¹Yasuhiro Oba et al. (>10)
Geochimica et Cosmochimica Acta (in Press) Link to Article [10.1016/j.gca.2026.06.040]
¹Institute of Low Temperature Science (ILTS), Hokkaido University, N19W8, Kita-ku, Sapporo, Hokkaido 060-0819, Japan
Copyright Elsevier

Carbonaceous meteorites preserve organic records of early Solar System chemistry, yet nucleobase inventories remain difficult to interpret owing to potential terrestrial contamination and parent–body processing effects. Here we report high–resolution liquid chromatography/Orbitrap mass spectrometry analyses of purine and pyrimidine bases in six Antarctic carbonaceous meteorites (CM: Y–791198, A–12236, Y–793321, B–7904; CR: A–881828, Y–002540) using rigorously controlled extractions (hot water and 20% HCl treatments) performed in ISO–class clean environments, together with Antarctic ice as an environmental blank. All five canonical nucleobases were identified in Y–791198, A–12236, and A–881828; subsets were found in Y–793321 and Y–002540; and none were detected in B–7904 or in the ice meltwater/hydrolysate. These patterns, coupled with the thermal metamorphic history of B–7904, indicate no detectable incorporation of nucleobases from Antarctic ice during ∼ 105–year residence. Total pyrimidines correlate positively with NH3 across Antarctic meteorites and previously reported extraterrestrial samples, whereas purines do not, implicating NH3-facilitated pyrimidine formation and the involvement of additional precursors (e.g., cyanides) in purine synthesis. Cytosine is systematically depleted relative to other canonical bases, likely reflecting its low–temperature hydrolysis to uracil; leaching losses appear negligible as highly water-soluble species (e.g., hydroxypyrimidines and NH3) are retained within the meteorites. Our results establish Antarctic meteorites as some of the least contaminated materials for constraining nucleobase distributions and underscore the need for direct cyanide measurements to resolve purine formation pathways.

¹Yuki Masuda, ²Yoshiaki Shiraishi, ²Tetsuya Yokoyama, ³Tsuyoshi Iizuka, ¹Martin Schiller, ¹Martin Bizzarro
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [10.1016/j.gca.2026.07.004]
¹Centre for Star and Planet Formation, Globe Institute, University of Copenhagen, Øster Voldgade 5-7, 1350 Copenhagen, Denmark
²Department of Earth and Planetary Sciences, Institute of Science Tokyo, Meguro, Tokyo 152-8551, Japan
³Department of Earth and Planetary Science, University of Tokyo, Hongo 7-3-1, Bunkyo, Tokyo 113-0033, Japan
Copyright Elsevier

Chondrules are high-temperature products formed in the protoplanetary disk and are ubiquitous components of undifferentiated extraterrestrial materials. Nucleosynthetic isotope anomalies preserved in chondrules provide a valuable record of isotopic evolution of solids from presolar dust to the accretion of planets. Among various types of chondrules, Al-rich chondrules (ARCs) possess intermediate isotopic and chemical compositions between calcium-aluminum-rich inclusions (CAIs) and ferromagnesian chondrules (FMCs), providing insights into mixing processes of various materials formed in different regions and/or at different times in the protoplanetary disk. This study performed analyses of the abundances of 54 elements and multi-elemental isotopic compositions of Ca-Ti-Cr-Sr on fourteen ARCs extracted from four Vigarano-type chondrites (CVs). Their element abundance patterns demonstrate enrichments reaching up to 10 times of Ivuna-type carbonaceous chondrites (CIs) in refractory elements and depletions down to < 0.05 × CI in volatile elements. Eight ARCs show highly fractionated rare-earth-elements (REEs) signatures, while six ARCs display flat REE patterns. These features suggest that CV ARCs have recycled refractory inclusions, including fine-grained CAIs (FG-CAIs) and other REE-unfractionated types, in addition to less-refractory components with chondritic or matrix-like compositions similar to those contributing to FMCs. The Ca, Ti, and Sr isotopic compositions of the ARCs exhibit variations ranging from those of non-carbonaceous chondrite (NC) components to coarse-grained CAIs (CG-CAIs) and FG-CAIs. The observed isotopic compositions are not consistent with a simple mixture of NC with a single type of refractory inclusion, suggesting that they contain various types of refractory materials. The Cr isotopic compositions of CV ARCs are intermediate between those of NCs and CIs. The observed isotopic variation indicates that components of NC, CI, and refractory inclusions coexisted in the CV chondrule-forming region. This is in contrast to NC chondrule-forming regions, which do not exhibit isotopic anomalies characteristic of refractory inclusions. The significant difference in the degree of CAI signatures between OC ARCs and CV ARCs suggests that CAIs were trapped between the accretion regions of NC and CC parent bodies, leading to an isotopic dichotomy based on the presence or absence of isotopically anomalous CAIs. Meanwhile, fine dust grains with NC or CI isotopic compositions, which are smaller in size than CAIs, were distributed extensively in NC and CC accretion regions, resulting in continuous variations in chondrule isotopic composition.

