¹Li Q.,¹Dai W.,^1,2,3Liu B.S.,⁴Sarre P.J.,⁵Xie M.H.,¹Cheung A.S-C.
Molecular Astrophysics 13, 22-29 Link to Article [https://doi.org/10.1016/j.molap.2018.09.002]
¹Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China
²Department of Chemistry, Tianjin University, Tianjin 300072, China
³The National Collaborative Innovative Center of Chem. Sci. Eng. Tianjin, Tianjin 300072, China
⁴School of Chemistry, The University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom
⁵Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong, China

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¹Hyun Na Kim,²Changkun Park,²Sun Young Park,²Hwayoung Kim,¹Min Sik Kim
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2019JE005998]
¹Department of Earth and Environmental SciencesKongju National University, Gongju, Republic of Korea
²Division of Polar Earth‐System Sciences, Korea Polar Research Institute, Incheon, Republic of Korea
Published by arrangement with John Wiley & Sons

Determining the formation mechanism of maskelynite is essential to understanding the shocked environments of meteorites on their parent bodies. Maskelynite has been accepted as a diaplectic glass for several decades, but there have been suggestions that it is a normal glass quenched from a dense melt. Morphological characteristics have been generally investigated to identify the formation mechanism of amorphous plagioclase in meteorites, but the chemical difference between crystalline and amorphous plagioclase has not been fully understood. In this study, we investigated the morphological, atomic‐scale structural, and chemical characteristics of amorphous plagioclase in the lunar meteorite DEW 12007 to constrain its formation mechanism via chemical analysis. The morphological characteristics showed that plagioclase was partially converted into amorphous phase through partial melting. Two‐dimensional Raman mapping confirmed the structural difference between amorphous and crystalline regions. Quantitative chemical analyses revealed that the amorphous regions were more albite‐rich than the crystalline regions, likely due to the partial melting of plagioclase. Under shocked conditions, the partial melting of plagioclase induced a chemical variation between amorphous and crystalline regions. The morphological and structural changes correspond well with the chemical variations, indicating that amorphization induced such variations. The chemical differences between amorphous and crystalline plagioclase in other meteorites also could be understood to be the results of partial melting. Thus, the chemical differences between amorphous and crystalline plagioclase in partially amorphized grains could elucidate the formation mechanism of amorphous plagioclase in many meteorites.

¹S.Potin,^1,2P.Beck,¹B.Schmitt,³F.Moynier
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2019.06.026]
¹Université Grenoble Alpes, CNRS, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), 414 rue de la Piscine, 38400 Saint-Martin d’Hères, France
²Institut Universitaire de France, Paris, France
³Institut de Physique du Globe de Paris (IPGP), 1 Rue Jussieu, 75005 Paris, France
Copyright Elsevier

Here were report on a laboratory study aiming to reproduce specificities of near-Earth Asteroid. We study how the elevated surface temperature, their surface roughness (rock or regolith), as well as observation geometry can affect the absorption features detected on asteroids. For that purpose, we selected a recent carbonaceous chondrite fall, the Mukundpura CM2 chondrite which fell in India in June 2017. Bidirectional reflectance spectroscopy was performed to analyze the effect of the geometrical configuration (incidence, emergence and azimuth angle) on the measurement. Our results show that reflectance spectra obtained under warm environment (NEA-like) tends to show shallower absorption bands compared to low-temperature conditions (MBA-like), but still detectable in our experiments under laboratory timescales. Irreversible alteration of the sample because of the warm environment (from room temperature to 250 °C) has been detected as an increase of the spectral slope and a decrease of the band depths (at 0.7 μm, 0.9 μm and 2.7 μm). Comparing the meteoritic chip and the powdered sample, we found that surface texture strongly affects the shape of the reflectance spectra of meteorites and thus of asteroids, where a dust-covered surface presents deeper absorption features. We found that all spectral parameters, such as the reflectance value, spectral slope and possible absorption bands are affected by the geometry of measurement. We observed the disappearance of the 0.7 μm absorption feature at phase angle larger than 120°, but the 3 μm band remains detectable on all measured spectra.

