¹S. Effraimidou, ¹I. Baziotis, ¹M. Simopoulou, ²L. Ferrière, ³C. Sanchez-Valle, ³S. Klemme, ³J. Berndt, ⁴P. D. Asimow
Meteoritics & Planetary Science (in Press) Open Access Link to Article [DOI: 10.1111/maps.70228]
¹Department of Natural Resources Management and Agricultural Engineering, Agricultural University of Athens, Athens, Greece
²Natural History Museum Abu Dhabi, Abu Dhabi, United Arab Emirates
³Institut für Mineralogie, Universität Münster, Münster, Germany
⁴Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA

Published by arrangement with John Wiley & Sons

This study investigates the petrography and mineralogy of three L-type ordinary chondrite meteorites: Northwest Africa (NWA) 4137 (L6), Homestead (L5), and Kunashak (L6). We studied the shock-related deformation features in the matrix and the characteristics of the melt veins, including the presence or absence of high-pressure (HP) phases. Our goal is to constrain the shock history of these meteorites, including constraints on peak shock conditions and on post-shock thermal histories. All three studied meteorites are strongly shocked, with textural evidence indicating shock stages up to S4 and development of melt veins. However, NWA 4137 is the only one of these meteorites in which HP phases were observed; we identified wadsleyite, majorite, albitic jadeite, tuite, and xieite within melt veins, indicating peak shock pressure in the range of 11–23 GPa. In contrast, the investigated melt veins in Homestead and Kunashak lack any HP phases despite indicators of comparable shock intensity to that observed in NWA 4137. The absence of HP phases in these two meteorites is attributed to a high post-shock temperature that favored back-transformation into low-P minerals during decompression over preservation of HP phases. These case studies testify to the importance of the full pressure (P)–temperature (T)–time (t) path experienced by meteoritic samples during shock events in determining their ultimate mineralogy.

¹Pengfei Liu (>10)
Proceedings of the National Academy of Sciences (in Press) Link to Article [DOI: 10.1073/pnas.2608395123]
¹Macau Institute of Space Technology and Application, Macau University of Science and Technology, Macau 999078, China
We currently do not have a copyright agreement with this publisher and cannot display the abstract here

On the lunar surface α-Fe and Fe-Ni alloys are widespread and the dominant carriers of the lunar remanent magnetization. Metallic γ-Fe, however, is stable only at high temperatures and has not been documented in lunar samples. Here we report the identification of ambient stable γ-Fe preserved as nanometer-scale particles in Chang’e-6 impact glass fragments from the South Pole-Aitken Basin. Electron holography analyses reveal that these γ-Fe particles have a magnetic vortex domain state. Based on these results, we propose that the formation and preservation of γ-Fe at lunar surface temperature requires incorporation of trace γ-phase-stabilizing elements together with extremely rapid quenching during lunar impact processes. Our findings provide a basis for understanding the lunar core dynamo evolution and impact-induced magnetic recording mechanisms.

¹B. J. K. Wilson, ²G. A. Arcuri, ²T. Casagrande, ²C. M. Andrei, ^2,3B. Langelier, ^2,4,5K. T. Tait, ¹M. G. Daly
Geochimica et Cosmochimica Acta (in Press)
Link to Article [DOI: 10.1016/j.gca.2026.09.024]
¹Centre for Research in Earth and Space Science, Lassonde School of Engineering, York University, Toronto, Ontario, Canada
²Canadian Centre for Electron Microscopy, McMaster University, Hamilton, Ontario, Canada
³Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario, Canada
⁴School of Earth, Environment, and Society, McMaster University, Hamilton, Ontario, Canada
⁵Department of Natural History, Center for Applied Planetary Mineralogy, Royal Ontario Museum, Toronto, Ontario, Canada
Copyright Elsevier

