Conor J. Benson, Daniel J. Scheeres

Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2025.116794]
University of Colorado Boulder, 3775 Discovery Drive, Boulder, CO 80303, USA
Copyright Elsevier

I.W. Iqbal¹, J.W. Head III^b, L. Wueller^a, H. Hiesinger^a, C.H. van der Bogert^a, D.R. Scott^b,c

Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2025.116791]
^aInstitut für Planetologie, Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
^bDepartment of Earth, Environmental and Planetary Sciences, Brown University, Providence, RI 02912, USA
^aApollo 15 Commander, USA
Copyright Elsevier

Eloy PENA-ASENSIO^1,2, Denis VIDA^3,4, Ingrid CNOSSEN⁵ , and Esteban FERRER²
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70046]
¹Department of Geosciences, University of Arizona Geosciences, Tucson, Arizona, USA
²School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, USA
³Lawrence Livermore National Laboratory, Livermore, California, US
Published by arrangement with John Wiley & Sons

Climate change is inducing a global atmospheric contraction above the tropopause (~10 km), leading to systematic decrease in neutral air density. The impact of climate change on small meteoroids has already been observed over the last two decades, with documented shifts in their ablation altitudes in the mesosphere (~50–85 km) and lower thermosphere (~85–120 km). This study evaluates the potential effect of these changes on meteorite-dropping fireballs, which typically penetrate the stratosphere (~10–50 km). As a case study, we simulate the atmospheric entry of the fragile Winchcombe carbonaceous chondrite under projected atmospheric conditions for the year 2100 assuming a moderate future emission scenario. Using a semi-empirical fragmentation and ablation model, we compare the meteoroid’s light curve and deceleration under present and future atmospheric density profiles. The results indicate a modest variation of the ablation heights, with the catastrophic fragmentation occurring 300 m lower and the luminous flight terminating 190 m higher. The absolute magnitude peak remains unchanged, but the fireball would appear 0.5 dimmer above ~120 km. The surviving meteorite mass is reduced by only 0.1 g. Our findings indicate that century-scale variations in atmospheric density caused by climate change moderately influence bright fireballs and have a minimal impact on meteorite survival.

Isaiah SPRING¹, Ananya MALLIK¹, Jason KIRK¹, Pranabendu MOITRA¹, Richard HERVIG², and Lars BORG³
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70047]
¹Department of Geosciences, University of Arizona Geosciences, Tucson, Arizona, USA
²School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, USA
³Lawrence Livermore National Laboratory, Livermore, California, US
Published by arrangement with John Wiley & Sons

We used trace element analyses of plagioclase from Mg-suite troctolite 76535 to estimate the Rare Earth Element (REE) concentrations of its parental liquid and assess the feasibility of an urKREEP contribution to the Mg-suite parental liquid. We measured 33 trace elements in 76535 plagioclase separates. Our measurements revealed enrichments in incompatible elements consistent with previous analyses. Using the measured REE concentrations, we estimated the REE concentrations of the unfractionated Mg-suite parental liquid using a RhyoliteMELTS-based forward model. Compared to chondritic concentrations, the Mg-suite parental liquid is ~100 times more enriched in light REEs and ~10 times more enriched in heavy REEs. We sought to explore the feasibility of reproducing these enrichments in the parental liquid through assimilation of urKREEP by a partial melt of rising LMO cumulates during cumulate mantle overturn. We show that these enrichments can be reproduced by a 30%–50% addition of fully molten urKREEP to the LMO cumulate melt, if the LMO cumulate melt and urKREEP are in thermal equilibrium with each other. However, the Mg# of these mixtures (57–68) is too low to produce the most Mg-rich olivine (Fo 91) observed in Mg-suite troctolites. Alternatively, assuming that the LMO cumulate melt and urKREEP are in thermal disequilibrium, we reproduced both the REE abundances and Mg# of the Mg-suite parental liquid with only a 10% addition of the urKREEP partial melt. These results support the feasibility of urKREEP assimilation as a mechanism for generating the incompatible element enrichments in Mg-suite magmas while preserving their major element chemistry.

