^1,2Lauren A. Jennings, ¹Stephan Klemme, ³Max Collinet, ²Julia Maia, ^1,2Carianna Herrera, ²Ana-Catalina Plesa
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2026.116986]
¹Institut für Mineralogie, Universität Münster, Corrensstraße 24, Münster 48149, Germany
²Institute of Space Research, German Aerospace Center (DLR), Berlin, Germany
³Institute of Life, Earth and Environment, Geology Department, University of Namur, Namur, Belgium
Copyright Elsevier

The mantle composition of Venus is often assumed to be similar to Earth, albeit with a lower iron content to account for the density differences between the two planets. However, it has yet to be tested whether partial melting of proposed Venusian mantle compositions can produce melts that are similar to the measured basaltic rock compositions analysed in-situ during the Venera 14 and Vega 2 missions. In this study, we used Perple_X to calculate melt compositions from several bulk mantle compositions of Venus and found they were unable to reliably produce primary melt compositions that are similar to the Venera 14 or Vega 2 basalts, regardless of the oxidation state or degree of fractional crystallisation. As such, we used an iterative approach to identify new mantle compositions for Venus that are able to produce Vega 2- and/or Venera 14-like melts over a large pressure and temperature range. We found 23 mantle compositions that are similar to the terrestrial composition of KLB-1, but have a high Al2O3 and low CaO abundance, resulting in a sub-chondritic CaO/Al2O3 and SiO2/Al2O3. We recommend two of these as new mantle compositions for Venus as they were the most successful at producing Venus-like melts. Lastly, we propose that the sub-chondritic ratios of these new mantle compositions are the result of igneous processes, such as magma ocean differentiation and Ca-rich carbonatite melt extraction, that altered the mantle composition prior to the melting that produced the basalts sampled by the Venera 14 and Vega 2 missions.

¹M.C. Benner, ^1,2T.J. Zega, ¹B.S. Prince, ³Z.E. Wilbur,^1,4,5H.C. Connolly Jr., ¹D.S. Lauretta
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2026.01.056]
¹Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
²Department of Materials Science & Engineering, University of Arizona, Tucson, AZ, USA
³Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA
⁴Department of Geology, Rowan University, Glassboro, NJ, USA
⁵Department of Earth and Planetary Science, American Museum of Natural History, New York, NY, USA
Copyright Elsevier

We report the discovery of fibrous mackinawite in samples of asteroid Bennu returned by the OSIRIS-REx mission. Mackinawite occurs primarily in particles belonging to Bennu’s hummocky lithology, with fibers that range from 75 to 250 nm in length and 10 to 30 nm in width. In Bennu particles, mackinawite displays both fibrous and tabular habits and forms flower-like clusters that resemble the texture of coarse-grained phyllosilicates previously described. Energy-dispersive X-ray spectroscopy indicates an Fe/S ratio of 1, and four-dimensional scanning transmission electron microscopy reveals a tetragonal structure consistent with mackinawite. Similar to terrestrial occurrences, the activities of Fe2+ and S2– in aqueous solution are likely the main drivers of mackinawite precipitation within Bennu’s parent body. We suggest that mackinawite formed via precipitation from solution following the dissolution of accreted metal and sulfides when Fe and S activities were high enough to support mackinawite stability. Based on comparison to terrestrial Pourbaix diagrams, we hypothesize that mackinawite precipitation within Bennu’s parent body was possible at 7 < pH < 10, –0.5 < Eh < –0.15, 10–9 ≤ aFe ≤ 10–6, and temperatures up to 70°C.

¹Jintuan Wang, ²Hongluo L. Zhang, ¹Le Zhang, ¹Yonghua Cao, ²Zhendun Qi, ¹Pengli He, ¹Mang Lin,¹Yi-Gang Xu
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2026.01.046]
¹State Key Laboratory of Deep Earth Processes and Resources, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
²State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China
Copyright Elsevier

