^1,2Julia Neukampf, ²Yves Marrocchi, ²Johan Villeneuve, ³Mathieu Roskosz
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2026.01.041]
¹The University of Manchester, Oxford Road, M13 9PL Manchester, UK
²Université de Lorraine, CNRS, CRPG F-54000 Nancy, France
³Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), Muséum national d’Histoire naturelle, Sorbonne Université, CNRS, F- 75005 Paris, France
Copyright Elsevier

We report high-precision lithium (Li) abundances and isotopic compositions of olivine crystals from type I chondrules in carbonaceous chondrites (Murchison, NWA 852, Renazzo) and type II chondrules in ordinary chondrites (NWA 11752, NWA 12462, NWA 12581, NWA 13501). Olivine crystals in type I chondrules exhibit large Li isotopic fractionations both within and between grains, with δ⁷Li values ranging from −46.6‰ to + 9.9‰ and Li concentrations of 3.8–9.0 ppm. Olivine grains in type II chondrules, including Mg-rich relict cores, show δ⁷Li values from −38.0‰ to + 8.4‰ (Li = 0.6–5.6 ppm), while their Fe-rich overgrowths exhibit lower variability, with δ⁷Li values between −30.6‰ and + 4.7‰ (Li = 0.6–11.9 ppm). Our data indicate that the observed variations are not attributable to low-temperature aqueous alteration or dry thermal metamorphism, fractional crystallisation, or simple degassing of the chondrule melt. Instead, the Li isotopic signatures are best explained by kinetic fractionation during open-system gas–melt exchange with a volatile-rich vapour, enriching the chondrule melts in Li. Such open-system processes produced larger isotopic fractionations than expected during closed-system crystallisation. These findings suggest that some type II chondrules may have originated from type I chondrules through reprocessing in an open-system environment, providing new insights into the complex physicochemical evolution of early solar system solids.

¹Ryan S. Jakubek, ²Marc D. Fries, ³Francis M. McCubbin, ³Devin L. Schrader, ⁴Andrew Steele, ²Jemma Davidson
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2026.01.036]
¹Amentum, NASA Johnson Space Center, Houston, TX, USA
²Astromaterials Acquisition and Curation Office (XI2), Astromaterials Research and Exploration Division, NASA Johnson Space Center, Houston, TX 77058, USA
³Astromaterials Research and Exploration Science (ARES) Division, XI3 Research Office, NASA Johnson Space Center, Houston, TX 77058, USA
⁴Carnegie Institute of Washington, Washington, DC, USA
Copyright Elsevier

We collected Raman images of 78 chondrules and their surrounding matrix from 12 Antarctic meteorite thin sections. We identified three spatially zoned, distinct structural populations of insoluble organic matter (IOM). A majority of IOM is spatially associated with the matrix and is consistent with Raman analysis of matrix and bulk demineralized IOM reported in the literature. We observe an IOM population within most chondrules that is more thermally altered compared to the chondrule’s surrounding matrix. The chondrule IOM population is observed in all chondrite types examined in this work: OC, CO, CV, CM, and CR, and shows a structural dependence on petrologic type, similar to that reported for matrix/bulk IOM, indicating that the chondrule IOM population was present during parent body thermal metamorphism. The structural differences between the chondrule and matrix IOM populations decrease with increasing petrologic type as thermal alteration homogenizes the IOM. Petrologic type 1–2 chondrites show the largest chondrule-matrix IOM structural differences, indicating significant differences between these populations at the time of parent body accretion. These results suggest that IOM material in matrix and chondrule precursors experienced different alteration histories prior to parent body accretion. The chondrule IOM Raman spectra contain features consistent with alteration by flash heating–cooling, possibly implicating the chondrule formation event(s) as an alteration pathway that differentiates it from matrix IOM. We also observe a disordered IOM population referred to as broad IOM. The broad IOM is observed across matrix, chondrules, and clasts, indicating its formation after parent body accretion. In several Raman images of low petrologic type CO meteorites, broad IOM is found co-located with magnetite though the current dataset is not sufficient to prove a statistical correlation. We hypothesize that broad IOM is an aqueous alteration product and propose a few possible formation pathways including oxidation of iron carbide and/or precipitation from a C-O–H bearing fluid.

