¹Aryavart Anand,¹Pascal M. Kruttasch,¹Klaus Mezger
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13916]
¹Institut für Geologie, Universität Bern, Baltzerstrasse 1+3, 3012 Bern, Switzerland
Published by arrangement with John Wiley & Sons

The meteorite Erg Chech (EC) 002 is the oldest felsic igneous rock from the solar system analyzed to date and provides a unique opportunity to study the formation of felsic crusts on differentiated protoplanets immediately after metal–silicate equilibration or core formation. The extinct ⁵³Mn-⁵³Cr chronometer provides chronological constraints on the formation of EC 002 by applying the isochron approach using chromite, metal–silicate–sulfide, and whole-rock fractions as well as “leachates” obtained by sequential digestion of a bulk sample. Assuming a chondritic evolution of its parent body, a ⁵³Cr/⁵²Cr model age is also obtained from the chromite fraction. The ⁵³Mn-⁵³Cr isochron age of 1.73 ± 0.96 Ma (anchored to D’Orbigny angrite) and the chromite model age constrained between $$ {1.46}_{-0.68}^{+0.78} $$ and $$ {2.18}_{-1.06}^{+1.32} $$ Ma after the formation of calcium-aluminium-rich inclusions (CAIs) agree with the ²⁶Al-²⁶Mg ages (anchored to CAIs) reported in previous studies. This indicates rapid cooling of EC 002 that allowed near-contemporaneous closure of multiple isotope systems. Additionally, excess in the neutron-rich ⁵⁴Cr (nucleosynthetic anomalies) combined with mass-independent isotope variations of ¹⁷O provides genealogical constraints on the accretion region of the EC 002 parent body. The ⁵⁴Cr and ¹⁷O isotope compositions of EC 002 confirm its origin in the “noncarbonaceous” reservoir and overlap with the vestoid material Northwest Africa 12217 and anomalous eucrite Elephant Moraine 92023. This indicates a common feeding zone during accretion in the protoplanetary disk between the source of EC 002 and vestoids. The enigmatic origin of iron meteorites remains still unresolved as EC 002, which is more like a differentiated crust, has an isotope composition that does not match known iron meteorite groups that were once planetesimal cores.

¹Takaaki Noguchi et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13919]
¹Division of Earth and Planetary Sciences, Kyoto University, Kitashirakawaoiwake-cho, Sakyo-ku, Kyoto, 606-8502 Japan
Published by arrangement with John Wiley & Sons

Asteroids and comets are thought to form in the inner and outer solar systems, respectively. Chondritic porous and smooth interplanetary dust particles (CP IDPs and CS IDPs, respectively) in the stratosphere are regarded as dust grains from comets and hydrated asteroids, respectively. Here, we describe an Antarctic micrometeorite (AMM) composed of lithologies of both CP and CS IDPs. In addition to the CS IDP-like compact lithology that experienced severe aqueous alteration, the CP IDP-like porous lithology shows evidence of very weak aqueous alteration. The structure of the organic matter in the porous lithology varies from that in the CP IDPs to aromatic-rich organic matter. In contrast, the structure of the organic matter in the compact lithology is homogenous, which is consistent with higher degrees of aqueous alteration. Its structure is more similar to that of CP IDPs and Wild 2 samples than that of meteoritic insoluble organic matter, suggesting that the compact lithology formed from the porous lithology. Some CP IDPs are related to cometary dust streams, such as those originating from 26P/Grigg-Skjellerup. In addition, the presence of this AMM indicates an additional origin of the CP IDPs and their equivalent AMMs. The mineralogy and organic chemistry of this AMM suggest that its parent body was composed of the same building blocks as those of the comets, and later experienced incomplete aqueous alteration. The AMM probably formed as microbreccia in the regolith layer composed of materials from a CP IDP-like crust and a hydrated interior.

