Jeremy Brossier

Ma_MISS is a miniaturized, modular VNIR spectrometer [1,2] on board of the ESA Rosalind Franklin rover [3]. The rover hosts a drill able for the first time to collect samples of astrobiological interest down to a depth of 2 meters. To reach that depth in the Martian shallow subsurface, the drill is composed of a tip and 3 rods of 50 cm each. Ma_MISS spectrometer module is located within the drill box while the optical head module is integrated into the drill tip; the spectrometer and the optical head are connected through optical fibers hosted within the tip and drill rods. The landing site is located within the Oxia Planum region where large deposits of Fe-Mg rich clays have been detected [4, 5, 6], formed when early Mars hosted habitable conditions. Thermal modelling (e.g. [7]) shows that at Oxia the thermal skin depth is located within approximately the first 30 cm (depending on the thermophysical parameters considered), and below that depth sub-zero temperatures are expected.In this work, we plan to investigate the impact of below freezing temperature conditions on the spectral behaviour of clays using the CAPSULA (Chamber for Analogues of Planetary Surfaces Laboratory) set-up [8]. CAPSULA consists of an environmental chamber equipped with a FTIR spectrometer to acquire spectra of planetary analogues in various conditions. The chamber is designed to obtain high vacuum (< 10−6mbar) and cryogenic T (< 50K) environmental conditions applicable to Mars. The goal is to support the data exploitation of the Ma_MISS instrument. Reflectance spectra of selected samples will be acquired in the InfraRed range (1-12 µm) at different temperatures relevant for Mars, investigating diurnal and seasonal temperature cycles, as well as samples with different hydration states. Acknowledgements: This work is supported by the ASI-INAF Mars Exploration agreement 2023-3-HH 0 References[1] De Sanctis M.C., et al. 2017, Astrobiology, Vol. 17, n.6-7, doi: 10.1089/ast.2016.1541, p. 612-620[2] De Sanctis M.C., et al., 2022, The Planetary Science Journal, 3:142, https://doi.org/10.3847/PSJ/ac694f [3] Vago, J., et al., 2017, Astrobiology, 17(6–7), 471–510. https://doi.org/10.1089/ast.2016.1533[4] Mandon L. et al., 2021, Astrobiology, 21(4), 464–480. https://doi.org/10.1089/ast.2020.2292. [5] Brossier, J., et al., 2022, Icarus, 386, 115114. https://doi.org/10.1016/j.icarus.2022.115114.[6] Auré, I.T., et al., 2026, Icarus in press, https://doi.org/10.1016/j.icarus.2026.117113[7] Formisano et al. 2021, Advances in Astronomy, 9924571, 10 pages, 2021][8] De Angelis S., et al., 2024, Mem. SAIt, Vol. 95, Issue 4, p. 91-102, https://www.memsait.it/volumi/Volume-95-n4-2024/2024MmSAI..4...91A.pdf

Mapping the global distribution of carbonate minerals on the Martian surface is a prerequisite for understanding the aqueous and atmospheric evolution of Mars, as these minerals represent a principal sink for atmospheric CO₂ and direct tracers of past liquid water activity. To date, the orbital data from CRISM offers our best opportunity for detecting the diagnostic vibrational signatures of these minerals; however, studies have focused almost entirely on the weak short-wave infrared (SWIR) overtone and combination bands near 2.3 and 2.5 µm [1,2]. These features can be spectrally degenerate with co-occurring phyllosilicates and are not always strong enough to reveal smaller or less exposed deposits, leaving a significant fraction of the carbonates undetected.The strongest spectroscopic signatures of carbonates lie in the mid-wave infrared (MWIR): the fundamental absorptions at 3.4 and 3.9 µm [2]. These features remain largely unexploited in CRISM data, due to the limited spectral range of the instrument, which does not fully cover the 3.9 µm band, and to the superposition of reflected solar radiance and planetary thermal emission in the 3–4 µm window, which renders band depth estimation challenging.To overcome this issue, we developed a dual-band detection framework based on two independent pipelines processing the SWIR and MWIR parts of the spectrum. While the SWIR pipeline works similarly to conventional detection methods, refining the 2.5 µm overtone absorption, the MWIR pipeline has to deal with the presence of thermal emission. Each pipeline produces a spatially filtered detection map with fully propagated, SNR-anchored uncertainties.In particular, the MWIR pipeline operates on the atmospherically corrected datacube and treats the observed signal as the sum of a reflected solar continuum, a surface thermal contribution, and channel noise. The solar continuum is estimated using an iteratively reweighted least-squares (IRLS) fit to a band-masked window between 1.8–2.6 µm, which serves as a robust estimator with a well-defined per-pixel noise level, avoiding the limitations that affect classical shoulder-based approaches. Using these residuals, the thermal contribution is estimated by a