¹Brandon Mahan, ^1,2Frédéric Moynier, ^2,3Pierre Beck, ¹Emily A. Pringle, ^1,2Julien Siebert
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2017.09.027]
¹Institut de Physique du Globe de Paris, Université Paris Diderot, Université Sorbonne Paris Cité, CNRS UMR 7154, 1 rue Jussieu, 75238 Paris Cedex 05, France
²Institut Universitaire de France, Paris, France
³UJF-Grenoble 1, CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), UMR 5274, Grenoble F-38041, France
Copyright Elsevier

Carbonaceous chondrites (CCs) may have been the carriers of water, volatile and moderately volatile elements to Earth. Investigating the abundances of these elements, their relative volatility, and isotopes of state-change tracer elements such as Zn, and linking these observations to water contents, provides vital information on the processes that govern the abundances and isotopic signatures of these species in CCs and other planetary bodies. Here we report Zn isotopic data for 28 CCs (20 CM, 6 CR, 1 C2-ung, and 1 CV3), as well as trace element data for Zn, In, Sn, Tl, Pb, and Bi in 16 samples (8 CM, 6 CR, 1 C2-ung, and 1 CV3), that display a range of elemental abundances from case-normative to intensely depleted. We use these data, water content data from literature and Zn isotopes to investigate volatile depletions and to discern between closed and open system heating. Trace element data have been used to construct relative volatility scales among the elements for the CM and CR chondrites. From least volatile to most, the scale in CM chondrites is Pb-Sn-Bi-In-Zn-Tl, and for CR chondrites it is Tl-Zn-Sn-Pb-Bi-In. These observations suggest that heated CM and CR chondrites underwent volatile loss under different conditions to one another and to that of the solar nebula, e.g. differing oxygen fugacities. Furthermore, the most water and volatile depleted samples are highly enriched in the heavy isotopes of Zn. Taken together, these lines of evidence strongly indicate that heated CM and CR chondrites incurred open system heating, stripping them of water and volatiles concomitantly, during post-accretionary shock impact(s).

¹Andrew Tillett, ^1,2John Dermigny, ^2,3Mark Emamian, ^1,6Yuri Tonin, ¹Igal Bucay, ^4,5Rachel L. Smith, ¹Michael Darken, ¹Corey Dearing, ¹Mikaela Orbon, ^1,2Christian Iliadis
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 871, 66-71 Link to Article [https://doi.org/10.1016/j.nima.2017.07.057]
¹Department of Physics and Astronomy, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
²Triangle Universities Nuclear Laboratory (TUNL), Durham, NC 27708, USA
³Department of Physics, Duke University, Durham, NC 27708, USA
⁴North Carolina Museum of Natural Sciences, 121 West Jones Street, Raleigh, NC 27603, USA
⁵Department of Physics and Astronomy, Appalachian State University, 525 Rivers Street, Boone, NC 28608-2106, USA
⁶CAPES Foundation, Ministry of Education of Brazil, Brasília, DF, 70.040-020, Brazil

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^1,2E.Palomba et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2017.09.020]
¹INAF-IAPS, via del Fosso del Cavaliere 100, I-00133 Rome, Italy
²Space Science Data Center-ASI, Via del Politecnico, snc, Edificio D, 00133 Rome, Italy
Copyright Elsevier

