Cosmochemistry Papers will be on Summer Break for the nex week. We will commence operations again on September, 1st.

¹R. G. Mayne,¹L. Caves,²T. J. McCoy,³R. D. Ash,³W. F. McDonough
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14031]
¹Monnig Meteorite Collection and Gallery, College of Science and Engineering, Texas Christian University, Fort Worth, Texas, USA
²Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, Washington, District of Columbia, USA
³Department of Geology, University of Maryland, College Park, Maryland, USA
Published by arrangement with John Wiley & Sons

Mesosiderites are an amalgamation of crustal silicates and molten metal, and their formational history is not well understood. It is widely believed that redox reactions occurred in the mesosiderites during metal–silicate mixing. Previous studies evaluated redox reactions by studying the silicates within mesosiderites, but little attention has been given to the metal for complementary evidence of such processes. Here, the evidence for redox within the metal portion of five mesosiderites is documented, most notably lower P content in the matrix metal relative to clast metal (nodule). These observations, together with the noted FeO reduction in silicates, provide further support for redox reactions occurring during metal–silicate mixing. Samples with differing Ir concentrations, such as Chaunskij and RKP A70015, have been previously classified as anomalous. However, the marked variation in highly siderophile element concentrations in all of these mesosiderites is consistent with fractional crystallization. These compositional trends could be explained by isolated metallic masses that underwent fractional crystallization before mixing or by hit-and-run collisions that produced metallic masses that ranged in size.

¹Miriam Rüfenacht,¹Précillia Morino,^1,2Yi-Jen Lai,¹Manuela A. Fehr,^1,3Makiko K. Haba,¹Maria Schönbächler
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2023.06.005]
¹Institute of Geochemistry and Petrology, ETH Zurich, Clausiusstrasse 25, CH-8092 Zurich, Switzerland
²Macquarie GeoAnalytical, Faculty of Science and Engineering, Macquarie University, Sydney 2109, NSW, Australia
³Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Ishikawadai Building 2-105, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan
Copyright Elsevier

Nucleosynthetic isotope variations are powerful tools to investigate genetic relationships between meteorite groups and planets. They are instrumental to assess the early evolution of the solar system, including mixing and reservoir formation in the protoplanetary disk, as well as planet formation. To address these questions, we report high-precision nucleosynthetic Ti isotope compositions of a wide range of bulk meteorites, partially complemented with new Cr isotope data. New Ti isotope data confirm the first order dichotomy observed between carbonaceous chondrites (CC), representing outer solar system compositions, and non-carbonaceous (NC) meteorites from the inner solar system. The data in combination with nucleosynthetic isotope data of other elements (e.g., Cr, Ca) indicate that isotopically heterogeneous reservoirs were also present as sub-reservoirs in the inner disk (NC reservoir), generating two or more clusters i.e., (i) the Vesta-like howardites-eucrites-diogenites (HEDs), mesosiderites, angrites, acapulcoites, lodranites, and brachinites and (ii) the Earth-Mars-like ordinary chondrites (OC), aubrites, enstatite chondrites (EC), winonaites, IAB silicates, rumuruti chondrites (R), Martian and terrestrial samples. These reservoirs likely represent disk substructures such as secondary gaps and ring-structures, created by spiral arms, which were emitted from the growing Jupiter and/or Saturn. The distinct isotopic compositions of these reservoirs may reflect thermal processing of material within the disk in combination with temporal isotopic variations either due to isotopically variable infalling material from a heterogeneous molecular cloud and/or thermal processing during the infall that induced such heterogeneities. Such effects were likely reinforced by thermal processing of the material within the disk itself and by physical size- and density sorting of dust caused by the giant planets, creating gaps and pressure bumps in the disk.

Genetic relationships of meteorite groups and their implications on parent body formation are evaluated. New high precision Ti isotope data are consistent with that (i) CH and CB meteorites derive from a common parent body, which most likely accreted material from the same isotopic reservoir as the parent body of CR chondrites, (ii) silicates of IAB irons and winonaites originate from the same parent body, and (iii) mesosiderites and HED meteorites have a common origin on Vesta. The indistinguishable Ti and Cr isotope compositions of HEDs/mesosiderites to acapulcoites are not attributed to a common parent body, because of petrologic and chemical differences in addition to their distinct O isotope compositions. Their parent bodies likely accreted in the same disk region, which showed a higher level of O isotope heterogeneity compared to that of Ti, Cr and other refractory nucleosynthetic tracers. The similarity in Ti isotope compositions of Martian meteorites and OCs indicates that OC-like material belongs to the main building blocks of Mars.

