¹Axel Wittmann,²Christian R. Kroemer,³Meenakshi Wadhwa,³Thomas G. Sharp,³Matthijs Van Soest,⁴Trevor Martin,⁴Tyler Goepfert
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14311]
¹Eyring Materials Center, Arizona State University, Tempe, Arizona, USA
²Earth and Planetary Sciences Department, University of California, Davis, California, USA
³School of Earth & Space Exploration, Arizona State University, Tempe, Arizona, USA
⁴Metals, Environmental and Terrestrial Analytical Laboratory, Arizona State University, Tempe, Arizona, USA
Published by arrangement with John Wiley & Sons

We studied lunar regolith breccia meteorite Northwest Africa (NWA) 13967 to explore its mineral and clast inventory with special focus on the ubiquitous occurrence of tissintite-II, a newly recognized, vacancy-rich high-pressure clinopyroxene with a feldspathic, Fe- and Mg-enriched composition. Lithic clasts in NWA 13967 indicate a provenance in the Feldspathic Highlands Terrane on the Moon. Most abundant are cumulate impact melt clasts (“poikilitic granulitic breccias”), granular impact melt rocks, vitric impact melt clasts including impact spherules, and anorthositic clasts, while basalt clasts are rare. The breccia groundmass is mostly fused to flow-textured, vesicular, crystallized impact melt that includes 1 μm corundum crystals and up to 5 μm tissintite-II near the contact with lithic clasts. Rare coesite occurs in moganite clasts entrained in the shock-melted groundmass and rimmed by tissintite-II. Petrographic features of NWA 13967 and its bulk rock chemical composition are most similar to the NWA 8046 clan of lunar meteorites, the largest known lunar meteorite. We discuss mineralogical and petrological characteristics of NWA 13967 to unravel chemical and structural changes of the lunar regolith during shock lithification, which may inform the ongoing exploration of the lunar surface.

¹Jiawei Zhao, ^1,2Long Xiao, ³Zhiyong Xiao, ¹Xiang Wu, ¹Qi He, ⁴Jialong Hao, ⁴Ruiying Li, ⁴Yangting Lin
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.01.021]
¹State Key Laboratory of Geological Processes and Mineral Resources, Planetary Science Institute, School of Earth Sciences, China University of Geosciences, Wuhan 430074 China
²State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau
³Planetary Environmental and Astrobiological Research Laboratory, School of Atmospheric Sciences, Sun Yat-sen University, Zhuhai 519082 China
⁴Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, Beijing 10029 China
Copyright Elsevier

Zircon has been used to chronicle the geological evolution of the Earth and other planetary bodies. In some circumstances the U-Pb radioisotopic system in zircon can be completely reset by shock metamorphism (e.g. high-pressure phase formation and reversion, and recrystallization), erasing the initial crystallization record and instead recording the impact age. These behaviors of element redistribution accompanied with structure variation in shocked zircon provide pivotal evidence to unravel the extreme impact processes. However, the contributions from a variety of shock effects to element redistribution within shocked zircons are not clear due to the complicated and protracted metamorphic processes associated with an impact event. Here we use high-resolution Nano secondary ion mass spectrometry (NanoSIMS) to show that zircon grains from the Chicxulub impact structure that contain microstructural features such as planar/irregular fractures, zircon twins, reidite and zircon granules, record three main types of element redistribution processes related to shock metamorphism and post-impact modification. The first is the preferential yttrium (Y) enrichments at the zircon-reidite boundaries that is closely related to the formation of the high-pressure polymorph reidite, but the primary zoning is preserved in reidite-bearing zircon. The second process involves shock-related heating, resulting in the solid-state transformation from reidite-bearing zircon to granular zircon, and the growth of neo-formed zircon granules. This process facilitates the loss of radiogenic lead (Pb) and allows the retain of primary zoning of uranium (U) in granular zircon due to the different element diffusion properties, thus providing the chance to date the impact event. Thirdly, the studied zircon grains within the Chicxulub impact structure experienced post-impact hydrothermal alteration to varying degrees by localized element incorporation of additional yttrium (Y), titanium (Ti), uranium (U), lead (Pb) and phosphorus (P). The U-Pb systematics altered by post-impact hydrothermal processes reveal a generally discordant line affected by the external input of U and common Pb, which could be an alternative mechanism of localized age resetting happened in shocked zircon grains. Particularly, this study demonstrates the systematic characteristics of element redistribution in shocked zircons that experienced the sequential metamorphic processes from reidite formation to growth of zircon granules, and subsequent hydrothermal alteration within the Chicxulub impact structure. These findings provide the effective constraints for behaviors and mechanisms of element redistribution and age resetting in zircon under extreme shock and post-impact metamorphic conditions in terrestrial impact craters.