¹Ajay Dev Asokan,¹Yogita Kadlag,²Yash Srivastava,³Khirod Kumar Das,³Rumanshu Hazarika,²James M. D. Day
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70099]
¹Geosciences Division, Physical Research Laboratory, Ahmedabad, Gujarat, India
²Scripps Institution of Oceanography, San Diego, California, USA
³Department of Geology, Babasaheb Bhimrao Ambedkar University, Lucknow, India
Published by arrangement with John Wiley & Sons

The Holocene Luna Structure in western India has been claimed to be the fourthand youngest impact crater on the Indian subcontinent. The circular shape; the unusualmineralogy including high-temperature mineral phases such as kirschsteinite and w€ustite;and the elevated abundance of highly siderophile elements (HSE: Os, Ir, Ru, Rh, Pt, andPd) have been provided as evidence in favor of an impact origin. Here, we present newmineralogical, bulk rock geochemical data including isotope-dilution HSE abundances and187 Re- 187 Os compositions of the suspected Luna impactites. The samples are dense irregularnodules with undulated surface and flow-like structures and are glassy to extremely finegrained, with or without vesicles. The new HSE data show no Ir enrichment compared toupper continental crust. The radiogenic measured 187 Os/ 188 Os compositions (0.2289–0.7253)further rule out any extraterrestrial contribution in the suspected impactites. The observedhigh-temperature mineral assemblage shows similarity to that of iron-rich archaeologicalslags. We reinterpret the Luna Structure materials as slags that are likely associated with theBronze Age in the Harappan Civilization and may have formed as a byproduct of coppersmelting. Considering the new evidence, the Luna Structure of western India is not ameteorite impact crater.

^1,2,3,4Anthony M. Gargano,²Justin I. Simon,⁴Erick Cano,^4,5Karen Ziegler,⁵Charles K. Shearer,³James M. D. Day,⁴Zachary Sharp
Proceedings of the National Academy of Sciences of the USA (PNAS) 123, e2531796123 Open Access Link to Article [https://doi.org/10.1073/pnas.2531796123]
¹Lunar and Planetary Institute, Houston, TX 77058
²Astromaterials Research and Exploration Science Division, NASA Johnson Space Center, Houston, TX 77058
³Scripps Institution of Oceanography, Geosciences Research Division, University of California San Diego, La Jolla, CA 92093
⁴Center for Stable Isotopes, University of New Mexico, Albuquerque, NM 87131-0001
⁵Institute of Meteoritics, University of New Mexico, Albuquerque, NM 87131

The impactor flux record to Earth has largely been erased by active tectonics, weathering, and continual reworking of the crust. Instead, a record of highly siderophile elements (HSE: Re, Os, Ir, Ru, Rh, Pt, Pd, and Au) in lunar impactites has been used as a proxy for the type of impactor material added to the Earth–Moon system. Quantifying impactor mass and flux with the HSE can potentially be complicated by numerous secondary processes, however, including silicate–metal segregation and multiple impact heritage. In contrast, because oxygen has an invariant geochemical affinity, triple oxygen isotope compositions have the potential to offer a robust long-term record of impactor fluxes in complex mixtures such as regolith. Here, we use high-precision triple oxygen isotopes to deconvolve the influences of meteorite addition and silicate vaporization and identify a ubiquitous impactor contaminant comprised of partially evaporated CM or ureilite-like material representing at least 1 wt% of the lunar regolith. Water delivered to Earth by meteorite material over 4 billion years therefore is only a fraction of an ocean’s worth of water but is a significant contributor to the ice reservoir of the lunar cold traps.

