¹Nicolas Dauphas,¹Zhe J. Zhang,¹Xi Chen,²Mélanie Barboni,^3,4Dawid Szymanowski,⁴Blair Schoene,⁵Ingo Leya,⁶Kevin D. McKeegan
Proceedings of the National Academy of Sciences (PNAS) 122, e2413802121 Link to Article [https://doi.org/10.1073/pnas.2413802121]
¹Origins Laboratory, Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, Chicago, IL 60637
²School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85281
³Institute of Geochemistry and Petrology, ETH Zurich, Zurich 8092, Switzerland
⁴Department of Geosciences, Princeton University, Princeton, NJ 08544
⁵Space Sciences and Planetology, University of Bern, Bern 3012, Switzerland
⁶Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, CA 90095

Crystallization of the lunar magma ocean yielded a chemically unique liquid residuum named KREEP. This component is expressed as a large patch on the near side of the Moon and a possible smaller patch in the northwest portion of the Moon’s South Pole-Aitken basin on the far side. Thermal models estimate that the crystallization of the lunar magma ocean (LMO) could have spanned from 10 and 200 My, while studies of radioactive decay systems have yielded inconsistent ages for the completion of LMO crystallization covering over 160 My. Here, we show that the Moon achieved >99% crystallization at 4,429 ± 76 Ma, indicating a lunar formation age of ~4,450 Ma or possibly older. Using the 176Lu–176Hf decay system (t1/2 = 37 Gy), we found that the initial 176Hf/177Hf ratios of lunar zircons with varied U–Pb ages are consistent with their crystallization from a KREEP-rich reservoir with a consistently low 176Lu/177Hf ratio of 0.0167 that emerged ~140 My after solar system formation. The previously proposed younger model age of ~4.33 Ga for the source of mare basalts (240 My after solar system formation) might reflect the timing of a large impact. Our results demonstrate that lunar magma ocean crystallization took place while the Moon was still battered by planetary embryos and planetesimals leftover from the main stage of planetary accretion. The study of Lu–Hf model ages for samples brought back from the South Pole-Aitken basin will help to assess the lateral continuity of KREEP and further understand its significance in the early history of the Moon.

¹Sandrine Péron, ¹Sujoy Mukhopadhyay
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2025.01.002]
¹Department of Earth and Planetary Sciences, University of California, Davis, Davis, CA 95616, USA
Copyright Elsevier

Accretion of volatile elements is a critical step to make a planet habitable. It is often assumed that terrestrial planets initially captured solar gases from the nebula, which are partially ingassed into their interior during the magma ocean phase, and then chondritic and/or cometary volatiles are delivered during the main accretion phase or after. Recent krypton isotopic measurements of the Martian meteorite Chassigny have however shown that chondritic volatiles were acquired on Mars in the first Myr of Solar System formation before nebular capture. Yet, Martian mantle is heterogeneous, with multiple reservoirs as evidenced with the hydrogen isotopic composition of shergottites, and it is unclear if this is also the case for noble gases. In this study, we investigate the noble gas (Ne, Ar, Kr, Xe) isotopic and elemental composition of the chassignite NWA 8694, which constitutes a link between chassignites and nakhlites, via laser step-heating in order to assess potential heterogeneities of the Martian mantle. Similar to Chassigny, we found evidence for high Ar, Kr and Xe abundances, potentially at least one order of magnitude higher than in the Earth’s mantle, in the NWA 8694 mantle source based on a low 40Ar/36Ar ratio. We also found a chondritic component and a Martian atmospheric component in NWA 8694, the latter with fractionated Ar/Kr/Xe elemental ratios compared to Mars’ atmosphere. This Martian atmosphere component was possibly introduced through aqueous alteration by surface fluids, as observed in MIL nakhlites. The chondritic component corresponds to the composition of the NWA 8694 mantle source and hence confirms previous observation in Chassigny. A chondritic Martian mantle is in stark contrast with the presence of solar Kr and Xe in the Martian atmosphere. This suggests that chondritic volatiles were delivered to terrestrial planets in the first Myr of Solar System formation in presence of the nebula. Solar gases in the atmosphere could have been captured from the nebula afterwards or delivered by material similar to comets. If captured from the nebula, it would require the solar gases to be trapped either in polar ice caps or the regolith so as not to be lost via hydrodynamic escape after the nebula dissipates. Alternatively, delivery of solar gases associated with comets could occur after cessation of hydrodynamic escape on Mars, but the one comet (67P/C-G) that has been measured so far does not show a pure solar-like Xe and Kr isotopic composition.

