¹E. Dobrică, ²J.P. Greenwood, ¹A.N. Krot, ³A.J. Brearley, ⁴E.P. Vicenzi, ⁵S. Itoh, ⁶N. Sakamoto, ⁷H. Yurimoto
Geochimica et Cosmochimica Acta (in Press) Link to Article [DOI: 10.1016/j.gca.2026.08.009]
¹Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, HI, USA
²Department of Earth and Environmental Sciences, Wesleyan University, Middletown, CT, USA
³Department of Earth and Planetary Sciences, University of New Mexico, NM, USA
⁴Smithsonian Institution, Museum Conservation Institute, Suitland, MD, USA
⁵Division of Earth and Planetary Sciences, Kyoto University, Kyoto, Japan
⁶Isotope Imaging Laboratory, Creative Research Institution, Hokkaido University, Sapporo, Japan
⁷Department of Natural History Sciences, Hokkaido University, Sapporo, Japan
Copyright Elsevier

Hydrogen isotopes in apatite are widely used to constrain the origin and evolution of water in Martian magmas and crustal reservoirs. However, the extent to which shock metamorphism modifies hydrogen-isotope compositions in apatites is poorly understood. In this study, we combine scanning electron microscopy (SEM), cathodoluminescence (CL), transmission electron microscopy (TEM) observations, and secondary ion mass spectrometry (SIMS) measurements of hydrogen isotopes and water contents in apatites from the Martian meteorite Los Angeles. Panchromatic CL imaging reveals distinct bright and dark domains within individual apatite grains. These domains correlate with variations in hydrogen-isotope composition, chlorine abundance, and shock metamorphic microstructures (dislocations, planar fractures, and shock-induced melting) observed at the nanoscale. Bright CL regions show higher defect densities, more abundant melt pockets, lower chlorine contents, and elevated δD values relative to dark CL regions. Defect density correlates positively with δD and melt pocket abundance but shows no systematic relationship with bulk H₂O content. These observations demonstrate that hydrogen-isotope modification can occur in heavily deformed apatite without requiring complete melting or recrystallization. Shock-induced defects therefore provide pathways for hydrogen redistribution and isotopic exchange at the micron scale. The results indicate that shock metamorphism can locally modify primary hydrogen isotope signatures in Martian meteorites while preserving bulk water contents within the typical Martian apatite range. Cathodoluminescence imaging provides a rapid and non-destructive method for identifying apatite domains that can correlate with deformation-enhanced and isotopically-modified regions. These findings have important implications for interpreting Martian volatile reservoirs and for future sample-return missions such as Martian Moons eXploration (MMX).

¹Shiori Inada, ^1,2Shogo Tachibana
Geochimica et Cosmochimica Acta (in Press) Open Source Link to Article [DOI: 10.1016/j.gca.2026.07.046]
¹Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan
²UTokyo Organization for Planetary and Space Science, The University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan
Copyright Elsevier

Effects of ambient gas are important for understanding evaporation of planetary materials in the protosolar disk. In this study, we experimentally investigated the evaporation kinetics of forsterite in H₂-H₂O gas mixtures to elucidate the dependences on H₂O abundance at  of 10⁻⁴–10⁻², temperatures of 1400–1600 K, and a total pressure of 1 Pa. We found that the evaporation rate decreases with increasing  with a reaction order of −1.02 ± 0.12 only above certain  (10⁻³–10⁻² depending on temperature). The activation energy increased when the evaporation is suppressed by H₂O (497 ± 11 kJ mol⁻¹, while 359 ± 1 kJ mol⁻¹ without the effect of H₂O). The  dependence of the evaporation rate is consistent with the previously proposed model based on the chemical equilibrium consideration and the Hertz-Knudsen equation. This consistency can be explained in terms of a reaction mechanism. Based on the experimentally determined evaporation kinetics, we evaluated conditions of the protosolar disk where H₂O affects evaporation of forsterite dust. This showed that H₂O suppresses the evaporation at 1300 K at  of the Solar abundance and 1600 K under H₂O-enriched conditions, which possibly affected moderate-temperature thermal processing of silicate dust and evaporation of chondrule melt under oxidizing conditions.

