^1,2,3Xiao Tian Deng,^1,2Hong Yi Chen,³Yang Li,^1,2Jin Yu Zhang,^1,2Lan Fang Xie,³Si Zhe Zhao,⁴Zhuang Guo,⁵Chen Li⁶Kai Rui Tai
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70085]
¹Institution of Meteorites and Planetary Materials Research, Key Laboratory of Planetary Geological Evolution of Guangxi Provincial Universities, Guilin University of Technology, Guilin, China
²Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration, Guilin University of Technology, Guilin, China
³Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
⁴Department of Geology, Northwest University, Xi’an, China
⁵School of Engineering, Yunnan University, Kunming, China
⁶College of Earth and Planetary Sciences, Chengdu University of Technology, Chengdu, China
Published by arrangement with John Wiley & Sons

The Campo del Cielo iron meteorite (IAB-MG) provides a unique window into earlysolar system processes, particularly the formation and evolution of carbon phases innon-magmatic iron meteorites. In this study, we conducted a systematic nanostructuralinvestigation of three distinct graphite occurrences—cliftonite (type I), interstitial graphite(type II), and silicate-associated graphite (type III)—within a single meteorite sample. Using amulti-technique approach, including scanning and transmission electron microscopy, Ramanspectroscopy, X-ray diffraction, and electron probe microanalysis, we characterized theircrystallographic properties, crystallinity, crystallite size, and crystallization temperatures. Ourresults reveal that type III graphite exhibits the highest crystallinity and largest crystallite size(average La = 287.4 nm), with a peak crystallization temperature of 1112°C, while types Iand II show comparable nanostructural features and lower crystallization temperatures(991°C and 1013°C, respectively). These differences reflect a crystallization sequence fromsilicate-associated with metal-encapsulated graphite, consistent with formation inimpact-generated metallic melt pools. The absence of diamond or diaphite structures indicatespeak shock pressures below 100 GPa. Combined with mineral chemistry data indicating areduced, magnesium-rich silicate assemblage akin to CR chondrites, our findings support anorigin via impact melting on a partially differentiated, CR-like parent body. This workunderscores the role of localized, shock-induced thermal processing in shaping the carboninventory of primitive planetary bodies and provides a mineralogical framework forunderstanding the complex formation history of IAB iron meteorites.

¹Isabelle S. Mattia,¹Matthew J. Genge,²Martin D. Suttle
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70105]
¹Department of Earth Sciences, Imperial College London, London, UK
²School of Physical Sciences, The Open University, Milton Keynes, UK
Published by arrangement with John Wiley & Sons

Fossil micrometeorites (MMs) recovered from lithified sedimentary rocks, particularlyiron-rich (I-type) cosmic spherules (CSs) provide valuable insights into past dust-forming events.Their abundances, when combined with estimates of local sedimentation rates can be used toreconstruct the flux of extraterrestrial dust. However, their preservation in the geological recordis highly susceptible to postdepositional diagenetic processes, complicating their quantificationand past flux calculations. This study investigated lenticular calcitic concretions as potential sitesof enhanced preservation of fossil MMs. A total of 17–18 I-types (but no silicate dominatedspherules, S-types) were recovered from Cenomanian sediments within the Cretaceous ChalkSupergroup at Lulworth Cove, England. The I-types, identified by optical and SEM–EDXanalyses, exhibited typical dendritic textures and varying degrees of alteration, including mottledsurfaces and loss of Ni and Cr by leaching. Calcitic concretions yielded a comparableconcentration of I-types to the surrounding hosting marl, but due to the added carbonatecementation during their growth, preservation per original sediment volume was shown to beenhanced (potentially by up to ~60%). Calcitic concretions can therefore act asmicroenvironments that enhance fossil MM preservation by limiting complete dissolution andloss of I-types. To constrain possible diagenetic effects on fossil MM quantification, futurestudies should compare cosmic dust yields across multiple sites exposing the same targetedsedimentary horizon.