¹Jiawen Zhao, ¹Koichi Mimura
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2025.01.003]
¹Department of Earth and Environmental Sciences, Graduate School of Environmental Studies, Nagoya University, Nagoya 464-8601, Japan
Copyright Elsevier

The abiotic supply of phospholipid precursors on the early Earth constitutes a critical stage in cellular evolution. Glycerophosphate (GP) and acylglycerol (AG) are potential precursors to the bonding of polar heads and lipidic chains attached to the glycerol backbone in phospholipids. A deeper understanding of the synthesis of GP and AG on early Earth is essential for unraveling the origin of life. In this study, we performed shock experiments to simulate the impact of extraterrestrial bodies on both wet and dry surfaces of early Earth to investigate the synthesis of GP and AG. These experiments were conducted in the temperature transition zone between negligible alteration and complete decomposition of organic materials. Despite GP and AG synthesis involving dehydration, our experiments revealed they can synthesize under both wet and dry conditions by impact shock. This suggests that the process occurs universally in both wet and dry environments and presents a feasible pathway for phosphorylation and acylation on the early Earth. Moreover, the crater created by the impact may evolve into “warm little ponds” that collect the synthesized GP and AG for further evolution. The dry-wet cycles in the ponds not only facilitate the assembly of vesicles but also provide opportunities for further evolution. Our findings indicate that impacts from extraterrestrial bodies may have contributed to cellular evolution by supplying phospholipid precursors on the early Earth.

¹Glenn J. MacPherson, ²Alexander N. Krot, ²Kazuhide Nagashima, ³Marina Ivanova
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.01.001]
¹US National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560, USA
²Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu, HI 96822, USA
³Vernadsky Institute, Kosygin St. 19, Moscow 119991, Russia
Copyright Elsevier

Refractory inclusions formed via high temperature events during the earliest stages of the solar system evolution. Studies of short-lived radionuclide systems in the inclusions provide constraints on the timing and nature of these thermal events. High-precision SIMS data for initial 26Al/27Al ratio [(26Al/27Al)0] in a suite of seven un-melted refractory inclusions (fine-grained spinel-rich and Fluffy Type A CAIs) from CV (Vigarano type) carbonaceous chondrites – which we interpret as primary nebular condensates or their very close derivatives – yield six values close to the canonical ratio of 5.2 × 10−5 and one marginally lower but still almost within error of 5.0 × 10–5. We specifically looked for but did not find much lower values like those reported recently by Kawasaki et al. (2020), as low as 3.4 × 10–5. Interpreted in terms of chronology, the accumulated high precision data acquired by us and others within the past 15 years for normal, 26Al-rich CAIs show no evidence for a significant condensation event that would correspond to (26Al/27Al)0 of (3–4) × 10–5. Rather, there appears to have been one major thermal event resulting in extensive evaporation and condensation in the CAI-forming region corresponding to (26Al/27Al)0 of 5.2 × 10–5 resulting in formation of most normal refractory inclusion precursors. Subsequent smaller events over the succeeding ∼200,000 years caused thermal modification and melting of many of them. Inclusions such as that studied by Kawasaki et al. (2020) could have formed either in an early event prior to significant isotopic mixing in the CAI-forming region, or later than most refractory inclusions during a thermal event that is not well represented in the meteorite record. Refractory inclusions characterized by low (26Al/27Al)0, < 1 × 10–5, such as FUN (Fractionation and Unidentified Nuclear effects) inclusions, PLACs (Platy Hibonite Crystals), and some corundum-, hibonite-, and grossite-rich CAIs formed during a much earlier heating event, likely prior to homogenization of 26Al in the early solar system. The initial 26Al/27Al values of such objects provide no quantitative chronological constraints.