¹Leire Coloma, ¹Fernando Alberquilla, ¹Julene Aramendia, ¹Gorka Arana, ²Ed Cloutis, ¹Juan Manuel Madariaga
Journal of Geophysical Research: Planets (in Press) Open Source Link to Article [DOI: 10.1029/2026JE009954]
¹Faculty of Science and Technology, Department of Analytical Chemistry, University of the Basque Country, Leioa, Spain
²Department of Geography, University of Winnipeg, Winnipeg, MB, Canada
Published by arrangement with John Wiley & Sons

The presence of minor minerals is a key factor distinguishing meteorite types, as they provide valuable insights into the formation processes, surface conditions, and evolutionary history of their parent bodies. In Martian nakhlites, one of the most distinctive minor phases is iron-titanium oxides forming characteristic skeletal textures. However, their mineralogical nature remains debated, with most studies identifying them as titanomagnetite, whereas others suggest ilmenite skeletal textures. This study uses Raman imaging to investigate the mineralogical distribution of these skeletal textures. Additionally, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) was used to assess titanium concentration gradients from the exterior to the core of the structures. Chemometric methods were applied to differentiate and represent the mineralogical distribution. Furthermore, similar skeletal textures observed in terrestrial analogs from the Timanfaya and Maciot volcanoes (Lanzarote, Canary Islands, Spain) were analyzed using Raman imaging to evaluate potential similarities or differences in composition and formation processes with those found in the paired meteorites studied. The results show that the skeletal textures in the MIL nakhlites consist of ilmenite surrounded by titanomagnetite and magnetite. In contrast, in the analogs, two types of skeletal textures were identified: some composed of ilmenite and others of magnetite. These findings indicate that skeletal oxide textures in Martian and terrestrial samples from two field sites formed through distinct processes and constitute sensitive recorders of the evolution of mafic magmatic systems. These differences reflect restricted redox conditions and limited subsolidus re-equilibration in the MIL nakhlites, versus oxidation and faster cooling histories in the terrestrial analogs.

¹B.G. Rider-Stokes, ^1,2A. Stephant, ³M. Nottingham, ⁴J. Gamblin, ⁴E. Füri, ^5,6S.S. Russell, ¹X. Zhao, ¹M. Anand, ⁴M.J. Whitehouse, ¹M.M. Grady
Geochimica et Cosmochimica Acta (in Press) Open Source Link to Article [DOI: 10.1016/j.gca.2026.07.047]
¹School of Physical Sciences, The Open University, Milton Keynes MK7 6AA, UK
²Istituto di Astrofisica e Planetologia Spaziali – INAF, 00111 Rome, Italy
³School of Geographical & Earth Sciences, University of Glasgow, G12 8QQ, UK
⁴Université de Lorraine, CNRS, CRPG, F-54000 Nancy, France
⁵Department of Earth Sciences, The Natural History Museum, London SW7 5BD, UK
⁶Department of Geosciences, Swedish Museum of Natural History, SE-104 05 Stockholm, Sweden
Copyright Elsevier

Evidence for SiO₂-rich melts on the ureilite parent body (UPB) stems from feldspathic clasts within polymict ureilites and has been additionally preserved and recorded in rare fragments of the Almahata Sitta meteorite suite, which originated from the asteroid 2008 TC₃. These unique fragments demonstrated that ancient crust-forming volcanism on small planetary bodies was not simply restricted to basaltic lithologies. Two recent Northwest Africa finds (NWA) 15,820 and NWA 16789 expand the known quantity of SiO₂-rich material from the UPB, allowing for a more representative investigation into the chemical and isotopic variations among these unique lithologies. Here, we measured the H abundance and isotopic composition (δD) of NWA 15820 and NWA 16789 to evaluate the bulk UPB water content, resulting in a revised minimum bulk water content of 13 µg/g H₂O. Furthermore, we report the δD of water in the UPB. While the D/H ratio of late-stage phosphates and glass is highly fractionated as a result of magmatic degassing, nominally anhydrous silicate pyroxene better records the original δD of the UPB. In particular, the pyroxene within NWA 16789 records a δD value of 83 ± 79‰, which we infer is the best estimate for the original δD of water in the UPB.

