^1,2Elizabeth Bailey,²Myriam Telus,³Phoebe J. Lam,⁴Samuel M. Webb
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70001]
¹Department of Astronomy and Astrophysics, University of California Santa Cruz, Santa Cruz, California, USA
²Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, California, USA
³Department of Ocean Sciences, University of California Santa Cruz, Santa Cruz, California, USA
⁴Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California, USA
Published by arrangement with John Wiley & Sons

Multiple generations of calcite and dolomite precipitated in CM chondrites during ice melting events that led to episodes of liquid water. Models and laboratory analysis have suggested a long-term transition from oxidizing to reducing conditions during aqueous alteration on the CM parent body. We found that synchrotron X-ray absorption near edge spectroscopy (XANES) can detect relative differences in the oxidation state of trace iron within these carbonates. In CM chondrites, previous work interpreted Mn abundance in calcite as an indicator of relatively early or late formation, and dolomite is understood to form relatively late. In the CM1 chondrite Meteorite Hills 01070, XANES maps reveal that Mn-poor calcite contains more oxidized iron relative to Mn-rich calcite. While these measurements of carbonates support increasing iron reduction with progressive aqueous alteration in MET 01070, comparison among different CM chondrites suggests a complex picture of redox evolution. In addition to carbonates, we performed XANES measurements of the phyllosilicate-rich matrix of Allan Hills 83,100. Pre-edge centroid analysis indicates that this CM1/2 has an oxidation state similar to typical CM2 chondrites. While additional measurements are warranted to confirm the full span of redox trends in CM carbonates, our data do not support a correlation between redox state and petrologic type.

^1,2Rachel Y. Sheppard, ³Jessica M. Weber, ⁴Laura E. Rodriguez, ³Cathy Trejo, ⁵Elisabeth M. Hausrath, ³Laura M. Barge
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2025.116769]
¹Planetary Science Institute, Tucson, AZ, USA
²Institut d’Astrophysique Spatiale, Université Paris-Saclay, CNRS, Orsay, France
³NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
⁴Lunar and Planetary Institute/USRA, Houston, TX, USA
⁵University of Nevada Las Vegas, Las Vegas, NV, USA
Copyright Elsevier

The high mobility of Li allows it to be used as a tracer for groundwater processes, recording past aqueous conditions. On Earth, a relationship has been noted in multiple field sites between clay mineral abundances and elevated Li in bedrock. Observations from the Curiosity MSL mission at Gale crater on Mars showed a high-clay mineral and high-Li area near the Vera Rubin ridge (VRR) and Glen Torridon region, suggesting Li was perhaps substituting into clay minerals as was seen in these terrestrial field settings. However, the process of this substitution has not been examined in the laboratory using non-field samples, especially not with Mars-relevant mineralogy. To investigate this open question in the laboratory using Mars-relevant regolith and clay minerals, we conducted continuous flow packed-bed reactor experiments to test whether clay minerals affect the Li concentration of Mars regolith simulant MGS-1 during aqueous alteration. The mechanism for Li sorption was also investigated by conducting experiments with clays mixed with glass beads and investigating changes in other elements alongside Li via laser-induced breakdown spectroscopy (LIBS). We tested four dioctahedral clay minerals (kaolinite, illite, nontronite, mixed layer illite/smectite) and two trioctahedral clay minerals (talc, saponite) and found that both talc and illite are capable of increasing the amount of Li sorbed compared to MGS-1 simulant when exposed to Li-bearing groundwater. For MGS-1, the glass beads, and the clay minerals (talc, illite) the primary mechanism appears to be Li substitution for Mg, Al, and K, respectively. This has implications for ongoing Mars missions as well as astrobiology, specifically relating to understanding habitability of areas on Mars and identifying aqueous environments for future mission concepts.

¹Siyu Li, ^1,2Yingnan Zhang, ^1,2Ziwei Wang, ^1,2Bing Yang, ^1,2Liping Qin
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.08.006]
¹Deep Space Exploration Laboratory/State Key Laboratory of Lithospheric and Environmental Coevolution, University of Science and Technology of China, Hefei 230026, China
²CAS Center for Excellence in Comparative Planetology, Hefei 230026, China
Copyright Elsevier