constrained Planck greybody fit in the 3–4 µm window, with temperature values restricted to a realistic Martian daytime range. Instrumental artifacts are subsequently identified and filtered both at the channel level and in map space before proceeding with the final detection step.The SWIR pipeline uses a pre-processed atmospherically corrected and denoised datacube, where thermal emission is absent. The 2.5 µm overtone is isolated with an iterative continuum fit and sub-pixel band-centre localisation, while band absorption is quantified via a Gaussian-kernel-weighted band-depth integration. SNR, band-centre location, and amplitude of the detected absorption serve as criteria for distinguishing carbonates from overlapping phyllosilicates and sulphates [3].As a first demonstration, the framework is applied to a single CRISM observation, FRT000186FA at Nili Fossae, a scene chosen for its close proximity to Jezero Crater, where carbonate presence has been independently established both from orbit [4] and in situ by the Perseverance rover [5,6]. Both pipelines detect a spatially coherent area of elevated absorption,with detection maps consistent in spatial extent and structure. Figure 1: Band depth integral at 2.5 µm (SWIR pipeline) for CRISM observation FRT000186FA (Nili Fossae). Figure 2: Band depth integral at 3.9 µm (MWIR pipeline, thermal-corrected) for CRISM observation FRT000186FA (Nili Fossae). Nili Fossae serves here as a validation benchmark, with the framework designed for systematic application across a geologically diverse sample of CRISM observations, moving toward a more complete carbonate inventory of Mars. This work is funded by the Italian Space Agency (ASI) [ASI-INAF n.23-3-HH.0][1] Harner, P.L., & Gilmore, M.S. (2015). Visible–near infrared spectra of hydrous carbonates, with implications for the detection of carbonates in hyperspectral data of Mars. Icarus 250, 204-214. http://dx.doi.org/10.1016/j.icarus.2014.11.037 [2] Bishop, J.L., et al. (2021). Spectral properties of anhydrous carbonates and nitrates. Earth and Space Science, 8, e2021EA001844. https://doi.org/10.1029/2021EA001844 [3] Plebani, E., et al. (2022). A machine learning toolkit for CRISM image analysis. Icarus 376, 114849. https://doi.org/10.1016/j.icarus.2021.114849 [4] Ehlmann, B.L., et al. (2008). Orbital Identification of Carbonate-Bearing Rocks on Mars. Science 322, 1828-1832. https://doi.org/10.1126/science.1164759 [5] Clavé, E., et al. (2023). Carbonate detection with SuperCam in igneous rocks on the floor of Jezero Crater, Mars. JGR Planets 128, e2022JE007463. https://doi.org/10.1029/2022JE007463[6] Clavé, E., et al. (2026). In Situ Carbonation of Sedimentary and Igneous Rocks of Ultramafic Composition in Jezero Crater, Mars. JGR Planets 131, e2025JE009107. https://doi.org/10.1029/2025JE009107

IntroductionOxia Planum (Fig. 1) is a region of Mars located on the margin between the old, heavily cratered highlands of Arabia Terra (Noachian-aged) and the younger, smoother lowlands of Chryse Planitia (Hesperian-aged). From orbit it shows several geomorphological records of past widespread water–rock interactions, including fractured, layered, clay-bearing deposits with high astrobiological potential [1, 2, 3]. For this reason, Oxia Planum has been selected as the landing site for the ESA Rosalind Franklin Mission (RFM). The main goal of the RFM is to search for past (and/or present) traces of life, particularly in the Martian shallow subsurface where material of astrobiological interest is better preserved. To achieve this, the RFM rover is equipped with a drill capable of collecting, for the first time for a mission on Mars, samples down to a depth of 2 meters, and with a suite of instruments designed to discriminate biosignatures in the samples, gathering supporting geological context information [4]. Figure 1: Oxia Planum, Mars with CTX basemap colored by elevation. The white ellipses represent the current landing ellipses, and the orange polygon in center represents the outline of the geologic map of the region [5], with the map’s cross-section added in orange. Note that two cubes selected for study overlap with the geologic map while one cube for study is towards the delta and outside the previously mapped area.Here, we focus on selected regions of interest (ROIs) within the Oxia Planum landing area (Fig. 2) to investigate how clay distribution relates to other geologic features. We incorporate an Oxia Planum survey of fractures mapped at 1:1250 scale in spaced windows (e.g., blue squares in Fig. 2) which provides the general fracture characteristics of multiple units. Within ROIs, we repeat this fracture mapping to connect the geomorphological and spectral analysis with bedrock fracture behavior to more fully characterize the rocks, and contribute to strategies for guiding the selection of drilling sites.Figure 2: CRISM spectral maps of the 2.3 micron band depth [3] where yellow