^1,2Lee, J.-E. et al. (>10)
Nature 649, 853-858 Link to Article [https://doi.org/10.1038/s41586-025-09939-3]
¹Department of Physics and Astronomy, Seoul National University, Seoul, Republic of Korea.
²SNU Astronomy Research Center, Seoul National University, Seoul, Republic of Korea

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

¹Heng-Ci Tian,¹Chi Zhang,²Wen-Jun Li,²Dingshuai Xue,²Jing Wang,¹Wei Yang,²Yan-Hong Liu,¹Yangting Lin,²Xian-Hua Li,²Fu-Yuan Wu
Proceedings of the National Academy of Sciences of the USA (PNAS) 123, e2515408123 Open Access Link to Article [https://doi.org/10.1073/pnas.2515408123]
¹Key Laboratory of Planetary Science and Frontier Technology, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
²State Key Laboratory of Lithospheric and Environmental Coevolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China

Recent studies suggest that the lunar farside experienced a magma ocean evolution similar to that of the nearside. Thus, the nearside-farside dichotomy, such as volcanism and crustal thickness, is likely related to the South Pole-Aitken (SPA) basin–forming impact. Although the noritic clasts found in Chang’e-6 (CE6) samples may originate from crustal remelting induced by the SPA impact, how (and whether) the lunar mantle was modified by this event remains unclear. Here, we present the first high-precision iron (Fe) and potassium (K) isotopic measurements of CE6 low-Ti basalts, revealing higher δ56Fe (0.13 to 0.21‰) and δ41K (0 to 0.09‰) in these basalts compared to their Apollo and Chang’e-5 (CE5) counterparts (δ56Fe: 0 to 0.11‰; δ41K: −0.29 to −0.04‰). The heavy Fe and K isotopic signatures are unlikely to be derived from cosmogenic effects or the addition of impactor-derived materials. Instead, the heavy Fe isotopes can be explained by partial melting and fractional crystallization processes. For K isotopes, however, the data require that the mantle source beneath the SPA basin had a heavier K isotopic composition than that of the nearside mantle, most likely resulting from evaporation caused by the SPA-forming impact. Our results thus provide robust evidence for significant impact-induced modification of the lunar mantle and demonstrate that large-scale impacts may have played a key role in creating lunar asymmetry.

¹Jeremy Brossier,¹Francesca Altieri,¹Maria Cristina De Sanctis,¹Alessandro Frigeri,¹Marco Ferrari,¹Simone De Angelis,¹Enrico Bruschini,¹Monica Rasmussen,¹Janko Trisic Ponce
Journal of Geophysical Research: Planets (in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009393]
¹Institute for Space Astrophysics and Planetology (IAPS), National Institute of Astrophysics (INAF), Rome, Italy
Published by arrangement with John Wiley & Sons

Extensive research over the past two decades has shown that early Mars likely had a warmer,wetter climate with widespread water activity. Ferromagnesian (Fe,Mg‐rich) clay deposits are compellingmarkers of these ancient environments, helping reconstruct Mars’ hydrologic evolution, assess past habitability,and guide future exploration. This study analyzes hyperspectral data from the Compact ReconnaissanceImaging Spectrometer for Mars (CRISM) aboard NASA’s Mars Reconnaissance Orbiter, focusing on regionsalong the Martian crustal dichotomy—where clay deposits occur at the boundary between the ancient southernhighlands and the younger northern lowlands. We systematically surveyed ∼1500 CRISM targeted observations(1–2.6 μm) to identify ferromagnesian clays, distinguish them from other hydrated minerals, and characterizecompositional differences between Fe‐ and Mg‐rich species using diagnostic absorptions around 1.4, 2.3, and2.4 μm. Results reveal spatial variations in clay mineralogy: Fe‐rich nontronites are prevalent around MawrthVallis, while Mg‐rich saponites are more locally distributed in Nili Fossae and Libya Montes. Oxia Planum—the Rosalind Franklin rover landing site—exhibits more compositionally intermediate clays such asvermiculites and ferrosaponites. These differences may reflect variations in the iron and magnesium abundanceor in the iron oxidation state. Moreover, a recurring absorption near 2.5 μm suggests co‐occurring carbonateslike magnesite and siderite, increasing the potential for biosignature preservation. These findings refine ourunderstanding of Mars’ aqueous history and offer an important mineralogical context for future rover andsample return missions. They also emphasize the need for a next‐generation orbital imaging spectrometer tosucceed CRISM and extend its legacy.