Space weathering alters the chemical and isotopic compositions of the lunar surface, potentially obscuring insights into the formation and evolution of the Moon and terrestrial planets. The contribution of micrometeorite bombardment to the space weathering process, however, is poorly understood. In this study, the Ni isotopic composition of the Chang’e-5 regolith from different depths of a drilling core was studied to examine both the meteoritic addition and evaporation within the local regolith. The Chang’e-5 lunar drill core samples exhibit significantly elevated Ni abundances and higher δ60Ni values (0.54–1.06 ‰) compared to lunar basalt samples (0.18 ± 0.01 ‰), indicating preferential loss of isotopically light Ni due to impact-induced evaporation of high-Ni-content impactors. Notably, the δ60Ni values decrease significantly with depth, while Ni content remains unchanged, suggesting that continuous micrometeorite bombardment, rather than simple mixing of evaporated impactor material, is responsible for the observed Ni isotopic fractionation. Based on the Ni/Co and the Ni isotopic compositions, we estimate that the primary micrometeorite impactors at the Chang’e-5 site are chondritic, contributing ∼1–2 wt% of the regolith, while ∼10–30 % of the Ni from the impactors was evaporated under near-saturated conditions. This process preferentially enriches the upper regolith in heavier Ni isotopes during more extensive micrometeorite bombardment, supporting continuous space weathering processes in relatively young regolith at the Chang’e-5 landing site. These findings not only highlight the long-term effects of micrometeorite-impact-induced degassing during the space weathering on the lunar surface but also provide new insights into regolith gardening and the progressive surface modification of airless planetary bodies.

¹Hikaru Hyuga,¹Yuichiro Cho,¹Yayoi N. Miura,¹Takashi Mikouchi,^1,2Seiji Sugita
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70022]
¹Department of Earth and Planetary Science, University of Tokyo, Bunkyo, Japan
²Planetary Exploration Research Center, Chiba Institute of Technology, Narashino, Japan
Published by arrangement with John Wiley & Sons

Dating rocks with a 2σ precision of 200 Ma is required to understand the history of Martian habitability and volcanic activity since ~4000 Ma. In situ K-Ar dating using a spot-by-spot laser ablation technique has been developed for isochron dating on Mars. The precision of isochron ages is determined mainly by the relationship between the laser spot diameter and the grain size of the sample. However, the achievable precision of age estimates using a realistic mineralogy of Martian rocks has yet to be investigated. We simulated isochrons under various conditions, including different laser spot sizes, K and Ar measurement errors, and numbers of analyses based on the mineral abundances of representative Martian meteorites (NWA 817, Zagami, and NWA 1068) analyzed using an electron probe microanalyzer. We found that attaining a precision of 200 Ma necessitates an isochron data range, defined as the ratio of the maximum to minimum K concentrations, of >6, a laser spot diameter of 250 μm, and measurement errors of <10% for both K and Ar. Reducing the laser spot size and selecting a sample with a large grain size are effective in obtaining a large K range. Furthermore, minimizing the variance in measurement errors between K and Ar is essential to increase the accuracy of the age estimates. We demonstrate that the precision required for in situ dating on Mars is achievable with realistic instrument settings, thus demonstrating the feasibility of establishing an in situ K-Ar geochronology for Mars.

¹Mohammad Tauseef,¹Ingo Leya,²Beda Hofmann
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70029]
¹Space Research and Planetary Sciences, Physics Institute, University of Bern, Bern, Switzerland
²Natural History Museum Bern, Bern, Switzerland
Published by arrangement with John Wiley & Sons

We present isotope concentrations of the light noble gases He and Ne for samples from five well-documented strewnfields and two individual meteorites from the Omani desert. Cosmogenic (22Ne/21Ne)cos for the strewnfield samples are low, as expected considering the total known masses. A (22Ne/21Ne)cos of 1.210 for the LL6 chondrite RaS 267 from Oman indicates a small pre-atmospheric size of less than 10 cm. The CRE ages for the Omani meteorites calculated using 21Necos range from 1 to 20 Ma. Using the (22Ne/21Ne)cos and previously established correlations, new shielding-corrected 14C and 14C-10Be terrestrial ages are calculated. For the strewnfield samples, the new ages are similar to the earlier ages but are more consistent. The new terrestrial age for RaS 267 is more than 20% lower than the previous age. Motivated by this success, we reinvestigated meteorites from other hot deserts (Acfer, Adrar, and Nullarbor regions) and Antarctica using literature data for 14C and (22Ne/21Ne)cos, along with the newly established correlations between 14C production rates and (22Ne/21Ne)cos. For these meteorites, the new terrestrial ages are systematically younger than the ages calculated earlier using a shielding-independent approach. Using shielding-corrected 14C terrestrial ages, the long-term puzzling problem that there is a lack of meteorites with short terrestrial ages disappears. The new histogram, though with only a limited number of data, shows the expected decrease in the number of meteorites with increasing terrestrial age. Therefore, the unexpected shape in the terrestrial age histogram was most likely due to a bias in the 14C dating system, that is, ages of small meteorites are overestimated.

