¹Adrien Néri,²François Guyot,¹ Bruno Reynard,³Christophe Sotin
Earth and Planetary Science Letters 530, 115920 Link to Article [https://doi.org/10.1016/j.epsl.2019.115920]
¹University of Lyon, ENS de Lyon, CNRS, Lyon, France
²Museum National d’Histoire Naturelle, Sorbonne Université, IMPMC, UMR CNRS 7590, IRD UMR206, Paris, France
³Jet Propulsion Laboratory-California Institute of Technology, Pasadena, CA, USA
Copyright Elsevier

The inner structure of icy moons comprises ices, liquid water, a silicate rocky core and sometimes an inner metallic core depending on thermal evolution and differentiation. Mineralogy and density models for the silicate part of the icy satellites cores were assessed assuming a carbonaceous chondritic (CI) bulk composition and using a free-energy minimization code and experiments. Densities of other components, solid and liquid sulfides, carbonaceous matter, were evaluated from available equations of state. Model densities for silicates are larger than assessed from magnesian terrestrial minerals, by 200 to 600 kg.m⁻³ for the hydrated silicates, and 300 to 500 kg.m⁻³ for the dry silicates, due to the high iron bulk concentration in CI. The stability of Na-phlogopite in the silicate fraction up to 1300 K favors the trapping of most ⁴⁰K in the rocky/carbonaceous cores with important consequences for modeling of the thermal evolution of icy satellites. We find that CI density models of icy satellite cores taking into account only the silicate and metal/sulfide fraction cannot account for the observed densities and reduced moment of inertia of Titan and Ganymede without adding a lower density component. We propose that this low-density component is carbonaceous matter derived from insoluble organic matter, in proportion of ∼30-40% in volume and 15-20% in mass. This proportion is compatible with contributions from CI and comets, making these primitive bodies including their carbonaceous matter component likely precursors of icy moons, and potentially of most of the objects formed behind the snow line of the solar system.

^1,2T.Mannel et al. (>10)
Astronomy & Astrophysics 630, A26 Link to Article
[https://doi.org/10.1051/0004-6361/201834851]
¹Space Research Institute of the Austrian Academy of Sciences, Schmiedlstrasse 6, 8042 Graz, Austria
²University of Graz, Universitätsplatz 3, 8010 Graz, Austria

¹Pavol Matlovič,¹Juraj Tóth,²Regina Rudawska,¹Leonard Kornoš,¹Adriana Pisarčíková
Astronomy & Astrophysics 629 A71 Link to Article
[https://doi.org/10.1051/0004-6361/201936093]
¹Faculty of Mathematics, Physics and Informatics, Comenius University, Bratislava, Slovakia
²ESTEC/ESA, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands

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¹M.A.Barucci et al. (>10)
Astronomy & Astrophysics 629 A13 Link to Article [https://doi.org/10.1051/0004-6361/201935851]
¹LESIA, Observatoire de Paris, PSL Research University, CNRS, Université Paris Diderot, Sorbonne Paris Cité, UPMC Université Paris 06, Sorbonne Universités, 5 place Jules Janssen, 92195 Meudon, France

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^1,2Wei Wu,^1,2Yi-Gang Xu,¹Zhao-Feng Zhang,¹Xin Li
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2019.12.001]
¹State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
²School of Earth and Planetary Science, University of Chinese Academy of Sciences, Beijing 100049, China
Copyright Elsevier

