et al. 2024).

By using a centrifuge in microgravity (on parabolic flights), we have experimentally simulated Martian slopes and observed the process described above under realistic conditions in terms of pressure, particle-properties, gravity and insolation. We have measured a pressure- and particle-size dependent reduction in the slope angle by several degrees, which can clearly be attributed to the irradiation.

This process could be relevant for the characteristics of Martian dunes, the formation of Recurring Slope Lineae, slope streaks as well as for the general dynamics of granular particles in the context of dust entrainment.

Tetyana Bila et al 2023 Planet. Sci. J. 4 16

Tetyana Bila et al 2024 Planet. Sci. J. 5 115

How to cite: Schönau, L., Wurm, G., Parteli, E., Bila, T., Gries, O., Onyeagusi, F. C., Keulen, M., and Teiser, J.: From Dawn Till Dusk: How Light Might Reduce Martian Slope Angles, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-653, https://doi.org/10.5194/epsc-dps2025-653, 2025.

Introduction

The surface of Mars records a complex history of tectonic deformation evidenced by tectonic faults including extensional grabens and compressional faults termed ‘wrinkle ridges’. The majority are thought to have formed in Mars’ ancient past, >3.6 Ga, during the Noachian and early Hesperian periods [e.g., 1]. Morphological evidence for more recent tectonism, particularly during Amazonian period (<~3.4 Ga) is much rarer, and more spatially limited [e.g., 2-5].

We present new evidence that tectonic activity occurred in the Bosporus Planum region of southern mid-latitudes since the mid-to-late Amazonian (<1 Gyr). We observe a wrinkle ridge – the surface expression of a compressional fault zone - which cross-cuts a debris-covered glacier of mid-to-late Amazonian-age (Figure 1).

Figure 1: A wrinkle ridge (tectonic fault) dissecting a concentric crater fill (CCF, debris-covered glacier) in Bosporus Planum, Mars. (A) Location on a MOLA elevation map. (B) CTX image of the faulted CCF. White arrows indicate the fault. White dotted line is the crater ejecta. (C) Oblique CTX image with examples from HiRISE where the fault cuts the crater rim and CCF surface.

Observations

The faulted glacier infills a 7.5 km-diameter mid-latitude impact crater. It is morphologically consistent with features termed ‘Concentric Crater Fills’ (CCFs). CCFs, along with other types of putative debris-covered glacier in Mars’ mid latitudes (generally termed ‘viscous flow features’), are thought to have formed in the last few hundred Myr to 1 Gyr [e.g., 6-11].

We observe the fault trace crossing the CCF surface, and cross-cutting the walls, rim and ejecta blanket of the CCF host crater, as well as the surrounding plains. The fault appears to be associated with a regionally extensive population of SW-NE-oriented wrinkle ridges recording compressional tectonism in Bosporus Planum. The ejecta of the CCF-hosting crater embays NW-SE-oriented grabens to the south. Combined with the SW-NE-oriented wrinkle ridges, these indicate a complex history of both extensional and compressional stresses in this region.

The cross-cutting relationship we present between the wrinkle ridge and the CCF provides strong, direct evidence that this fault has been active since the CCF formed, and hence that syn-glacial, compressional tectonism has occurred in Bosporus Planum in the geologically recent past.

Estimating the timing of fault activity

To constrain the approximate timing of fault activity, we combine photogeologic mapping of the Bosporus Planum region with impact crater retention age estimation for various glacial and non-glacial units with different stratigraphic relationships to the tectonic faults in the region. We first generated a regional photogeologic map of the major geomorphic units and wrinkle ridges aligned with the CCF fault, using a basemap of 100 m/pixel Thermal Emission Imaging System (THEMIS) daytime and nighttime infrared images [12-13], and 6 m/pixel Context Camera (CTX) panchromatic images [14]. We are now performing targeted impact crater size-frequency analyses with a combination of CTX and 25 cm/pixel High Resolution Imaging Science Experiment (HiRISE) images [15] to estimate the impact crater retention ages of: (a) the regional population of CCFs; (b) the ejecta blanket of the impact crater hosting the faulted CCF; (c) the surrounding plains which are dissected by the fault; and (d) the ejecta blanket of a 33 km-wide crater 100 km NE of the faulted CCF, which also hosts evidence for faulting (though with a somewhat more ambiguous stratigraphic relationship between the ejecta and the associated fault).

To estimate the impact crater retention ages [e.g., 1] of the regional population of CCFs, we combined the CCF inventory of [16] with original observations and mapping to delimit crater counting areas for 114 CCFs across Bosporus Planum, avoiding portions of CCF surfaces which are significantly obscured by later deposits including aeolian bedforms and ice-rich mantling deposits. The combined area for CCF surface crater counting is 1140 km². Our CCF crater counts are based on CTX images, and impact craters with diameters >50 m. Below this diameter, it becomes challenging to distinguish impact craters from decametre-scale pits which commonly occur in ice-rich materials. We acknowledge the significant uncertainties which arise from impact crater counting on young, ice-rich surfaces, and we have classified the CCFs according to the level of apparent degradation, and additionally classified the impact craters in their surfaces into morphological categories which may reflect different degrees of CCF surface degradation or resurfacing. This allows us to scrutinise the influence of the different morphological subpopulations, and the potential CCF-surface modification processes they record, on the size-frequency distributions we observe.

