^1,2Xiaolong Guo,^1,2Peixin Du,³Hongmei Liu,⁴Jiacheng Liu,⁵Shangying Li,^1,2Xinyi Xiang,⁶Shun Wang,⁷Peng Yuan
Journal of Geophysical Research: Planets (in Press) Link to Article [https://doi.org/10.1029/2025JE009644]
¹State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau, China
²CNSA Macau Center for Space Exploration and Science, Macau, China
³Guangdong Provincial Key Laboratory ofMineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China
⁴Department of Earth Sciences and Laboratory for Space Research, The University of Hong Kong, Hong Kong, China
⁵School of Land Engineering, Chang’an University, Xi’an, China
⁶Qinghai Provincial Key Laboratory of Geology andEnvironment of Salt Lakes, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining, China
⁷School ofEnvironmental Science and Engineering, Guangdong University of Technology, Guangzhou, China
Published by arrangement with John Wiley & Sons

Poorly ordered Al/Si phases are widely distributed across the surface of Mars, among which allophane and amorphous silica are the two main constituents. Both allophane and amorphous silica can form in Al-Si systems through surface chemical weathering or subsurface hydrothermal alteration of volcanic materials. Nevertheless, our comprehension of the products derived from Al-Si hydrolysis systems remains poorly constrained. Hydrolysis experiments were conducted on Al-Si systems across an unprecedentedly wide range of Si/(Al + Si) molar ratios (n, 0 ≤ n ≤ 0.9), followed by characterizing the products using multiple techniques. At n ≤ 0.1, the products consist predominantly of Al30 (an Al polycation with a Keggin structure) and poorly ordered Al hydroxides. The introduction of Si resulted in formation of a small amount of proto-allophane. At n = 0.2 and 0.3, poorly ordered materials were still dominant, along with the presence of well-crystallized bayerite and gibbsite. The proto-allophane increased in quantity and began to assemble into allophane. At n = 0.5, well-crystallized minerals were absent and allophane dominated the product. At n = 0.7, the amount of allophane decreased significantly and at n = 0.8 and 0.9, allophane was probably absent, although proto-allophane still formed. Meanwhile, an increasing amount of amorphous silica was formed. X-ray diffraction, Fourier transform infrared, and VNIR provide information for differentiating Al-rich phases and Si-rich phases but show limited capability in identifying poorly ordered Al/Si-rich phases. NMR is powerful for identifying poorly ordered Al/Si phases, although widespread iron on the martian surface and the large instrument pose challenges to its application on Mars.

^1,2,3Fengke Cao et al. (>10)
Journal of Geophysical Research: Planets (in Press) Link to Article [https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JE009228]
¹Research Center for Planetary Science, College of Earth and Planetary Sciences, Chengdu University of Technology,Chengdu, China
²Department of Earth Sciences, Western University, London, ON, Canada
³Institute for Earth & SpaceExploration, Western University, London, ON, Canada
Published by arrangement with John Wiley & Sons

Northwest Africa (NWA) 7034 and its paired meteorites represent polymict regolith breccias derived from the ancient Martian crust. We employed micro-X-ray diffraction and Raman spectroscopy to quantitatively assess impact-induced metamorphism in plagioclase and alkali feldspar. Strain-related mosaicity (SRM) was measured via full width at half maximum in the Debye ring or chi (χ) dimension (FWHMχ) from 2D XRD images. A total of 149 plagioclase and 21 alkali feldspar grains were analyzed. Plagioclase exhibits FWHMχ values from 0.5° to 10.9°, and alkali feldspar shows a range of 2.1°–9.7°. Plagioclase grains record peak shock pressures from 0 GPa (unshocked) to 28–30 GPa based on calibrations for experimentally shocked andesine. Approximately 26% of grains show no detectable shock deformation (<1.0 GPa), while ∼4% preserve evidence of severe shock (>21.0 GPa), indicative of exposure to at least moderate shock metamorphism prior to ejection from Mars. Alkali feldspar records higher apparent peak pressures, possibly spanning 4.7–28.5 GPa. Martian crustal minerals experienced highly heterogeneous shock effects, which highlights the complex and varied impact histories of feldspar minerals during the impact-induced brecciation process. Pressure differences between plagioclase and alkali feldspar may reflect distinct source regions, pre-lithification shock events, or differing shock responses. This study highlights the importance of multi-mineral analytical approaches to enhance the accuracy of shock pressure quantification in Martian regolith breccias and to reconstruct the planet’s impact processes. This methodology should also be applied to other extraterrestrial samples to characterize shock effects across planetary bodies in the solar system.

¹Pengyu Ren,¹Changqing Liu,¹Yuzhen Wang,¹Enming Ju,¹Xin Wang,¹Ruize Zhang,¹Yanqing Xin,¹Ying-Bo Lu,¹Zongcheng Ling
Journal of Geophysical Research: Planets (in Press) Link to Article [https://doi.org/10.1029/2025JE009532]
¹Shandong Key Laboratory of Space Environment and Exploration Technology, School of Space Science and Technology,Institute of Space Sciences, Shandong University, Weihai, China
Published by arrangement with John Wiley & Sons

The Mars Mineralogical Spectrometer (MMS) onboard the Tianwen-1 orbiter can obtain high-resolution visible and infrared reflectance spectra of the Martian surface, that supports detailed analysis of mineral types and their spatial distribution across Mars. However, raw MMS data cannot be directly applied to scientific analysis. To address this limitation, this paper develops a processing pipeline for MMS data, including radiance to I/F conversion, photometric correction, inhomogeneity correction, and geometric correction. Three global maps of ferric oxides were obtained using the processed MMS data. Results reveal that the ferric oxides are nearly ubiquitous across the Martian surface, and they primarily exist in the form of nanophase ferric oxides in the bright regions of Mars (e.g., Amazonis Planitia, Tharsis Montes, and Arabia Terra). Subsequently, the distribution of gray crystalline hematite is identified in Meridiani Planum and Aram Chaos using data from MMS. Additionally, a new deposit of red crystalline hematite is detected in the southeastern part of Aram Chaos. These findings provide crucial evidence for the existence of past aqueous environments in these regions, including Fe-rich aqueous fluids under ambient conditions, hydrothermal fluids, and in-place oxidative weathering of Fe-bearing rocks under the influence of surface water. Notably, the processing pipeline and methods established in this study are critical for advancing our understanding of the ferric oxide distribution across the Martian surface using MMS data.

^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.