¹A.Longobardo et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2017.09.022]
¹INAF-IAPS, via Fosso del Cavaliere 100, I-00133 Rome, Italy
Copyright Elsevier

We present an analysis of the areal distribution of spectral parameters derived from the VIR imaging spectrometer on board NASA/Dawn spacecraft. Specifically we studied the Occator quadrangle of Ceres, which is bounded by latitudes 22°S to 22°N and longitudes 214°E to 288°E, as part of the overall study of Ceres’ surface composition reported in this special publication. The spectral parameters used are the photometrically corrected reflectance at 1.2 µm, the infrared spectral slope (1.1–1.9 µm), and depths of the absorption bands at 2.7 µm and 3.1 µm that are ascribed to hydrated and ammoniated materials, respectively.

We find an overall correlation between 2.7 µm and 3.1 µm band depths, in agreement with Ceres global behavior, and band depths are shallower and the spectral slope is flatter for younger craters, probably due to physical properties of regolith such as grain size. Spectral variations correlated with the tali geological unit also suggest differences in physical properties. The deepest band, indicating enrichment of ammoniated phyllosilicates, are associated with ejecta generated by impacts that occurred in southern quadrangles.

The most peculiar region of this quadrangle is the Occator crater (20°N 240°E). The internal crater area contains two faculae, which are the brightest areas on Ceres due to exposure of sodium carbonates, and by two types of ejecta, dark and bright, with different spectral properties, probably due to different formation, evolution or age.

^1,2Zachary D.Sharp
Chemical Geology 448, 137-150 Link to Article [https://doi.org/10.1016/j.chemgeo.2016.11.018]
¹Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131, United States
²Center for Stable Isotopes, University of New Mexico, Albuquerque, NM 87131, United States

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¹Frank Gyngard, ¹Sachiko Amari, ¹Ernst Zinner, ¹Kuljeet Kaur Marhas2
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2017.09.031]
¹Laboratory for Space Sciences and the Department of Physics, Washington University, One Brookings Drive, St. Louis, MO 63130, USA
Copyright Elsevier

We report correlated Si, and Ti isotopic compositions and elemental concentrations of 238 presolar SiC grains from the Murchison CM2 meteorite. Combined with measurements of the C and N isotopic compositions of these 238 grains, 220 were determined to be of type mainstream, 10 type AB, 4 type Y and 4 type Z. SiC grains of diameter ≳2.5µm, to ensure enough material to attempt Ti measurements, were randomly chosen without any other prejudice. The Ti isotopic compositions of the majority of the grains are characterized by enrichments in 46Ti, 47Ti, 49Ti, and 50Ti relative to 48Ti, and show linear isotopic correlations indicative of galactic chemical evolution and neutron capture of the grains parent stars. The variability in the observed Ti signal as a function of depth in most of the grains indicates the presence of distinct subgrains, likely TiC that have been previously observed in TEM studies. Vandium-51 concentrations correlate with those of Ti, indicating V substitutes for Ti in the TiC matrix in many of the grains. No isotopic anomalies in 52Cr/53Cr ratios were observed, and Cr concentrations did not correlate with those of either Ti or V.

¹C. Ashley Norris, ¹Bernard J. Wood
Nature 549, 507-510 Link to Article [doi:10.1038/nature23645]
¹Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK

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¹Remco C. Hin,¹Christopher D. Coath,²Philip J. Carter, ³Francis Nimmo, Yi-Jen Lai,^1,4Philip A. E. Pogge von Strandmann, ¹Matthias Willbold, ²Zoë M. Leinhardt, ¹Michael J. Walter, ¹Tim Elliott
Nature 549, 511-515 Link to Article [doi:10.1038/nature23899]
¹School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, UK
²School of Physics, University of Bristol, H. H. Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL, UK
³Department of Earth and Planetary Sciences, University of California, Santa Cruz, Santa Cruz, California 95064, USA
⁴London Geochemistry and Isotope Centre, Department of Earth Sciences, University College London, and Department of Earth and Planetary Sciences, Birkbeck, University of London, Gower Street, London WC1E 6BT, UK

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