¹M.C. Benner, ^1,5 V.R. Manga, ¹B.S. Prince, ^2,3,4L.M. Ziurys, ^1,5T.J. Zega
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.01.012]
¹Lunar and Planetary Laboratory, University of Arizona, 1629 E. University Blvd., Tucson, AZ 85721, USA
²Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
³Department of Astronomy, Steward Observatory, University of Arizona, 933 North Cherry Ave., Tucson, AZ 85721, USA
⁴Arizona Radio Observatory, Steward Observatory, University of Arizona, 933 North Cherry Ave., Tucson, AZ 85721, USA
⁵Department of Materials Science and Engineering, 1235 E. James E. Rogers Way, University of Arizona, Tucson, AZ 85721, USA
Copyright Elsevier

As the limiting element in the development of living systems, it is crucial to understand the history of phosphorus (P), from its stellar origins to its arrival on planet surfaces. A key component in this cycle is understanding the forms of P delivered to the presolar nebula and their subsequent evolution on planetary bodies, including meteorites. Here, we report on the P distribution in the Bishunpur (LL3.15), Queen Alexandra Range (QUE) 97,008 (L3.05), and Allan Hills (ALHA) 77,307 (CO3.0) chondrites to determine its origins and secondary processing in the solar protoplanetary disk and on meteorite parent bodies using a coordinated analytical approach. In support of the microstructural characterization, we used density functional theory (DFT) to calculate the Gibbs free energy of the Fe3P – Ni3P binary under non-ideal mixing conditions in its entire range of composition and temperature space and performed equilibrium condensation modeling. We identified 106P-bearing regions in these petrologic type-3 chondrites and find that the major P-bearing minerals are schreibersite ((Fe, Ni)3P) and merrillite (Ca9NaMg(PO4)7). Bishunpur predominately contains merrillite, which occurs in rims on chondrules and as hopper crystals. QUE 97008 primarily contains merrillite in association with metal and sulfides. Microstructural evaluation of merrillite in Bishunpur suggests igneous origins within the chondrule-forming region, whereas merrillite in QUE 97008 formed via condensation. In comparison, the dominant P-bearing phase in ALHA 77307 is P-bearing metal, including several Ni-rich schreibersite grains that are composed of 45 and 52.5 at. % Ni, far higher than predicted by equilibrium condensation. The equilibrium thermodynamic model, including our newly described non-ideal schreibersite solid solution, predicts the formation of a miscibility gap where (Fe0.63, Ni0.37)3P and Ni3P form via nebular condensation. We therefore suggest that Ni-rich schreibersite formed through non-equilibrium condensation.

^1,2,3Meike Fischer,^1,4Stefan T. M. Peters,^6,7Daniel Herwartz,²Paul Hartogh,¹Tommaso Di Rocco,¹Andreas Pack
Proceedings of the National Academy of Sciences (PNAS) 121, e2321070121 Open Access Link to Article [https://doi.org/10.1073/pnas.2321070121]
¹Geowissenschaftliches Zentrum, Abteilung für Geochemie und Isotopengeologie, Georg-August-Universität Göttingen, Göttingen 37077, Germany
²Max-Planck-Institut für Sonnensystemfoschung, Abteilung Planeten und Kometen, Göttingen 37077, Germany
³Thermo Fisher Scientific (Bremen) GmbH, Bremen 28199, Germany
⁴Zentrum für Biodiversitätsmonitoring & Naturschutzforschung, Leibniz-Institut zur Analyse des
⁵Biodiversitätswandels–Standort Hamburg, Hamburg 20146, Germany
⁶Institut für Mineralogie und Petrologie, Universität Köln, Köln 50674, Germany
⁷Ruhr-Universtät Bochum, Institut für Geologie, Mineralogie und Geophysik, Bochum 44801, Germany

The Moon formed 4.5 Ga ago through a collision between proto-Earth and a planetesimal known as Theia. The compositional similarity of Earth and Moon puts tight limits on the isotopic contrast between Theia and proto-Earth, or it requires intense homogenization of Theia and proto-Earth material during and in the aftermath of the Moon-forming impact, or a combination of both. We conducted precise measurements of oxygen isotope ratios of lunar and terrestrial rocks. The absence of an isotopic difference between the Moon and Earth on the sub-ppm level, as well as the absence of isotope heterogeneity in Earth’s upper mantle and the Moon, is discussed in relation to published Moon formation scenarios and the collisional erosion of Theia’s silicate mantles prior to colliding with proto-Earth. The data provide valuable insights into the origin of volatiles in the Earth and Moon as they suggest that the water on the Earth may not have been delivered by the late veneer. The study also highlights the scientific value of samples returned by space missions, when compared to analyses of meteorite material, which may have interacted with terrestrial water.

¹Andrew S. Rivkin,²Cristina A. Thomas,^3,4Ian Wong,⁴Bryan Holler,⁵Helena C. Bates,⁶Ellen S. Howell,⁷Bethany L. Ehlmann,³Stefanie N. Milam,⁸Heidi B. Hammel
The Planetary Science Journal 6, 9 Link to Article [DOI 10.3847/PSJ/ad944c]
¹Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD, 20723, USA
²Northern Arizona University, Department of Astronomy and Planetary Science, PO Box 6010, Flagstaff, AZ 86011, USA
³NASA Goddard Space Flight Center, Astrochemistry Laboratory, Greenbelt, MD 20771, USA
⁴Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
⁵Planetary Materials Group, Natural History Museum, Cromwell Road, London SW7 5BD, UK
⁶Lunar & Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA
⁷Division of Geological & Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
⁸Association of Universities for Research in Astronomy, 1212 New York Avenue NW, Suite 450, Washington, DC 20005, USA

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

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.