¹Mohammad Tauseef,¹Ingo Leya,²Jérôme Gattacceca,³Beda Hofmann,⁴Sönke Szidat,⁴Régis Braucher,⁴ASTER Team
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14144]
¹Space Research and Planetary Science, Physics Institute, University of Bern, Bern, Switzerland
²CNRS, IRD, INRAE, CEREGE, Aix Marseille Univ, Aix-en-Provence, France
³Natural History Museum Bern, Bern, Switzerland
⁴Department of Chemistry, Biochemistry and Pharmaceutical Sciences, Oeschger Center for Climate Change Research, University of Bern, Bern, Switzerland
Published by arrangement with John Wiley & Sons

We perform a systematic and detailed study of the 14C and 14C-10Be dating systems for meteorite terrestrial ages. Physical model calculations indicate that neither the 14C production rates nor the 14C/10Be production rate ratios are constant enough to be reasonably approximated by average values. By using simple averages, one introduces a significant size-dependent bias into the database for meteorite terrestrial ages. By combining modeled 14C production rates and 14C/10Be production rate ratios with (22Ne/21Ne)cos ratios and assuming ~80% ablation losses, relatively easy to use correlations of 14C production rates and 14C/10Be production rate ratios as a function of (22Ne/21Ne)cos are established. The new correlations enable the determination of terrestrial ages that are more accurate than ages based solely on average values for 14C and/or 14C/10Be. We validate the model predictions by measuring 14C activity concentrations, 14C/10Be production rate ratios, 21Necos concentrations, and (22Ne/21Ne)cos ratios in four recently fallen meteorites: Mt. Tazerzait, Boumdeid (2011), Bensour, and SaU 606. The experimental data confirmed the model predictions, although the available data are insufficient to be conclusive. More data from freshly fallen meteorites are needed for validating the model predictions for different chondrite sizes and chondrite types.

^1,2Chitrangada Datta,^1,3Yuri Amelin,^1,4,5Evgenii Krestianinov,⁶Anthony J. Irving,¹Ian S. Williams
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2024.115979]
¹Research School of Earth Sciences, The Australian National University, Canberra, ACT 2601, Australia
²School of Earth, Atmosphere & Environment, Monash University, Clayton, VIC 3168, Australia
³Korea Basic Science Institute, Ochang, Cheongwon, Cheongju, Chungbuk 28119, Republic of Korea
⁴Department of Geological Sciences, Universidad Catolica del Norte, UCN, Antofagasta, Chile
⁵Center for Excellence in Astrophysics and Associated Technologies, CATA, Santiago, Chile
⁶Department of Earth & Space Sciences, University of Washington, Seattle, WA 98195, USA
Copyright Elsevier

Pb-isotopic dating of the recently discovered diabasic angrite Northwest Africa (NWA) 12,320 yielded ages of 4564.17 ± 0.50 Ma and 4562.82 ± 0.37 Ma for acid-insoluble and soluble minerals respectively. These ages are calculated using measured 238U/235U ratios of soluble and insoluble minerals, thereby excluding the possibility that the apparent age difference is caused by internal U-isotopic variations. The age of the insoluble minerals is indistinguishable from published Pb isotopic ages of other medium-grained angrites SAH 99555 and D’Orbigny. The age of acid-soluble minerals is distinctly younger, with a 1.35 ± 0.62 Ma age gap between the Pbsingle bondPb ages of the two mineral fractions. The mineral hosts of U, Th and radiogenic Pb in the meteorite were identified through in-situ SIMS measurements of these elements in all minerals. The principal carriers of U, Th and radiogenic Pb are acid insoluble Al-Ti-rich augite and soluble Si-rich phosphate. Closure temperatures for diffusion of radiogenic Pb in these minerals are calculated to be respectively 820 ± 90 °C and 450 ± 80 °C using the observed range of crystal dimensions and the published experimental data for Pb diffusion in augite and apatite. The age difference between the pyroxene and phosphates has two potential explanations: (1) a late reheating event >450 °C which may have re-set the Usingle bondPb systematics of the phosphates but not the pyroxenes or (2) slow cooling of the rock from ~450–820 °C. If slow cooling is the reason for the age difference, we can estimate a model cooling rate of 270 ± 150 °C/Ma over the estimated closure temperature range between pyroxenes and phosphates. This rate is ~11 orders of magnitude slower than petrologic cooling rates of quenched angrites at temperatures above 1000 °C determined experimentally using the composition of Asuka 881,371 groundmass (Keil, 2012), which is similar to NWA 12320 groundmass. If there was no late reheating event, the discrepancy between fast cooling rates at high temperatures near the solidus, followed by much slower cooling at lower temperatures, might have been caused by impact melting. It could also be attributed to the initial eruption of the source magma of NWA 12320 near the surface of the parent body, followed by burial due to subsequent eruptions.

