^1,2Yash Srivastava,¹Amit Basu Sarbadhikari,³James M. D. Day,⁴Akira Yamaguchi,^4,5Atsushi Takenouchi
Nature Communications 13, 7594 Open Access Link to Article [DOI https://doi.org/10.1038/s41467-022-35260-y]
¹Physical Research Laboratory, Ahmedabad, 380009, India
²Indian Institute of Technology Gandhinagar, Gujarat, 382355, India
³Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, 92093-0244, USA
⁴National Institute of Polar Research (NIPR), Tokyo, 190-8518, Japan
⁵The Kyoto University Museum, Kyoto University, Kyoto, 606-8501, Japan

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

^1,2Matthew J. Genge et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.13937]
¹Department of Earth Science and Engineering, Imperial College London, London, SW7 2A UK
²Planetary Materials Group, Natural History Museum, London, SW7 5BD UK
Published by arrangement with John Wiley & Sons

Fusion crusts form during the atmospheric entry heating of meteorites and preserve a record of the conditions that occurred during deceleration in the atmosphere. The fusion crust of the Winchcombe meteorite closely resembles that of other stony meteorites, and in particular CM2 chondrites, since it is dominated by olivine phenocrysts set in a glassy mesostasis with magnetite, and is highly vesicular. Dehydration cracks are unusually abundant in Winchcombe. Failure of this weak layer is an additional ablation mechanism to produce large numbers of particles during deceleration, consistent with the observation of pulses of plasma in videos of the Winchcombe fireball. Calving events might provide an observable phenomenon related to meteorites that are particularly susceptible to dehydration. Oscillatory zoning is observed within olivine phenocrysts in the fusion crust, in contrast to other meteorites, perhaps owing to temperature fluctuations resulting from calving events. Magnetite monolayers are found in the crust, and have also not been previously reported, and form discontinuous strata. These features grade into magnetite rims formed on the external surface of the crust and suggest the trapping of surface magnetite by collapse of melt. Magnetite monolayers may be a feature of meteorites that undergo significant degassing. Silicate warts with dendritic textures were observed and are suggested to be droplets ablated from another stone in the shower. They, therefore, represent the first evidence for intershower transfer of ablation materials and are consistent with the other evidence in the Winchcombe meteorite for unusually intense gas loss and ablation, despite its low entry velocity.

¹Brittany A. Cymes,¹Katherine D. Burgess,¹Rhonda M. Stroud
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13941]
¹U.S. Naval Research Laboratory, 4555 Overlook Ave. SW, Washington, District of Columbia, 20375 USA
Published by arrangement with John Wiley & Sons

To shed light on the mechanism of formation of nanophase iron particles (npFe) in space-weathered materials from airless bodies, we analyzed exsolved and unexsolved space-weathered lunar pyroxenes from Apollo 17 sample 71501. The exsolved pyroxene allowed for the observation of the effects of space weathering on similar mineral phases with variable composition. Using coordinated scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy (EELS), we determined that two coexisting pyroxenes in the exsolved grain showed systematic variations in response to space weathering, despite equivalent exposure conditions. The npFe in the space-weathered rim of augite lamellae were smaller and fewer than the npFe in the rim of pigeonite lamellae. EELS spectrum imaging revealed the presence and heterogeneous distribution of Fe0, Fe2+, and Fe3+ in the exsolved pyroxene. Metallic iron occurred in the npFe, a mixture of Fe2+ and Fe3+ occurred in the pigeonite lamellae, and the augite lamellae contained virtually all Fe3+. Approximately 50% of the total Fe measured in the exsolved pyroxene grain was ferric. Partitioning of Fe2+ and Fe3+ among the lamellae is invoked to explain the difference in npFe development in pigeonite and augite. The results of this study, the first to identify Fe3+ in a crystalline lunar ferromagnesian silicate, have implications for our understanding of how space weathering might proceed in oxidized phases. Furthermore, the discovery of an Fe3+-rich pyroxene also supports attribution of the 0.7 μm absorption feature observed in Galileo Solid State Imager data to oxidized Fe in clinopyroxenes.