Lunar basalts are much more reduced than their terrestrial counterparts and exhibit more than three orders of magnitude variability in oxygen fugacity (fO2). However, the origin of this large fO2 variation remains enigmatic. The Chang’e-5 (CE-5) basalt, derived from a pyroxene-bearing mantle source, provides a unprecedented opportunity to decipher the redox variation of lunar samples. The mineral/melt partitioning behaviors of vanadium (V) and europium (Eu) are sensitive to fO2, and thus capable of evaluating the fO2 of rocks. However, previous oxybarometers based on the partitioning behaviours of V and Eu are not applicable to CE-5 basalt due to the difference in composition and formation P−T conditions. Here we performed experiments at 1120−1140 °C and fO2 range of IW −1.2 to IW+3.3 (IW, iron-wüstite buffer) on a synthesized CE-5 whole rock (WR) composition and calibrated oxybarometers (olivine/melt and spinel/melt V and plagioclase/melt Eu partitioning) pertinent to the CE-5 lunar basalt. Applying the calibrated oxybarometers to CE-5 basalt, we estimated the fO2 of the CE-5 basalt to be
, which is generally more oxidized than most lunar basalts. To further investigate the cause for the high fO2 of CE-5 basalt, we performed crystallization modeling of the lunar magma ocean. The results reveal that the lunar mantle is stratified with Fe3+/FeT and fO2, with the shallower regions being more oxidized, suggesting that the oxidized nature of CE-5 basalt likely induced by the involvement of oxidized shallow mantle reservoirs. Moreover, the results found a unified framework to explain the large fO2 variation in lunar samples.

^1,2Alexander A. NEMCHIN,³Marc D. NORMAN,⁴Martin J. WHITEHOUSE,⁵Evgenia SALIN,²Nicholas E. TIMMS,⁶Tao LONG,⁶Xiaochao CHE,⁷Renaud MERLE,²Fred JOURDAN,⁸Tao LUO
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70103]
¹School of Earth Sciences and Engineering, Nanjing University, Nanjing, China
²Space Science and Technology Centre, School of Earth and Planetary Sciences, Curtin University, Perth, Western Australia,Australia
³Research School of Earth Sciences, The Australian National University, Canberra, Australian Capital Territory, Australia
⁴Department of Geosciences, Swedish Museum of Natural History, Stockholm, Sweden
⁵Department of Geology and Mineralogy, ˚Abo Akademi University, Turku, Finland
⁶Beijing SHRIMP Center, Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China
⁷Department of Earth Sciences, Uppsala University, Uppsala, Sweden
⁸State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan, China
Published by arrangement with John Wiley & Sons

Rapidly quenched droplets of pyroclastically erupted lava are common in lunar regolith at landing sites proximal to the maria. Here, we document the U-Pb chronologies, major element, and trace element compositions of picritic glassy particles from Apollo 17 regolith sample 76501. These particles are dominated by high-Ti compositions similar to those of the established Apollo 17 orange and black pyroclastic deposits, but the textures of some beads indicate slower cooling and/or equilibration at lower temperatures. Using a new approach to calibrate SIMS U-Pb isotopic analysis of vitrophyric beads, we show that their U-Pb ages are consistent with a single or closely timed multiple eruptions ~50–100 Ma younger than the 3752 ± 9 to 3758 ± 12 Ma crystalline mare basalts collected at this site. A few picritic beads with very low-Ti compositions may be younger, but their ages are not well defined and can be ~3.3–3.6 Ga.

¹Sophie Benaroya,¹Christopher D. K. Herd,¹David T. Flannery,¹Nicolas Randazzo
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70104]
¹Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, Canada
²School of Earth and Atmospheric Sciences, Queensland University of Technology, Brisbane, Queensland, Australia
Published by arrangement with John Wiley & Sons

Mars Sample Return (MSR) is expected to transform planetary science by providingunprecedented access to pristine Martian material. Initial characterization in the samplereceiving facility (SRF) will rely on nondestructive techniques such as X-ray computedtomography (XCT) to document the condition, distribution, and internal features of sealedcore samples. To test XCT protocols in advance of MSR, we analyzed terrestrial analog corescollected during the Pilbara Sample Return campaign in Western Australia. Sedimentary andregolith samples were scanned at both whole-core and fragment scales to evaluate scan times,optimal energy conditions, and resolution limits. Our results demonstrate that XCT offerscritical insights into fragment size distributions, internal banding, porosity, and fracturenetworks before sample opening, information that is essential for subsampling and preservingastrobiologically relevant textures. Integration with Raman spectroscopy, optical microscopy,and EPMA confirmed that XCT reliably identifies high-attenuation (high-l) phases (e.g.,oxides, sulfides) but cannot distinguish between common silicates, underscoring the need formulti-modal characterization. We also demonstrate how XCT data sets can be used to tracksample mass, restore fragment orientation, and potentially reconstruct stratigraphic context.Updated sample mass estimates indicate that the MSR collection is sufficient to meetcommunity science objectives, with required masses (12–15 g per core) well below expectedreturns. These results highlight XCT as a cornerstone of SRF pre-basic characterization,providing both immediate triage value and a foundation for long-term digital curation.

^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.