¹Connor A. Diaz, ¹Rebecca M. Flowers, ¹Carolyn A. Crow, ¹James R. Metcalf, ²Rita Economos
Earth and Planetary Science Letters 679, 119826 Link to Article [https://doi.org/10.1016/j.epsl.2026.119826]
¹Department of Geological Sciences, University of Colorado Boulder, 2200 Colorado Avenue, UCB 399, Boulder, CO 80309-0399, USA
²Hawaiʻi Institute of Geophysics and Planetology, University of Hawaiʻi at Mānoa, Honolulu HI 96822, USA
Copyright Elsevier

Understanding the shock conditions of shergottites during their ejection from the Martian surface is important for deconvolving the pre-ejection thermal and geological history from the ejection overprint in Martian meteorite samples. Here, we investigate Martian meteorite Northwest Africa (NWA) 12241 to better quantify absolute temperatures and local variability in shock-induced thermal events and implications for deciphering the Martian meteorite record. NWA 12241 is classified petrologically as low-shock based on its limited shock features. However, new Raman identification of tuite, a high-pressure phosphate polymorph, demonstrates that minimum temperatures of 1100 °C were achieved in some regions of the sample during ejection. (U-Th)/He dating of merrillite yields a wide range of dates from 2.0 ± 0.3 Ma to 191.7 ± 2.7 Ma, interpreted as the ejection and crystallization ages of NWA 12241, respectively. Thermal history modeling suggests that heterogeneous shock heating is required to explain the merrillite data distribution, with local shock temperatures of ≤570 °C necessary to account for preservation of the older dates. Together, the tuite occurrence and (U-Th)/He data support at least 530 °C (and up to 1730 °C) of variability in the peak shock temperature across this small (7.21 g, ∼4 cm) sample. These findings highlight intense thermal heterogeneity and localized high-temperature microenvironments in an otherwise low-shock meteorite, illustrating the value of (U-Th)/He thermochronology for refining interpretations of localized shock effects in Martian meteorites.

¹Yutong Ma, ²Zhuang Guo, ³Aicheng Zhang, ⁴Jingjing Niu, ¹Shan Qin
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2026.01.037]
¹Key Laboratory of Orogenic Belts and Crustal Evolution, MOE, School of Earth and Space Sciences, Peking University, Beijing 100871, China
²State Key Laboratory of Continental Evolution and Early Life, NWU-HKU Joint Center of Earth and Planetary Sciences, Department of Geology, Northwest University, Xi’an 710069, China
³School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China
⁴State Key Laboratory of Tibetan Plateau Earth System Science, Resources and Environment (TPESRE), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China
Copyright Elsevier

Nanophase iron particles are ubiquitous in lunar soils and are largely attributed to space weathering; however, no nanophase iron particles formed in lunar crystalline minerals via impact events have been reported. Their growth, migration, spatial distribution, and interactions with host minerals under impact remain poorly understood. Here, we report the discovery of impact-induced dusty olivine clasts (containing nanoscale to submicron iron metal particles) in the lunar breccia meteorite Bechar 012. These clasts encapsulate a comprehensive record of iron particle formation and distribution within their crystalline host. Their well-preserved state provides a clear snapshot of the microscopic mineral processes often obscured in more heavily processed soils or breccias, making Bechar 012 an ideal natural sample for study. Crystallographic orientation analysis suggests that these dusty olivine grains undergo plastic deformation, with iron metal particles concentrated within the deformed regions, indicating a correlation between deformation microstructures and iron metal particle formation. We propose a three-step model for the formation of dusty olivine and the iron metal particles therein: (1) impact-induced plastic deformation of olivine; (2) sub-solidus olivine decomposition (Fe2SiO4 = 2Fe + SiO + 3/2O2) within partially amorphous zones, leading to the nucleation of nanosized iron metal particles, with SiO and O2 diffusing away through disordered pathways (e.g., partially amorphous zones, dislocations and pores) in the deformed olivine; and (3) capture of particles by migrating dislocations, followed by aggregation and oriented attachment (OA)-driven growth along the olivine lattice at dislocations and subgrain boundaries, resulting in the formation of submicron-sized iron metal particles. These processes indicate an equilibrium shock pressure below 16 GPa, with temperatures between 1000 °C and 1650 °C. These results confirm the pivotal role of impact-induced olivine deformation in facilitating the formation, migration, and growth of iron metal particles and highlight the significance of OA in their coarsening. The discovery of impact-induced iron metal particles in the lunar meteorite indicates that these particles can be broadly formed within crystalline minerals, rather than being limited to the amorphous rims of lunar regolith minerals and glassy impactites, while also offering a potential explanation for the lunar magnetic anomalies.