¹Jüri Plado,^2,3Ania Losiak,¹Argo Jõeleht,⁴Jens Ormö,⁵Helena Alexanderson,⁵Carl Alwmark,⁶Eva Maria Wild,⁶Peter Steier,²Marek Awdankiewicz,³Claire Belcher
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13914]
¹Department of Geology, University of Tartu, Ravila 14A, EE 50411 Tartu, Estonia
²Institute of Geological Sciences, Polish Academy of Sciences, Podwale 75, PL 50-449 Wrocław, Poland
³WildFIRE Lab, University of Exeter, Exeter, EX4 4PS UK
⁴Centro de Astrobiología CSIC-INTA, Instituto Nacional de Técnica Aeroespacial, 28850 Torrejon de Ardoz, Spain
⁵Department of Geology, Lund University, SE-22362 Lund, Sweden
⁶VERA Laboratory, Faculty of Physics, Isotope Physics, University of Vienna, Währinger Straße 17, A-1090 Vienna, Austria
Published by arrangement with Johne Wiley & Sons

Compared to intensive research on km-sized meteorite impact craters, fewer studies focus on smaller craters. The small craters are often hard or impossible to recognize using “classical” criteria like the presence of shatter cones, shocked quartz, and geochemical indicators. Therefore, a long list of candidate structures awaiting approval/disapproval of their origin has been formed over the last decades. One of them is the Tor structure in central Sweden. To test a hypothesis of an impact origin of this structure, we have performed topographical analysis, geophysical studies, 10Be exposure dating of boulders, and 14C dating of Tor-associated charcoal. None of the methods gave us a reason to claim the Tor structure is of impact origin. Thus, we support a recently suggested idea of Tor being formed by a grounded iceberg within a glacial lake.

¹Victoria Froh,¹Maitrayee Bose,^2,3Martin D.Suttle,⁴Jacopo Nava,^2,5Luigi Folco,¹Lynda B.Williams,⁶JulieCastillo-Rogez
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2022.115300]
¹School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA
²School of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
³Dipartimento di Scienze della Terra, Università di Pisa, 56126 Pisa, Italy
⁴University of Padova, Department of Geosciences, Via G.Gradenigo 6, 35131 Padova, Italy
⁵CISUP, Centro per l’Integrazione della Strumentazione dell’Università di Pisa, Lungarno Pacinotti 43, 56126 Pisa, Italy
⁶Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
Copyright: Elsevier

Micrometeorites represent a major potential source of volatiles for the early Earth, although often overlooked due to their small sizes and the effects of atmospheric entry. In this study we explore an unusual ~2000 μm, fine-grained unmelted micrometeorite TAM19B-7 derived from a water-rich C-type asteroid. Previous analysis revealed a unique O-isotope composition and intensely aqueously altered geological history. We investigated its carbon isotopic composition using the NanoSIMS and characterized the carbon-bearing carriers using Raman and Near-Infrared spectroscopy. We found that TAM19B-7 has a 13C enriched bulk composition (δ13C = +3 ± 8 ‰), including a domain with 13C depletion (δ13C = −27.1 ‰). Furthermore, a few micro-scale domains show 13C enrichments (δ13C from +12.9 ‰ to +32.7 ‰) suggesting much of the particle’s carbon content was reprocessed into fine-grained carbonates, likely calcite. The heavy bulk C-isotope composition of TAM19B-7 indicates either open system gas loss during aqueous alteration or carbonate formation from isotopically heavy soluble organics. Carbonates have been detected on small body surfaces, including across dwarf planet Ceres, and on the C-type asteroids Bennu and Ryugu. The preservation of both carbonates with 13C enrichments and organic carbon with 13C depletion in TAM19B-7, despite having been flash heated to high temperatures (<1000 °C), demonstrates the importance of cosmic dust as a volatile reservoir.

^1,2Allison Pease,²Jie Li
Earth and Planetary Science Letters 599, 117865 Link to Article [https://doi.org/10.1016/j.epsl.2022.117865]
¹Department of Earth and Environmental Sciences, Michigan State University, East Lansing, MI, 48824, USA
²Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, 48109, USA
Copyright Elsevier

Mercury has fascinated researchers for decades due to its sizable metallic core and weak magnetic field. The behavior of Fe-S and (Fe, Ni)-S systems provides constraints on core conditions and regimes of solidification to predict magnetic field strength. In this study, we investigate the melting behavior of the (Fe, Ni)-S system, a candidate composition to model the Mercurian core. We observe that the Fe-S liquidus has an inflection point at ∼10 wt.% S at 14 GPa and ∼11.5 wt.% S at 24 GPa, while (Fe, Ni)-S does not. At 24 GPa, Ni may lower the melting point of the Fe-S system by as much as 300 °C, indicating that solidification models and adiabatic calculations must account for the presence of Ni.