A. N. KROT¹, K. NAGASHIMA¹ , S. EBERT², M. I. PETAEV³, C. MA⁴, J. HAN⁵, and T. L. DUNN⁶
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70044]
¹Hawai’i Institute of Geophysics & Planetology, School of Ocean and Earth Science and Technology, University of Hawai‘i at
Manoa, Honolulu, Hawaii, USA
²Institut für Planetologie, University of Münster, Münster, Germany
³Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts, USA
⁴Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
⁵Amentum, NASA Johnson Space Center, Houston, Texas, USA
¹6Department of Geology, Colby College, Waterville, Maine, USA
Published by arrangement with John Wiley & Sons

We report on the mineralogy, petrography, and oxygen and aluminum-magnesium isotopic systematics of the corundum-bearing Ca,Al-rich inclusions (CAIs) from the CK3 (Karoonda-type) carbonaceous chondrites NWA (Northwest Africa) 4964-#1 and -Homer, NWA 5343-#1, and LAR (Larkman Nunatak) 12002-#1. These CAIs experienced extensive metasomatic alteration: melilite and possibly anorthite and AlTi-diopside are nearly completely replaced by secondary corundum, grossular, CaNa-plagioclase, FeAl-diopside, and FeO-rich spinel; perovskite is largely replaced by ilmenite. Two types of corundum grains occur in the NWA 4964 CAIs: (1) compact, FeO-poor grains zoned in cathodoluminescent (CL) images and (2) FeO-bearing (up to 1.5 wt% FeO), porous grains showing no detectable CL; the porous corundum grains overgrow the compact ones. Corundum grains in CAIs from LAR 12002 and NWA 5343 belong to the first and second types, respectively. Hibonite, primary spinel, and rare perovskite inclusions in spinel retained the original, ¹⁶O-rich compositions (Δ¹⁷O ~ −24 ± 2‰), whereas melilite, most perovskite grains, and secondary corundum and spinel are ¹⁶O-depleted (Δ¹⁷O ~ −5 ± 2‰). Hibonite and melilite have excesses of radiogenic ²⁶Mg (²⁶Mg*) corresponding to approximately the canonical initial ²⁶Al/²⁷Al ratio [(²⁶Al/²⁷Al)₀] of ~5 × 10⁻⁵ suggesting that corundum-bearing CAIs studied belong to a population of the canonical inclusions, dominant in most chondrite groups. Corundum grains in LAR 12002-#1, NWA 4964-#1, NWA 4964-Homer, and NWA 5343-#1 show resolvable ²⁶Mg* correlated with ²⁷Al/²⁴Mg ratio which corresponds to much lower than the canonical (²⁶Al/²⁷Al)₀: (3.10 ± 0.48) × 10⁻⁶, (3.03 ± 0.23) × 10⁻⁶, (2.72 ± 0.19) × 10⁻⁶, and (3.5 ± 1.2) × 10⁻⁷, respectively. Porous Fe-bearing corundum grains in NWA 4964 CAIs Homer and #1 have low ²⁶Mg* not correlated with ²⁷Al/²⁴Mg ratio. We conclude that compact corundum grains in the CK3 CAIs studied are secondary parent body products that resulted from metasomatic alteration of the host inclusions by hydrothermal fluid ~3−5 Ma after their crystallization. Porous corundum grains may have formed by dehydration of diaspore [AlO(OH)] during subsequent thermal metamorphism.

Le ZHANG¹ et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70048]
¹State Key Laboratory of Deep Earth Processes and Resources, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China
Published by arrangement with John Wiley & Sons