^1,2Anna-Irene Landi,³Cristian Carli,⁴Alessandro Maturilli,⁴Giulia Alemanno,⁴Océane Barraud,Fabrizio Capaccioni,²Giovanni Pratesi
Journal of Geophysical Research: Planets (in Press) Link to Article [https://doi.org/10.1029/2025JE009382]
¹Dipartimento di Fisica, Università degli Studi di Trento, Trento, Italy,
²Dipartimento di Scienze della Terra, Universitàdegli Studi di Firenze, Firenze, Italy,
³INAF‐IAPS, Area della Ricerca Tor Vergata, Roma, Italy,
⁴Institute for SpaceResearch, German Aerospace Center DLR, Berlin, Germany
Published by arrangement with John Wiley & Sons

Boninites are high‐magnesium volcanic rocks proposed as terrestrial analogs for Mercury’ssurface, based on elemental data from NASA’s MErcury Surface, Space Environment, Geochemistry andRanging (MESSENGER) mission. In this study, we investigated boninite samples from the Troodos Massif(Cyprus) using a multi‐methodological approach to characterize their mineralogical, chemical, andspectroscopic properties, including reflectance and emissivity spectra. Geochemical analyses confirm that thebulk composition of the samples closely matches Mercury’s geochemical terrains in terms of SiO2, MgO, andAl2O3 content, though FeO concentrations are higher (∼8 wt% vs. 1–2 wt%). Samples from different localitiesshow some mineralogical differences but generally contain less orthopyroxene and albitic plagioclase thanexpected on Mercury, along with hydrated minerals from aqueous alteration, which are not expected on theplanet’s surface. Reflectance spectra in the ultraviolet (UV), visible (VIS), and near‐infrared (NIR) range showmajor absorption features around 1 μm, associated with mafic minerals, and minor bands at ∼1.4 μm, ∼1.9 μm,and 2.2–2.3 μm, linked to hydrated phases, with spectral variations reflecting mineralogical differences. In themid‐infrared (MIR) range and emissivity spectra, we observe Christiansen Features (CF) and ReststrahlenBands (RB) at different positions, mainly influenced by plagioclase content, and shifts in emissivity minimawith increasing temperature. Spectral differences between the boninites and Mercury mainly result from theintrinsic mineralogy of the samples. Nonetheless, Troodos boninites represent one of the best Mercury analogscurrently available on Earth, and understanding their spectral behavior in relation to their mineralogy couldsupport future investigations with the ESA/JAXA BepiColombo mission.

^1,2Kecheng Du,^1,2Sicong Liu,¹Xiaohua Tong,³Ming Jin,^1,2Huan Xie,^1,2Yongjiu Feng,^1,2Yanmin Jin,^1,2Jie Zhang
Journal of Geophysical Research: Planets (in Press) Link to Article [https://doi.org/10.1029/2024JE008842]
¹College of Surveying and Geo‐Informatics, Tongji University, Shanghai, China,
²Shanghai Key Laboratory for Planetary Mapping and Remote Sensing for Deep Space Exploration, Tongji University, Shanghai, China,
³Institute of Geology,Chinese Academy of Geological Sciences, Beijing, China
Published by arrangement with John Wiley & Sons

The lunar south polar region has been a focus of human exploration due to its potential rich water-ice and mineral resources. However, scientific exploration of this area based on spectral data is limited due to challenging lighting conditions and complex topography. In this work, we used the Moon Mineralogy Mapper (M3) and Lunar Orbiter Laser Altimeter (LOLA) reflectance data to construct a hyperspectral cube in the lunar 83°–90°S region. Mineralogical abundance maps of the four major lunar minerals were derived from M3 data at a spatial resolution of ∼193 m/pixel. Quantitative mineral maps of four common lunar minerals, including high-calcium pyroxene (HCP), low-calcium pyroxene (LCP), olivine, and plagioclase, were derived from the M3 data, with abundance ranges consistent with those from the Kaguya Spectral Profiler (SP) data. The high-resolution mineral maps enhance the identification of mineral distribution details, such as purest anorthosite enrichment in the crater wall and floor of the Shackleton Crater. Comprehensive analysis of the mineral abundance maps reveals geological characteristics and potential effects of impact events, with particular emphasis on Artemis III mission landing site candidates. Pyroxene enrichment detected in the De Gerlache-Kocher Massif region may present an opportunity to collect South Pole-Aitken ejecta materials.