^1,2C. Deligny,¹M. J. Whitehouse,³R. E. Merle,¹H. Jeon,^4,5A. A. Nemchin,⁶B. L. Jolliff
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70204]
¹Department of Geosciences, Swedish Museum of Natural History, Stockholm, Sweden
²School of Physical Sciences, The Open University, Milton Keynes, UK
³Department of Earth Sciences, Uppsala University, Uppsala, Sweden
⁴School of Earth and Planetary Sciences, Curtin University, Perth, Australia
⁵School of Earth Sciences and Engineering, Nanjing University, Nanjing, China
⁶Department of Earth, Environmental, and Planetary Sciences and the McDonnell Center for the Space Sciences, WashingtonUniversity in St. Louis, St. Louis, Missouri, USA
Published by arrangement with John Wiley & Sons

Basaltic sample 12032,366-18 from the Apollo 12 landing site is distinct among basalts collected at this site, other Apollo landing sites, and lunar meteorites in terms of its age, bulk rock composition, and isotopic composition. We present new Pb isotopic data obtained by in situ Secondary Ion Mass Spectrometry on multiple mineral phases in 12032,366–18. These data yield a crystallization age of 3400 ± 16 Ma, older than other Apollo 12 basalts, which crystallized between ~3.1 and 3.3 Ga. The initial Pb isotopic composition plots slightly below the mixing line between KREEP (an incompatible-element-rich lunar reservoir enriched in K, rare Earth elements, and P) and a depleted lunar mantle reservoir with low-μ (μ = ²³⁸U/²⁰⁴Pb) value. The bulk composition is characterized by elevated incompatible trace element abundances, including high thorium (~7 ppm), relatively high FeO, and intermediate Ti contents, distinguishing it from other Apollo 12 and lunar basalts. Although it shares some affinities with Apollo KREEP basalts, its higher bulk rock Al₂O₃ content and the presence of olivine are more consistent with high-Al basalts. Together, 12032,366–18 is not indigenous to the Apollo 12 landing site but instead represents material transported from a distant source region, most plausibly within western Oceanus Procellarum, potentially linked to the Kepler impact crater region.

^1,2Jennika Greer,³Alexander M. Kling,^4,5,6Luke Daly,^7,8Dieter Isheim,^7,8David N. Seidman,³Michelle S. Thompson,^2,9Philipp R. Heck
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70196]
¹Division of Microstructure Physics, Chalmers University of Technology, Göteborg, Sweden
²Robert A. Pritzker Center for Meteoritics and Polar Studies, Negaunee Integrative Research Center, Field Museum of NaturalHistory, Chicago, Illinois, USA
³Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, Indiana, USA
⁴School of Geographical & Earth Sciences, University of Glasgow, Glasgow, UK
⁵Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, New South Wales, Australia
⁶Department of Materials, University of Oxford, Oxford, UK
⁷Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois, USA
⁸Northwestern University Center for Atom Probe Tomography, Northwestern University, Evanston, Illinois, USA
⁹Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois, USA
Published by arrangement with John Wile & Sons