Tarda is a C2-ungrouped carbonaceous chondrite that preserves a record of low-temperature
aqueous alteration on its parent asteroid. While the original fluid has disappeared, constraining its
composition is essential for understanding the chemical environment that influenced both
secondary mineral formation and prebiotic organic chemistry. Magnetite framboids are an
abundant aqueous alteration product in Tarda and likely recorded some of the chemical species
from its mother solution, entrained within the framboidal magnetite grain boundaries. To
investigate this, we conducted a nanoscale study on five magnetite framboids using transmission
electron microscopy, energy dispersive x-ray spectroscopy, and atom probe tomography.
Magnetite framboids in Tarda exhibit a wide range of textures, crystallite sizes, and packing
arrangements, reflecting a progressive sequence of discrete nucleation and growth events likely
occurring in isolated water droplets. Energy dispersive x-ray spectroscopy analysis of four
interacting framboids reveals trace element enrichments of mostly Ti and Si along ~5 nm thick
grain boundaries, with the strongest enrichments observed in the framboids with smaller
crystallites, which likely precipitated at the beginning and end of the local precipitation sequence.
Using atom probe tomography, we captured a ~5 nm thick planar feature enriched in trace
abundances of Na, Mg, Ca, Mn, and Si, likely corresponding to a magnetite boundary. These
findings suggest that magnetite framboids in Tarda formed from a generally alkaline fluid that
contained a diverse suite of cations and evolved as water-rock interaction progressed. While the
fluid composition inferred here resembles alkaline, metal-containing fluids known to promote
organic synthesis on Earth, experimental work is needed to determine how such conditions could
influence complex organic synthesis in asteroid environments

¹Megan D. Mouser, ¹Yingwei Fei
Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.70230]
¹Amentum, Astromaterials Research and Exploration Science (ARES) Division, NASA Johnson Space Center, Houston, TX, USA

Published by arrangement with John Wiley & Sons

Early terrestrial planetary formation processes included melting of chondritic material, leading to differentiation of small planetary bodies. The differentiation process may have been different for various sized objects in the solar system, where some may have gone through total melting (i.e., magma ocean) to form a core and silicate mantle, while others may have experienced partial melting that modified and differentiated the planetary embryo to varying degrees. Based on evidence of differentiated meteorite specimens and spectroscope evidence of silicate and metal asteroids, differentiated planetary bodies are common in the solar system. This work experimentally explores the partial melting process and how that could lead to core formation on a planetary embryo with internal pressures up to 5 GPa. We identified an efficient mechanism to mobilize metal materials when the silicate matrix reached ≥20% partial melting at pressures >3 GPa that usually disrupt interconnected metallic melt because of the large dihedral angle. The predicted percolative velocity of these metallic blebs would be fast enough to percolate toward the center of a smaller planetary body within a few million years while heat from the decay of short-lived radioisotopes is still prevalent.

¹D. Das et al. (>10)
Meteoritics & Planetary Science (in Press)
Open Access
Link to Article [DOI: 10.1111/maps.70237]
Los Alamos National Laboratory, Los Alamos, New Mexico, USA

Published by arrangement with John Wiley & Sons

Boron and lithium have been observed in Ca-sulfate veins of Gale crater. These elements are highly water mobile and can inform us regarding the aqueous processes that may have taken place in Gale crater. However, the analysis of B in Gale crater is limited to low-Fe rocks and minerals due to spectral interference of Fe with B in ChemCam data. We investigate the distribution of B and Li in various phases (veins, sheet silicate mineral-rich sedimentary rocks, salts, and igneous materials) within samples collected from Death Valley and surrounding locations in Southern California, which we use as a terrestrial analog for Gale crater. In the terrestrial analog samples set that we study, B concentration is found to be predominantly associated with borate minerals while elevated Li concentration is linked with the presence of sheet silicate minerals. Based on these observations, we suggest that B enrichment as evaporites such as borates may have formed during evaporation of borate-enriched fluids in drier atmospheric conditions while Li enrichment may have taken place due to surface adsorption to sheet silicate minerals. Prior literature indicated that different fluid pH conditions and atmospheric humidity levels are necessary for borate enrichment and Li adsorption. The process of adsorption to the surface of sheet silicates is attributed to high pH aqueous conditions while the formation of borate minerals is attributed to a combination of low aqueous pH and high evaporative atmospheric conditions. We infer that the coexistence of borate minerals and Li-containing sheet silicates is indicative of multiple generations of aqueous conditions that likely took place over multiple seasonal cycles. We extend our inference to Gale crater and draw from the similarities between dry-lake deposits of Death Valley to provide a terrestrial-analog backed hypothesis on B and Li enrichment on Mars. We conclude that multiple early and late-stage aqueous events that may have involved the participation of groundwater activity were likely present to account for the observations in Gale crater.