¹Xiaoying Liu, ¹Chi Zhang, ¹Zongyu Yue, ¹Lixin Gu, ¹Jing Li, ¹Heng-Ci Tian, ¹Sen Hu, ¹Yangting Lin
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2026.116969]
¹Key Laboratory of Planetary Science and Frontier Technology, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
Copyright Elsevier

Meteorite impact is a key process on the Moon, having profoundly reshaped the lunar surface, modified the physical properties of lunar regolith, and transported water and other volatiles on the surface. However, the temperature-pressure conditions of impact-induced plumes and their duration were poorly constrained. Here, we report the first discovery of immiscibility a FeNi-P-S bead from Chang’e-5 lunar soils, which consists of abundant spherules of metallic FeNi and sulfide both evenly dispersed in phosphide-rich matrix. The observed texture and compositions are consistent with quenching of an FeNi-P-S melt droplet, generated during an iron meteorite impact. The initial droplet was homogeneous and formed at >1800 °C and > 11–16 GPa within the impact plume, based on high-pressure experiments of the Fe-P-S system. As the plume expanding, FeNi spherules emerged from the droplet at 11–16 GPa, estimated by P partitioning between the metal and P-S-rich melt. Subsequent separation of the P-S-rich melt into immiscible sulfide-rich spherules and phosphide-rich mesostasis occurred at 1 bar–3 GPa and 1000–1100 °C. The duration of the pressure declining from >11–16 GPa to 1 bar–3 GPa was estimated to be 0.5–1 s, combining the impact plume expansion model with the cooling rate inferred from the metallic bead. This study demonstrates that high-pressure conditions of impact plumes can be retained for second timescales, which is critical for chemical reactions and water and other volatile migration on the Moon’s surface.

¹Edward A. Cloutis et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2026.116952]
¹Centre for Terrestrial and Planetary Exploration, University of Winnipeg, 515 Portage Avenue, Winnipeg, MB R3B 2E9, Canada
Copyright Elsevier

Four carbonaceous chondrite (CC) meteorites – MET 00432, Tagish Lake, Tarda, and WIS 91600 – have been proposed to be members of a CC grouplet, hereafter termed the Carbonaceous Tagish Lake Grouplet (CTG). We investigated their possible affinities via a spectral reflectance-focused study of them, as chips and variously sized powders. We also considered possible spectrum-altering effects of space weathering and composition of the organic component on such red-sloped spectra. Ultraviolet-region spectra (200-400 nm) exhibit absorption features attributable to unspecific Fe2+-O and/or Fe3+-O charge transfers, possibly due to Fe-rich phyllosilicates. Both albedo and spectral slope vary as a function of grain size. The 0.35-2.50 μm interval is characterized by dark, variably red-sloped spectra with low albedos in the visible region (<6% reflectance at 0.550 μm). Spectral slopes are redder for powders than slabs or chips. CTG spectra also exhibit shallow (<4% deep) absorption bands attributable to known components, such as magnetite and phyllosilicates, particularly in the 1 μm region. Spectral analysis of an extensive suite of phyllosilicate+opaque mixtures suggests that only a subset of CTG opaque components can cause darkening and overall red spectral slopes, in particular low H/C ratio carbonaceous compounds. Other opaque components, such as iron sulfides, magnetite and other carbonaceous materials, some of which are red-sloped when pure, cause spectral bluing or only slight spectral reddening. Albedo and spectral slopes and shapes are affected by physical properties, such as grain size, as well as the types, compositions, abundances, dispersion, and grain sizes of opaque components. At longer wavelengths (to 14 μm), CTG spectra exhibit a number of absorption features that can be related to their silicate, carbonate, and organic components. A prominent absorption feature is present in the 2.7-3.1 μm region attributable to phyllosilicates ± H2O, some of which is likely attributable to terrestrial alteration. Petrological, mineralogical, and isotopic information provide support for these meteorites having strong affinities to each other and comprising a grouplet. Additional CTG meteorites may lurk among the many tens of CCs that have been incompletely characterized.