¹Yves Marrocchi,²Emmanuel Jacquet,²Julia Neukampf,²Johan Villeneuve,³Michael E. Zolensky
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13947]
¹Université de Lorraine, CNRS, CRPG, UMR 7358, Vandœuvre-lès-Nancy, 54500 France
²Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), Muséum national d’Histoire naturelle, Sorbonne Université, CNRS, CP52, 57 rue Cuvier, 75005 Paris, France
³X12 Astromaterials Research and Exploration Science, NASA Johnson Space Center, Houston, Texas, 77058 USA
Published by arrangement with John Wiley & Sons

The ungrouped carbonaceous chondrite (CC) Bells has long been considered petrographically similar to CM chondrites based on its matrix abundance and degree of aqueous alteration, but also shows significant isotopic affinities to CR chondrites. Its taxonomic status is thus important for clarifying the relationship of the CRHB (formerly “CR”) clan with other CCs. In this study, we measured the oxygen isotopic compositions of olivines in type I chondrules and isolated olivine grains in Bells. Bells olivines mostly have ∆17O > −4‰, similar to CR chondrites but unlike other CCs that are rich in refractory inclusions, in which chondrules are generally richer in 16O. Therefore, Bells is a CR chondrite (albeit an anomalous one), most similar to the rare, matrix-rich CRs like Al Rais. These chondrites (i) may not necessarily derive from the same primary parent body as mainstream CRs, (ii) bear witness to significant variations of the matrix/chondrule ratio within the CRHB clan, and (iii) may be a good analog for samples retrieved by the space mission OSIRIS-REx.

^1,2A. Stephant,¹C. Carli,²M. Anand,³A. Néri,⁴J. Davidson,^1,5G. Pratesi,⁵T. Cuppone,²R. C. Greenwood,²I. A. Franchi
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.13944]
¹Istituto di Astrofisica e Planetologia Spaziali – INAF, Rome, 00133 Italy
²School of Physical Sciences, The Open University, Milton Keynes, MK7 6AA UK
³Bayerisches Geoinstitut, University of Bayreuth, Bayreuth, 95447 Germany
⁴Buseck Center for Meteorite Studies, School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, 85287 USA
⁵Dipartimento di Scienze della Terra, Università degli Studi di Firenze, Firenze, 50121 Italy
Published by arrangement with John Wiley & Sons

The Northwest Africa (NWA) 090 meteorite, initially classified as an acapulcoite, presents petrological, chemical, and isotopic characteristics comparable to a group of seven primitive winonaites: Dhofar 1222, NWA 725, NWA 1052, NWA 1054, NWA 1058, NWA 1463, and NWA 8614. Five of these samples were previously classified as acapulcoites or ungrouped achondrites before being reclassified as winonaites based on their oxygen isotopic compositions. These misclassifications are indicative of the particular compositional nature of these primitive achondrites. All contain relict chondrules and a lower closure temperature of metamorphism of 820 ± 20 °C compared to other typical winonaites, as well as mineral elemental compositions similar to those of acapulcoites. The oxygen isotopic signature of these samples, δ17O of 1.18 ± 0.17‰, δ18O of 3.18 ± 0.30‰, and Δ17O of −0.47 ± 0.02, is in fact resolvable from both acapulcoites and winonaites. We investigate the relationship between these eight primitive achondrites, typical winonaites, and acapulcoites, to redefine petrological, mineralogical, and geochemical criteria of primitive achondrite classification. Distinguishing between winonaites, acapulcoites, and this group of eight primitive achondrites can be unambiguously done using a combination of several mineralogical and chemical criteria. A combination of olivine fayalite content and FeO/MnO ratio, as well as plagioclase potassium content allow us to separate these three groups without the absolute necessity of oxygen isotope analyses. NWA 090 as well as the other seven primitive achondrites, although related to winonaites, are most likely derived from a parent body distinct from winonaites and acapulcoites–lodranites, and define a new group of primitive achondrites that can be referred to as tissemouminites.