This study presents a comprehensive analysis of the mineralogical, geochemical properties, and in situ Sr-Nd-Pb isotopic systematics of a newly discovered unbrecciated lunar basaltic meteorite NWA 14526 (NWA refers to northwest Africa). Bulk composition derived through both mineral modes and impact melt vein classifies NWA 14526 as a low-Ti, low-Al, and low-K mare basalt. In situ Pb isotopic analyses define a Pb–Pb isochron yielding an age of 3009 ± 43 Ma, representing the meteorite’s crystallization age. In situ Rb-Sr isotopic analyses of plagioclase and maskelynite provide an initial ⁸⁷Sr/⁸⁶Sr ratio of 0.69969 ± 0.00024 (2σ), while phosphate and mesostasis in situ Sm-Nd analyses yield an initial εNd value of +10.7 ± 2.1 (2σ). Although NWA 14526 shares comparable mineralogical, bulk-rock composition, and Sr isotopic characteristics with contemporaneous lunar basaltic meteorites (NWA 4734, LAP 02205, NWA 14137, and NWA 10597), its significantly elevated εNd values preclude genetic pairing with these specimens. Isotopic modeling indicates minimal KREEP component contribution (<0.5%) in its mantle source. Our compilation of lunar Sr-Nd isotopic data reveals two distinct evolutionary trends corresponding to depleted lunar mantle and urKREEP reservoirs, respectively. Notably, no temporal correlation between basalt source KREEP enrichment and eruption age is observed, suggesting that the KREEP component did not necessarily play a decisive role in driving late-stage lunar magmatism and volcanism.

George D. Cody^a, et al. (>10)

Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.09.009]
^aEarth and Planets Laboratory, Carnegie Science, Washington, DC, United States
Copyright Elsevier

We present the first investigation into the molecular structure of organic solids (insoluble organic matter, IOM) in samples of the carbonaceous asteroid (101955) Bennu returned by the OSIRIS-REx mission. We used ¹H and ¹³C solid-sate nuclear magnetic resonance (ssNMR) to analyze three subsamples of aggregate Bennu material. However, the IOM isolated from two of the three subsamples exhibited substantial magnetic inhomogeneity, due to contaminant magnetic grains. The resulting magnetic interference degraded NMR signals for both ¹H and ¹³C and likely introduced spectral distortions. The third subsample was pretreated with 6 N HCl prior to IOM isolation and exhibited minimal (i.e., typical) magnetic interference. In this subsample’s IOM, we find a very low fraction of aromatic carbon, and a high fraction of aliphatic hydrogen, relative to IOM from Bennu’s closest meteoritic analogs, the petrologic type 1 and 2 carbonaceous chondrites. Elemental analysis–isotope ratio mass spectrometry (EA-IRMS) further reveals a high H/C × 100 atomic values, relative to type 1 and 2 chondritic IOM. These data indicate that Bennu’s organic solids, at least in this aggregate sample, suffered minimal to no molecular evolution from thermal perturbation throughout this material’s long history—starting with accretion of a planetesimal, followed by disruption and gravitational reassembly to form a rubble-pile asteroid, and ultimately migration from the Main Belt to a near-Earth orbit. The state of molecular evolution recorded in IOM places a strong constraint on the magnitude of temperature and pressure derived from impact events that yielded the rubble-pile asteroid Bennu.

Laura KOTOMAA¹, Markku VÄISÄNEN² , Jussi S. HEINONEN^1,3, Ermei MÄKILÄ⁴ ,Hugh O’BRIEN⁵, and Arto PELTOLA²
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70049]
¹Geology and Mineralogy, Abo Akademi University, Turku, Finland
²Department of Geography and Geology, University of Turku, Turku, Finland
³Department of Geosciences and Geography, University of Helsinki, Helsinki, Finland
⁴Department of Physics and Astronomy, University of Turku, Turku, Finland
⁵Geological Survey, of Finland, Espoo, Finland
Published by arrangement with John Wiley & Sons

Löpönvaara is a rare new phosphorus-rich iron meteorite find from Löpönvaara, Finland. The ~164 g meteorite was discovered in 2017 from the same area as the ungrouped Lieksa pallasite. Löpönvaara was classified as an ungrouped iron meteorite due to its unusually high concentration of P (>4 wt%), coupled with a moderate concentration of Ni (~11 wt%), and Ga–Ge abundances in the “III” range. The meteorite consists of ~75 vol% kamacite and ~22 vol% schreibersite, with accessory troilite (<0.1 vol%), and minor terrestrial weathering products. The kamacite in Löpönvaara occurs as three different types: (1) rare, large 2–5 mm partially resorbed clasts; (2) round, ≤0.5 mm partially resorbed clasts; and (3) small, several tens of μm to sub-μm exsolution blebs and globules in the matrix. Schreibersite occurs solely as microscopic matrix material in between the type (1) and (2) kamacite clasts. The lack of taenite and the overall compositional and textural features of Löpönvaara suggest that it retained its composition possibly from a P-rich portion of immiscible melt at late stages of fractional crystallization, but its textural features suggest that the meteorite suffered impact-related metamorphism. The meteorite has no close textural or compositional affinities, which makes it unique and an important target for future studies.