Conclusions

Preliminary results indicate that CCFs in Bosporus Planum have a combined impact crater retention age of <1 Gyr. This confirms our hypothesis that the tectonic fault which cross-cuts a CCF in Bosporus Planum was active during the Amazonian period, and perhaps as recently as the mid-to-late Amazonian. At this meeting, we will present our full age estimation results, including for the ejecta blanket of the host crater and other units crossed by tectonic faults in Bosporus Planum.

References

[1] Michael, G. G., 2013. Icarus 226, 885–890.

[2] Goudy, C. L. et al. 2005. J. Geophys. Res. Planets 110, E10005.

[3] Bouley S. et al. 2018. Earth Planet. Sci. Lett. 488, 126–133.

[4] Woodley, S. Z. et al. 2024. Geophys. Res. Lett. 51(9), e2023GL107757.

[5] Pieterek, B. et al. 2024. Icarus 420, 116198.

[6] Levy, J. et al. 2010. Icarus 209(2), 390–404.

[7] Baker, D. M. H., and Carter, L. M. 2019. Icarus 319, 264–280.

[8] Woodley, S. Z. et al. 2022. Icarus 386, 115147.

[9] Butcher, F. E. G. et al. 2017. J. Geophys. Res. Planets 122(12), 2445–2468.

[10] Butcher, F. E. G. et al. 2021. Icarus 357, 114131.

[11] Madeleine, J.-B. et al. 2009. Icarus 203, 390–405.

[12] Christensen, P. R. et al. 2004. Space. Sci. Rev. 110(1–2), 85–130.

[13] Edwards, C. S. et al. 2011. J. Geophys. Res. Planets. 116(E10), E10008.

[14] Malin, M. C. et al. 2007. J. Geophys. Res. Planets. 112(E5), E05S04.

[15] McEwen, A.S. et al. 2007. J. Geophys. Res. Planets. 112(E5), E05S02.

[16] Levy, J. S. et al. 2014. J. Geophys. Planets. 119, 2188–2196.

How to cite: Butcher, F. E. G., Fawdon, P., Wright, J., Woodley, S. Z., and Cornford, B. T.: Amazonian syn-glacial tectonism in Bosporus Planum, Mars, evidenced by a tectonic fault cross-cutting a crater-filling glacier., EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-676, https://doi.org/10.5194/epsc-dps2025-676, 2025.

Abstract

Potential endorheic basins that are not contained within an impact crater have been studied only to a limited extent on Mars. These basins, characterised by the absence of outgoing channels, are of particular interest in planetary science due to their potential to preserve evidence for ancient hydrological activity and possible biosignatures [1,2]. This study investigates an inter-crater depression on Mars, located within the Terra Cimmeria region, by analysing both its geological and mineralogical aspects. Remote sensing data were collected, and a detailed geological map of this Martian basin was constructed, revealing various geological features suggesting a past aqueous environment. The analysis of CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) data was then conducted to investigate the mineralogy of the basin-fill deposits. The basin was observed to be rich in pyroxene and olivine, together with evidence of hydrated minerals in some locations.

Introduction

On Mars, open paleolake basins [2] and closed paleolake basins within impact craters [1] have been described often guided by the presence of deltaic bodies and other lacustrine deposits. However, examining terrestrial analogues such as the Makgadikgadi Pans in Botswana, it is revealed that endorheic lake basins do not form only within impact craters on Earth; instead, they can be formed by tectonic processes that result in formation of depressions [3, 4, 5, 6]. Similar tectonic or non-tectonic (i.e., inter-crater) endorheic lacustrine basins might have formed on the Martian surface outside impact craters.

Study Area

The study area lies within the Terra Cimmeria region of Mars' southern hemisphere (34.457°S, 147.973°E). This region features a potential endorheic basin that exhibits characteristics similar to those found near the Huygens Basin on Mars [7, 8]. These endorheic basins can be compared with the Makgadikgadi Pans (Botswana) previously described as potential terrestrial analogues of Mars playa environments [4, 5].

Geological Map

High-resolution Sterio Camera (HRSC), Context Camera (CTX), and High-Resolution Imaging Science Experiment (HiRISE) datasets were used to create a detailed geological map of the Martian basin, constructed using QGIS software, showcasing different geological features present (Fig.1). Digital Elevation Models (DEMs) from the Mars Orbiter Laser Altimeter (MOLA) were also utilised to create a topographical profile of the study area.