¹Carine Sadaka, ¹Jérôme Gattacceca, ^1,2,3Florian Dumas, ¹Régis Braucher, ¹ASTER Team, ⁴Matthieu Gounelle, ⁵Dilyara Kuzina, ⁶Cyril Lorenz, ⁷Alexandre Corgne, ⁸Pierre Sempéré
Meteoritics & Planetary Science (in Press) Open Source Link to Article [DOI: 10.1111/maps.70219]
¹Aix-Marseille Univ, CNRS, IRD, INRAE, CEREGE, Aix-en-Provence, France
²Laboratoire G-Time, Université Libre de Bruxelles, Brussels, Belgium
³AMGC, Vrije Universiteit Brussel, Brussels, Belgium
⁴Institut de minéralogie, de physique des matériaux et de cosmochimie—UMR7590, Muséum National d’Histoire Naturelle, Paris, France
⁵Institute of Geology and Petroleum Technologies, Kazan Federal University, Kazan, Russia
⁶Vernadsky Institute of Geochemistry and Analytical Chemistry, Moscow, Russia
⁷Instituto de Ciencias de la Tierra, Universidad Austral de Chile, Valdivia, Chile
⁸Independent Contributor, Agen, France
Published by arrangement with John Wiley & Sons

We present a comprehensive study of a meteorite collection from the Atacama Desert (Chile), the driest and most climatically stable desert in the world. This collection includes meteorites from three adjacent Dense Collection Areas (DCAs) in the northern part of the Atacama Desert: Calama, Sierra Gorda, and Chug Chug, referred to as the “Calama area.” Within this region (~550 km²), we conducted a systematic search over a 2.5 km² zone in the Calama DCA and compared the resulting density to the nonsystematic recovery density in the Calama area. We also present the ³⁶Cl-based terrestrial ages of 49 ordinary chondrites selected from the Calama area. The systematic search yielded a meteorite recovery density of 38 meteorites per km² (15 meteorites per km² for meteorites >20 g), and the collection exhibits a median terrestrial age of 303 ka. Notably, compared with the El Médano and Catalina DCAs, the Calama area is characterized by a lower meteorite density and younger meteorite terrestrial ages, most likely reflecting the region’s more humid climate and more dynamic geomorphology due to its proximity to the pre-Andean range. Our results further show that meteorite weathering is not correlated with terrestrial age but is instead essentially controlled by the initial porosity of the meteorite, itself related to shock stage. Nevertheless, the Calama area still exhibits higher densities and older terrestrial ages than any other hot desert in the world, confirming that the long-term preservation of meteorites is observed across the entire Atacama Desert.

¹Ji-In Jung, ^1,2Sophia Gaal, ^1,3Sonia M. Tikoo, ¹Ethan Lopes, ¹Jonathan Mells, ³Dale H. Burns, ⁴Robert G. Hatfield
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.70217]
¹Department of Geophysics, Stanford University, Stanford, California, USA
²Department of Geological Sciences, The University of Alabama, Tuscaloosa, Alabama, USA
³Department of Earth and Planetary Sciences, Stanford University, Stanford, California, USA
⁴Department of Geological Sciences, University of Florida, Gainesville, Florida, USA
Published by arrangement with John Wiley & Sons

Paleomagnetic investigations of pallasites are important for understanding the dynamo histories of their parent bodies and the formation mechanisms of these meteorites themselves. To understand the temporal evolution of pallasite parent-body dynamos, additional paleomagnetic studies of new meteorites are needed. However, such efforts require a thorough understanding of magnetic carriers and recording properties of pallasites to ensure that any observed remanence reflects primary magnetic records. Here, we investigate olivine grains in the main group Sericho pallasite to evaluate their suitability for paleomagnetic studies. Electron microscopy, combined with rock magnetic analyses, reveals colloidal, euhedral magnetite grains hosted within iron oxide veins (likely goethite) formed during post-fall aqueous alteration within our Sericho sample. All results indicate that secondary mineral phases dominate the remanence, precluding reliable recovery of primary parent-body magnetic fields. Our study presents a cautionary tale about how different samples of the same meteorite can experience heterogeneous degrees of weathering, ranging from effectively pristine to so altered that paleomagnetic studies probing parent body processes cannot be conducted. As such, meteorites must be carefully scrutinized on an individual-sample basis before paleomagnetic studies to ensure high-fidelity results.

