^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.

¹R. Christoffersen,²M. J. Loeffler,^1,3S. Kanee,⁴C. J. Cline II,⁴L. P. Keller,¹T. M. Erickson,^5,6J. Fontanese,⁷T. Munsat,^5,6M. Horányi
Journal of Geophysical Research: Planets Open Access Link to Article [https://doi.org/10.1029/2025JE009257]
¹Amentum, NASA Johnson Space Center, Houston, TX, USA,
²Department of Astronomy and Planetary Science, NorthernArizona University, Flagstaff, AZ, USA,
³Now at Department of Earth & Environment, Boston University, Boston, MA,USA,
⁴NASA Johnson Space Center, Houston, TX, USA,
⁵Laboratory for Atmospheric and Space Physics, University ofColorado, Boulder, CO, USA,
⁶NASA SSERVI’s Institute for Modeling Plasma, Atmospheres and Cosmic Dust(IMPACT), University of Colorado, Boulder, CO, USA,
⁷Department of Physics, University of Colorado, Boulder,CO, USA
Published by arrangement with John Wiley & Sons

The flux of solar system meteoroids is dominated by objects less than 1 mm in diameter whose impact effects play a major role in the space weathering of airless body surfaces. These effects remain poorly characterized with respect to their dependence on the range of impact speeds for meteoroids across the inner solar system. We investigated this dependence specifically for the mineral olivine using an electrostatic dust accelerator to bombard olivine single crystals with a stream of Fe metal dust particles traveling at measured speeds between 0.3 and 20 km s⁻¹. The impacting particles produced microcraters 0.2–5.2 μm in diameter whose content of impact melt, and brittle/ductile shock-induced deformation features, were characterized by scanning and transmission electron microscopy. While particles traveling <1 km s⁻¹ were not able to form microcraters, analysis of the size versus speed relations for the faster particles allowed their impact speeds and maximum shock pressures to be statistically constrained. Microcraters 0.2–0.5 μm in diameter contain olivine-composition shock melt estimated to have formed at impact speeds as high as 15–20 km s⁻¹, and shock pressures more than 250 GPa. Transmission electron microscope studies of shock melt in larger, ∼1.5 μm diameter, microcraters found it was free of impact-generated nanophase metallic Fe (npFe⁰). The impact speeds for these craters of 3.0–5.0 km s⁻¹ suggest that in asteroid regoliths dominated by olivine, still higher impact speeds may be necessary to allow npFe⁰ to be produced.

¹F. Alberquilla et al. (>10)
Journal of Geophysical Research: Planets 131, e2025JE009515 Open Access Link to Article [https://doi.org/10.1029/2025JE009515]
¹IBeA Research Group (Ikerkuntza eta Berrikuntza Analitikoa ‐ Analytical Research and Innovation), Department ofAnalytical Chemistry, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), Leioa, Spain
Published by arrangement with John Wiley & Sons

The study of terrestrial lava tubes is essential for understanding geological processes occurring during volcanic activity on other planetary bodies, such as Mars. These processes lead to the formation of minerals analogous to those found on other planets. Volcanic eruptions are often associated with hydrothermal activity and gas emissions (e.g., CO2, SO2, H2S, HCl, H2O, H2) through fumaroles, which can simulate Martian atmospheric conditions. These gases and fluids interact with the host rock, leading to mineral alteration and the formation of secondary minerals. This study analyzes the Cueva del Vidrio lava tube on La Palma (Canary Islands, Spain), formed during the 1949 San Juan eruption. Although its materials exhibit low alteration due to their relatively recent origin, the 2021 Tajogaite eruption introduced new gas emissions, groundwater interactions, and surface runoff, thereby promoting the formation of alteration crusts and coatings. The methodology combined minimally invasive techniques, such as X-ray diffraction, and non-destructive techniques, including X-ray fluorescence (μEDXRF) and Raman spectroscopy. In order to facilitate the interpretation of the results, runoff waters were analyzed by ion chromatography. The results highlight the presence of carbonates, sulfates, and iron oxides, notably hematite, which likely formed from silicate weathering, particularly olivine alteration, leading to iron depletion and magnesium enrichment. Additionally, amorphous silica was identified, likely formed through reactions involving sulfate and carbonate precipitation, which leached silicon from silicate-rich host rocks. Similar processes have been described on Mars, where opal is considered a key mineral for astrobiological investigations due to its potential for preserving biosignatures.