¹M. Mijjum,²B. J. Andrews,²T. J. McCoy,²C. M. Corrigan,^1,3M. W. Caffee,¹M. M. Tremblay
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14309]
¹Department of Earth, Atmospheric and Planetary Sciences, Purdue University, West Lafayette, Indiana, USA
²Department of Mineral Sciences, Smithsonian National Museum of Natural History, Washington, DC, USA
³Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana, USA
Published by arrangement with John Wiley & Sons

Cosmic ray exposure (CRE) ages provide information about the parent bodies and source regions of meteorite classes. Cosmogenic noble gases are often used to quantify exposure time scales ranging from tens of ka to hundreds of Ma. The production rate of cosmogenic noble gases is primarily controlled by a meteorite’s chemical composition. Historically, an average chemical composition for an entire meteorite class or subgroup was used to calculate production rates. At the scale needed for noble gas measurements, however, some meteorites exhibit mineral abundance variabilities that translate into chemical heterogeneities, necessitating subsample-specific production rates. We find that the metal and sulfide content can vary significantly between ~100 and 300 mg subsamples of the same enstatite (E) chondrite, leading to >10% differences in cosmogenic 21Ne production rates between subsamples. We demonstrate an approach to determining subsample-specific production rates using E chondrites. We use electron microprobe analysis and X-ray computed microtomography to quantify the chemical composition and abundances, respectively, of metal, sulfide, and silicate minerals in six E chondrites and calculate subsample-specific production rates of 3He and 21Ne. By applying this method to more E chondrite subsamples alongside noble gas measurements, we may begin to address broader questions, such as whether peaks in the E chondrite CRE age distribution can be attributed to distinct impact events.

¹Carine Sadaka,¹Jérôme Gattacceca,²Matthieu Gounelle,²Mathieu Roskosz,^1,3,4Anthony Lagain,⁵Romain Tartese,⁶Lydie Bonal,¹Clara Maurel,⁷Rodrigo Martinez,^8,9Millarca Valenzuela
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14307]
¹Aix-Marseille Université, CNRS, IRD, INRAE, CEREGE, Aix-en-Provence, France
²Muséum National d’Histoire Naturelle, Institut de minéralogie, de physique des matériaux et de cosmochimie—UMR7590, Paris, France
³Aix-Marseille Université, Institut ORIGINES, Marseille, France
⁴Space Science and Technology Centre, School of Earth and Planetary Sciences, Curtin University, Perth, Western Australia, Australia
⁵Department of Earth and Environmental Sciences, The University of Manchester, Manchester, UK
⁶Institut de Planétologie et d’Astrophysique, Université Grenoble Alpes, Grenoble, France
⁷Museo del Meteorito, San Pedro de Atacama, Chile
⁸Universidad Católica del Norte, Antofagasta, Chile
⁹Center of Astrophysics and Associated Technologies CATA, Santiago, Chile
Published by arrangement with John Wiley & Sons

We present the outcome of search campaigns conducted in the Catalina Dense Collection area (DCA) located in the central depression of the Atacama Desert, Chile. The “Catalina Systematic Collection” (CSC) was assembled through systematic on-foot searches, resulting in a total of 1599 meteorites, before pairing, collected over a surface of 6.80 km2. This yielded a recovery density of 235 meteorites per km2 (67 meteorites >20 g per km2), making it the densest among hot deserts, even higher than the neighboring El Médano DCA collection. This confirms that the central depression of the Atacama Desert holds the highest meteorite density among hot deserts. We classified 457 meteorites weighing more than 20 g. After correcting for various recovery biases, we estimated a true meteorite density on the ground of 131 meteorites per km2 for meteorites >20 g before pairing. Using a probabilistic approach, we calculated an average pairing likelihood, yielding 71 meteorites >20 g per km2 after pairing. This high density is likely linked to an old age of the CSC, which would also explain the absence of carbonaceous chondrites, as they are more prone to alteration by abrasion. This long meteorite accumulation period is related to the long-term hyper-aridity and surface stability of the Atacama Desert, which have persisted for several million years. Meteorites from the CSC show less chemical weathering on average than in other hot deserts, despite the long accumulation period. The H/L ratio in the CSC is higher than in meteorites from other hot deserts, Antarctica, and falls, but similar to the El Médano collection, potentially reflecting variations in the composition of the meteorite flux over the past Myr.