^1,2,3Poole, Graeme M.,¹Stumpf, Roland,¹Rehkämper, Mark
Journal of Analytical Atomic Spectrometry 37, 783-794 Open Access Link to Article [DOI 10.1039/d1ja00468a]
¹Department of Earth Science and Engineering, Imperial College London, London, SW7 2AZ, United Kingdom
²School of Earth Sciences, University of Bristol, Bristol, BS8 1RJ, United Kingdom
³Imaging and Analysis Centre, Natural History Museum, London, SW7 5BD, United Kingdom

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¹Tian, Shengyu,¹Moynier, Frederic,¹Inglis, Edward C.,²Jensen, Ninna K.,²Deng, Zhengbin,²Schiller, Martin,^1,2Bizzarro, Martin
Journal of Analytical Atomic Spectrometry 37, 656 – 662 Link to Article [DOI 10.1039/d1ja00418b]
¹Université de Paris, Institut de Physique Du Globe de Paris, CNRS, Paris cedex 05, France
²Centre for Star and Planet Formation, Globe Institute, University of Copenhagen, Copenhagen, Denmark

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^1,2Greber, Nicolas D.,³Van Zuilenc, Kirsten
Chimia 76, 18-25 Open Access Link to Article [DOI 10.2533/chimia.2022.18]
¹Natural History Museum of Geneva, Route de Malagnou 1, Geneva, CH-1208, Switzerland
²Institute of Geological Sciences, University of Bern, Baltzerstrasse 1+3, Bern, CH-3012, Switzerland
³Vrije Universiteit, De Boelelaan 1085, Amsterdam, 1081 HV, Netherlands

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¹Wieler, Rainer
Chimia 76, 9-17 Open Access Link to Article [DOI 10.2533/chimia.2022.9]
¹ETH Zürich, Department of Earth Sciences, Clausiusstrasse 25, Zurich, CH-8092, Switzerland

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^1,2Damanveer S.Grewal,¹Tao Sun,^1,3Sanath Aithala,¹Taylor Hough,¹Rajdeep Dasgupta,^1,4Laurence Y.Yeung,⁵Edwin Schauble
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.10.025]
¹Department of Earth, Environmental and Planetary Sciences, Rice University, 6100 Main Street, MS 126, Houston, TX 77005, USA
²Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125, USA
³Department of Earth and Environmental Sciences, University of Minnesota, Minneapolis, MN 55455, USA
⁴Department of Chemistry, Rice University, 6100 Main Street, MS 126, Houston, TX 77005, USA
⁵Department of Earth and Space Sciences, University of California, Los Angeles, CA 90095, USA
Copyright Elsevier

15N/14N ratios of meteorites are a powerful tool for tracing the journey of life-essential volatiles like nitrogen (N), carbon and water from nebular solids to the present-day rocky planets, including Earth. The utility of 15N/14N ratios of samples originating from differentiated protoplanets (e.g., iron meteorites) and planets (e.g., Earth’s mantle) for tracing this journey could be affected by the fractionation of N isotopes during core-mantle differentiation, which would overprint their primitive compositions. The extent of N isotopic fractionation during core-mantle differentiation and its effect on the 15N/14N ratios of resulting metallic and silicate reservoirs is, however, poorly understood. Using high pressure-temperature experiments, here we show that N isotopic fractionation between metallic and silicate melts (Δ15Nalloy–silicate = δ15Nalloy – δ15Nsilicate = –3.3‰ to –1.0‰) is limited across a wide range of oxygen fugacity and is much smaller than previous estimates. Also, we present ab initio calculations based on the relevant N speciation in metallic and silicate melts confirming both the magnitude and direction of N isotopic fractionation predicted by our experimental results. Limited N isotopic fractionation during core-mantle differentiation suggests that the core and mantle relicts largely preserve the N isotopic compositions of their bulk bodies. Based on the δ15N values of non-carbonaceous iron meteorites (as low as –95‰), we predict that the extent of variations in the N isotopic compositions of inner solar system protoplanets was larger than that recorded by enstatite chondrites (δ15N = –29‰ to –6‰). As most of the Earth grew primarily via the accretion of similar inner solar system protoplanets, a relatively high δ15N value of present-day Earth’s primitive mantle (–5‰) cannot be explained by the accretion of enstatite chondrite-like materials alone and necessitates a significant contribution of 15N-rich materials to the Earth’s interior.