¹S. De Angelis, ^1,2F. Furnari, ¹M. Ferrari, ¹E. La Francesca, ¹C. Carli, ¹G. Piccioni, ¹S. Rubino, ¹S. Stefani, ¹F. Tosi
Journal of Geophysical Research: Planets, 131, e2026JE009723 Link to Article [DOI: 10.1029/2026JE009723]
¹Institute for Space Astrophysics and Planetology—INAF‐IAPS, Rome, Italy
²Sapienza University of Rome, Rome, Italy
Published by arrangement with John Wiley & Sons

Hexahydrite (MgSO₄·6H₂O) is among the possible candidates of the hydrated salts composing the “non-icy” materials on the surface of Europa. However, given the conditions of extreme vacuum characterizing the surfaces of icy and other airless Solar System bodies, a crucial aspect is to determine the conditions of stability of such hydrated salts in a wide range of pressures from ambient to high vacuum. The effect of varying temperatures in conjunction with variable vacuum is another important aspect to be considered. Studying the stability field of such compounds is crucial to establish the conditions of their presence on icy moons. In this work, we conducted an infrared (1–12 μm) and Raman spectral study on hexahydrite samples from ambient pressure to high vacuum, at ambient and low temperatures. We observe two main effects occurring upon lowering the pressure at which the sample is exposed, that is (a) de-hydration of the sample and consequent (b) loss of crystallinity and increase of structural disorder of the material. While the de-hydration is clear from the notable modification of H₂O absorption bands in the near-infrared, the effect of loss of crystallinity is observable in the mid-IR spectral region and also confirmed by Raman analyses. The transition is marked by the progressive loss of fine structure in the 1.5 and 2 μm hydration bands and by the collapse of the ∼9 μm Reststrahlen peak. Our measurements provide important laboratory constraints concerning the stability conditions of such hydrated materials that should provide aid in interpretation of mission data.

^1,2Lilin Huang, ^3,4Yanxue Wu, ¹Riqiang Wen, ⁵Chunwen Huang, ¹Chunmei Li, ¹Jiangmin Ma
Journal of Geophysical Research: Planets, 131, e2026JE010002 Link to Article [DOI: 10.1029/2026JE010002]
¹Hezhou University, Hezhou, China
²Key Laboratory of Planetary Geological Evolution at Universities of Guangxi Province, Institute of Meteorites and Planetary Materials Research, Guilin University of Technology, Guilin, China
³State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau, China
⁴Analysis and Test Center, Guangdong University of Technology, Guangzhou, China
⁵Hezhou Information Network Center of Science and Technology, Hezhou, China
Published by arrangement with John Wiley & Sons

In this study, we report amorphous silica dendrites in three eucritic pyroxene grains from a howardite meteorite NWA 14701. These textures exhibit enhanced metasomatic features characterized by irregular or rounded amorphous silica containing numerous nanoscale ilmenite and chromian ulvöspinel inclusions distributed along both sides of fractures to form dendritic networks in the host pyroxene. These dendritic networks manifest as a discontinuous series of discrete, equant-shaped silica masses that project as embayments into the walls of the fractures. We propose that the formation mechanism of these amorphous silica dendrites was related to fluid-mediated alteration processes, as recorded by pyroxene decomposition to Fe–Ti–Cr oxides and amorphous silica along fractures. Such fluid preferentially leached and removed highly mobile cations (e.g., Mg, Ca, and Fe). Concomitantly, high field-strength elements (Cr and Ti) with extremely low mobility became passively enriched in situ due to their limited transportability within the fluid phase, subsequently crystallizing as ilmenite and chromian ulvöspinel at nanoscale dimensions. Meanwhile, the Si-O framework of the original host pyroxene, depleted in most interstitial cations, was preserved as a chemically inert amorphous silica framework. Our work suggests that the amorphous silica dendrites represent an unique type of secondary alteration texture on the HED parent asteroid that was previously undocumented, and they may also occur on other airless, differentiated planetary bodies.