tones represent high Fe,Mg-phyllosilicate signatures, with CTX basemap as background and the geologic cross-section [5] overlain in orange. The ROIs are shown and labeled in white. Dark blue squares represent areas where regional fracture analysis has been performed to aid in extending the geologic mapping to unmapped areas. Inset of ROI 10 shows the fractures which have been mapped (blue) on HiRISE imagery (shown), and exhibit a strong correlation with clay-rich areas. Data and MethodsROIs were chosen based on (1) mapped contacts between bedrock units [5], (2) stratigraphic exposures within mounds and/or crater walls, (3) association with the geologic cross-section [5], and/or (4) high likelihood of encountering phyllosilicates (Fe,Mg-rich clays), based on CRISM cube analysis [3]. The southernmost CRISM cube of interest, FRT09A16 (Fig. 1), is located near the delta containing sediments derived from the highlands, thus providing a key insight into the stratigraphic relationships and depositional modes of the units farther downslope. Within ROIs, we created meter-scale resolution digital terrain models (DTMs) using the NASA Ames Stereo Pipeline and HiRISE stereopairs, tied to MOLA elevations.Fracture mapping was performed on HiRISE images which were manually georeferenced to improve their correlation with CRISM data. Mapping at 1:2000 scale (minimum resolvable fracture size approximately 10m) provides comparable data to the fracture survey, providing a dataset that aids in expanding geologic units beyond the current bounds of the map [5]. Detailed mapping at 1:1000 scale, following [8], has sufficient detail to analyze fracture topology, improving unit characterization and providing insight into fracture formation mechanisms [e.g., 9].Preliminary results and Discussion Figure 3 compares the DTM created from HiRISE using the NASA Ames Stereo Pipeline [6] with the MADNET DTM [7] created through machine learning, both of which are based on HiRISE images. The example shows the subdued elevation changes of the MADNET DTM, where the elevation decrease from west to east is partially inherited within the crater rim elevations. The Ames Stereo Pipeline DTM shows a more accurate crater depth-to-width ratio of approximately 0.1, with the crater rim maintaining a realistic cross-sectional shape and the elevation change mostly impacting the surrounding landforms.Figure 3: Example DTM quality comparison at a crater near transect 9 (Fig. 2), with the MADNET DTM [7] shown in red and the DTM from Ames Stereo Pipeline [6] shown in purple (this work).Fracture mapping performed across the broader area shows that the phyllosilicate clays exhibit a higher number (fracture density) and sum length (fracture intensity) of fractures per area, relative to low-clay areas that are also mapped as bedrock units. Preliminary results suggest that this trend is consistent within the ROIs. In the southernmost ROIs which the geologic map does not cover, CTX brightness and CRISM clay signatures are used to identify the clay-rich bedrock groups. We then manually assign unit designations based on comparison with the stratigraphic relationships, fracture characteristics, and geomorphological behavior of the units in mapped regions, leveraging the fracture survey to inform unit extents.By combining multiple datasets (CTX, CRISM, HiRISE) with different scientific approaches (spectral, fracture, and geomorphological analysis) we provide further context for RFM. Although orbital data only provides information on the surface and limited subsurface exposures, using a combination of geologic approaches allows us to propose realistic subsurface scenarios, critical for mission success in drilling the near subsurface. Acknowledgements: This work is supported by the ASI-INAF Mars Exploration agreement 2023-3-HH 0 and the European Space...

Carbonates on Mars provide key evidence of past environmental conditions because they can form through alteration of ultramafic rocks by liquid water in a dense CO2–rich atmosphere. We searched for carbonates by examining the 2.3, 2.5, and 3.5 µm absorption bands in 540 CRISM near-infrared hyperspectral cubes. The detected carbonates are best described as Fe–Mg solid solutions within the siderite–magnesite series, likely formed under reducing conditions and preserved despite later acidic, oxidizing environments. We identify new carbonate-rich deposits associated with clay-bearing terrains, revealing a more widespread co-occurrence of carbonates and clays than previously recognized, partly because carbonates can be spectrally masked by clays. Their association suggests formation in neutral to mildly alkaline waters early in Mars’ history, implying prolonged aqueous alteration, sustained liquid water, and environments potentially favorable for microbial life. These findings expand the known distribution of carbonates and highlight promising targets for future biosignature exploration.