^1,2G.K. Indu et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14308]
¹Department of Geology, University of Kerala, Thiruvananthapuram, Kerala, India
²University College, Thiruvananthapuram, Kerala, India
Published by arrangement with John Wiley & Sons

Luna is a potential impact crater located in the Banni Plains of the Kutch Basin in western India. The suspected impactites, collected from a 1-m deep trench near the vicinity of the Luna structure, possess a range of physical (porosity and magnetism) properties. Petrographic studies reveal that these impactites are dominated by wüstite, kirschsteinite, spinel, olivine, and quartz (in decreasing order of abundance), with a few silica grains exhibiting potential planar fractures (PF). These impactites can be grouped into three distinct melt classes based on their wüstite and kirschsteinite content (classified as Ca-rich, Ca-poor, and transitional type). Spectroscopic analysis indicates a higher concentration of wüstite in magnetic samples, whereas weakly magnetic to non-magnetic samples have an elevated presence of kirschsteinite. Major oxide geochemistry comparison between the impactites and the surrounding Banni Plain sediments show that some Luna impactites have a chemical affinity with a terrestrial or transitional setting, whereas the remaining samples portray a non-terrestrial trend suggesting notable mixing of target rock and projectile material. Optically stimulated luminescence dating of the sediment layer containing the impactites yielded an age of 4045 ± 182 years for the impact, consistent with the earlier proposed age of <6900 years based on radiocarbon dating. The revised age places the Luna impact event much closer to the time frame of the Harappan Civilization’s decline, suggesting that it may have had a greater impact on the Harappan Civilization than previously thought.

^1,2Y. Li,^1,2P. J. A. McCausland,^1,2R. L. Flemming,^1,2G. R. Osinski
Meteoritics & Planetary Society (in Press) Link to Article [https://doi.org/10.1111/maps.14301]
¹Department of Earth Sciences, Western University, London, Ontario, Canada
²Institute for Earth and Space Exploration, Western University, London, Ontario, Canada
Published by arrangement with John Wiley & Sons

Lunar impact breccia meteorites contain clasts from unknown lunar regions, including areas not studied by past missions. These meteorites offer a unique opportunity to expand our knowledge of the Moon’s crustal and mantle composition and processes. The recently classified lunar meteorite Northwest Africa (NWA) 11515 is a moderately shocked feldspathic breccia with anorthite plagioclase and mafic minerals. In this work, we report the shock history of lithic clasts using 2-D micro-X-ray diffraction, detailed mineralogy from micro-X-ray fluorescence, and electron probe microanalysis. NWA 11515 shows moderately shocked anorthite and highly shocked olivine and pyroxene. The plagioclase composition is invariant (An96.4 ± 0.7, n = 52), with variable mafic clasts overlapping Mg- and FAN-suite lithologies (Mg# 84.5 to 45.6 for olivine; Mg# 85.6 to 32.2 for pyroxene), similar to KREEP-depleted troctolites in Allan Hills A81005. Spinel-group oxides vary from aluminous spinel to chromite and ulvöspinel. We also observed slow-cooled augite Ca-poor pyroxene exsolution clasts and fast-quenched fine-grained anorthite–olivine co-crystallized clasts (<5 μm), indicating different cooling histories. Combining petrological observations with published geochemical data, we show NWA 11515 has the mixed lithology of ferroan anorthosites with KREEP-poor magnesian rock fragments. With shock analysis, the materials are likely from a crater with minimum size of 7 km. Finally, we examined the published geochemical data for other lunar meteorites and hypothesize that other typical feldspathic breccias could contain magnesian clasts, suggesting the subdivision of typical feldspathic breccia into magnesian clast-hosting breccia and ferroan feldspathic breccia. This implies that non-KREEP magnesian magmatism might be more widespread in the post-LMO era on lunar highlands.

¹P. Ghaznavi,²C. Burkhardt,³F. L. H. Tissot,¹I. Leya
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14300]
¹Space Science and Planetology, Physics Institute, University of Bern, Bern, Switzerland
²Max-Planck Institut für Sonnensystemforschung, Göttingen, Germany
³Division of Geological and Planetary Sciences, The Isotoparium, Caltech, Pasadena, California, USA
Published by arrangement with John Wiley & Sons