¹Yan Hu,¹Frédéric Moynier,^2,3Xin Yang
Earth and Planetary Science Letters 620, 118319 Link to Article [https://doi.org/10.1016/j.epsl.2023.118319]
¹Université Paris Cité, Institut de Physique du Globe de Paris, CNRS, UMR 7154, Paris 75005, France
²Department of the Geophysical Sciences, The University of Chicago, Chicago, IL 60637, USA
³Robert A. Pritzker Center for Meteoritics and Polar Studies, Negaunee Integrative Research Center, Field Museum of Natural History, Chicago, IL, USA
Copyright Elsevier

The stable potassium isotopic ratios (41K/39K) of Earth and Mars have been interpreted to reflect either nucleosynthetic isotope anomalies or volatility-driven K depletion. Chondrites comprise primordial materials from which planetary bodies are assembled, and thus are critical samples for this discussion. Here, we present high-precision K isotopic analyses (reported as
K) of 33 chondrites and two achondrites, which reveal unprecedented variation from −1.08 to 4.68‰. In addition, there is considerable overlap in
K values between carbonaceous and non-carbonaceous meteorites despite their contrasting nucleosynthetic isotope anomalies. These findings are inconsistent with the nucleosynthetic origin of 41K variations in meteorites. Instead, the
K values of chondrites correlate positively with the isotopic compositions of other moderately volatile elements (e.g., Rb, Cu, Zn, Sn, Ga, and Te). These correlations suggest that volatility-controlled fractionation is a common mechanism for mass-dependent isotopic variations in the Solar System. In particular, carbonaceous chondrites and the angrite parent body exhibit a trend of concomitant decreases in K and its heavier isotope due to incomplete K condensation. Earth and Mars also follow this trend, suggesting that their K depletion may reflect similar volatile-depleting processes that occurred with their respective precursors. That Mars is isotopically heavier than Earth is consistent with it having less K-depleted precursors, in addition to the previous suggestion of a later-stage K loss from proto-Mars during accretionary collisions.

¹Qin Zhou et al. (>10)
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2023.08.017]
¹Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, China
Copyright Elsevier

The U(Pb)-Pb age of zircon is commonly used to represent the crystallization age for igneous rocks due to its high closure temperature and robust resistance to impact disturbance. However, no zircon crystallization age has yet been reported for Chang’e-5 (CE-5) basalt due to their limited occurrence in mare basalt. In this study, rare zircon grains from CE-5 lunar samples were investigated by the in-situ Pb isotopic analysis, and a precise zircon crystallization age of 2036 ± 19 Ma was determined from Pb-Pb isochron. This is hitherto the youngest reported crystallization age of lunar zircon, similar to the ages of CE-5 lunar basalts obtained by zirconium (Zr)-bearing minerals such as baddeleyite, tranquillityite, and zirconolite. Petrographic evidence and rare-earth element geochemistry indicate that zircon in the CE-5 lunar basalts were formed by the reaction of early-formed baddeleyite with SiO2 melt within the latest residue of extreme fractionation of a non-KREEP (an acronym for potassium, REE, and phosphorus) basaltic magma. In contrast to the prevailing view that lunar zircon have formed in late-stage enriched melts resulting from extensive fractional crystallization of the Lunar Magma Ocean, this study shows that zircon could be derived from extreme fractionation of non-KREEP basaltic magma unrelated to Lunar Magma Ocean.

^1,2Akaogi, Masaki, ¹Miyazaki, Natsuki,¹Tajima, Taisuke,¹Kojitani, Hiroshi
Physics and Chemistry of Minerals 50, 23 Link to Article [DOI 10.1007/s00269-023-01247-4]
¹Department of Chemistry, Gakushuin University, Mejiro, Toshima-ku, Tokyo, 171-8588, Japan
²Geochemical Research Center, Graduate School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan

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

¹Ali Ettehadi,¹Mehdi Mokhtari,¹Maksym Chuprin,²Robert C. Anderson,³Gursat Altun,⁴Ezat Heydari
Icarus (in Press) Link to Article[https://doi.org/10.1016/j.icarus.2023.115760]
¹University of Louisiana at Lafayette, Louisiana, USA
²Jet Propulsion Laboratory (JPL), California, USA
³Istanbul Technical University, Istanbul, Turkey
⁴Jackson State University, MS, USA
Copyright Elsevier