^1,2M.D. Suttle et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.13938]
¹School of Physical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA UK
²Planetary Materials Group, Natural History Museum, Cromwell Road, London, SW7 5BD UK
Published by arrangement with John Wiley & Sons

The Winchcombe meteorite is a CM chondrite breccia composed of eight distinct lithological units plus a cataclastic matrix. The degree of aqueous alteration varies between intensely altered CM2.0 and moderately altered CM2.6. Although no lithology dominates, three heavily altered rock types (CM2.1–2.3) represent >70 area%. Tochilinite–cronstedtite intergrowths (TCIs) are common in several lithologies. Their compositions can vary significantly, even within a single lithology, which can prevent a clear assessment of alteration extent if only TCI composition is considered. We suggest that this is due to early alteration under localized geochemical microenvironments creating a diversity of compositions and because later reprocessing was incomplete, leaving a record of the parent body’s fluid history. In Winchcombe, the fragments of primary accretionary rock are held within a cataclastic matrix (~15 area%). This material is impact-derived fallback debris. Its grain size and texture suggest that the disruption of the original parent asteroid responded by intergranular fracture at grain sizes <100 μm, while larger phases, such as whole chondrules, splintered apart. Re-accretion formed a poorly lithified body. During atmospheric entry, the Winchcombe meteoroid broke apart with new fractures preferentially cutting through the weaker cataclastic matrix and separating the breccia into its component clasts. The strength of the cataclastic matrix imparts a control on the survival of CM chondrite meteoroids. Winchcombe’s unweathered state and diversity of lithologies make it an ideal sample for exploring the geological history of the CM chondrite group.

^1,2Ildiko Gyollai,^2,3Ákos Kereszturi,^4,5Elias Chatzitheodoridis,⁶Zsolt Kereszty,^1,2Máté Szabó,^2,7Csilla Király,^2,7Zoltan Szalai
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13931]
¹Institute for Geological and Geochemical Research, Research Centre for Astronomy and Earth Sciences, Eötvös Loránd Research Network, Budaorsi ut 45, H-1112 Budapest, Hungary
²CSFK, MTA Centre of Excellence, Konkoly Thege Miklós út 15-17, H-1121 Budapest, Hungary
³Konkoly Thege Miklos Astronomical Institute, Research Centre for Astronomy and Earth Sciences, Eötvös Loránd Research Network, Konkoly Thege Miklós út 15-17, H-1121 Budapest, Hungary
⁴Department of Geological Sciences, School of Mining and Metallurgical Engineering, National Technical University of Athens 9, Heroon Polytechneiou str., GR-15780 Zografou, Athens, Greece
⁵Network of Researchers on the Chemical Evolution of Life (NoRCEL), LS2 9JT Leeds, UK
⁶Private Collector at IMCA (IMCA#6251) and Meteoritical Society, H-9010 Győr, Hungary
⁷Geographical Research Institute, Research Centre for Astronomy and Earth Sciences, Eötvös Loránd Research Network, Budaorsi ut 45, H-1112 Budapest, Hungary
Published by arrangement with John Wiley & Sons
The analysis of the Csatalja H4 chondrite (which was found in August 2012) suggests shock-related textures and spatial inhomogeneities, indicating a complex geological history. In the most heavily fractured and sheared units, small opaque grains and older fractures have locally enhanced the shock effect, producing melt. While the impact textures were evident in most units of the meteorite, mechanical shearing is apparent in only two units, suggesting that these units might have been present at somewhat different locations inside the parent body. Shearing also occurred at the border of the so-called xenolith unit, confirming its mechanical mixing with the other units. Besides fragmentation and melting, chemical changes due to impact have also been identified, producing compositional homogenization of olivines in 30% of the investigated area of the sample’s thin section (23 mm2), and moderate accumulation of Fe, Ca, and Na in the strongly shocked zones, initiating crystallization of feldspar in veins with a specific spatial distribution (feldspar glass with metal–sulfide globules). Analyzing the high P–T minerals, the peak shock pressure and temperature values differed substantially in the various units, ranging between 2 and 17 GPa, 100 and >1200 °C. The xenolith unit crystallized more slowly after the impact event and does not show shock impact alterations, suggesting that it was formed in a deeper region of the parent body. This was later shifted to its current surroundings and was lithified (fixed) to the rest of the sample. This “randomly selected” Csatalja sample provides information on the range of the formation temperatures, pressures, and processes that contributed to the heterogeneity of meteorites at the mm spatial scale, in general. The identified heterogeneity is a result not purely of the shock effects but also of the different pre-shock structural characteristics. The shock also mixed fragments mechanically that have been formed at different environments, with at least several dozens or even 100 m depth in the parent body.