¹E. Dobrică,¹A. N. Krot,²A. J. Brearley
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70102]
¹Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Mānoa, Hawai‘i, USA
²Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico, USA
Published by arrangement with John Wiley & Sons

Returned regolith samples from the asteroid Itokawa provide a unique opportunity to compare shock metamorphic effects in unconsolidated regolith materials with those preserved in lithified meteorites, that is, megaregolith. We analyzed four Itokawa particles (Ueda—RA-QD02-0519, Narahara—RA-QD02-0573, Domon—RA-QD02-0588, Ishiuchi—RX-MD03-0212) containing phosphates (merrillite and apatite) to assess their impact history. To place these observations in context, we also describe the associated mineral assemblages (silicates and chromite). While both space weathering effects, irradiation and impact, are present, the primary focus of this study is on impact-related modifications. We identified microcratering with a density comparable to that measured for Murchison, rare comminution effects in subsurface regolith materials, localized melting and vaporization, and partial decomposition of chromite into a high-pressure Fe2Cr2O5 phase (modified ludwigite-type). The two apatite crystals analyzed lack any brittle deformation; however, one shows strong submicron-scale chlorine heterogeneity and porosity that are consistent with partial melting and volatile redistribution. In contrast, the two merrillite grains, identified in two different particles, contain dislocations. Their microstructures indicate distinct shock histories: one particle preserves only limited, localized deformation probably induced by micrometeoroid impacts, whereas the other shows extensive brittle deformation features consistent with a more pervasive shock event. The combination of ductile and brittle deformation, along with melting and comminution, reflects a more intense and spatially extensive shock metamorphic process. Dislocation densities are comparable to those observed in ordinary chondrites (OCs) of shock stage S2 (5–10 GPa). This study shows that phosphates in Itokawa regolith record highly localized and heterogeneous shock metamorphic overprints, in contrast to the more uniform relationship between shock metamorphic stage and phosphate deformation described in megaregolith OCs. Phosphates are sensitive shock metamorphic tracers in asteroidal regolith, but meteorite-based calibrations must be applied cautiously to unconsolidated materials.

¹B.G. Rider-Stokes, ¹F.A. Davies, ²T.H. Burbine, ³E. MacLennan, ¹R.C. Greenwood, ¹S.L. Jackson, ¹M. Anand, ⁴D. Sheikh, ¹M.M. Grady
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2026.116965]
¹School of Physical Sciences, The Open University, Milton Keynes MK7 6AA, UK.
²Department of Physics & Astronomy, Mount Holyoke College; 50 College Street, South Hadley, MA 01075, USA
³Department of Physics, University of Helsinki, Finland
⁴Department of Geology, Cascadia Meteorite Laboratory, Portland State University, USA
Copyright Elsevier

Brachinite meteorites are typically linked to the olivine-rich A-type asteroids. In this study, however, they appear to exhibit unexpected spectral diversity. Spectroscopic analysis of seven meteorites from the brachinite clan reveals two distinct populations in band parameters, overlapping with both the A-type and S-complex asteroids. This dual association shows that a single meteorite group can originate from multiple asteroid taxonomies. Notably, one S-complex-like specimen, Northwest Africa (NWA) 14,635, displays band parameters similar to those of asteroid (65803) Didymos, the target of the European Space Agency’s (ESA) ongoing Hera mission. These results underscore the value of spectroscopic characterization of poorly understood meteorite groups and identifying potential analogs that are highly relevant for current and future mission planning.