The MSL (Mars Science Lab) Curiosity rover has documented the presence of natural fractures at the Gale crater on Mars. Through the utilization of the ChemCam instrument, the chemical composition of the veins on Mars has been analyzed, revealing their mineralogy as calcium sulfate. However, there is limited knowledge regarding the mechanical properties of these veins, which hinders a deeper understanding of their origin. This work aims to characterize the mechanical properties of gypsiferous Triassic Moenkopi mudrocks as the terrestrial rock analog to Mars. The Digital Image Correlation (DIC) technique was used in tandem with the Indirect Tensile Strength test to acquire the required spatial full-field strain maps for characterizing the fracture propagation with complex geometries in addition to the derived mechanical properties. The effect of the primary vein orientation on the exerted load on the load-strain profile, fracture initiation and propagation, and tensile strength was established. The dynamic spatial horizontal, vertical, and shear strains’ progression was distinguished through DIC imaging. The key findings include: (1) Different failure modes were observed in samples with and without calcium sulfate veins, with higher tensile strength perpendicular to lamination; (2) Most samples with veins exhibited reduced tensile strength, except when oriented 90° to the load; (3) Fracture paths were influenced by the orientation angle, with irregular paths at certain angles and more regular paths for centrally located veins; (4) Digital image correlation revealed a fracture process zone before macro-crack initiation and subsequent shear crack propagation; (5) Shear strain accumulation preceded shear crack propagation, with potential initiation of tensile cracks.

^1,2Yoko Kebukawa et al.(>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14064]
¹Department of Chemistry and Life Science, Yokohama National University, Yokohama, Japan
²Yoko Kebukawa, Department of Chemistry and Life Science, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan.
Published by arrangement withe John Wiley & Sons

The infrared spectral characteristics of organic-rich acid residues prepared from Ryugu samples returned by the JAXA Hayabusa2 mission generally match those from unheated carbonaceous chondrite meteorites, but the residues from Ryugu are richer in methyl and methylene functional groups and have higher CH2/CH3 ratios. Moreover, two distinct outlier carbonaceous phases are found; one with spectral characteristics of N-H functional groups, likely amides, and a second phase containing less nitrogen. Such infrared characteristics of Ryugu organic matter might indicate the pristine nature of the freshly collected samples and reflect the near-surface chemistry in the parent asteroid.

¹Liam D. Peterson,¹Megan E. Newcombe,²Conel M.O’D. Alexander,²Jianhua Wang,⁴Frieder Klein,^3,5,6David V. Bekaert,^3,5Sune G. Nielsen
Earth and Planetary Science Letters 620, 118341 Link to Article [https://doi.org/10.1016/j.epsl.2023.118341]
¹Department of Geology, University of Maryland, College Park, MD 20740, United States
²Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC 20015, United States
³NIRVANA Labs, Woods Hole Oceanographic Institution, Woods Hole, MA 02540, United States
⁴Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02540, United States
⁵Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02540, United States
⁶Université de Lorraine, CNRS, CRPG, 54000 Nancy, France
Copyright Elsevier

Aubrites and enstatite chondrites (ECs) are isotopically similar to the Earth and therefore may resemble the primary materials that accreted to form our planet. Recent bulk H elemental and isotopic analyses of ECs and the Norton County aubrite suggest that enstatite-rich materials are H-rich and may represent a significant source of terrestrial water, with measured values of 3000±2000 μg/g H2O and 5300±900 μg/g H2O in the bulk and enstatite fractions of Norton County (Piani et al., Science, 2020). Here, we present a detailed investigation of in situ H2O concentrations in enstatite, diopside, forsterite, and plagioclase from a suite of main group aubrites, including Norton County, and Shallowater. We find that enstatite (4±2 μg/g H2O), diopside (4.8±0.5 μg/g H2O), and forsterite (5±3 μg/g H2O) have similar H2O concentrations, and all are significantly lower than plagioclase (24±3 μg/g H2O). We combine our in situ analyses of H2O contents with equilibrium partition coefficients and bulk mineralogies to estimate the bulk H2O content of our samples. We compare these first order estimates with bulk volatile analyses conducted using sample pyrolysis and find that the previous bulk H2O analyses of aubrites predominantly reflect terrestrial contamination and alteration. If our conclusion that the reported bulk H2O analyses of Norton County primarily reflect terrestrial contamination and alteration extends to bulk analyses of ECs, then EC-like material may not be a significant source of terrestrial water. Our results support the hypothesis that thermal metamorphism, melting, and differentiation leads to efficient desiccation of planetesimals relative to chondrites, and that differentiated planetesimals contributed, at most, trace amounts to Earth’s water budget.

¹Chandran, Saranya R.,¹James S.,¹Aswathi J.,¹Padmakumar, Devika,¹Marjan, T. Sadeeda,¹Kumar, R.B. Binoj,^2,4Chavan, Anil,²Bhandari, Subhash ^1,3Sajinkumar K.S.
Earth-Science Reviews 243, 104508 Link to Article [DOI 10.1016/j.earscirev.2023.104508]
¹Department of Geology, University of Kerala, Thiruvananthapuram, 695581, India
²Department of Earth and Environmental Science, K.S.K.V. Kachchh University, Bhuj-Kachchh, 370001, India
³Department of Geological and Mining Engineering and Sciences, Michigan Technological University, Houghton, 49931, MI, United States
⁴Physical Research Laboratory, Ahmedabad, 380009, India

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