¹Ryan Scott Jakubek,¹Marc D. Fries
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13940]
¹Jacobs, NASA Johnson Space Center, Mail Code XI2, Houston, Texas, 77058 USA
²NASA Johnson Space Center, Houston, Texas, 77058 USA
Published ba arrangement with John Wiley & Sons

The study of astromaterials generally involves the distribution of limited sample to many laboratories for analysis. Maximum scientific yield for a sample occurs when the data and results from different studies are examined as a collective. This collective examination of results will be particularly important for upcoming sample return missions including Mars sample return and OSIRIS-REx. When comparing results across laboratories, instrument calibration is of key importance. For Raman data, this includes the calibration of all three Raman band parameters: peak wavenumber position, bandwidth, and intensity. Although wavenumber is routinely calibrated, bandwidth and intensity are not; though they are commonly compared across studies. In addition, Raman instrument calibration is time dependent. An understanding of the time dependence of instrument calibration is important for proper calibration. Here, we use a mixture of well-established and recently developed calibration techniques to propose a standard method of calibrating Raman astromaterial data across laboratories to maximize the scientific value of the data.

¹Georgy V.Makhatadze(Георгий В. Махатадзе),¹Martin Schiller,¹Martin Bizzarro
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.12.020]
¹Centre for Star and Planet Formation (StarPlan), Globe Institute, Faculty of Health and Medical Sciences, University of Copenhagen, Øster Voldgade 5-7, 1350 Copenhagen K, Denmark
Coypright Elsevier

Various chemical elements including nickel (Ni) exhibit mass-independent isotope heterogeneity on a bulk meteorite level, which is generally accepted to reflect the heterogeneous distribution of presolar carrier(s) from different nucleosynthetic sources. Thus, understanding the nature of the carriers can help decipher the origin of the observed nucleosynthetic variability, which remains elusive. In this study, we present the first high precision measurements of mass-independent and mass-dependent Ni isotope compositions for step-leaches of the CI chondrite Ivuna and Efremovka CAIs supplemented by bulk chondrite measurements. Step-leaches record highly anomalous Ni isotope signatures that can be attributed to at least four diverse nucleosynthetic sources. The most anomalous leachates show either large deficits (up to 0.1 %) in the neutron-poor 58Ni and 60Ni nuclides (L11, thought to contain mainly s-process derived Ni) or minor enrichments and deficits (∼100 ppm) in 60Ni or 64Ni (L6, L8, L9 and L10, all thought to derive mainly from supernovae). Pristine CAIs record Ni isotope compositions typified by enrichments in 58Ni of up to 400 ppm. Our new data for bulk chondrites agree with earlier work and emphasize the appropriateness of using the 62Ni/61Ni ratio for internal normalization. Based on the compositional relations between the step-leaches data, CAIs, and bulk meteorites, we show that 60Ni variability is consistent with being of nucleosynthetic origin as opposed to reflecting variable Fe/Ni ratios in the presence of live 60Fe. Finally, we infer that the observed Ni nucleosynthetic disk variability is predominantly driven by a combination of processes separating different nucleosynthetic carriers in the disk from each other, including thermal processing and size-based sorting.