¹Merislava Anguelova,²Nicolas Vilela,³Sebastian Kommescher,^2,4Nicolas D. Greber,¹Manuela A. Fehr,¹Maria Schönbächler
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2024.01.026]
¹Institute of Geochemistry and Petrology, ETH Zurich, 8092 Zurich, Switzerland
²Institute of Geological Sciences, University of Bern, 3012 Bern, Switzerland
³Institut für Geologie, Mineralogie und Geophysik, Ruhr-Universität Bochum, 44801 Bochum, Germany
⁴Muséum d’histoire naturelle de Genève, 1208 Genève, Switzerland
Copyright Elsevier

Titanium isotopes are a promising tracer for planetary differentiation processes. The application of this tracer is, however, currently hampered by the lack of a robust estimate for the chondritic reservoir. Here, we conducted an inter-comparison Ti isotope study of three laboratories with the aim of providing an accurate and precise estimate for the chondritic reservoir. While previous estimates may suffer from heterogeneities on the sampling scale, we chose ordinary chondrites to minimise uncertainties associated with the necessary corrections for nucleosynthetic isotope variations in chondrites, and to allow the analysis of sufficiently large sample sizes representative for bulk meteorites. Titanium isotope data reported by the different laboratories are in good agreement with each other. Ordinary chondrites of different subgroups (H, L, LL) and petrologic types (3–6) display identical Ti isotope compositions within uncertainties (average δ49Ti = +0.023 ± 0.009 ‰, 2SE, n = 20; permille deviation of 49Ti/47Ti from the OL-Ti standard). The average Ti isotope composition of ordinary chondrites is within 2SE identical to that of OIBs (+0.029 ± 0.005 ‰, 2SE, n = 52) and all pre 2.7 Ga mafic and komatiitic rocks (+0.019 ± 0.006 ‰, 2SE, n = 58), indicating that the δ49Ti values of the bulk silicate Earth and ordinary chondrites are indistinguishable. Furthermore, our average Ti isotope composition of ordinary chondrites overlaps with those of the Moon, Mars and Vesta, suggesting a homogeneous inner Solar System in terms of mass-dependent Ti isotopes.

^1,2Philipp R. Heck,^1,3Birger Schmitz,¹Xenia Ritter,^1,2Surya S. Rout,⁴Noriko T. Kita,⁵Céline Defouilloy,^1,2Katarina Keating,¹Kevin Eisenstein,³Fredrik Terfelt
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14133]
¹Robert A. Pritzker Center for Meteoritics and Polar Studies, Negaunee Integrative Research Center, Field
Museum of Natural History, Chicago, Illinois, USA
²Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois, USA
³Astrogeobiology Laboratory, Department of Physics, Lund University, Lund, Sweden
⁴WiscSIMS, Department of Geoscience, University of Wisconsin, Madison, Wisconsin, USA
⁵Cameca, Gennevilliers, France
Published by arrangement with John Wiley & Sons