Studying the geomorphology of crater ejecta at Martian mid- to high-latitudes is essential for understanding how impact-generated flows and debris patterns indicate subsurface ice or water at the time of impact. By analyzing ejecta morphologies, such as rampart structures, lobate flows, and layered deposits, we can reconstruct the distribution and abundance of volatiles in the Martian subsurface. These morphological observations provide the basis for stratigraphic correlations and spectroscopic analyses, enabling more precise quantification of past and present water-ice concentrations in the upper crust. Our study focuses on a fresh crater (43.81N, 301.53E) located roughly 225km NE of Timoshenko crater, in Tempe Terra. By using Digital Terrain Models (DTMs) at different scales (CTX at 6m ppx and HiRISE at 0.3m ppx) we map the different ejecta blankets that comprise this crater and classify it based on their topography and shape. We created DTMs using the Ames Stereo Pipeline (ASP, [1]) and two stereopairs per instrument (CTX J14_050126_2236_XN_43N058W and P12_005807_2238_XI_43N058W, HiRISE ESP_059370_22401 and ESP_077029_2240), aligned to overlying MOLA data from PDS ([2]), and then projected within a GIS software (QGIS, v3.40.5), which helps in DTM manipulation, visualization, and topographic studies of the ejecta layers and their subsequent plotting, while using different data formats. From CTX imagery, we recognize 2 ejecta layers: one proximal to the crater (500m from crater rim), with a slope of 20˚ and smoother topography, which ends in a small (~10m) edge step; and a second more distal, showing a radial lobate pattern exuding from the crater, composed of rougher materials, with little to no slope (~3˚).Following [3]’s classification, we classify this as a type 2 (double ejecta facies) or type 3 (multiple facies) crater. This uncertainty is related to the resolution limits of CTX; it is difficult to determine whether the second ejecta layer is further subdivided into more layers, as the contacts become diffuse, and the more distal parts of it appear as isolated ejecta clusters, disconnected from the main facies, especially in the NW and SE margins. Our multi-scale morphological analysis of the crater will place it into context with its surroundings [4] and prepare for specific studies, such as the spectroscopic analysis of specific areas [5]. Using CTX DTMs as a basemap will provide a robust and smooth topography, which can be better interpreted and used for mapping; HiRISE will offer very high resolution, allowing a more robust identification of smaller features. The accurate development of DTMs at appropriate resolution is key and we will concentrate efforts on uncertainty analyses of these higher-level data products. We are applying these techniques into operational mission-driven scenarios like the Oxia Planum landing site of the ESA/ExoMars Rosalind Franklin Rover [5].This work is funded by the Italian Space Agency (ASI) [Grant ASI-INAF n. 2023–3–HH.0].References: [1] Beyer et al. (2018) ESS 5(9), 537-548; [2] Smith et al. (2001) JGR Journal of Geophysical Research: Planets 106.(E10); 2156-2202. [3] Mouginis-Mark (1979) JGR Solid Earth 84(B14), 8011-8022. [4] Rasmussen et al., (2025) GSA A&Ps 57(6), p. 4976. [5] Altieri et al. (2026), this conference.