Space weathering significantly alters the optical, chemical, and structural properties of lunar regolith at micro- and nanoscales; yet detailed nanoscale variability within individual soils remains underexplored. Here we apply transmission electron microscopy (TEM) and atom probe tomography to four mineral grains (olivine, ilmenite, and two agglutinitic grains) from mature Apollo 17 soil 79221, characterizing solar wind-induced damage, vesiculation, nanophase Fe formation, and volatile retention with nanometer resolution. Our analyses reveal pronounced heterogeneity in vesicle morphology, nanophase Fe abundance, and volatile content that varies with mineralogy and exposure history. Oxygen depletion near grain surfaces indicates sputtering effects. Beyond confirming nanoscale heterogeneity, our coordinated analyses resolve, by APT, the Fe-depleted halos around npFe0 in mature ilmenite that we previously documented with the same technique in submature Apollo 17 ilmenite. We identify impact-melt quench textures that contribute non-weathering npFe0 to agglutinitic grains, and find a thick damage rim with few npFe0 in Mg-rich olivine accumulates. TEM observations of elongated, linear vesicles aligned parallel to ilmenite blade margins within a bladed agglutinitic grain further suggest crystallographic rather than directional control of vesicles in ilmenite inclusions. We also establish that vesicles distort APT reconstructions and degas during field evaporation, complicating quantitative inventories of npFe0 and volatiles in space-weathered grains.

¹Chi Ma,^2,3Alan E. Rubin
American Mineralogist 111, 1186-1191 Link to Article [https://doi.org/10.2138/am-2025-10003]
¹Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, U.S.A.
²Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, California 90095, U.S.A.
³Maine Mineral & Gem Museum, 99 Main Street, P.O. Box 500, Bethel, Maine 04217, U.S.A.
Copyright: The Mineralogical Society of America

Colomeraite (IMA 2021-061), with an end-member formula NaTi³⁺Si₂O₆, is a new Na pyroxene identified in the Colomera IIE iron meteorite. Colomeraite occurs with albite and K-feldspar in a silicate inclusion. The mean chemical composition of type colomeraite by electron probe microanalysis is (wt%) SiO₂ 54.82, Ti₂O₃ 17.15, TiO₂ 5.58, NaO₂ 12.33, MgO 3.93, FeO 3.59, CaO 1.98, MnO 0.28, Al₂O₃ 0.24, Cr₂O₃ 0.13, K₂O 0.02, total 100.05, giving rise to an empirical formula of (Na_0.88Ca_0.08Mg_0.04)(⁠Mg_0.17Fe_0.11Mn_0.01Al_0.01)Si_2.01O₆, with Ti³⁺ and Ti⁴⁺ partitioned, based on stoichiometry. Colomeraite has the C2/c diopside-type structure with a = 9.70(1) Å, b = 8.88(1) Å, c = 5.30(1) Å, β = 106.8(1)°, V = 437(2) ų, and Z = 4, as revealed by electron backscatter diffraction. The calculated density using the measured composition is 3.36 g/cm³. Colomeraite is a high-pressure and high-temperature Na-Ti³⁺-pyroxene, probably formed from an alkali plagioclase-Ti-rich phase melt via impact mixing of metal and silicates under extremely reducing conditions. The mineral is named after the host meteorite “Colomera.”

^1,2,3Yiping Yang et al. (>10)
American Mineralogist 111, 1036-1045 Link to Article [https://doi.org/10.2138/am-2025-9674]
¹Key Laboratory for Deep Earth Processes and Strategic Mineral Resources, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
²Center for Advanced Planetary Science (CAPS), Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
³Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
Copyright: The Mineralogical Society of America

Mineral structures record the formation and evolution of the Earth-Moon system. Here we report the discovery of correlated disorder in a silicate mineral kuratite [ideal formula ], which cannot be well documented by classical crystallography, in breccia clasts from near and far sides of the Moon. We employed the advanced three-dimensional electron diffraction (3DED) method in combination with spherical aberration corrected transmission electron microscopy to thoroughly characterize its structural features. The results indicate that the kuratite, coexisting with dendritic pigeonite and ulvöspinel, displays intricate correlated disorder features. These are characterized by alternating arrangements of five correlated site pairs confined within a single disordered layer. The occurrence of a vitrified dendritic pigeonite with similar composition suggests that kuratite formed during the impact-induced melting-cooling processes. This finding shows consistency in impact-driven surface processes between the lunar near and far sides, while demonstrating the utility of advanced nanoscale crystallographic methods for decoding extraterrestrial mineral formation mechanisms.