Crater counting for age determination

High-resolution imagery in JMARS was utilised to identify and catalogue impact craters within the study area. Each crater was measured and classified based on its size and state of preservation. To reduce secondary crater contamination, craters with a diameter of less than 1 km were avoided. The collected data were then analysed using the Craterstats software [9], which allowed for the estimation of surface ages by fitting the observed crater distributions to established Martian cratering models.

Mineralogical Investigation

Both CRISM hyperspectral (Map-projected Targeted Reduced Data Records-MTRDR) and multispectral (Multispectral Reduced Data Records-MRDR) data were employed for the detailed spectral analysis of the basin. Data were analysed using ENVI version 4.7. Using spectral indexes and browse products such as the MAF and PHY products, the spectral analysis is focused mainly on detecting mafic and hydrated minerals.
The multispectral tile t0472_35s148 was used to globally assess the mineralogy of the study area, including the craters surrounding the basin. Additionally, four CRISM-targeted images (frt0000a3b5_07, frt00009648_07, hrs0000aa66_07, hrl00013bfa_07) were used for detailed investigations.

Results and interpretation

The study area shows a drainage network, consisting of channels and tributaries mapped in the study, which might have created and sustained the lacustrine water body. The crater counting results suggest that this basin dates back to the Late Noachian period, a time when Mars likely had a more temperate climate capable of sustaining liquid water on its surface for extended periods [10]. Our preliminary CRISM analysis within the study area shows the presence of hydrated minerals [Fig.2], which strengthens a possible past hydrological environment in the area. Other minerals observed are olivine and pyroxene, which are consistent with a previous study [11].
This study laid the foundations for understanding the Terra Cimmeria basin as a potential paleo-endorheic basin. 

Figures

Figure 1: Mini Geological Map of the endorheic basin in Terra Cimmeria, Mars

Figure 2: Multispectral tile (t0472_35s148) analysed in PHY browse product with locations of the different regions used for CRISM analysis. (A) Reddish areas are olivine-rich (B). Blue areas indicate possible hydrated minerals. (C)  CRISM spectra with the 1.9 µm feature highlighting the presence of hydrated minerals.

References

[1]    Goudge, T.A., et al. 2015. Icarus 260, 346–367.
[2]    Goudge, T.A., et al. 2012. Icarus 219 (1), 211–229.
[3]    Franchi, F., et al. 2022. Frontiers in Ecology and Evolution, 10, 818417.
[4]    Franchi, F., et al. 2020. Planetary and Space Science, 192, 105048.
[5]    Kahsay, T. H., et al. 2024. Planetary and Space Science, 249.
[6]    Schmidt, G., 2023. Tectonophysics 846, 229678.
[7]    Mukherjee, S., et al. 2020. Geomorphology, 351.
[8]    Singh, D., 2022. Icarus, 372, 114757.
[9]    Michael, G.G., et al. 2010. Earth Planet. Sci. Lett. 294 (3-4), 223–229.
[10]  Andrews‐Hanna, J. C., 2011. Journal of Geophysical Research: Planets, 116(E2).
[11]   Cowart, J. C., et al. 2019. Journal of Geophysical Research: Planets, 124(12), 3181–3204.

How to cite: Motlhasedi, A. J., Franchi, F., Komatsu, G., Pondrelli, M., and Baschetti, B.: Investigation Of A Potential Endorheic Basin In Terra Cimmeria, Mars, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1070, https://doi.org/10.5194/epsc-dps2025-1070, 2025.

Introduction 

During the whole Holocene, the Sahara Desert underwent a series of cyclic climatic fluctuations resulting in alternating arid and humid phases. Current arid conditions began ~6,000 BP. Prior to that, from ~14,500 to ~6,000 BP, widespread and abundant rainfall characterized the so-called ‘Green Sahara’, the last African Humid Period (AHP) when the Sahara was vegetated. [1, 2]. Evidence of the extensive pluvial activity that characterized the AHP can be documented even in areas close to presently hyperarid zones such as the Tanezrouft. The Ahnet Basin, situated at the northeastern margin of the Tanezrouft, is indeed characterized by a wide range of morphologies and deposits that testimony the wet past of the basin. 

Our work focused on establishing the relationship between the paleohydrography of the basin, still visible, and its Quaternary deposits to infer, through mapping and stratigraphicrelationships:

• A better understanding of how the wet to arid climatic transition influenced the deposits and their distribution inside the basin;

• The possibilities to use the Ahnet Basin as a terrestrial analog for the evaporitic, alluvial, and eolian deposits directly related to the wet-to-arid transition on Mars at the end of the Hesperian.

Geological and Geographical Setting 

The Ahnet Basin (~65,000 km²) lies in the Algerian Sahara, ~1,200 km south of Algiers, [3, 4] and is one of the ‘Peri-Hoggar Basins’ that formed during the Pan-African Orogeny (600–500 Ma). The metamorphic basement of Precambrian age is unconformably covered by Paleozoic successions of siliciclastic sediments up to 7 km in thickness. They consist of NNW-dipping sandstones and shales with few Devonian and Carboniferous limestone intercalations. The origin of the deposits is predominantly marine with continental fluviatile facies gradually transitioning to shallow marine and then to offshore moving from South to North [5, 6, 7]. The Mesozoic sedimentary record, due to a strong Triassic erosional phase, is completely absent from the basin. Finally, the Quaternary deposits, which we intend to analyze, appear to reflect a range of different genetic agents.