The European Space Agency (ESA) Rosalind Franklin rover Mission (RFM) is expected to land at Oxia Planum, Mars in 2030. Orbital spectral data and imagery reveal layered, clay-rich sedimentary deposits, often overlain by or interbedded with a dark, more resistant rock rich in mafic minerals [e.g., 1, 2]. The 1:30k scale geologic map of the landing site [1] associates two geologic units to their VNIR color and fracture spacing; Apuzzo et al. [3] studied directional statistics of fractures in selected regions of interest. However, complete quantitative fracture metrics over the RFM landing area are not yet available. Since at least 35% of the landing site is covered by fractures [3], a comprehensive study of fractures, and the composition of their hosting bedrock, is critical for elucidating whether formation mechanism, alteration history, and/or mineralogy vary across the Oxia Planum site.Here, we present fracture density (number of fractures/m^2) and topological connectivity of fractures within an unbiased collection of 33 approximately 500x500 m square windows spaced along transects over the center of the predicted landing footprint of the RFM. Multiple windows overlap with Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) spectral cubes for which Fe,Mg-clay abundance has been qualitatively estimated [2]. Fractures are mapped manually as linear segments in QGIS software, using visual interpretation of High Resolution Imaging Science Experiment (HiRISE) images (0.3 m/px) in the red spectral range. We map at 1:1250 scale resulting in a minimum resolvable fracture length of about five pixels, or 1.5 m. The NetworkGT QGIS software plugin [4] is used to extract node connectivity, fracture orientations, and fracture lengths.Topological analysis of node types and fracture-bounded polygon shapes is then leveraged to aid in interpreting (1) changes in fracture behavior across previously mapped unit boundaries, and (2) formation mechanisms of the fracture networks, following [5]. We also compare fracture mapping within and outside specific clay-rich areas of interest [2, 6] to determine if they have unique mechanical or formation characteristics. Preliminary analysisindicates that fracture density is often higher within more clay-rich areas, and that the majority of mapped fractures are “I-node”, meaning they terminate without connecting to another fracture. Where fractures do connect, three- and four-sided polygon shapes dominate. We compare these findings with previous topological network characterization [e.g., 5] to enhance our interpretation of the possible scenarios of formation and current unit composition at Oxia Planum, considering topological characteristics will better constrain our understanding of past aqueous activity. Our results will support the better selection of analog materials for terrestrial drill testing before mission launch, and help inform drill site selection when the rover reaches Mars’ surface.References: [1] Fawdon et al. (2024) Journal of Maps 20, 2302361. [2] Brossier et al. (2022) Icarus 386, 115114. [3] Apuzzo et al. (2025) PSS 267, 106169. [4] Nyberg et al. (2018) Geosphere 14(4) 10.1130/GES01595.1. [5] Silver et al. (2025) PNAS 22 (10) e2411738122. [6] Altieri et al. (2026), this conference.Acknowledgements: This work is funded by the Italian Space Agency (ASI) [Grant ASI-INAF n. 2023–3–HH.0].

Oxia Planum, the landing site of the Rosalind Franklin Mission (RFM), is located between the ancient highlands of Arabia Terra and the younger plains of Chryse Planitia [1]. The region preserves clear evidence of past water-rock interactions, particularly layered clay-rich deposits that are considered prime targets for astrobiological investigation [2, 3]. This study focuses on a selection of Regions of Interest (ROIs), areas with the highest concentrations of ferromagnesian clays as identified through remote sensing analyses. We derive local digital terrain models from stereo photogrammetry and quantify horizontal and vertical accuracy [4], a key requirement for interpreting water-related processes and stratigraphic relationships in the low-relief Oxia Planum. Our objective is to examine how clay distribution relates to other geologic elements, in particular fractures [5, 6], to better constrain their geologic interpretation and stratigraphic context [7], contributing to strategies for guiding the selection of drilling sites once the rover arrives on Mars. This work is funded by the Italian Space Agency (ASI) [Grant ASI-INAF n. 2023–3–HH.0]. References: [1] Quantin-Nataf et al. (2021) Astrobiology 21, 345–366. [2] Mandon et al. (2021) Astrobiology 21, 464–480. [3] Brossier et al. (2022) Icarus 386, 115114. [4] Trisic Ponce et al. (2026), this conference. [5] Apuzzo et al. (2025) PSS 267, 106169. [6] Rasmussen et al. (2026), this conference. [7] Fawdon et al. (2024) Journal of Maps 20, 2302361.

