^1,2Robert Platt,^1,2Rossella Arcucci,^1,3Cédric M. John
Journal of Geophysical Research: Planets (in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009473]
¹Department of Earth Science and Engineering, Imperial College London, London, UK,
²Data Science Institute, ImperialCollege London, London, UK,
³Digital Environment Research Institute (DERI), Queen Mary University of London,London, UK
Published ny arrangement with John Wiley & Sons

Orbital remote sensing observations are a lynchpin of planetary science research. Hyperspectral infrared spectroscopy in particular is key for planetary mineralogical exploration, for example, CRISM for Mars, as this underpins our understanding of the distribution of specific lithologies and the geological process leading to their formation. Yet routine analysis workflows involving summary parameters have significant limitations and are highly time-consuming. This work presents a novel methodology and framework for the analysis and classification of CRISM SWIR reflectance spectroscopy, leveraging Machine Learning (ML). We train a model to classify 37 minerals previously manually identified on the planet. We show this model is highly performant, with test data across Mars and a case study within Jezero crater, where ML results match previous manual analyses and rover observations. We also adapt Expected Cost (EC) to remote sensing data for use in geological context for the first time. We demonstrate that EC can be used to dynamically weight misclassification penalties based on geological context, as a rigorous measure of automated classification methods. We envision this model to make analysis of CRISM data more accessible to the planetary science community, allowing rapid searches for a vast range of minerals across a global/regional scale. As a result, areas of interest for further satellite or rover exploration can be quickly identified, leading to greater understanding of geological processes on Mars.

¹J. M. Meusburger,¹T. F. Bristow,¹D. T. Vaniman,¹E. B. Rampe,¹S. J. Chipera,¹D. F. Blake,¹S. L. Simpson,¹R. Y. Sheppard,¹G. Berlanga
Journal of Geophysical Research: Planets (in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009631]
¹Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
Published by arrangement with John Wiley & Sons

X-ray amorphous sulfate hydrates are a substantial component (up to 23 wt%) of the sedimentary rocks and sands analyzed to date by the Mars Science Laboratory Curiosity rover at Gale crater. Recently, the CheMin X-ray diffractometer observed the amorphization of the crystalline sulfate starkeyite (MgSO4 · 4H2O) upon exposure to the dry and relatively warm atmosphere inside the rover body. To assess the extent to which interactions between minerals and the rover environment contribute to the amorphous component, we investigated the stability of several hydrated minerals under Curiosity-like conditions. Our results show that highly hydrated minerals are more prone to transformation inside the rover than lower hydrates. Minerals that readily become amorphous under rover conditions are also likely to be unstable when exposed to the dry Martian atmosphere during the warm periods at noon. We therefore suggest that much of the observed amorphization occurred at the Martian surface prior to sampling. Future missions such as the Rosalind Franklin rover and Mars Life Explorer propose to drill into the substantially colder subsurface at Martian mid-latitudes and are likely to encounter temperature and humidity-sensitive cryohydrates. To evaluate the original mineral assemblage of rocks on such missions, it will be critical to maintain controlled temperature and relative humidity (RH) conditions inside the rover body. We find that increasing ambient humidity may induce the recrystallization of amorphous salt hydrates, thus controlling RH and temperature inside the rover would significantly enhance the analytical capabilities of a next generation X-ray diffractometer on Mars.

^1,2Aditya Das,¹Dwijesh Ray,³B. Astha,⁴Avirup Bose
Journal of Geophysical Research: Planets (in Press) Link to Article [https://doi.org/10.1029/2025JE009278]
¹Physical Research Laboratory, Ahmedabad, India
²Indian Institute of Technology Gandhinagar, Gandhinagar, India
³Indian Institute of Technology, Mumbai, India
⁴Indian Institute of Technology (Indian School of Mines), Dhanbad, India
Published by arrangement with John Wiley & Sons

The olivine of the Deccan Traps basalts undergoes aqueous alteration to iddingsite along fractures, irrespective of their forsterite (Fo) content. Low Fo olivine typically displays wide and relatively straight fractures, while picritic (high Fo) olivine shows serrated (saw-tooth) fractures, indicative of an in situ dissolution process. Low Fo olivine attributes a relatively higher degree of aqueous alteration as compared to high Fo under low-temperature conditions. The clay minerals associated with low Fo experienced mildly reducing conditions, reflecting multiple aqueous alteration events. High Fo in picritic basalts is characterized by a lower pH and water-to-rock ratio than low Fo in tholeiitic basalts. The higher concentration of Si in the clay mineral saponite suggests an acidic hydrothermal alteration process. Geochemical modeling suggests a closed system operating at low temperatures. Although the total duration of alteration was brief in both scenarios, low Fo underwent alteration over a longer period, resulting in a similar quantity of altered products. These findings may provide insights into the alteration processes of Mars by defining geochemical conditions and hydrodynamic properties. This may also reveal whether Martian meteorites (Nakhlites) mineral cracks changed in a single event or multiple occurrences. While terrestrial analogs differ in essential mineral composition (such as Fe and Mg levels), the alteration products and conditions closely resemble those of Martian meteorites, helping to understand Mars’ water-crust interaction. Additionally, phyllosilicates/clay minerals may induce the preservation of biosignatures on Mars, which remains a top priority of ongoing missions.