¹Philip M.Reger,²Yvonne Roebbert,³Wladimir Neumann,⁴Abdelmouhcine Gannoun,⁵Marcel Regelous,³Winfried H.Schwarz,³Thomas Ludwig,³Mario Trieloff,²Stefan Weyer,^6,1Audrey Bouvier
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.12.025]
¹Department of Earth Sciences, Institute of Earth and Space Exploration, University of Western Ontario, N6A 5B7 London, Ontario, Canada
²Institut für Mineralogie, Leibniz-Universität Hannover, 30167 Hannover, Germany
³Institut für Geowissenschaften, Klaus-Tschira-Labor für Kosmochemie, Universität Heidelberg, 69120 Heidelberg, Germany
⁴Laboratoire Magmas et Volcans, Université Clermont-Auvergne, F-63000 Clermont-Ferrand, France
⁵GeoZentrum Nordbayern, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
⁶Bayerisches Geoinstitut, Universität Bayreuth, 95447 Bayreuth, Germany
Copyright Elsevier

Achondrite meteorites are remnants of the earliest planetary differentiation processes in the Solar System. They have been used to anchor short-lived radiochronometers to absolute ages determined from long-lived radiochronometers. More specifically, when comparing the isotopic systematics of the short-lived ²⁶Al-²⁶Mg chronometer anchored to absolute U-corrected Pb-Pb ages, inferences about the distribution of ²⁶Al (half-life of ∼717 000 yr) in the protoplanetary disk can be evaluated. The ungrouped achondrite Erg Chech (EC) 002 has a distinct mineralogy and more evolved elemental composition compared to basaltic achondrites. In situ and solution ²⁶Al-²⁶Mg chronometry and ⁵³Mn-⁵³Cr chronometry suggest that EC 002 formed within ∼0.7 to 2.2 Ma after the formation of Ca-Al-rich inclusions (CAIs), making it the oldest known sample of igneous crust in the Solar System (Barrat et al., 2021, Anand et al., 2022, Zhu et al., 2022, Fang et al., 2022). Here we present the U-corrected Pb-Pb age and ²⁶Al-²⁶Mg age obtained by MC-ICPMS solution analysis of the same mineral separate samples of EC 002. In addition, six merrillite grains were analyzed by in-situ SIMS to determine their Pb-Pb individual ages.

The U isotope composition of EC 002 exhibits internal heterogeneities between leached pyroxene (²³⁸U/²³⁵U = 137.766 ± 0.027) and the bulk rock (²³⁸U/²³⁵U = 137.8190 ± 0.0074). The Pb isotope composition of progressively leached pyroxenes are characterized by radiogenic ²⁰⁶Pb/²⁰⁴Pb ratios (ranging from 41 to 23487). Using the U isotope composition of the leached pyroxenes, the resulting age of the ²⁰⁷Pb/²⁰⁶Pb-²⁰⁴Pb/²⁰⁶Pb isochron is 4565.87 ± 0.30 Ma (2σ). The weighted mean of the Pb-Pb ages of seven SIMS analyses of merrillites are 4564.3 ± 5.2 Ma (2σ). These similar ages (within uncertainty) indicate rapid cooling and the absence of significant thermal events after ∼4559 Ma on the parent body of EC 002. The ²⁶Al-²⁶Mg isochron through a bulk rock, pyroxene, fine-grained and four plagioclase fractions defines an initial ²⁶Al/²⁷Al ratio of [8.89 ± 0.79] × 10⁻⁶ corresponding to a formation age of 1.83 ± 0.12 Ma after CAIs ([5.23 ± 0.13] × 10⁻⁵; Jacobsen et al., 2008). The initial ²⁶Al abundance is consistent with previous MC-ICP-MS ²⁶Al-²⁶Mg reported systematics for EC 002 (Fang et al., 2022), but 0.46 ± 0.13 Myr older than the in situ SIMS ²⁶Al-²⁶Mg age previously reported by Barrat et al. (2021).When anchored to the absolute Pb-Pb age of CV3 CAIs (4567.30 ± 0.16 Ma; Connelly et al., 2012), the Al-Mg model age of EC 002 is 4565.47 ± 0.20 Ma, slightly younger than its U-corrected Pb-Pb age.

The concordance of the Pb-Pb and ²⁶Al-²⁶Mg ages of ungrouped CC achondrites when anchored to EC 002 suggest that ²⁶Al was homogeneously distributed between the NC and CC reservoirs at the time of their parent body accretion. Furthermore, the presence of internal U isotope heterogeneities found between mineral and whole-rock samples of EC 002 supports the need of U isotope analysis of meteoritic samples dated using the Pb-Pb chronometer.