Carbonates on Mars provide key insights into the planet’s past environmental conditions, as their formation typically results from interaction between CO2-bearing alkaline waters and ultramafic rocks commonly associated with a dense, CO2-rich atmosphere. While ferromagnesian (Fe,Mg-rich) clays are particularly widespread across the Martian surface [1,2], carbonates remain comparatively rare in orbital observations. This scarcity suggests that carbonates may be buried, altered, or spectrally obscured within clay-bearing rocks [3]. Here, we examine the presence of possible carbonates, along with clays, by analyzing approximately 517 near-infrared (1–4 µm) spectral cubes acquired by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). Our results reveal new carbonate-rich deposits and confirm earlier detections. A detailed investigation of the absorption bands near 2.3, 2.5 µm and around 3.4–3.5 µm indicates that carbonates on Mars are best represented as Fe–Mg solid solutions spanning the siderite–magnesite series, rather than pure endmembers [4]. Such compositions are geochemically plausible on Mars; they likely formed under reducing conditions and may have persisted despite later exposure to the more acidic, oxidizing surface environment [5]. Spectral mixing models better clarify the influence of clays on carbonate signatures and provide important constraints for further laboratory analog studies [6,7]. The recurring spatial asso-ciation of carbonates and clays across multiple outcrops implies either coprecipitation or closely related formation pathways within neutral to alkaline aqueous environments during the Noachian (3.7–4.0 Gyr ago), offering strong evidence for sustained liquid water and conditions potentially favorable to microbial life. Our results expand the known distribution of carbonates on Mars, emphasize their astrobiological relevance, and provide strategic guidance for future rover operations and sample-return site selection targeting preserved biomarkers (organic compounds). Overall, this work advances our understanding of early Martian habitability and the role of carbonates in recording ancient CO2-water interactions.This study closely aligns with the objectives of ESA’s “Rosalind Franklin” mission [8], whose rover will explore Oxia Planum and investigate clay-bearing terrains and possible carbonates in the search for well-preserved biosignatures throughout subsurface rocks and soils [9-11]. This work is thereby financially supported by the Italian Space Agency (ASI) [Grant ASI-INAF n. 2023–3–HH.0].References: [1] Carter et al. (2013) JGR Planets 118, 831–858. [2] Brossier et al. (2026) JGR Planets 131, e2025JE009393. [3] Ehlmann et al. (2008) Science 322, 1828–1832. [4] Beck et al. (2024) Earth and Space Science 11, e2024EA003666. [5] Niles et al. (2013) Space and Science Reviews 174, 301–328. [6] Bishop et al. (2013) JGR Planets 118, 635–650. [7] Bishop et al. (2021) Earth and Space Science 8, e2021EA001844. [8] Vago et al. (2017) Astrobiology 17, 471–510. [9] Quantin-Nataf et al. (2021) Astrobiology 21, 345–366. [10] Mandon et al. (2021) Astrobiology 21, 464–480. [11] Brossier et al. (2022) Icarus 386, 115114.

Extensive research over the past two decades has shown that early Mars likely had a warmer, wetter climate with widespread water activity. Ferromagnesian (Fe,Mg‐rich) clay deposits are compelling markers of these ancient environments, helping reconstruct Mars' hydrologic evolution, assess past habitability, and guide future exploration. This study analyzes hyperspectral data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) aboard NASA's Mars Reconnaissance Orbiter , focusing on regions along the Martian crustal dichotomy—where clay deposits occur at the boundary between the ancient southern highlands and the younger northern lowlands. We systematically surveyed ∼1500 CRISM targeted observations (1–2.6 μm) to identify ferromagnesian clays, distinguish them from other hydrated minerals, and characterize compositional differences between Fe‐ and Mg‐rich species using diagnostic absorptions around 1.4, 2.3, and 2.4 μm. Results reveal spatial variations in clay mineralogy: Fe‐rich nontronites are prevalent around Mawrth Vallis, while Mg‐rich saponites are more locally distributed in Nili Fossae and Libya Montes. Oxia Planum—the Rosalind Franklin rover landing site—exhibits more compositionally intermediate clays such as vermiculites and ferrosaponites. These differences may reflect variations in the iron and magnesium abundance or in the iron oxidation state. Moreover, a recurring absorption near 2.5 μm suggests co‐occurring carbonates like magnesite and siderite, increasing the potential for biosignature preservation. These findings refine our understanding of Mars' aqueous history and offer an important mineralogical context for future rover and sample return missions. They also emphasize the need for a next‐generation orbital imaging spectrometer to succeed CRISM and extend its legacy.

Several missions to Venus have recently been selected for launch, opening a new era for the exploration of the planet. A key question these missions seek to address is whether Venus is geologically active today. Detecting active volcanism on Venus would contribute to a better understanding of volcanic and atmospheric processes on Earth. The Analogs for VENus' GEologically Recent Surfaces (AVENGERS) initiative provides a comparative framework for the identification and analysis of terrestrial analog sites relevant to recent and possibly ongoing volcanic activity on Venus. Although this review focuses on terrestrial analogs for Venus exploration, the AVENGERS initiative also includes investigations that use Venus and Earth as analogs to better understand the evolution of terrestrial exoplanets. In addition, the AVENGERS initiative facilitates international collaboration by connecting Venus mission teams with the broader planetary and exoplanetary science communities. This review describes the scientific context of AVENGERS, details the selection criteria for terrestrial analog sites, and summarizes a set of suitable locations. Methodological approaches in analog studies that support the interpretation of Venus observations are also discussed.