¹Timms, N.E. et al. (>10)
Contributions to Mineralogy and Petrology 174, 38 Link to Article [DOI: 10.1007/s00410-019-1565-7]
¹The Institute for Geoscience Research (TIGeR), Space Science and Technology Centre, School of Earth and Planetary Sciences, Curtin University, GPO Box U1987, Perth, WA 6845, Australia

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¹Jin, Z.,¹Bose, M.
Science Advances 5, eaav8106 Link to Article [DOI: 10.1126/sciadv.aav8106]
¹School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287-1404, United States

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¹Hwang, S.-L.,²Shen, P.,³Chu, H.-T.,⁴Yui, T.-F.,⁵Varela, M.-E.,⁴Iizuka, Y.
Mineralogical Magazine 83, 293-313 Link to Article [DOI: 10.1180/mgm.2018.125]
¹Department of Materials Science and Engineering, National Dong Hwa University, Hualien, Taiwan
²Department of Materials Science and Optoelectronic Science, National Sun Yat-sen University, Kaohsiung, Taiwan
³Central Geological Survey, PO Box 968, Taipei, Taiwan
⁴Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan
⁵Instituto de Ciencias Astronómicas de la Tierra y Del Espacio (ICATE), Avenida España 1512 sur, San Juan, J5402DSP, Argentina

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^1,2Koschny, D. et al. (>10)
Space Science Reviews 215, 34 Link to Article [DOI: 10.1007/s11214-019-0597-7]
¹SCI-S, European Space Agency, Keplerlaan 1, Noordwijk ZH, 2200 AZ, Netherlands
²Lehrstuhl für Raumfahrttechnik, Technische Universität München, Boltzmannstr. 15, Garching, 85748, Germany

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¹Clément Ganino,^2,3Guy Libourel,⁴Akiko M.Nakamura,²Patrick Michel
Planetary and Space Science (in Press) Link to Article [https://doi.org/10.1016/j.pss.2019.06.008]
¹Université Côte D’Azur, OCA, CNRS, Géoazur, 250 Rue Albert Einstein, Sophia-Antipolis, 06560, Valbonne, France
²Université Côte D’Azur, OCA, CNRS, Lagrange, Boulevard de L’Observatoire, CS 34229, 06304, Nice Cedex 4, France
³Hawai‘i Institute of Geophysics and Planetology, School of Ocean, Earth Science and Technology, University of Hawai‘i at Mānoa, Honolulu, Hawai‘i, 96821, USA
⁴Graduate School of Science, Kobe University, 1-1 Rokkoudai-cho, Nada-ku, Kobe, 657-8501, Japan

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¹D.E.Moser et al. (>10)
Nature Geoscience 12, 522-527 Link to Article [DOI
https://doi.org/10.1038/s41561-019-0380-0]
¹Department of Earth Sciences, University of Western Ontario, London, Ontario, Canada

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¹Lionel G. Vacher,²Laurent Truche,¹François Faure,¹Laurent Tissandier,³Régine Mosser‐Ruck,¹Yves Marrocchi
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13317]
¹CRPG, CNRS, Université de Lorraine, UMR 7358, Vandoeuvre‐les‐Nancy, F‐54501 France
²ISTerre, UMR 5275, CNRS, Université Grenoble Alpes, 1381 rue de la Piscine, BP53 38041 Grenoble, CEDEX 9, France
³GeoRessources, UMR 7359, CNRS, Université de Lorraine, Campus Aiguillettes, 54506 Vandoeuvre‐lès‐Nancy, France
Published by arrangement with John Wiley & Sons

Tochilinite/cronstedtite intergrowths are commonly observed as alteration products in CM chondrite matrices, but the conditions under which they formed are still largely underconstrained due to their scarcity in terrestrial environments. Here, we report low temperature (80 °C) anoxic hydrothermal experiments using starting assemblages similar to the constituents of the matrices of the most pristine CM chondrite and S‐rich and S‐free fluids. Cronstedtite crystals formed only in S‐free experiments under circumneutral conditions with the highest Fe/Si ratios. Fe‐rich tochilinite with chemical and structural characteristics similar to chondritic tochilinite was observed in S‐bearing experiments. We observed a positive correlation between the Mg content in the hydroxide layer of synthetic tochilinite and temperature, suggesting that the composition of tochilinite is a proxy for the alteration temperature in CM chondrites. Using this relation, we estimate the mean precipitation temperatures of tochilinite to be 120–160 °C for CM chondrites. Given the different temperature ranges of tochilinite and cronstedtite in our experiments, we propose that Fe‐rich tochilinite crystals resulted from the alteration of metal beads under S‐bearing alkaline conditions at T = 120–160 °C followed by cronstedtite crystals formed by the reaction of matrix amorphous silicates, metal beads, and water at a low temperature (50–120 °C).