Calcium-aluminum-rich inclusions (CAIs) are the first objects that formed in the solar accretion disk and therefore provide valuable insights into the evolution of the early solar system. A long-standing question regarding this earliest formative period relates to the storage of CAIs in the 1–4 Myr time period between their formation and later accretion into chondrite parent bodies. Were the CAIs stored in a pre-existing parent body, or in distant parts of the solar accretion disk? In the latter scenario, CAIs might have been exposed to cosmic rays, either from the galaxy or from the Sun and such pre-accretion irradiation effects might be detectable. We searched for such pre-accretional irradiation effects in 7 fine- and 11 coarse-grained CAIs from the CV 3.6 carbonaceous chondrite Allende. The extracted samples were analyzed for their major chemical composition and all samples were analyzed using μCT techniques. Using physical model calculations, ²¹Ne_cos and (²²Ne/²¹Ne)_cos production rate ratios were calculated for each CAI by fully considering their individual chemical composition. Measured He, Ne, Ar, and Kr isotope compositions of the CAIs show cosmogenic signals; clear signals for He and Ne isotopes; and detectable signals for some of the Ar and Kr isotopes. In addition, most samples show clear indications for radiogenic ⁴He and some samples show evidence for radiogenic ⁴⁰Ar. Higher ³⁶Ar/³⁸Ar, ²²Ne/²¹Ne, ⁸⁰Kr/⁸⁴Kr, and ⁸²Kr/⁸⁴Kr ratios together with lower cosmogenic ³⁸Ar_cos concentrations in fine-grained CAIs compared to coarse-grained CAIs are consistent with more alteration of the former compared to the latter. The CRE ages for the CAIs range between 4.12 ± 0.41 Myr and 6.40 ± 0.63 Myr. Statistical tests indicate that the data are normally distributed with no outliers, indicating that all CAIs share a common irradiation history, likely the irradiation in the Allende meteoroid. The average CRE age of 4.87 ± 0.19 Myr agrees with the nominally accepted CRE age of Allende of ~5.2 Myr. There is no correlation between ²¹Ne_cos concentrations and indicators of aqueous alteration like Na and/or U concentrations. The lack of correlation together with the finding of normally distributed modeled CRE ages indicates that either none of the studied CAIs experienced a pre-accretion irradiation before parent body compaction and/or that any pre-accretion irradiation effects have been completely erased during aqueous alteration events. Taking alteration aside, the findings are not in favor of X-wind type models but are more consistent with the idea of CAI outward transport in an expanding disk.

¹Pietro Demattê Avona,¹Alvaro Penteado Crósta,²Marcos Alberto Rodrigues Vasconcelos,^3,4Evan Bjonnes,¹Fernando Lessa Pereira,⁵Ana Maria Góes
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14306]
¹Institute of Geosciences, Universidade Estadual de Campinas, Campinas, SP, Brazil
²Institute of Geosciences, Federal University of Bahia, Salvador, BA, Brazil
³Lawrence Livermore National Laboratory, Livermore, CA, USA
⁴Lunar and Planetary Institute, Houston, TX, USA
⁵Institute of Geosciences, University of São Paulo, São Paulo, SP, Brazil
Published by arrangement with John Wiley & Sons

Nova Colinas, centered at 07°09′33″ S/46°06′30″ W, is the ninth confirmed complex impact structure in Brazil and the fifth in the Parnaíba Basin, with a diameter of ~6.5–7 km and a nearly circular shape. Impactites include shocked siltstones from the Pedra de Fogo Fm. found at the central peak, brecciated sandstone from the Sambaíba Fm. bearing microscopic shock features, and brecciated basalt from the Mosquito Fm. bearing shatter cones. The impact event’s age has been constrained to the interval from ~130 to ~199 Ma based on the local stratigraphy. Due to its moderate to advanced stage of erosion, geophysical modeling combined with geological field data were employed for its characterization. A new geological map was produced through field observations and remote sensing image interpretation, as well as a 3-D model based on ground gravity data and numerical modeling. iSALE2D shock physics code was employed to simulate the formation of Nova Colinas crater. The results revealed its main structural zones: the central uplift, annular basin, and outer rim, each associated with specific lithostratigraphic units from the Parnaíba Basin. Bouguer residual anomalies ranged from −3.6 to 1.2 mGal, with a nearly circular positive anomaly at the center of the structure, surrounded by a negative anomaly. 3-D gravity data inversion indicated a buried high-density body, likely due to the uplift of a diabase sill. Results of the numerical modeling point out that the final crater reached gravitational stability with a diameter of ~7 km and a depth of ~240 m, suggesting that a narrow outcrop strip of the Motuca Fm. was uplifted to a higher level compared to the Sambaíba Fm. strata, forming an antiform-like “arch” that creates an inner ring that exposes rocks of the Motuca Formation.