¹Mehmet Yesiltas,²Andrew Dopilka,²Robert Kostecki,¹Timothy D. Glotch,¹Paul Northrup
Proceedings of the National Academy of Sciences of the USA (PNAS) 123, e2601891123 Link to Article [https://doi.org/10.1073/pnas.2601891123]
¹Department of Geosciences, Stony Brook University, Stony Brook, NY 11794
²Energy Technologies and Systems Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720

Asteroid Bennu preserves primitive material from the early solar system, and returned samples allow direct examination of how organics and minerals were assembled and altered. We applied nanoscale infrared spectroscopy together with Raman spectroscopy to the Bennu sample OREX-800066-3 to characterize chemical variability at ~20 nm scales. Analysis of nano-Fourier-transform infrared spectroscopy spectra identifies three recurring compositional domains; aliphatic-rich, carbonate-rich, and nitrogen-bearing organic-rich regions. Statistical evaluation shows that these domains are compositionally and spatially distinct at the nanoscale, with strong negative correlations between aliphatic signatures and both carbonates and N-bearing organics, and negligible correlation between carbonates and N-bearing organics. Organosulfur compounds are spatially restricted to carbonate-rich regions, indicating organic-sulfate interactions during late-stage brine evolution. Raman spectra indicate highly disordered, thermally minimally metamorphosed carbonaceous matter, consistent with preservation of labile functional groups. These results demonstrate that Bennu’s angular lithology (characterized by planar facets and sharp edges) is not chemically uniform and records heterogeneous aqueous alteration rather than pervasive uniform processing. N-bearing organic functional groups are widely preserved despite extensive alteration, and carbonate-rich areas show intimate nanoscale mixing of different carbonate species. The coexistence of distinct organic- and carbonate-rich domains suggests contributions from both primordial compositional diversity and subsequent rock–fluid interaction. Comparison with Ryugu samples highlights shared features but key differences in organic-carbonate associations and carbonate distributions. Overall, Bennu’s nanoscale heterogeneity provides constraints on organic preservation, carbonate formation, organic-sulfate chemistry, and parent-body evolution in volatile-rich early solar system materials.

¹Thomas M. McCollom,²Sally L. Potter-McIntyre,¹Andres Reyes,³Bruce Moskowitz,³Peter Solheid,⁴Victoria E. Hamilton
Jpurnal of Geophysical Research: Planets Link to Article [https://doi.org/10.1029/2025JE009489]
¹Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO, USA
²Southern Illinois University, Carbondale, IL, USA
³Department of Earth and Environmental Sciences and Institute for Rock Magnetism, University of Minnesota, Minneapolis, MN, USA
⁴Southwest Research Institute, Boulder, CO, USA
Published by arrangement with John Wiley & Sons

A key early discovery of the Mars Exploration Rover Opportunity on Meridiani Planum was the hematite spherules that are a ubiquitous component of the Burns formation sandstones at the rover’s landing site (colloquially known as “blueberries”). The Meridiani spherules possess a suite of characteristics that are collectively very rare in terrestrial settings, including their gray color, a thermal spectral signature that indicates preferential exposure of the c crystal axis, a spherical shape that is evidently attributable to radially oriented crystallite growth, and high chemical and mineralogical purity. The origin of the Meridiani “blueberries” has remained a matter of considerable debate, but one leading hypothesis is that they formed through the decomposition of iron-rich sulfate minerals from the alunite group, specifically jarosite. To date, however, there has been no described terrestrial analog where the formation of hematite spherules is shown to be directly linked to jarosite decomposition. Here, we report the discovery of hematite spherules in Aztec Sandstone that possess many of the same characteristics as the martian “blueberries,” albeit with substantially smaller size. The spherules occur primarily in narrow gray bands within mineralized fractures where the pore spaces are predominantly occupied by jarosite-alunite solid solutions (JASS). The spherules formed through partial decomposition and release of Fe³⁺ from adjacent JASS, supporting the possibility that analogous processes may have been responsible for the formation of hematite spherules during diagenesis of the sulfate-rich Burns sandstones on Mars. Continued study of the Aztec Sandstone spherules may provide new constraints on near-surface environmental conditions on early Mars.

^1,2Marina E. Gemma,³Katherine A. Shirley,¹Timothy D. Glotch,^2,4,5Denton S. Ebel,^2,5,6Kieren T. Howard
Journal of Geopyhsical Research: Planets (in Press) Link to Article [https://doi.org/10.1029/2025JE008963]
¹Department of Geosciences, Stony Brook University, Stony Brook, NY, USA
²Department of Earth and PlanetarySciences, American Museum of Natural History, New York, NY, USA,
³Atmospheric, Oceanic, and Planetary Physics,University of Oxford, Oxford, UK
⁴Lamont‐Doherty Earth Observatory, Columbia University, Palisades, NY, USA
⁵Department of Earth and Environmental Sciences, Graduate Center of the City University of New York, New York, NY,USA
⁶Department of Physical Sciences, Kingsborough College, City University of New York, Brooklyn, NY, USA
Published by arrangement with John Wiley & Sons

