¹Shornikov, S.I.
Geochemistry International 57, 865-872 Link to Article [DOI: 10.1134/S001670291908010X]
¹Vernadsky Institute of Geochemistry and Analytical Chemistry (GEOKhI), Russian Academy of Sciences, Moscow, 119991, Russian Federation

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¹A.J.King,^1,2H.C.Bates,³D.Krietsch,³H.Busemann,⁴P.L.Clay,¹P.F.Schofield,¹S.S.Russell
Geochemistry (Chemie der Erde) (In Press) Link to Article [https://doi.org/10.1016/j.chemer.2019.08.003]
¹Planetary Materials Group, Department of Earth Sciences, Natural History Museum, Cromwell Road, London, SW7 5BD, UK
²Atmospheric, Oceanic and Planetary Physics Department, Clarendon Laboratory, University of Oxford, Sherrington Road, Oxford, OX1 3P, UK
³Institute of Geochemistry and Petrology, ETH Zürich, Clausiusstrasse 25, 8092 Zürich, Switzerland
⁴School of Earth and Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK
Copyright Elsevier

We report new mineralogical, petrographic and noble gas analyses of the carbonaceous chondrite meteorites Y-82162 (C1/2_ung), Y-980115 (CI1), Y-86029 (CI1), Y-86720 (C2_ung), Y-86789 (C2_ung), and B-7904 (C2_ung). Combining our results with literature data we show that these meteorites experienced varying degrees of aqueous alteration followed by short-lived thermal metamorphism at temperatures of >500 °C. These meteorites have similar mineralogy, textures and chemical characteristics suggesting that they are genetically related, and we strongly support the conclusion of Ikeda (1992) that they form a distinct group, the CYs (“Yamato-type”). The CY chondrites have the heaviest oxygen isotopic compositions (δ¹⁷O ˜12 ‰, δ¹⁸O ˜22 ‰) of any meteorite group, high abundances of Fe-sulphides (˜10 ‒ 30 vol%) and phosphates, and contain large grains of periclase and unusual objects of secondary minerals not reported in other carbonaceous chondrites. These features cannot be attributed to parent body processes alone, and indicate that the CYs had a different starting mineralogy and/or alteration history to other chondrite groups, perhaps because they formed in a different region of the protoplanetary disk. The short cosmic-ray exposure ages (≤1.3 Ma) of the CY chondrites suggest that they are derived from a near-Earth source, with recent observations by the Hayabusa2 spacecraft highlighting a possible link to the rubble-pile asteroid Ryugu.

^1,2R.Jaumann et al. (>10)
Science 365, 817-820 Link to Article [DOI: 10.1126/science.aaw8627]
¹German Aerospace Center (DLR), Institute of Planetary Research, Berlin, Germany.
²Free University of Berlin, Institute of Geosciences, Berlin, Germany.
Reprinted with permission from AAAS

The near-Earth asteroid (162173) Ryugu is a 900-m-diameter dark object expected to contain primordial material from the solar nebula. The Mobile Asteroid Surface Scout (MASCOT) landed on Ryugu’s surface on 3 October 2018. We present images from the MASCOT camera (MASCam) taken during the descent and while on the surface. The surface is covered by decimeter- to meter-sized rocks, with no deposits of fine-grained material. Rocks appear either bright, with smooth faces and sharp edges, or dark, with a cauliflower-like, crumbly surface. Close-up images of a rock of the latter type reveal a dark matrix with small, bright, spectrally different inclusions, implying that it did not experience extensive aqueous alteration. The inclusions appear similar to those in carbonaceous chondrite meteorites.