Data and Methods 

The study was performed inside a GIS environment and, focusing onfour areas originally selected to be part of a sampling campaign. We produced four hybrid geomorphological maps, one for each area, making use of true color Sentinel-2A images as basemap (resolution: 10 m/px) and the Copernicus 30 m DEM for topographic and morphological characterization. The hydrography was digitalized both manually and automatically using GRASS GIS. Stratigraphic relationships were studied using Google Earth imagery and GIS 3D models.

Results 

Mapping at 1:10,000 scale identified ~10 litho-morphological units across all study areas (see Fig. 1 for example). Tectonic structures were also mapped in this phase, while a more detailed characterization of the geomorphological elements will be presented in a future publication. This process revealed the extensive presence inside the basin of alluvial deposits directly linked to a dense and well-developed valley network. Despite the limitations set by our DSM in the analysis of such a pervasive hydrography, we managed to automatically extract channels up to the 11^th Strahler order. These data, however, clash with the present-time climate whose numerical parameters were collected from three weather stations located all across the basin. Precipitation is <15 mm/yr (Fig. 2), confirming hyperaridity. Current valley reactivation is likely only during rare catastrophic events. Instead, in good accordance with these numbers, is the existence of evaporitic and eolian deposits which can also consistently be found in all areas.

Stratigraphic relationships revealed periodic channel reactivation and desiccation involving alluvial and evaporitic deposits. Fig. 3 depicts, for example, the interaction between an alluvial fan and a sabkha inside one of the study areas. The numerous instances of reactivated channelized activity, rather than to some episodic precipitation events, could possibly point to a slow climatic transition from humid to arid. Further investigations is needed to confirm the climatic interpretation, this association of deposits appears to be, from both a morphological and stratigraphical point of view, an analog for Arabia Terra’s light-toned layer deposits and inverted channels. As such, the study of the effect of climatic shifting on these terrestrial deposits could shed some insights on the Noachian-Hesperian transition on Mars.

Acknowledgements

We acknowledge financial support under the National Recovery and Resilience Plan (NRRP), Mission 4, Component 2, Investment 1.1, Call (2.2.2022) by the MUR, funded by the European Union – NextGenerationEU– Project Title Tanezrouft salt flat deposits (Sahara Desert): a priority target for a Mars Sample Return mission – CUP D53D23002600006 - Grant Assignment Decree No. 962 adopted on 30/06/2023 by the Italian Ministry of Ministry of University and Research (MUR).

This study was carried out within the Space It Up project funded by the ASI and the MUR (Contract n. 2024-5-E.0 - CUP n. I53D24000060005).

References

[1] deMenocal, P. B. et al. (2000). Quaternary Science Reviews, 19: 347–361.

[2] Tierney, J. E., et al. (2017). Science Advances, 3:e1601503.

[3] Perron, P. et al (2018). Solid Earth, 9: 1239-1275.

[4] Mostefai R. et al. (2023). Iraqi Geological Journal, 56: 1-13.

[5] Wendt, J. et al. (2006). Geological Magazine, 143: 269-299.

[6] Black, R., et al. (1994). Geology, 640-644.

[7] Zieliński, M. (2012). Marine and Petroleum Geology, 38: 166-176.

How to cite: Caddeo, Y., Pondrelli, M., Mancini, F., Abdelali, A., and Cavalazzi, B.: Water in the Ahnet Basin (Algeria): Traces of the Wet Past of the Sahara Desert as an Analog for the Hesperian-Amazonian Transition in Arabia Terra (Mars), EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1671, https://doi.org/10.5194/epsc-dps2025-1671, 2025.

We present our work on developing the 1:1M scale geologic map of a quadrangle of Mars in the Northeastern Tempe Terra region, next to the transition between Martian highlands and lowlands. The MTM 45302 quadrangle covers an area of about 200 by 300 kilometers, centered at 302.5°E, 42.5°N. We based our mapping on data from NASA’s Mars Global Surveyor, Mars Odyssey,  Mars Reconnaissance Orbiter, the ESA’s Mars Express, and CNSA’s Tianwen-1.