¹A. C. Zhang, ¹T. R. Du, ¹L. Zhang, ¹Z. G. Zhang, ²Q. Zhou, ¹R. C. Wang
Journal of Geophysical Research: Planets, 131, e2026JE009945 Link to Article [DOI: https://doi.org/10.1029/2026JE009945]
¹State Key Laboratory of Critical Earth Material Cycling and Mineral Deposits, School of Earth Sciences and Engineering, Nanjing University, Nanjing, China
²Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China
Published by arrangement with John Wiley & Sons

Lunar mantle material could have been excavated during the formation of South Pole-Aitken (SPA) basin and is potentially present in the Chang’e-6 lunar soil retrieved from the basin. Here, we report the petrography and mineral composition of highly magnesian olivine and enstatite in Chang’e-6 lunar soil. Most of the highly magnesian olivine grains have compositions consistent with source rocks from impact-related norites and Mg-suite rocks, while some lithic clasts containing highly magnesian olivine grains can be attributed to impact-induced melting and recrystallization with material contribution from chondrite meteorite. Some highly magnesian olivine grains display a high-Ni feature with high Al₂O₃, Cr₂O₃, and CaO contents, which could be attributed to impact origin rather than lunar mantle origin. Most of the highly magnesian enstatite grains have compositions comparable to those from impact-related SPA noritic clasts, indicating that they probably share similar source rocks; whereas, some highly magnesian enstatite grains in Chang’e-6 lunar soil are probably derived from Mg-suite rocks. The observations suggest that there are no unambiguous mantle minerals in Chang’e-6 lunar soil, which are instead potentially found in the regions surrounding the SPA basin in the future. We find that Chang’e-6 highly magnesian enstatite grains show systematically lower TiO₂ contents than those from the Moon’s near side and suggest that the relative Ti-depletion in highly magnesian enstatite from Chang’e-6 lunar soil could be due to high modal abundance of enstatite in their parent rocks, consistent with the orthopyroxene dominance in the far-side lunar mantle.

¹Chuansheng Xu, ^1,2Yifei Cui, ¹Ao Luo, ¹Guodong Wang, ^1,3Lu Jing, ⁴Jiayan Nie
Journal of Geophysical Research: Planets, 131, e2025JE009536 Link to Article [DOI: 10.1029/2025JE009536]
¹State Key Laboratory of Hydroscience and Engineering, Department of Hydraulic Engineering, Tsinghua University, Beijing, China
²Key Laboratory of Hydrosphere Sciences of the Ministry of Water Resources, Tsinghua University, Beijing, China
³Shenzhen International Graduate School, Institute for Ocean Engineering, Tsinghua University, Shenzhen, China
⁴School of Civil Engineering, Wuhan University, Wuhan, P. R. China
Published by arrangement with John Wiley & Sons

Lunar lithic fragments (micrometer–millimeter scale) mainly consist of basalt, breccia, agglutinates, leucocratic fragments, and glass. Their morphology, surface properties, and frictional behavior fundamentally control the mechanical characteristics of lunar regolith, which can be effectively characterized by the angle of repose (AoR)—a simple and intuitive parameter obtained through rapid experiments that reflects the frictional, flow, and stability features of granular materials. This study analyzes five representative lithic fragment types from Chang’e−6 samples (30 particles) to investigate how morphology, surface energy, and friction jointly influence the AoR and develops a predictive model coupling multi-scale particle parameters. Results show that for particles larger than 200 μm, complex shapes (Overall regularity 0.6) and high friction coefficients (0.55) increase AoR by 10°–20° through enhanced interlocking. For smaller particles, surface energy dominates interparticle forces but is constrained by surface roughness, reducing its effective range. Under lunar gravity, the effects of morphology and friction are weakened, and the threshold size separating friction-shape-dominated and adhesion-dominated regimes shifts from ∼100 μm on Earth to ∼200 μm on the Moon. In coarse-grained assemblages, agglutinates dominate the variation in AoR, while glass content is weakly negatively correlated with it. The model reveals intrinsic mechanisms of lunar soil behavior and provides a theoretical basis for regolith handling and construction in future lunar missions.