¹Le Zhang et al. (>10)
Journal of Geophysical Research: Planets (in Press) Link to Article [https://doi.org/10.1029/2026JE009725]
¹State Key Laboratory of Deep Earth Processes and Resources, Guangzhou Institute of Geochemistry, Chinese Academy ofSciences, Guangzhou, China
Published by arrangement with John Wiley & Sons

The Moon’s crust is proposed to be composed of an anorthositic upper crust and a noritic lower crust. While the upper crust was the result of the floatation of plagioclase crystallized at the late-stage of lunar magma ocean (LMO), the petrogenesis of the lower crust is in debate. In this study, we found three high-MgO impact glasses in the Chang’e-6 lunar soil, one being troctolitic (P032) and other two being noritic (P133 and P138). A combination match suggests P133 and P138 likely originated from the Apollo basin’s peak ring, representing lower crust at Apollo basin. The high Mg# and rare earth element signatures of both glasses support a petrogenesis involving the assimilation of KREEP-bearing crust by partial melts derived from early mafic cumulates of the LMO. This study hence indicates that despite the predominant concentration of KREEP material on the lunar nearside, KREEP components are also locally present on the farside.

¹C. Wang,^1,2T. Usui,^3,4M. Melwani Daswani
Journal of Geophysical Research: Planets (in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009358]
¹Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Tokyo, Japan,
²Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Japan,
³The SETIInstitute, Mountain View, CA, USA,
⁴Earth‐Life Science Institute, Institute of Science Tokyo, Tokyo, Japan
Published by arrangement with John Wiley & Sons

Feldspar-rich rocks have increasingly been discovered on the martian surface. They may have been an important part of the ancient martian crust and may be related to Ca/Fe-rich carbonates (one of two types of carbonates on Mars and the other being Mg-rich carbonates), but compared to mafic rocks, their interaction with water on ancient Mars is poorly understood. We conducted 1-D thermochemical modeling to determine how mafic or feldspar-rich rock composition controls the products of aqueous alteration on ancient Mars, with a focus on carbonates, considering the effects of groundwater flow and alteration duration in low-temperature environments. Evaporation of the alteration fluid was also simulated. We found that protolith composition, fluid transport process, and duration of alteration together control the composition, abundance, and distribution of carbonates and other secondary minerals. A causal link may exist between feldspar-rich rocks and some Ca/Fe-carbonates on Mars: Dominantly Mg-rich carbonates form only from mafic protoliths, while Ca/Fe-carbonates can form from either a feldspar-rich protolith generally or from a mafic protolith with a short alteration process. Percolation of atmospheric CO2-equilibrated water also provides a mechanism to suppress surface carbonate formation, dissolve shallow subsurface carbonates, and bury them deeply underground. These idealized scenarios employ simplified assumptions (equilibrium precipitation, laboratory dissolution rates, and specified transport). Absolute timescales are uncertain, so we focus on robust qualitative controls. The simulations demonstrate that crustal heterogeneity can explain the observed dichotomy and that carbonate composition may indicate protolith composition where direct detection is difficult.

^1,2,3,4,5Yuhuan Yuan,^1,2,3,4Ke Wen,^1,2,3,4Yiping Yang,⁶Chaoqun Zhang,^1,2Xiaorong Qin,^1,2,3,4,5Jianxi Zhu,^1,2,3,4,5Hongping He,⁷Joseph W. Stucki
Journal of Geophysical Research: Planets (in Press) Link to Article [https://doi.org/10.1029/2026JE009683]
¹State Key Laboratory of Deep Earth Processes and Resources, Guangzhou Institute of Geochemistry, Chinese Academy ofSciences, Guangzhou, PR China,
²Guangdong Provincial Key Laboratory of Mineral Physics and Materials, GuangzhouInstitute of Geochemistry, Chinese Academy of Sciences, Guangzhou, PR China,
³Center for Advanced Planetary Science,Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, PR China,
⁴Guangdong Research Centerfor Strategic Metals and Green Utilization, Guangzhou, PR China,
⁵University of Chinese Academy of Sciences, Beijing,PR China,
⁶Key Laboratory of Deep Petroleum Intelligent Exploration and Development, Institute of Geology andGeophysics, Chinese Academy of Sciences, Beijing, PR China,
⁷Department of Natural Resources and EnvironmentalSciences, University of Illinois at Urbana–Champaign, Urbana, IL, USA
Published by arrangement with John Wiley & Sons