The regional topography in the area dips towards the northeast, with a total elevation decrease of about 2000 meters. We defined three plateau units in the area, with morphologies of wide, gently-dipping flat surfaces bounded by cliffs.  Moderate resolution imagery shows spots with evidence of layering within the plateaus units. Crater size frequency distribution indicates ages of 3.9 to 3.4 Ga for the plateau units. The three mapped units are separated stratigraphically by erosional unconformities, cross-cutting craters, and linear features. The middle and most extensive plateau unit is cut by parallel elongated valleys oriented NNE-SSW, exposing mounds, pitted terrain, fan deltas, and inverted channels in the lower plateau unit. The mapped channel axes are often associated with the trend of the valleys formed by the erosion of plateaus. Wrinkle ridges are present on each plateau unit, and their tectonic expression is confined to each relative unit. In the south portion of the quadrangle, ENE-WSW trending linear tectonic features of the Tempe Terra system cut through all the units. Craters in the MTM exhibit pedestal, radial, single- and multi-layer ejecta morphologies, and different infill styles. Several crater floors contain curvilinear ridges and troughs. We are currently reviewing the interpretation of the mapped features, their stratigraphic relationship and building hypotheses on the geologic evolution of the area, preparing the final geologic mapping product.

Besides the purpose of describing the evolution in space and time of the area, our mapping project serves as a context for a companion study about the presence of ice in the shallow Martian crust, observed from imaging spectroscopy at a spatial resolution of about 20 meters per pixel.  The area of our map also contains six ~0.5 - 2 km diameter, relatively recent impact craters with similar thermal inertia and crater morphology characteristics, including radial ejecta which exhibit unusually bright thermal inertia at night. Furnari et al. (2024)  studied one of these craters using spectral analysis, highlighting an anomalously large abundance of seasonal water ice on the ejecta, offering new insights on ice variation in the Martian ground. Additionally, crater analysis by Gou et al. (2024) in the lowlands Chryse Planitia region to the southeast of our study area posits that craters with multi-layer ejecta at this latitude indicate the presence of subsurface volatiles. 

The stratigraphic and structural relations of the geologic features mapped in this work provide the key to reconstruct the geologic evolution of processes that occurred on Mars in an area where the southern highlands are transitioning to the northern lowlands.  Evidences for ice-related processes in the geologic history, combined with the instrumental record of ice in relatively recent craters, suggests that this region likely hosted ice in the past and potentially in the present.

Acknowledgements: This work is supported by the ASI-INAF Mars Exploration agreement  2023-3-HH 0.

References: Furnari et al., 2024, Study of the seasonal water ice in the ejecta of a small crater on Mars. Congresso di Scienze Planetarie, Bormio, Italy, 5-9 Febbraio 2024;  Gou et al., 2024, Paleoenvironment implications of layered ejecta craters in the Chryse Planitia, Mars, Icarus, Volume 410, 115918.

How to cite: Frigeri, A., Rasmussen, M., Brossier, J., Apuzzo, A., Altieri, F., and De Sanctis, M. C.: The Geologic Map of the MTM 45302 quadrangle in Northeastern Tempe Terra on Mars., EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-811, https://doi.org/10.5194/epsc-dps2025-811, 2025.

Isotopic analysis is a critical tool for understanding planetary water cycles and quantifying the role of distinct atmospheric processes. This study investigates the spatio-temporal distribution and controlling factors of the HDO/H₂O ratio in water vapor within the tropospheres of Earth and Mars, highlighting the similarities and differences in water vapor transport and phase changes on both planets.

We found significant isotopic enrichment from ice sublimation on both planets, with a stronger effect observed on Mars due to longer ice-crystal residence times, lower atmospheric pressures, and substantial temperature fluctuations. In contrast, Earth's near-surface oceans buffer these isotopic variations. Quantifying ice sublimation effects through observational data could help improve the microphysical parameterization in atmospheric models.

Moreover, during Mars's global dust storm, the D/H ratio markedly increased and propagated upward due to reduced condensation and the absence of liquid precipitation. In contrast, Earth-based observations during typhoon events indicate isotopic depletion propagating northward from tropical regions, driven primarily by raindrop evaporation within convective systems. Thus, storm events lead to opposite isotopic responses on Earth (depletion) and Mars (enrichment). Consequently, isotopic signals have considerable potential as proxies for reconstructing storm history and intensity across planetary environments.

This comparative analysis underscores both shared and planet-specific aspects of tropospheric water cycling, supporting a unified conceptual framework that effectively explains isotopic distributions under differing planetary conditions. Our results may enhance climate and weather models by improving representations of cloud microphysics and atmospheric water transport, while offering new tools for interpreting past climate events based on isotopic evidence.

How to cite: Wang, D., Risi, C., Montmessin, F., Tian, L., Bowen, G., Petzold, G., Vals, M., Gourion, E., Fan, S., and Sun, C.: Comparative Analysis of Tropospheric Water Isotope Distributions on Mars and Earth: Insights into Ice Cloud Microphysical Processes and Storm Dynamics, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1507, https://doi.org/10.5194/epsc-dps2025-1507, 2025.

