^1,2S. R. Sutton,¹A. Lanzirotti,¹M. Newville,^3,4M. D. Dyar,⁵M. McCanta, ANGSA Team
Journal of Geophysical Research: Planets (in Press) Link to Article [https://doi.org/10.1029/2025JE009416]
¹Center for Advanced Radiation Sources, The University of Chicago, Chicago, IL, USA
²Department of the GeophysicalSciences, The University of Chicago, Chicago, IL, USA
³Planetary Science Institute, Tucson, AZ, USA
⁴Department ofAstronomy, Mount Holyoke College, South Hadley, MA, USA
⁵Department of Earth and Planetary Sciences, University ofTennessee, Knoxville, TN, USA
Published by arrangement with John Wiley & Sons

Chromium and vanadium valence measurements were obtained on 17 lunar glass beads from Apollo 15 and 17 regolith materials using microscale X-ray absorption spectroscopy methods. Interior Cr valences ranged from 1.97 ± 0.02 to 2.88 ± 0.02 (Cr2+ to Cr3+). Interior V valences ranged from 2.82 ± 0.02 to 3.76 ± 0.10 (V2+/V3+ mix to V3+/V4+ mix). The interior valences of most beads cluster near V3+ and Cr2+/Cr3+ ≅ 0.6, that is, close to valences expected at IW-1, but there is significant variability and several outliers exist. For main cluster beads, Cr valence-inferred fO2 ranged from IW-1.5 to IW+1. These beads have V valence-inferred fO2 ranges from IW-2 to IW. These ranges significantly overlap but V tends to be slightly more reduced than Cr, suggesting there could be some decoupling of the Cr and V barometers. Valences for the Apollo 15 glass beads are tightly clustered, as are the Apollo 17 bottom drive tube samples 73001. In contrast, the Apollo 17 upper-drive tube samples 73002 are variable. Cr in the bead rims tended to be oxidized relative to the interiors, whereas V tended to show no redox difference between the rims and interiors. Processes responsible for establishing the redox states of the rims must be complex. Apparent fO2 conditions inferred from Cr valence tended to be slightly more oxidized than those inferred from V. Parental magmas may have possessed variable compositions that in turn experienced varying degrees of assimilation of Cr3+-rich phase(s). Valence-altering secondary processes may also have been significant.

¹Sayantan Guha,¹Shiba Shankar Acharya,²Mruganka Kumar Panigrahi
Journal of Geophysical Research: Planets (in Press) Link to Article [https://doi.org/10.1029/2025JE009601]
¹Department of Geology, Presidency University, Kolkata, India
²Department of Geology and Geophysics, Indian Instituteof Technology, Kharagpur, India
Published by arrangement with John Wiley & Sons

The western Kutch basin, India, provides a unique window into aqueous alteration under extreme acid-sulfate conditions. While previous research focused primarily on the Matanomadh Formation, this study presents a systematic investigation of hydroxy-sulfate minerals-including jarosite, alunite, minamiite, gypsum-across several chronostratigraphic units, spanning the pre-Deccan Ghuneri Member (Late Cretaceous) through post-Deccan formations (Matanomadh, Naredi, Harudi). Using a comprehensive analytical suite (XRD, XRF, FTIR, Raman, SEM-EDS, δ34S) and laboratory-synthesized potassium jarosite dissolution experiments, this work provides a complete solution to the source, formation, and preservation of these minerals. Isotopic data identify the primary source of iron and sulfur as the oxidation of precursor pyrite by meteoric water. A significant finding is the documentation of a natural natrojarosite–natroalunite solid solution, where Al-substitution enhances structural stability, making Na-jarosite more abundant than K-jarosite. Notably, field associations and geochemical data indicate that host-rock composition exerts only a minor influence on the formation of these jarosites. Crucially, our data reveal that the formation of these hydroxy-sulfate phases cannot be attributed to a single geological event or a specific past timeframe. Instead, we demonstrate that these minerals are geologically recent and continue to form as an ongoing process under current environmental conditions. The long-term preservation of these assemblages is primarily governed by the region’s prevailing aridity and localized mineral buffering associated with their mode of occurrence along the fractures of host rock. The discovery of the natrojarosite–natroalunite solid solution provides key insights into acid-sulfate system evolution on both Earth and Mars.