Extraterrestrial chrome spinel and chromite extracted from the sedimentary rock record are relicts from coarse micrometeorites and rarely meteorites. They are studied to reconstruct the paleoflux of meteorites to the Earth and the collisional history of the asteroid belt. Minor element concentrations of Ti and V, and oxygen isotopic compositions of these relict minerals were used to classify the meteorite type they stem from, and thus to determine the relative meteorite group abundances through time. While coarse sediment-dispersed extraterrestrial chrome-spinel (SEC) grains from ordinary chondrites dominate through the studied time windows in the Phanerozoic, there are exceptions: We have shown that ~467 Ma ago, 1 Ma before the breakup of the L chondrite parent body (LCPB), more than half of the largest (>63 μm diameter) grains were achondritic and originated from differentiated asteroids in contrast to ordinary chondrites which dominated the meteorite flux throughout most of the past 500 Ma. Here, we present a new data set of oxygen isotopic compositions and elemental compositions of 136 grains of a smaller size fraction (32–63 μm) in ~467 Ma old pre-LCPB limestone from the Lynna River section in western Russia, that was previously studied by elemental analysis. Our study constitutes the most comprehensive oxygen isotopic data set of sediment-dispersed extraterrestrial chrome spinel to date. We also introduce a Raman spectroscopy-based method to identify SEC grains and distinguish them from terrestrial chrome spinel with ~97% reliability. We calibrated the Raman method with the established approach using titanium and vanadium concentrations and oxygen isotopic compositions. We find that ordinary chondrites are approximately three times more abundant in the 32–63 μm fraction than achondrites. While abundances of achondrites compared to ordinary chondrites are lower in the 32–63 μm size fraction than in the >63 μm one, achondrites are approximately three times more abundant in the 32–62 μm fraction than they are in the present flux. We find that the sources of SEC grains vary for different grain sizes, mainly as a result of parent body thermal metamorphism. We conclude that the meteorite flux composition ~467 Ma ago ~1 Ma before the breakup of the LCPB was fundamentally different from today and from other time windows studied in the Phanerozoic, but that in contrast to the large size fraction ordinary chondrites dominated the flux in the small size fraction. The high abundance of ordinary chondrites in the studied samples is consistent with the findings based on coarse extraterrestrial chrome-spinel from other time windows.

¹Simone Cogliati,¹Michael C. Macey
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14141]
¹AstrobiologyOU, Faculty of Science, Technology, Engineering and Mathematics, The Open University, Milton Keynes, UK
Published by arrangement with John Wiley & Sons

To assess whether life existed on Mars, it is crucial to identify geochemical biosignatures that are relevant to specific Martian environments. In this paper, thermochemical modeling was used to investigate fluid chemistries and secondary minerals that would have evolved biotically over geological time scales in Martian fluvio-lacustrine and evaporitic settings, and that could be used as potential inorganic biosignatures for life detection on Mars. Modeling was performed using fluid and rock chemistries relevant to Gale crater aqueous environments. Potential inorganic biosignatures were identified investigating alteration deposits found at the surface of a simulant exposed to short-term bio-mediated weathering and comparing experimental and modeling results. In a fluvio-lacustrine setting (water/rock of 2000–278), models suggest that less complex mineral assemblages form during biotic basalt dissolution and subsequent brine evaporation compared to what would happen in an abiotic system. Mainly nontronite, kaolinite, and quartz form under biotic conditions, whereas celadonite, talc, and goethite would also precipitate abiotically. Quartz, sepiolite, and gypsum would precipitate from the evaporation of fluids evolved biotically, whereas nontronite, talc, zeolite, and gypsum would form in an abiotic evaporitic environment. These results could be used to distinguish products of abiotic and biotic processes, aiding the interpretation of data from Mars exploration missions.

¹Kazuhiko Ninomiya et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14135]
¹Institute for Radiation Sciences, Osaka University, Toyonaka, Japan
Published by arrangement with John Wiley & Sons

Samples from asteroid Ryugu, brought back by asteroid explorer Hayabusa2, are important for investigating the origin and evolution of the solar system. Here, we report the elemental compositions of a 123-mg Ryugu sample determined with a nondestructive muon elemental analysis method. This method is a powerful tool for determining bulk chemical composition, including light elements such as C, N, and O. From the muonic x-ray spectra with three carbonaceous chondrites, the relationship between the elemental composition and muonic x-ray intensity was determined for each element. Calibration curves showed linearity, and the elemental composition of Ryugu was quantitatively determined. The results reflect the average bulk elemental composition of asteroid Ryugu owing to the large amount of samples. Ryugu has an elemental composition similar to that of Orgueil (CI1) and should be classified as CI1. However, the O/Si ratio of Ryugu is 25% lower than that of Orgueil, indicating that Orgueil may have been seriously contaminated by terrestrial materials after its fall to Earth. These results indicate that the Ryugu sample is more representative than the CI chondrites as a solid material of the solar system.