Introduction: Gravity and topography are valuable tools for understanding climate records on Mars. Specifically, they help constrain the volume and composition of large ice masses including the Polar Layered Deposits (PLDs) and subsurface ice sheets in the mid-latitude regions. The South Polar Layered Deposits (SPLDs) in particular are known to reach up to ~3.7 km thick [1] and have a composition primarily of water-ice mixed with dust [e.g., 2]. Understanding vertical and lateral dust variations across the SPLD will advance our ability to understand how material is deposited and sublimated over time in response to an orbitally controlled climate. Mid-latitude ice deposits share similarities in composition [3] as well as implications for understanding Mars’ climate and habitability. They may also represent water resources for potential human exploration [4], such as the Arcadia plains and the glacial deposits of Deuteronilus Mensae [5]. However, debates regarding the spatial distribution, structure, thickness, and total volume of these deposits remain [e.g., 3,6].

Methods: We use localized effective density techniques. Although the analysis of ice deposits with gravity is challenging because of the current precision and resolution of the Martian gravity field (known to spherical harmonic degree and order 120 [7]), these techniques allow us to quantify bulk density at different spatial scales by comparing free-air gravity to the Bouguer correction (gravity predicted from topographic relief) [8]. Our work advances on that of [9] by using these techniques to specifically constrain ice deposits. For the SPLD, density variations can inform us on variations in dust content. For the mid-latitude deposits, we can either match the thickest ice deposits to other independent data sets (such as the ice consistency maps of [5]) or place upper limits on their thicknesses. In both settings, these techniques can help set measurement requirements for future gravity data to address scientific questions. We obtain localized effective density (ρ_eff) estimates by filtering the window of the gravity field in spherical harmonics with Slepian functions [e.g., 10], which define a spatial concentration from an angular size θ and a spectral concentration from a bandwidth L. Using the Python package SHTOOLS [11] and the methods described in [9], we compute localized ρ_eff spectra across the Martian surface at specified latitudes and longitudes.

Results: Mars’ gravity field has highest resolution at the south pole, allowing us to work with higher bandwidths and examine the SPLD regionally. The effective density of the south polar region of Mars is shown in Figure 1. We use L=20 and θ=10°, yielding a best-concentrated localization window with a concentration factor of 0.96. Between 90°S and 70°S, we calculate ρ_eff spectra at longitudinal increments of 2° and latitudinal increments of 1°. To mitigate noise in the gravity data, we take a flexible approach in interpreting different spherical harmonic degrees in different regions. Up to the maximum degree we can consider given the local degree strength and L, (typically between degrees 60<l<75), we select the ρ_eff value corresponding to the spherical harmonic degree with the highest correlation between free-air gravity and gravity-from-topography. We do not report ρ_eff in regions where the maximum correlation <0.5, as these areas probably produce unreliable density estimates due to low correlation. We additionally track the maximum correlation between 60<l<75 and the degree at which the highest correlation occurs, which are shown as polar projections in Figure 1.

In the region of the SPLD, we observe 650<ρ_eff<2600 kg/m³, encompassing a past bulk estimate of 1220 kg/m³ [2]. We can interpret lateral variations in ρ_eff as potential variations in dust content and compare to the density maps of [12,13]. Similar to [12], we find some of the lowest densities close to the south pole as well as lower densities at Ultima Lingula. Similar to [13], we observe low densities between longitudes 0°-180°E across Australe Lingula, Promethei Lingula, and Ultima Lingula. We observe a similar trend towards higher densities near Australe Scopuli, and especially high densities between longitudes 180°-225°E that can be interpreted as a very low-ice content region, subsurface mass anomalies, or noise in the gravity data.

Discussion and Future Work: Our initial results for the SPLD quantify possible lateral variations in dust content, which may reflect different climate records at different past times. Ongoing work involves applying the same effective density approach elsewhere on Mars, focusing on density variations at the upper mid-latitude regions and forward modeling the effective density spectra (similar to the approach of [14]) of ice deposits. Additionally, our modeling approach will be used to set upper limits on ice sheet thicknesses from the current gravity data and inform measurement requirements for testing ice and climate-related hypotheses with the acquisition of future gravity data at Mars [15], such as from the MaQuIs mission concept [16].

Figure 1: Maps of the south polar region, including effective density (left) corresponding to the highest correlation between 60<l<75, the values of those highest local correlations (middle), and the degree l at which the highest correlation occurs (right).

References: [1] Plaut, J., et al. (2007) Science, 316, 92-95. [2] Zuber, M., et al. (2007) Science, 317, 1718-1719. [3] Bramson, A., et al. (2015) GRL, 42, 6566-6574. [4] Dundas, C., et al. (2018) Science, 359, 199-201. [5] Morgan, G., et al. (2021) Nat. Astron., 5, 230-236. [6] Campbell, B., & Morgan, G. (2018) GRL, 45, 1759-1766. [7] Genova, A., et al. (2016) Icarus, 272, 228-245. [8] Besserer, J., et al. (2014) GRL, 41, 5771-5777. [9] Goossens, S., et al. (2017) GRL, 44, 7686-7694. [10] Wieczorek, M., and Simons, F. (2005) GJI, 162, 655-675. [11] Wieczorek, M. & Meschede, M. (2018) G3, 19, 2574-2592. [12] Li, J., et al. (2012) JGR: Planets, 117. [13] Genova, A., et al. (2024) Icarus, 414, 116025. [14] Izquierdo, K., et al. (2024) JGR: Planets, 129(2), e2023JE007867. [15] Sori, M., et al. (2024), 10th Int. Conf. on Mars, Abstract #3037. [16] Wörner, L., et al. (2023), Planet Space Sci., 239, 105800

How to cite: Dunnigan, A. and Sori, M.: Constraining Martian Ice Deposits from an Effective Density Approach to Gravity and Topography and Implications for a future Mars Gravity Mission, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-931, https://doi.org/10.5194/epsc-dps2025-931, 2025.