Nontronite, a Fe3+-rich smectite widely identified on Mars, serves as a key mineral indicator for reconstructing paleo-redox and paleo-aqueous environments. However, uncertainties in interpreting its spectral data hinder a precise understanding of its formation conditions and paleoenvironmental implications. To fill this gap, the present study investigated the controls of nontronite formation and its crystallographic-spectral relationships by synthesizing a series of Fe-Si-Al samples with varying Fe/Si molar ratios under hydrothermal conditions. Results demonstrated that crystalline nontronite forms exclusively within a Fe/Si molar ratio of 0.21–0.48 under the simulated alkaline conditions. Incorporation of Fe3+ into tetrahedral sites as [IV]Fe3+ reduced the tetrahedral-octahedral sheet mismatch, thereby enhancing the crystallinity of nontronite. This crystallographic evolution was systematically observed in Mid Infrared and Visible-Shortwave Infrared spectra: [IV]Fe3+ content negatively correlated with the Si-O vibration wavenumber (near 1,000 cm−1) but positively correlated with the 2Fe3+-OH band position (∼1,430 nm) and depth. Furthermore, band depths at ∼1,430 and ∼2,290 nm are robust proxies for the crystallinity of nontronite in the absence of byproducts. These findings constrain the formation of nontronite on Mars to oxidizing, alkaline subsurface hydrothermal environments during the early Noachian, which represents one of the possible pathways for nontronite formation. These results provide a refined framework for interpreting orbital and in situ spectral data, advancing the understanding of clay mineral formation and environmental evolution on Mars.

¹J. Shawcross,^2,3D. J. Adams,^3,4M. L. Wong,^1,5,6K. J. Smith,^1,7Y. L. Yung
Journal of Geopyhsical Research: Planets (in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009146]
¹Department of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
²Departmentof Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA
³NHFP Sagan Fellow, NASA HubbleFellowship Program, Space Telescope Science Institute, Baltimore, MD, USA
⁴Earth and Planets Laboratory, CarnegieInstitution for Science, Washington, DC, USA
⁵Department of Water Resources Management, Environmental EngineeringProgram, Central State University, Wilberforce, OH, USA
⁶Department of Planetary Sciences, The University of Arizona,Tucson, AZ, USA, 7NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
Published by arrangement with John Wiley & Sons

Noachian and early Hesperian Mars were likely warm and wet, with an atmosphere abundant in molecular nitrogen. The recent discovery of nitrate deposits in the Yellowknife Bay mudstones at Gale Crater confirm the existence of nitrogen oxides (NO_X) on Noachian Mars. The processes responsible for the production of these nitrates would fractionate nitrogen isotopes: nitrogen oxides will have different isotopic signatures depending on how they were formed—lightning, solar energetic particles (SEPs) and galactic cosmic rays, or photolysis. We used the Caltech–JPL 1D photochemical and transport model KINETICS to simulate nitrogen isotope fractionation in the formation of nitrogen oxide species. At the surface, where deposition occurs, we predict a depletion of δ¹⁵N = −0.845‰ relative to the isotopic composition of atmospheric N₂. Near 200 km altitude, photolysis contributes to positive fractionation. From 300 km to the top of the modeled atmosphere, mass fractionation in the negative direction becomes relevant and produces a depletion of ¹⁵N above 450 km relative to source N₂. Our study predicts a depletion of ¹⁵N in atmospherically derived NO_X relative to the assumed background ratio, which is critical knowledge for constraining the formation history of nitrate on Mars, and whether nitrogen isotopic fractionation could be used as a biosignature.