¹Christian J. Renggli, ²Andreas Morlok, ²Iris Weber, ²Maximilian P. Reitze, ³Tommaso Di Rocco, ⁴Jasper Berndt, ³Andreas Pack, ²Harald Hiesinger
Planetary Research, 1, 226
Open Access
Link to Article [DOI: 10.53480/bf74-m226]
¹Max Planck Institute for Solar System Research, Göttingen, Germany
²Institut für Planetologie, Universität Münster, Münster, Germany
³Geowissenschaftliches Zentrum, Abteilung Geochemie und Isotopengeologie, Universität Göttingen, Germany
⁴Institut für Mineralogie, Universität Münster, Münster, Germany

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

^1,2,3,4Shengdong Chen et al. (>10)
Journal of Geophysical Research: Planets, 131, e2026JE009777
Link to Article [DOI: 10.1029/2026JE009777]
¹State Key Laboratory of Deep Earth Processes and Resources, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, PR China
²Center for Advanced Planetary Science (CAPS), Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, PR China
³Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, PR China
⁴University of Chinese Academy of Sciences, Beijing, PR China
Published by arrangement with John Wiley & Sons

The Moon’s highly reduced nature contrasts with recent findings of ferric iron (Fe³⁺)-bearing phases, suggesting an active redox cycle on the Moon. While solar wind proton reduction and impact-vaporization oxygen loss from minerals are proposed drivers for lunar reduction, direct nanometer-scale evidence for impact-driven deoxygenation has been lacking. Here we report the discovery of oxygen-deficient magnetite within impact melt glass in Chang’e-6 lunar farside samples from the South Pole-Aitken basin. This subhedral magnetite grain (Length 2.5 μm; width 1.5 μm.) exhibits a non-stoichiometric composition and crystal chemical formula [(Fe²⁺_1.158(7)Mg_0.070(5))_∑1.228(Fe³⁺_1.534(9)Cr³⁺_0.137(14)Al_0.101(8))_∑1.772]_∑3.000(O_3.886□_0.114)_∑4.000, confirming significant oxygen vacancies (□). Magnetite heating experiments (1000°C, in Ar atmosphere) replicated these features, demonstrating thermal deoxygenation generates oxygen vacancies through O₂ evolution and concurrent Fe³⁺ reduction. Our findings provide the first mineral structural evidence that post-shock heating drives deoxygenation in oxygen-bearing minerals, establishing impact-induced oxygen removal as a fundamental mechanism making the localized lunar surface chemically reduced.

^1,2S. N. Mantsevich, ¹Yu. S. Dobrolenskiy, ³O. V. Zakusina, ³T. A. Koroleva, ^3,4V. V. Krupskaya, ⁵N. A. Evdokimova
Journal of Geophysical Research: Planets, 131 e2026JE009946
Link to Article [DOI: 10.1029/2026JE009946]
¹Space Research Institute (IKI RAS), Moscow, Russia
²Physics Department, M.V. Lomonosov Moscow State University, Moscow, Russia
³Institute of Ore Geology, Petrography, Mineralogy and Geochemistry (IGEM RAS), Moscow, Russia
⁴Faculty of Geology, M.V. Lomonosov Moscow State University, Moscow, Russia
⁵Geophysical Institute, University of Alaska, Fairbanks, AK, USA
Published by arrangement with John Wiley & Sons

The acousto-optic tuneable filters can be used as main dispersive or auxiliary elements in compact spectrometers applied for various purposes such as atmospheric gas composition analysis, agriculture, or mineralogical analysis. This paper describes the features that arise when the problem of mineral identification is solved using an acousto-optic spectrometer. Estimates of such spectral device sensitivity are given in terms of the direct minimum detectable percentage ratio between the parent rock and the mineral being identified. It is shown that the minimum detectable value of the mineral percentage content depends significantly on its absorption band characteristics. The presented results can be generalized to reflectance spectra obtained by other types of optical spectrometers with similar characteristics and are of importance for the mineralogical analysis both in studies of the Earth’s surface and other objects in the Solar System.