Introduction:
Understanding the long-term evolution of the Martian climate and its reservoirs is a key challenge in planetary science. Mars experiences large obliquity variations (0°–60°), which are known to drive its climate [1]. In particular, the North Polar Layered Deposits (NPLD) is believed to preserve a valuable stratigraphic archive of past environmental changes over the last few to tens of millions of years [2,3]. Yet, a major question remains: linking the orbital forcings with the layers evolution under climate dynamics [4]. To investigate these processes at geologic timescales, we developed the Planetary Evolution Model (PEM), a new modeling framework to bridge the gap between short-term General Circulation Models (GCM) and long-term climate dynamics.
In this contribution, we present the conceptual and physical basis of the PEM and illustrate its first applications focused on the formation and evolution of the Martian NPLD.

The Planetary Evolution Model (PEM):
Traditional Mars GCM convincingly simulate atmospheric processes but are limited to short periods (typically decades) due to computational costs. 1D climate or stratigraphic models handle long durations but often neglect key dynamical couplings, limiting their applicability. Moreover, all these models typically rely on paramatrized fluxes and prescribed reservoirs (glaciers, subsurface ice) whose initialization can lead to unrealistic outcomes. Hence, GCM are unsuitable for simulating orbital-scale climate variations. The PEM addresses this issue by focusing on long-term changes while bypassing sub-year variability. It is based on asynchronous coupling with a GCM, here we use the Mars Planetary Climate Model (PCM) [3].
The core idea of the PEM is to compute tendencies from two consecutive PCM years and then to extrapolate them to evolve climate-relevant reservoirs until stopping criteria are met (e.g. surface pressure change, ice area loss/gain or orbital shift). At that point, the PEM halts and, with the updated climate state, it re-runs the PCM to obtain new tendencies. This cycle repeats until the desired simulation length is reached. The PEM can be used in two ways: (i) to determine steady-state configurations (e.g. realistic distribution of glaciers) for given orbital parameters, which can then be used as initial states in other simulations; and (ii) to perform transient simulations over full orbital cycles.
Key physical processes in the PEM include:
    • CO₂/H₂O surface ice evolution: local tendencies are computed from interannual minima of the ice in the PCM (perennial ice). The PEM assumes fast atmospheric equilibration for water with only transfers between sublimating and condensing reservoirs.
    • Glacier flow: a statistical sub-grid slope parameterization accounts for North–South orientation effects [6], reproducing slope-dependent layering.
    • Subsurface H₂O ice: ice table depth is dynamically adjusted based on thermal diffusion, pressure and surface humidity, following Norbert Schorghofer's work [7].
    • Soil properties: the PEM uses a multilayer subsurface (regolith, breccia, bedrock) whose thermal properties adapt to pressure and pore-filling ice. The yearly-averaged surface and subsurface temperatures are updated according to surface ice accumulation/depletion.
    • CO₂/H₂O adsorption/desorption: adsorbed species are maintained in equilibrium with the atmosphere.
Furthermore, the PEM performs several subsequent adaptations to make the aforementioned processes internally consistent and to simulate the co-evolution of reservoirs and atmosphere. For instance, the PEM adjusts the yearly-averaged surface pressure based on CO₂ mass balance. This necessitates to scale the volume mixing ratios accordingly and to correct the CO₂ tendencies obtained from the PCM.

Layered Deposits:
The NPLD exhibit a complex stratigraphic structure made of layers with varying composition (H₂O ice, dust and possibly tempoeary CO₂ ice) and geometry (thickness, unconformities). The alternation of dusty and icy layers has long been hypothesized to record obliquity-driven climate cycles. High obliquities (>30°) typically lead to ice loss, while low obliquities (<20°) enable accumulation provided that a source is available [8,9].
Additionally, CO₂ and H₂O sublimation/condensation thresholds interact to create diverse physical siturations. For instance, water may act as a lag layer above CO₂ glaciers, as observed and modeled by Buhler et al. [10] for the South Polar Layered Deposits (SPLD).
To reproduce such features, the PEM includes a novel dynamic layer-tracking model. Each deposition or ablation event modifies the local stratigraphy by adding new layers with appropriate dust/ice content or generating dust lag deposits upon ice sublimation. 
As a first scientific application, we used the PEM to simulate the growth and evolution of the NPLD under an orbital forcing scenario. The goal is to test whether the PEM can reproduce observed stratigraphic features and evaluate the role of orbital cycles in shaping the NPLD.