aboratory spectral analysis of well-characterized meteorite samples can be employed to more quantitatively analyze asteroid remote sensing data in conjunction with returned extraterrestrial samples. In this work, we examine the combined effects of physical (temperature, particle size) and chemical (petrologic type, metal fraction) variables on visible and near-infrared (VNIR) spectra of ordinary chondrite meteorite powders. Six equilibrated ordinary chondrite meteorite falls were prepared at a variety of particle sizes to capture the spectral diversity associated with asteroid regoliths dominated by various grain sizes. Mineral compositions and abundance were determined from electron microprobe analysis of meteorite thick sections to precisely characterize changes in spectral features due to variations in mineralogy. VNIR spectra of the ordinary chondrites were measured under simulated asteroid surface conditions at a series of temperatures chosen to mimic near-Earth asteroid surfaces. The resulting spectra show minimal variation in both major absorption bands across the simulated near-Earth asteroid temperature regime. Changes in particle size result in variations in band centers and band area ratios for material of the same composition, two key parameters typically used to derive asteroid composition. Unlike previous spectral investigations of ordinary chondrites, we retained the metal fraction in our powders instead of analyzing only the silicate fraction. Metal has a subtle but non-negligible effect on the VNIR spectra of ordinary chondrites. The more petrologically pristine samples from each ordinary chondrite group display relatively weaker absorption bands than their more thermally altered counterparts. The band centers shift to longer wavelengths as grain size and petrologic type increase.

¹S. P. Aithala,¹R. A. Lange,¹M. M. Hirschmann
Journal of Geophysical Research: Planets (in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009148]
¹Department of Earth and Environmental Sciences, University of Minnesota, Minneapolis, MN, USA, 2Department ofEarth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA
Published by arrangement with John Wiley & Sons

To elucidate the relationship between oxygen fugacities (f_O2) recorded in martian basalts and redox processes in the martian interior, superliquidus 100-kPa furnace experiments on a composition similar to Humphrey (Adirondack basalt) were conducted at variable f_O2 and temperature. Quenched glasses were analyzed by EPMA, Mössbauer spectroscopy, colorimetric wet chemistry, and microbeam X-ray absorption near edge structure (XANES) spectroscopy. The experiments reveal Mössbauer and wet chemical determinations of silicate glass Fe³⁺/Fe^T agreeing within uncertainty, supporting the accuracy of extended-Voigt-based fitting of Mössbauer spectra when recoil-free fraction is considered. Fe³⁺/Fe^T ratios determined from Mössbauer spectroscopy from Humphrey and previously studied martian-relevant glass compositions are combined to calibrate models that characterize the relationship between Fe³⁺/Fe^T, f_O2, temperature, and composition in martian silicate liquids. The models demonstrate, similar to previously investigated silicate liquids, that the correlation between $$ and log f_O2 in martian magmas has a slope less than the value (0.25) expected if ferric and ferrous iron oxide mixed ideally. Martian magma Fe³⁺/Fe^T ratios are more temperature-sensitive compared to non-martian compositions, suggesting that temperature variations may contribute to comparatively large f_O2 variations in martian basalt. The models are applied to demonstrate that the Fe³⁺/Fe^T increases required to explain multiple-log unit changes in f_O2 in shergottite magma would not increase terrestrial magma f_O2 as effectively. To aid in future investigations of martian magma redox, a XANES technique that allows for non-destructive, microanalytical characterization of Fe³⁺/Fe^T in natural martian materials and martian-relevant experiments is introduced.

¹Megan Broussardet al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [doi: 10.1111/maps.701381]
¹Department of Earth, Environmental, and Planetary Sciences and the McDonnell Center for the Space Sciences,Washington University in St. Louis, St. Louis, Missouri, USA
Published by arrangement with John Wiley & Sons

CI chondrites are a compositionally primitive group of meteorites that haveundergone extensive aqueous alteration, providing insights into the evolution of primitiveplanetesimals. Oued Chebeika 002 is the most pristine CI chondrite to date. In this work,we report its mineralogy, bulk chemistry, oxygen and potassium isotope ratios, andcosmogenic radionuclides 10 Be, 26 Al, and 36 Cl. The 10 Be cosmic ray exposure ages of OuedChebeika 002 samples are 2.6 0.5 and 2.9 0.7 Myr. The d41 K of two samples is0.114 0.019 and 0.247 0.044 &. We find that the mineralogy, oxygen isotopes,potassium isotopes, and bulk chemistry of Oued Chebeika 002 overlap with those ofsamples returned from the asteroids Ryugu and Bennu. We therefore propose that CI chondrites and the asteroids Bennu and Ryugu may have originated from a common parentbody, for which we propose the name “Naunet,” after an Egyptian goddess of primordialwater. Naunet formed in the outer solar system and underwent aqueous alteration. In themain belt, Naunet broke up, producing rubble-pile asteroids, including Bennu, Ryugu, andthe secondary CI chondrite parent body/bodies, fragments of which survived passage to theEarth’s surface, becoming CI chondrites.