¹Gowri Giri et al. (>10)
Journal of Geophysical Research: Planets (in Press)
Link to Article [DOI: 10.1029/2026JE009913]
¹Department of Geology, University of Kerala, Thiruvananthapuram, Kerala, India Published by arrangement with John Wiley & Sons Gypsum is a key mineral to reconstruct aqueous processes on Mars. Thus, this study compares gypsum from two contrasting terrestrial environments: the hyperarid Atacama Desert of Chile and the semi-arid Tiruchirappalli Badlands of India, and its comparison with multiple sites on Mars, serving as end-member analogs for Martian gypsum. Using field observations, petrography, X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), and hyperspectral reflectance, we characterized samples from both localities. In Atacama, gypsum occurs as fibrous veinlets within mudstone, with coexisting bassanite and anhydrite. Whereas in Tiruchirappalli, it forms fracture-filling veins with fluid inclusions and iron staining, and is associated with kaolinite-hematite within the Cretaceous mudstones of the Karai Formation. Raman and FTIR confirm the presence of gypsum at both sites, with an additional anhydrite phase in Atacama. These sites exhibit similar hyperspectral absorption features that match those observed by CRISM at Olympia Undae, Columbus Crater, and Mawrth Vallis. When Atacama gypsum formed as a primary evaporite through groundwater evaporation under extreme aridity, Tiruchirappalli gypsum formed diagenetically, precipitating from sulfate-rich fluids into fractures during burial and uplift, with tropical weathering. This spectral equivalence from different pathways shows that orbital spectra alone cannot determine gypsum genesis on Mars without geological context. The framework matches Atacama gypsum to Olympia Undae, Tiruchirappalli to Columbus Crater, and both to Mawrth Vallis. Fluid inclusions and endolithic communities highlight gypsum’s potential to preserve biosignatures. Together, these findings strengthen interpretations of the Martian paleoenvironment and guide gypsum-focused habitability assessments.

¹A. Sedaghat, ¹C. McLeod, ²M. Loocke, ³B. Shaulis
Icarus (in Press) Open Access Link to Article [DOI: 10.1016/j.icarus.2026.117331]
¹Department of Geology and Environmental Earth Science, Miami University, Oxford, OH 45056, USA
²Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803, USA
³Trace Element and Radiogenic Isotope Laboratory (TRAIL), University of Arkansas, Fayetteville, AR 72701, USA
Copyright Elsevier

Through integrated textural, mineralogical, and geochemical studies, symplectites provide fundamental constraints on the evolution and stability of geological systems. The returned 2018–2019 Antarctic Search for Meteorites Dominion (DOM) Range lunar meteorites contain ubiquitous three-phase symplectites consisting of fayalitic olivine (Fa), Ca-Fe-rich pyroxene (Px), and a silica phase (Si). Here, the textures and compositions of two textural symplectite types in DOM 18509 and DOM 18543 are investigated. Typical symplectites are characterized by a relatively uniform distribution of Fa-Px-Si and fine grain sizes (≤5 μm). Fayalite is Fe-rich (Fa_91–96) with associated pyroxene at Wo_31–40En_6–11Fs_51–61. Bulk compositions determined via reconstruction and broad beam analyses yielded lunar pyroxferroite compositions. The preservation of rare pyroxferroite in lunar materials is reported for DOM 18509: Wo_12-13En_9-10Fs_77–78. In contrast, non-typical symplectites exhibit variable grain sizes and consist of a Ca-rich host pyroxene (Wo_23–40En_8-18Fs_49–68) containing blebs of olivine (Fa_86–95) and silica. Reconstruction for the bulk precursor material yields a metastable pyroxene (Wo_24-26En_12-16Fs_58–64). While both symplectite types are interpreted as subsolidus breakdown products during slow cooling, their formation is associated with different breakdown pathways from distinct precursor phases. During late-stage crystallization in highly evolved lunar basaltic systems, pyroxene compositions enter the forbidden zone. At this stage, metastable Ca-rich pyroxene forms, followed by crystallization of metastable pyroxferroite during extreme Fe-enrichment. Subsequently, non-typical symplectites form through the subsolidus multistep breakdown of metastable Ca-rich pyroxene, whereas typical symplectites form through the direct subsolidus breakdown of pyroxferroite. These two symplectite textures record the evolution of metastable phases within reduced magmatic conditions in extraterrestrial environments.