^1,2Ting Cao,²Huapei Wang,²Shaochen Hu,^3,4Kaixian Qi
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14136]
¹School of Earth Sciences, China University of Geosciences, Wuhan, Hubei, China
²Paleomagnetism and Planetary Magnetism Laboratory, School of Geophysics and Geomatics, China University of Geosciences, Wuhan, Hubei, China
³State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
⁴College of Earth and Planetary Sciences, University of the Chinese Academy of Sciences, Beijing, China
Published by arrangement with John Wiley & Sons

We present the first rock magnetic and paleomagnetic analyses of the Martian meteorite Grove Mountains (GRV) 020090, a suitable candidate for paleomagnetic study due to its low degree of weathering and shock metamorphism. Petrological and rock magnetic investigation indicates that pyrrhotite is the dominant magnetic mineral in GRV 020090, where it occurs as a primary phase without significant shock metamorphism or alteration. The magnetic grains in GRV 020090 exhibit single-domain behavior that facilitates high-fidelity magnetic recording. We obtained a positive fusion-crust baked contact test, which supports an extraterrestrial origin of the primary remanence in GRV 020090. The nature of the primary remanence was identified as thermoremanence acquired during crystallization of the rock on Mars. Anhysteretic remanent magnetization and isothermal remanent magnetization paleointensity methods indicated paleofield strengths of 1.6 and 2.6 μT, respectively, for the primary remanence. However, the shock pressure that GRV 020090 experienced may have partially demagnetized the primary remanence, leading to underestimated paleointensity values. Therefore, 1.6 μT is regarded as the lower limit on the paleointensity of GRV 020090. This lower limit is higher than the model-predicted surface magnetic field strength in the source region for GRV 020090, suggesting that it may have recorded a small-scale crustal magnetic field previously undetected by orbital magnetic data. This small-scale crustal field is likely generated by the underlying ancient, magnetized layers, as the crustal magnetization of the surficial terrane with lithology similar to GRV 020090 is too weak to produce such a crustal field.

^1,2M. Kimura,^3,4M. K. Weisberg,¹A. Yamaguchi
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14129]
¹National Institute of Polar Research, Tokyo, Japan
²Ibaraki University, Mito, Japan
³Kingsborough College and Graduate Center of the City University of New York, New York City, New York, USA
⁴American Museum of Natural History, New York City, New York, USA
Published by arrangement with John Wiley & Sons

Type 3 chondrites are subdivided into 3.0–3.9. Subtype 3.0 chondrites nearly preserve all of their primitive features. Many criteria have been proposed to distinguish such primitive chondrites. Here, we compiled mineral data and reconsider the petrologic classification criteria for subtype 3.0. Chondrites are classified into subtypes by the minor element distribution of olivine and textural and chemical features of Fe-Ni metal. The []Si4O8 and MgO components of feldspar also distinguish subtype 3.0 from subtypes ≥3.1. Other features, such as the occurrence of near pure chromite, are also indicators of subtype 3.0. It is difficult to distinguish between subtypes 3.0 and ≤2.9 based on mineral chemistry. Therefore, we propose the following criteria to distinguish between subtypes 3.0 and ≤2.9. In type 3.0 chondrites, major silicate (olivine, pyroxene, and plagioclase), oxide, metal, and sulfide minerals do not show aqueous alteration features. Melilite, anorthite, and glass show no or mild aqueous alteration features. Subtype 3.0 has not been identified in all chondrite groups. The absence of subtype 3.0 from some groups mainly reflects differences in the degrees of secondary parent body processes among the chondrite groups.