^1,2,3,4Wei Wu, ^2,3,4Yigang Xu, ⁵Zhaofeng Zhang
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2026.01.014]
¹School of Tourism and Geography, Shaoguan University, Shaoguan 512005 Guangdong, China
²State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 Guangdong, China
³Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), 511458 Guangdong, China
⁴School of Earth and Planetary Science, University of Chinese Academy of Sciences, Beijing 100049, China
⁵Research Center for Planetary Science, College of Geosciences, Chengdu University of Technology, Chengdu 610059 Sichuan, China
Copyright Elsevier

To constrain calcium isotopic fractionation during magma differentiation and its significance for planetary geochemistry, this study analyzed δ44/40Ca compositions of whole rocks, clinopyroxene, and plagioclase in mafic–ultramafic intrusions from two major large igneous provinces: the Tarim Large Igneous Province (Xiaohaizi intrusion) and the Emeishan Large Igneous Province (Panzhihua intrusion). Whole-rock δ44/40Ca ranges from 0.75 to 1.00 ‰ for Xiaohaizi and 0.82 to 0.97 ‰ for Panzhihua, while Pl δ44/40Ca varies from 0.69 to 1.07 ‰ (Xiaohaizi) and 0.78 to 0.99 ‰ (Panzhihua). Disequilibrium in selected samples is attributed to distinct geological processes: magma replenishment (Panzhihua) and crustal material assimilation (Xiaohaizi). For equilibrium samples, the Ca isotopic fractionation factor between Pl and melt (1000lnαPl-melt) exhibits no correlation with Pl An content and remains stable under specific temperature–pressure conditions for mafic to ultramafic plagioclase. By integrating this new dataset with published Δ44/40CaCpx-Pl data (including ab initio predictions and magmatic evolution model results), we determined 1000lnαPl-melt at 1273 K is −0.07 ± 0.10 ‰ (2SD, N = 28). This study clarifies the role of Pl in magmatic Ca isotopic fractionation, providing a reliable framework for tracing magma evolution and reconstructing early crust formation processes of terrestrial planets.

¹Jesse T. Gu, ¹Rebecca A. Fischer, ¹Lucy Jacobsen, ¹Michail I. Petaev
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2026.01.013]
¹Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA
Copyright Elsevier

Moderately volatile elements are depleted in the Earth relative to chondrites, but it remains uncertain to what extent these depletions of siderophile volatile elements are controlled by volatility versus core formation. Here, we report new metal–silicate partitioning experiments on Pb at pressures and temperatures up to 65 GPa and 5520 K, respectively. Combined with other moderately volatile elements, we use core formation models to show that homogeneous volatile accretion results in an overabundance of volatile siderophile elements relative to lithophile elements in the bulk Earth. Late volatile addition with metal–silicate equilibration at higher pressures and temperatures could potentially resolve this discrepancy by lowering bulk Earth abundances of volatile siderophile elements to be within uncertainty of the lithophile volatility trend. However, uncertainties in core formation parameters, element volatilities, volatile loss mechanisms, and the lithophile volatility trend complicate this interpretation. Our data support a relatively larger role for volatile depletion than for core formation in establishing the Pb content of the bulk silicate Earth.

^1,2Christopher A. Parendo, ¹Stein B. Jacobsen, ¹Michail I. Petaev
Earth and Planetary Science Letters 678, 119825 Link to Articles [https://doi.org/10.1016/j.epsl.2026.119825]
¹Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138, United Kingdom
²Department of Earth & Planetary Sciences, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208, USA
Copyright Elsevier

Calcium-aluminum-rich inclusions (CAIs), the oldest dated solids in the Solar System, preserve elemental and isotopic records of the thermal evolution of the early solar nebula—but some aspects, such as the processes driving large Ca-isotope variations, remain ambiguous. Previous studies observed isotopically light Ca in some CAIs, but whether these signatures arose from evaporation or condensation remains unresolved. We report new Ca-isotope and elemental data for 19 CAIs and 2 AOAs from the Allende meteorite and apply kinetic modeling to evaluate whether evaporation or condensation can account for the observed signatures. Our data confirm that CAIs exhibiting volatility-related REE fractionation have lighter Ca-isotope compositions than those with unfractionated REEs. Modeling demonstrates that evaporation cannot produce materials with both isotopically light Ca and near-chondritic Al/Ca ratios, requiring condensation as the cause of the observed Ca-isotope variations. Notably, modeled rates indicate that condensation occurred rapidly, over ∼10-1000 days, much faster than secular cooling of the solar nebula. These results constrain CAI thermal histories and offer insight into high-temperature processes in the early Solar System.