At the beginning of the Ceres investigation, the Dawn-NASA mission discovered a large bright spot (BS) in the Occator crater floor. Several other smaller bright spots were discovered during the following phases of the mission. In this paper, a complete survey for the detection of BS on the Ceres surface have been made by using the hyperspectral data acquired by Visible and Infrared Mapping Spectrometer (VIR). The hyperspectral images span the spectral range from 0.2 to 5 µm, by using two channel, the VIS channel with a spectral sampling of 1.8 nm and a IR channel with a spectral sampling of 9.8 nm. Finally a catalogue of 92 BS has been compiled and their compositional properties have been examined. In particular, five spectral parameters have been applied to perform the analysis: the photometrically corrected reflectance and four band depths, related to spectral absorptions at 2.7 µm (OH fundamental indicative of phyllosilicates), at 3.05 µm (due to ammoniated clays), at 3.4 and 4.0 µm (carbonate overtones). The 90% of BS are impact-related features (ejecta, crater rim, crater floor, crater wall). The two brightest BS, Cerealia and Vinalia Faculae, are located on the Occator crater floor. Most of BSs show features similar to the average Ceres surface, which has low reflectance and is composed of Mg-phyllosilicates and ammoniated clays, with a reduced abundance of Mgsingle bondCa carbonates. Cerealia and Vinalia Faculae are a peculiar BS family, with a high abundance of Na-carbonates and Al-rich phyllosilicates. Oxo and a companion bright spot represents a third category, depleted in phyllosilicates and with a high to moderate albedo. Carbonate composition ranges from Mg/Ca to Na components. Haulani, Ernutet, Kupalo, and other two BS’s represent another group, with intermediate properties between the typical BS and the Oxo family: they are moderately rich in carbonates and slightly depleted in Mg- and ammoniated phyllosilicates. The four families probably explain a single evolutionary path followed by the BS from the formation to their maturity: initially the very fresh bright spots would possess characteristics similar to Cerealia and Vinalia Faculae; with time, salts and OH volatilize and a light mixing with surrounding material would produce Oxo-like BS’s; additional strong mixing would form Haulani-like BS, which finally become a typical bright spots.

^1,2,3Martin Schmieder, ³Trudi Kennedy, ³Fred Jourdan, ^4,5Elmar Buchner, ^6,7,8Wolf Uwe Reimold
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2017.09.036]
¹Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, TX 77058, USA
²NASA–Solar System Exploration Research Virtual Institute (SSERVI)
³Western Australian Argon Isotope Facility, Department of Applied Geology and John de Laeter Centre for Isotope Research, Curtin University of Technology, GPO Box U1987, Perth, WA 6845, Australia
⁴HNU – Neu-Ulm University, Wileystraße 1, D-89231 Neu-Ulm, Germany
⁵Institut für Mineralogie und Kristallchemie, Universität Stuttgart, Azenbergstraße 18, D-70174 Stuttgart, Germany
⁶Museum für Naturkunde – Leibniz Institute for Evolution and Biodiversity Science, Invalidenstrasse 43, D-10115 Berlin, Germany
⁷Humboldt Universität zu Berlin, Unter den Linden 6, 10099 Berlin, Germany
⁸Geochronology Laboratory, University of Brasília, Brasília, Brazil
Copyright Elsevier

40Ar/39Ar dating of specimens of moldavite, the formation of which is linked to the Ries impact in southern Germany, with a latest-generation ARGUS VI multi-collector mass spectrometer yielded three fully concordant plateau ages with a weighted mean age of 14.808 ± 0.021 Ma (± 0.038 Ma including all external uncertainties; 2σ; MSWD = 0.40, P = 0.67). This new best-estimate age for the Nördlinger Ries is in general agreement with previous 40Ar/39Ar results for moldavites, but constitutes a significantly improved precision with respect to the formation age of the distal Ries-produced tektites. Separates of impact glass from proximal Ries ejecta (suevite glass from three different surface outcrops) and partially melted feldspar particles from impact melt rock of the SUBO 18 Enkingen drill core failed to produce meaningful ages. These glasses show evidence for excess 40Ar introduction, which may have been incurred during interaction with hydrothermal fluids. Only partially reset 40Ar/39Ar could be determined for the feldspathic melt separates from the Enkingen core. The new 40Ar/39Ar results for the Ries impact structure constrain the duration of crater cooling, during the prevailing hydrothermal activity, to locally at least ∼60 kyr. With respect to the dating of terrestrial impact events, this paper briefly discusses a number of potential issues and effects that may be the cause for seemingly precise, but on a kyr-scale inaccurate, impact ages.