Rei KANEMARU¹ et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70045]
¹Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), Sagamihara, Kanagawa, Japan
Published by arrangement with John Wiley & Sons

Silica polymorphs in meteorites provide critical constraints on crystallization processes associated with thermal activity in the early solar system. A detailed investigation of silica polymorphs in eucrites (the largest group of achondrites) using cathodoluminescence imaging and laser-Raman spectroscopy revealed significant variations in the relative abundance of silica polymorphs. Based on these variations, the eucrites were divided into four “Si-groups” according to their dominant silica phase: Si-0 (cristobalite-dominant eucrites), Si-I (quartz-dominant eucrites), Si-II (quartz and tridymite-dominant eucrites), and Si-III (tridymite-dominant eucrites). In studied eucrites, tridymite and cristobalite form lathy euhedral shapes, while quartz is anhedral, coexistent with opaques and phosphates, suggesting that silica polymorphs were crystallized from different stages and formation processes. We propose a new model that explains the formation pathways of silica minerals in eucrites and accounts for the distinct formation histories represented by each Si-group: tridymite crystallizes from alkali-rich immiscible melts (starting at ≥ ~1060°C), cristobalite crystallizes from quenched melts (~1060°C), and quartz crystallizes from extremely differentiated melts and/or by solid-state transformation from tridymite and cristobalite through interactions with sulfur-rich vapor below ~1025°C. This model explains the occurrences of silica polymorphs in eucrites without requiring secondary heating or shock processes.

Megan Broussard^a, Mason Neuman^a, Piers Koefoed^a, Frédéric Moynier^b, Nicole X. Nie^c, Richard V. Morris^d, Bradley L. Jolliff^a, Kun Wang^a

Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.09.004]
^aDepartment of Earth, Environmental, and Planetary Sciences and the McDonnell Center for the Space Sciences, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130, USA
^bUniversité Paris Cité, Institut de Physique du Globe de Paris, CNRS, UMR 7154, F-75005 Paris, France
^cDepartment of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
^dAstromaterials Research and Exploration Science Division, NASA Johnson Space Center, Houston, TX 77058, USA
Copyright Elsevier

As a part of the Apollo Next Generation Sample Analysis Program, we report the Cu and Zn isotopes in the Apollo 17 regolith core, double-drive tube 73001/2. The intervals in the upper core, which sampled the regolith closest to the lunar surface, are enriched in heavy Cu and Zn isotopes compared to the deeper intervals. The top 2 cm have a δ⁶⁵Cu value of 2.85 ± 0.01 ‰ and a δ⁶⁶Zn value of 5.54 ± 0.02 ‰. The intervals become lighter in isotopic composition to a depth of 8 cm. Below this depth, the average δ⁶⁵Cu is 1.02 ± 0.08 ‰, while the average δ⁶⁶Zn is 2.27 ± 0.24 ‰. We find strong correlations between the isotopic fractionations of Cu and Zn and the maturity index I_S/FeO. These correlations in the core result from a binary mixing between highly space-weathered soil at the lunar surface and deeper, shielded soil, with isotopic fractionation occurring at the surface due to space weathering and soil mixing occurring due to impact gardening. Using the K, Fe, Cu, and Zn isotopes measured in 73001/2, we find a strong correlation between the degree of isotope fractionation and volatility. We model the isotopic fractionation of K, Fe, Cu, and Zn by space weathering in lunar soils using mass balance equations between the lunar atmosphere and lunar soil and find agreement with the fractionation observed in 73001/2. Using the fractionation observed in 73001/2, we present a new exposure age model using Cu isotope fractionation in lunar soils.