¹Yaozhu Li,¹Phil J. A. McCausland,¹Roberta L. Flemming,¹Callum J. Hetherington,¹Bo. Zhao
Journal of Geophysical Research: Planets Open Access Link to Article [https://doi.org/10.1029/2026JE009662]
¹Department of Earth Sciences, Western University, London, ON, Canada, 2Department of Geosciences, Texas TechUniversity, Lubbock, TX, US
Published by arrangement with John Wiley & Sons

Ureilites are ultramafic achondrites for which the parent body is unknown. Monomict ureilites, consisting primarily of olivine and pyroxene, are thought to represent mantle residues, carrying essential information for their parent body deformation history. All monomict ureilites are found to be shocked variously, complicating the interpretation of their deformation history. In this work, four monomict ureilites, Elephant Moraine 96042, Northwest Africa 2221, Larkman Nunatak 04315, and Alan Hills A81101, are examined using electron backscatter diffraction to study shock-related and post-shock microstructural development in the strained olivine. We calculated the unit segment length (USL) to quantify the subdomain development in those olivine grains, and we further applied a modified misorientation index to study the role of shock in subdomain misorientation. A positive trend of increasing USL with increasing shock level is identified, indicating increased microstructural subdivision and decreasing subdomain size with increasing shock deformation. In LAR 04315 and ALH A81101, the development of low-angle subdomain boundaries defines an apparent foliation, consistent with a non-instantaneous, high-temperature deformation overprint following shock. Together, these results demonstrate that EBSD-derived microstructural metrics provide a robust, quantitative framework for distinguishing shock-related deformation from post-shock microstructural modification in ureilitic olivine.

^1,2Kewei Shen, ¹Panming Xue, ¹Duojun Wang, ¹Rui Zhang, ²Guangchao Chen, ¹Kexuan Zhang, ¹Liang Wei
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2026.117132]
¹High Pressure Experiment Science Center, College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China
²College of Materials Science and Optoelectronic Technology, University of Chinese Academy of Sciences, Beijing, China
Copyright Elsevier

The Moon shows marked differences in geophysical and geological properties between its nearside and farside, long attributed to internal thermal state. However, the present-day lunar thermal gradient remains poorly constrained. In this study, we measured the thermal conductivity and diffusivity of lunar mantle olivine under 0.5–4.0 GPa and 298–1273 K, demonstrating that lattice conduction was the dominant heat transport mechanism. Combining with regional variation parameters including crustal thickness, radiogenic heat production, and modeled surface heat flow, we constructed thermal profiles for distinct lunar regions. Our results revealed a significant nearside-farside thermal asymmetry, with temperature differences reaching ~79–180 K at depth. Elevated nearside mantle temperatures suggested that partial melting may still persist at depths greater than ~700 km. This localized partial melting likely contributes to the observed low seismic velocity and high electrical conductivity anomalies, as well as the occurrence of deep moonquakes beneath the nearside.

¹Evgeniya V. Petrova,¹Victor I. Grokhovsky,²Anna Kartashova
Icarus (inPress) Link to Article [https://doi.org/10.1016/j.icarus.2026.117147]
¹Ural Federal University, Mira Str., 19/5, 620002 Ekaterinburg, Russia
²Institute of Astronomy RAS, Pyatnitskaya Str., 48, 119017 Moscow, Russia
Copyright Elsevier

Fragmentation, ablation and significant loss of mass occur when the meteoroid passes through the Earth’s atmosphere. There a combined action of melting and shearing takes place, so a fusion crust is forming on the surface of the fragments. It combined a subsurface layer of heated matter and an outer layer consisting of remaining melted meteoroid substance.
In this publication we focused on the process of ablation from different points of view: i – registered spectra of fireballs; ii – fusion crust composition study; iii – ablation modeling ground experiments.

¹Koske Matsubara,¹Yukari Yamaguchi,¹Akiko M. Nakamura,²Sunao Hasegawa,³Takafumi Niihara,^4,5Takehiko Wada
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2026.117135]
¹Department of Planetology, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe 657-8501, Japan
²Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210, Japan
³Department of Applied Sciences, Okayama University of Science, 1-1 Ridai-cho, Kita-ku, Okayama-City, Okayama 700-0005, Japan
⁴National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
⁵Astronomical Science Program, The Graduate University for Advanced Studies, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
Copyright Elsevier

The presence of water on the Moon and on asteroids that are thought to be poor in water, either because they formed inside the snow line or because they lost much of their water during differentiation, has been suggested by multiple studies; however, its form and origin remain unclear. In this study, we conducted hypervelocity impact experiments between serpentinite projectiles and steel targets. Serpentinite contains hydroxyl and simulates hydrated impactors such as primitive asteroids. The effects of impact velocity and angle on the survival and form of water delivered to the target surface were investigated using near-infrared reflectance spectroscopy and microscopic Raman spectroscopy. Reflectance spectra of projectile materials adhered to the crater surfaces suggested that, in all head-on impact experiments with velocities of 3–7 km s−1, hydroxyl pre-existing in the projectile was almost completely lost. The spectra also showed olivine absorption features at shock pressures exceeding ~80 GPa, and the olivine Raman peaks became narrower at higher impact velocities. Based on the comparisons with results from impact experiments with anhydrous projectiles, it is suggested that molecular water can be trapped in the melt at shock pressures below ~100 GPa. In contrast, in the oblique impact experiments conducted in this study, decomposition of projectile material was suppressed, and hydroxyl was detected in crater samples. The current results, along with comparisons to impact velocities of asteroids in the main belt and on the Moon, suggest that molecular water derived from hydrated impactors can be detectable through spectroscopic observations.