¹Pascal M. Kruttasch,¹Klaus Mezger
Science Advances 11, eadw1280 Open Access Link to Article [DOI: 10.1126/sciadv.adw12]
¹Institut für Geologie, Universität Bern, 3012 Bern, Switzerland.

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

^1,2,3Laura Noel García,^4,5Péter Némenth,⁶Ronan Henry,⁷Robert Luther,^1,2Maria Eugenia Varela
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70024]
¹Instituto de Ciencias Astronómicas, de la Tierra y del Espacio, Universidad Nacional de San Juan, CONICET, San Juan, Argentina
²Instituto y Museo de Ciencias Naturales, Universidad Nacional de San Juan, San Juan, Argentina
³Instituto de Mecánica Aplicada, Universidad Nacional de San Juan, San Juan, Argentina
⁴Institute for Geological and Geochemical Research, HUN-REN Research Centre for Astronomy and Earth Sciences (MTA Centre of Excellence), Budapest, Hungary
⁵Research Institute of Biomolecular and Chemical Engineering, University of Pannonia, Veszprém, Hungary
⁶Groupe de Physique des Matériaux, UMR CNRS 6634, Saint Etienne du Rouvray, France
⁷Museum für Naturkunde Berlin-Leibniz Institute for Evolution and Biodiversity Science, Berlin, Germany
Published by arrangement with John Wiley & Sons

Cliftonites, polycrystalline aggregates of graphite with unusual cuboid morphology, are important carbon components of certain iron meteorites. Although they consist predominantly of sp2-bonded carbon, recent studies suggest that those from the Canyon Diablo (IAB) meteorite also include composite sp2- and sp3-bonded structures, named diaphites. Here, we investigate the nanostructure of cliftonites in a Campo del Cielo specimen and demonstrate that these cliftonites also contain a nanocomposite mixture of well-ordered 3R graphite regions interfingered with type 1 diaphite structure, consisting of <01–10> projected graphite and <011> projected diamond domains. This finding suggests that certain pieces of the Campo del Cielo meteorite experienced moderate shock pressures (>~10 GPa), which exceed the 4–10 GPa pressure range previously reported for the main meteorite. We propose that a portion of Campo del Cielo cliftonites provides evidence for the shock-induced diamondization of graphite and the “projectile decapitation” process during terrestrial impact. The complexity of the initial carbonaceous material, combined with the wide range of pressures encountered during terrestrial impact events, may explain the diversity of nanostructures in the Campo del Cielo and Canyon Diablo cliftonites. Our findings could assist in the development of a pressure/shock classification system for characterizing impact events in graphite-bearing meteorites.

^1,2,3Haiyang Xian et al. (>10)
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.epsl.2025.119556]
¹State Key Laboratory of Deep Earth Processes and Resources, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China
²Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China
³Center for Advanced Planetary Science (CAPS), Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China
Copyright Elsevier

Recent discoveries regarding oxidized materials on the moon have challenged the traditional belief that the moon is highly reduced. The oxidized materials occur in either crystalline minerals or glasses, and the complex occurrence makes the origin of these oxidized lunar materials still unclear. Here we report a highly oxidized impact melt clast retrieved by Chang’e 6 mission from the South Pole-Aitken (SPA) basin. The impact melt clast hosts a high content of ferric iron (Fe³⁺) in matrix pigeonite with an Fe³⁺/∑Fe ratio of 0.44 ± 0.06, while xenocryst pyroxene only contains ferrous (Fe²⁺) iron. The observed high Fe³⁺ content indicates that the oxidation state of the local impact clast is even more oxidized than that of Earth’s mantle. The widespread presence of non-spherical Fe-Ni alloy nanoparticles in the impact melt clast suggests that the oxidized materials may have been delivered to the moon by meteorite. These findings reveal an external source of oxidized materials on the moon, emphasizing the potential role of meteoritic materials in the redox cycling of the lunar surface.