^1,2F. Campanale,^2,3E. Mugnaioli,^2,3L. Folco,⁴P. Parlanti,⁴M. Gemmi
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14137]
¹Dipartimento di Scienze dell’Ambiente e Della Terra, Università degli Studi di Milano-Bicocca, Milan, Italy
²Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy
³CISUP, Centro per l’Integrazione della Strumentazione dell’Università di Pisa, Pisa, Italy
⁴Centre for Materials Interfaces, Electron Crystallography, Istituto Italiano di Tecnologia, Pontedera, Italy
Copyright Elsevier

TiO2II, a high-pressure polymorph of titanium dioxide, is a diagnostic indicator of shock metamorphism in impact rocks. Due to its typical micro-to-nanometer scale, there are no ab initio structure solutions of natural TiO2II, thereby generating uncertainty about its crystal structure and its known similarity with srilankite (Ti0.67,Zr0.33)O2. Nanoscale electron diffraction investigation of TiO2II from the Australasian tektite strewn field provides the first ab initio structure solution revealing a primitive orthorhombic lattice with cell parameters a = 4.547 Å, b = 5.481 Å, c = 4.891 Å, and space group Pbcn, that is, the same as srilankite and scrutinyite α-PbO2. The linear a and c decrease, and b increase with Ti content indicate TiO2II as Zr-free srilankite endmember in the binary system ZrO2-TiO2. Thereby the name srilankite should be used referring to TiO2II, according to the International Mineralogical Association recommendations. We provide the first evidence for a topotactic subsolidus rutile-to-TiO2II transition, founding their finely intermixing nanocrystals in the same TiO2 crystal, where TiO2II is within the crystal and surrounded by rutile in direct contact. They also show recurrent iso-orientation, with TiO2II [100] parallel to rutile [100], TiO2II [010] parallel to rutile [011], and TiO2II [001] parallel to rutile (0–11). The rutile-TiO2II iso-orientation suggests the compression of rutile (0–11) planes as a possible transition mechanism from rutile to TiO2II, with a consequent shortening of ~0.5 Å per cell. The presence of TiO2II in the distal (~1200 km) impact ejecta from the Australasian tektite strewn field indicates shock pressures of ~12–15 GPa and post-shock temperatures below 500°C followed by rapid quenching.

¹J. Aléon et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14139]
¹Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Sorbonne Université, Museum National d’Histoire Naturelle, CNRS UMR 7590, IRD, Paris, France
Published by arrangement with John Wiley & Sons

In order to gain insights on the conditions of aqueous alteration on asteroid Ryugu and the origin of water in the outer solar system, we developed the measurement of water content in magnetite at the micrometer scale by secondary ion mass spectrometry (NanoSIMS) and determined the H and Si content of coarse-grained euhedral magnetite grains (polyhedral magnetite) and coarse-grained fibrous (spherulitic) magnetite from the Ryugu polished section A0058-C1001. The hydrogen content in magnetite ranges between ~900 and ~3300 wt ppm equivalent water and is correlated with the Si content. Polyhedral magnetite has low and homogenous silicon and water content, whereas fibrous magnetite shows correlated Si and water excesses. These excesses can be explained by the presence of hydrous Si-rich amorphous nanoinclusions trapped during the precipitation of fibrous magnetite away from equilibrium and testify that fibrous magnetite formed from a hydrous gel with possibly more than 20 wt% water. An attempt to determine the water content in sub-μm framboids indicates that additional calibration and contamination issues must be addressed before a safe conclusion can be drawn, but hints at elevated water content as well. The high water content in fibrous magnetite, expected to be among the first minerals to crystallize at low water–rock ratio, points to the control of water content by local conditions of magnetite precipitation rather than large-scale alteration conditions. Systematic lithological variations associated with water-rich and water-poor magnetite suggest that the global context of alteration may be better understood if local water concentrations are compared with millimeter-scale distribution of the various morphologies of magnetite. Finally, the high water content in the magnetite precursor gel indicates that the initial O isotopic composition in alteration water must not have been very different from that of the earliest magnetite crystals.