Perspectives:
The PEM is a new-generation tool to study the evolution of Mars’ climate and volatile reservoirs over orbital timescales and understand its present-day geomorphological imprints. Our first applications to the NPLD demonstrate the PEM potential to resolve long-term polar stratigraphy and test hypotheses on past Martian environments, bringing us closer to decoding the Mars’ deep climate memory.
Our ongoing work aims to improve the PEM models to explore atmospheric collapse/inflation scenarios and to fully couple the PEM with an hydrological model (lakes, river systems) to study early Mars.

References:
[1] Laskar J. et al. (2004) Icarus, 170(2), 343–364.
[2] Phillips R. J. et al. (2011) Science, 332, 838.
[3] Levrard B. et al. (2007) J. Geophys. Res., 112, E06012.
[4] Smith I. B. et al. (2020) Planetary and Space Science, 184, 104841.
[5] Forget F. et al. (1999) J. Geophys. Res., 104(E10), 24155–24175.
[6] Lange L. et al. (2023) Journal of Geophysical Research: Planets, 128, e2023JE007915.
[7] Schorghofer N. (2007) Nature, 449, 192-194.
[8] Hvidberg C. S. et al. (2012) Icarus, 221(1), 405-419.
[9] Vos E. et al. (2022) J. Geophys. Res., 127(3), e2021JE007115.
[10] Buhler P. B. et al. (2020) Nature Astronomy, 4, 364-371.

How to cite: Clément, J.-B., Forget, F., Vos, E., Lange, L., and Millour, E.: Long-term simulation of Martian Polar Layered Deposits: introducing the Planetary Evolution Model, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-792, https://doi.org/10.5194/epsc-dps2025-792, 2025.

Introduction

Mars’ mid latitudes contain thousands of ‘viscous flow features’ (VFFs), akin to debris-covered glaciers on Earth [e.g. 1,2]. They are thought to have formed within the last several Myr to 100s Myr [3,4] during martian ‘ice ages’, driven by variations in Mars’ spin-axis obliquity [5,6]. Knowledge of the emplacement age of ice within VFFs is key to understanding the palaeoclimate histories likely contained within them.

Current VFF age estimates rely on the size-frequency distributions of impact craters across their surfaces [e.g. 3,4]. Such ages likely reflect the time since emplacement or last major modification of the surficial debris layer; they provide no direct information about the emplacement ages of the underlying ice, and implicitly assume a uniform age across the sampled area. However, ice flow physics causes spatial variations in ice flow, which will lead to the age of ice varying across VFF surfaces and with depth. Here, we develop a new physically-based approach to estimate the age of ice in VFFs, and apply this method to a small VFF in Mars’ southern mid-latitudes (Figure 1), the subject of our previous study [7].

Figure 1. VFF in Nereidum Montes (51.24°W, 42.53°S). (A) 6 m/pixel Context Camera (CTX) image P14_006572_1367_XN_43S051W showing the VFF (terminating at the white dashed line), and major arcuate VFF-surface structures cut through by a gully [8]. Inset: Mars Orbiter Laser Altimeter (MOLA) elevation map of Mars showing location of Nereidum Montes. (B) Oblique view of the VFF overlain by schematic map identifying key landscape features, adapted from [7]. Base image: orthorectified 25 cm/pixel HiRISE [10] image ESP_051036_1370, overlain on 1 m/pixel HiRISE DTM.

Methods

Our age-estimation method combines a 3-dimensional ice flow model [ISSM; 8] with particle tracking. We conduct a range of experiments with different assumed ice flow mechanisms with different exponents in the ice flow law (n = 2 or 3,  [9]), assumed VFF surface temperatures (T_s) ranging from 200 K to 230 K, and ice grain sizes from 0.5 mm to 5 mm. We take n = 3, T_s= 210K as the “standard” run. We track a dense network of 4860 “seed” particles across the VFF surface from emplacement, through transport within the VFF, to re-emergence onto the surface. Integrating the modelled velocity along each path allows calculation of the age of the surface at particle emergence points, and the age/depth relationship for any point within the VFF.

Results

Figure 2 shows the calculated VFF surface age for the standard run, with example particle paths and depths for 21 particles emerging along three of the major arcuate surface structures (Figure 1). There is a strong, rapid increase in surface age toward the VFF terminus; particle paths emerging nearer the terminus have come from furthest upstream (Figure 2B), and reach greater depths within the VFF. Vertical transects through the VFF (Figure 2C) show particle paths become increasingly tilted toward the ice surface toward the terminus (due to flow compression [8]); isochrons also become tilted upwards. The upstream area of the VFF shows younger ages; particles emplaced here move downwards into the VFF due to flow divergence, emerging at lower elevations (Figure 2B).