¹Zhengyang Wu, ¹Chang Pu, ¹Xiujin Gao, ¹Jinfeng Li, ²Zhixue Du, ¹Zhicheng Jing
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.07.024]
¹Department of Earth and Space Sciences, Southern University of Science and Technology, Shenzhen 518055, China
²State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
Copyright Elsevier

Gallium (Ga) and germanium (Ge) are moderately siderophile and volatile elements whose metal-silicate partitioning behaviors are valuable to understand both core-formation and volatile accretion processes. In this study, we performed metal-silicate partitioning experiments at pressures of 22–70 GPa and temperatures of 3728–4740 K, using laser-heated diamond anvil cells, to explore the effects of pressure, temperature, and metal composition on Ga and Ge partitioning. Thermodynamic modeling using our experimental data and those from the literature reveals that the metal affinities of both Ga and Ge decrease as pressure and temperature increase, with Ga being less siderophile than Ge. Our fitting results confirm that the presence of S and Si in metal can reduce the siderophility of both Ga and Ge, consistent with previous findings at relatively low pressures and temperatures. Our results also demonstrate that O in metal has opposing effects on the metal-silicate partitioning of Ga and Ge. It increases the metal affinity of Ga, contrary to previous thought, but decreases that of Ge. Incorporating these partitioning behaviors, we performed multi-stage core formation modeling to search for accretion scenarios and factors that can reproduce the bulk silicate Earth abundances of Ga, Ge, and S. Our results suggest that Ga and Ge were likely accreted throughout the entire stages of Earth’s accretion rather than accreted solely in the late stage for the final 10–20 % of Earth’s mass growth.

¹Krämer Ruggiu Lisa, ²Villeneuve Johan, ³Da Silva Anne-Christine, ⁴Debaille Vinciane, ⁵Decrée Sophie, ⁶Lutz Hecht, ⁶Felix E.D. Kaufmann, ¹Goderis Steven
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2025.07.016]
¹Archaeology, Environmental Changes & Geo-Chemistry, Vrije Universiteit Brussel, Brussels, Belgium
²CRPG, CNRS, Université de Lorraine, UMR 7358, Vandoeuvre-lès-Nancy 54501, France
³SediCClim Laboratory, Geology Department, Liège University, Liège, Belgium
⁴Laboratoire G-Time, Université Libre de Bruxelles, Brussels, Belgium
⁵Institute of Natural Sciences, Geological Survey of Belgium, Brussels, Belgium
⁶Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstrasse 43, Berlin 10115, Germany
Copyright Elsevier

A total of 1222 Micrometeorites (MMs) from the late Devonian period were extracted from 26 kg of carbonates host rock fragments from the Chanxhe section in Belgium, from the Latest Famennian around 360 Myr, through magnetic separation and optical picking following dissolution with mild HCl, making it one of the largest fossil MMs collection, the largest from the late Devonian. The collection shows a wide diversity of texture, comparable to modern day collection but with different distribution. The majority of the MMs were I-type (90 %), with G-type particles constituting 6 % and S-type particles at 1 %. Some of the S-types spherules are amongst the first silicate-type spherules, and amongst the most well-preserved in terms of texture and composition, to be described in fossil MMs collections. Additionally, intermediate type G/I representing <1 % of the sample are introduced for future fossil MMs classification. Distinguishing extraterrestrial (ET) MMs from terrestrial spherules is challenging due to weathering effects that modify both texture and composition during long residency time on Earth. The Na2O + K2O versus Fe/Si ratio plot is used for distinguishing ET from terrestrial spherules. Using textural and compositional data in combination creates a reliable ET spherule identification. I-type spherules show significant terrestrial alteration with notable loss of Ni and Cr, also observed in S-type spherules, with their silicate phases recrystallized in palagonite. G-type spherules display a mix of characteristics from I-type and S-type MMs. The study also highlights the presence of smaller spherules (<125 µm) compared to modern micrometeorites (210–330 µm), attributed to the predominance of I- and G-type spherules and long-term dissolution effects. Despite some alteration for some spherules, due diagenesis of the sedimentary host rocks, the collection shows extremely well-preserved spherules, with even some oxygen isotopes signature being preserved. Indeed, triple oxygen isotope analysis reveals that 5.8 % of the particles are related to ordinary chondrites (OC) and 33 % to carbonaceous chondrites (CCs), yielding a CC/OC ratio of approximately 5.6, with comparable distribution for all major types. Also, 9 % of I- and G/I-types are OC-related. Most I-type spherules likely originate from CM, CR, or H chondrites, with some possibly from iron meteorites. The findings suggest that the source materials of the ET flux have remained relatively consistent over the past 360 Myr, providing insights into historical Solar System events and Earth’s environmental changes and extends the study of ET flux to Earth to CC compared to meteorites. In addition, combined with chemical and isotopic proxies and chrome spinel, the fossil MMs could assess the complete flux of cosmic dust to Earth. Finally, the use of fossil MMs could represent potential proxies for paleo-atmospheric oxygen levels and CO2 contents.