Calcium isotopes have the potential to explore genetic links between the Moon and Earth. Here, we constrain calcium isotopic composition of the bulk silicate Moon (BSM), using petrological, geochemical and calcium isotopic data obtained from five lunar meteorites (two basalts and three feldspathic breccia rocks), and on four anorthite crystals from two feldspathic breccia meteorites. The δ^44/40Ca of lunar feldspathic breccias are 0.76 ± 0.06‰ (2SD, n=3), 0.78 ± 0.10‰ (2SD, n=6) and 0.82 ± 0.02‰ (2SD, n=3), respectively, consistent with previously determined calcium isotopic composition of feldspathic breccias. Four anorthite crystals yield a mean δ^44/40Ca value of 0.75 ± 0.13‰ (2SD, n=4), inferred to represent the δ^44/40Ca value of the lunar crust. The δ^44/40Ca values of the two lunar basalts are 0.90 ± 0.07‰ (2SD,n=3) and 0.96 ± 0.11‰ (2SD, n=4), respectively, slightly heavier than the feldspathic breccias and anorthites. The δ^44/40Ca of the studied lunar basalts and literature data show negative correlations with CaO, Al₂O₃, and anorthite mode, pointing to the effect of contamination by lunar crust rocks. Using the heaviest δ^44/40Ca found in the least contaminated lunar basalts and a 0.10–0.20‰ fractionation of calcium isotopes during partial melting, we estimate the δ^44/40Ca value of the lunar mantle to be 0.96-1.11‰. The δ^44/40Ca values of the BSM is estimated to be 0.89-0.95‰, using a two-end member mixing model. The Ca isotopic composition of the BSM is within error to that of the bulk silicate Earth (0.94 ± 0.05‰), providing insights into the information of the comparison of the Earth-Moon system and the planets of inner Solar System.

¹Hans-Peter Gail,²Mario Trieloff
Astronomy & Astrophysics 628, A77 Link to Article [https://doi.org/10.1051/0004-6361/201936020]
¹Zentrum für Astronomie, Institut für Theoretische Astrophysik, Universität Heidelberg, Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany
²Klaus-Tschira-Labor für Kosmochemie, Institut für Geowissenschaften, Universität Heidelberg, Im Neuenheimer Feld 236, 69120 Heidelberg, Germany

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¹F. Comerón,²B. Merín,³B. Reipurth,¹H.-W. Yen
Astronomy & Astrophysics 628, A97 Link to Article
[https://doi.org/10.1051/0004-6361/201834743]
¹European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
²European Space Astronomy Centre (ESAC), European Space Agency (ESA), 28691 Villanueva de la Cañada, Spain
³Institute for Astronomy, University of Hawaii at Manoa, 640 N. Aohoku Place, Hilo, HI 96720, USA

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¹S. Massalkhi,¹M. Agúndez,¹J. Cernicharo
Astronomy & Astrophysics 628, A62 Link to Article
[https://doi.org/10.1051/0004-6361/201935069]
¹Instituto de Física Fundamental, CSIC, C/Serrano 123, 28006 Madrid, Spain

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¹M. Bhatt,²C. Wöhler,²A. Grumpe,^3,4N. Hasebe,^4,5M. Naito
Astronomy & Astrophysics 627, A155 Link to Article
[https://doi.org/10.1051/0004-6361/201935773]
¹Physical Research Laboratory, Ahmedabad 380009, India
²Image Analysis Group, Dortmund University of Technology, Otto-Hahn Str. 4, 44227 Dortmund, Germany
³School of Advanced Science and Engineering, Waseda University, Tokyo 1698555, Japan
⁴Research Institute for Science and Engineering, Waseda University, Tokyo 1698555, Japan
⁵National Institute for Quantum and Radiological Science and Technology (QST), Chiba 2638555, Japan

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¹B. Augé,²E. Dartois,¹J. Duprat,¹C. Engrand,¹G. Slodzian,³T. D. Wu,³J. L. Guerquin-Kern,⁴H. Vermesse,⁵A. N. Agnihotri,⁵P. Boduch,⁵H. Rothard
Astronomy & Astrophysics 627, A122 Link to Article [https://doi.org/10.1051/0004-6361/201935143]
¹Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Université Paris Sud, UMR 8609-CNRS/IN2P3, 91405 Orsay, France
²Institut des Sciences Moléculaires d’Orsay (ISMO), Université Paris Sud, UMR 8609-CNRS/IN2P3, 91405 Orsay, France
³Institut Curie, PSL Research University, INSERM, U1196, 91405 Orsay, France
⁴IFP Energies Nouvelles, direction Géosciences, 92500 Rueil-Malmaison, France
⁵Centre de Recherche sur les Ions, les Matériaux et la Photonique (CIMAP) CEA/CNRS/ENSICAEN/Université de Caen Normandie, Boulevard Henri Becquerel, BP 5133 14070 Caen Cedex 05, France

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