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).

¹Trudi Kennedy,¹Fred Jourdan,²Ela Eroglu,¹Celia Mayers
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2019.06.027]
¹Western Australian Argon Isotope Facility, JdL Centre & Applied Geology, Curtin University, GPO Box U1987, Perth, Western Australia 6845, Australia
²Department of Chemical Engineering, Curtin University, GPO Box U1987, Perth, Western Australia 6845, Australia
Copyright Elsevier

¹Litasov, K.D.,²Badyukov, D.D.,¹Pokhilenko, N.P.
Doklady Earth Sciences 485, 327-330 Link to Article [DOI: 10.1134/S1028334X19030322]
¹Sobolev Institute of Geology and Mineralogy, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090, Russian Federation
²Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Moscow, 119991, Russian Federation

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¹M. B. Biren,²J.‐A. Wartho,¹M. C. VAN Soest,¹K. V. Hodges,^3,4H. Cathey,⁵B. P. Glass,^6,7C. Koeberl,⁸J. W. Horton Jr,⁹W. Hale
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13316]
¹Group 18 Laboratories, School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, 85287 USA
²GEOMAR Helmholtz Centre for Ocean Research Kiel, D‐24148 Kiel, Germany
³LeRoy Eyring Center for Solid State Science, Arizona State University, Tempe, Arizona, 84287 USA
⁴Central Analytical Research Facility, Queensland University of Technology, Brisbane, Queensland, 4000 Australia
⁵Department of Geological Sciences, University of Delaware, Newark, Delaware, 19716 USA
⁶Department of Lithospheric Research, University of Vienna, A‐1090 Vienna, Austria
⁷Natural History Museum, Burgring 7, A‐1010 Vienna, Austria
⁸U.S. Geological Survey, 926A National Center, Reston, Virginia, 20192 USA
⁹IODP Core Repository, Bremen, D‐28359 Germany
Published by arrangement with John Wiley & Sons

Single crystal (U‐Th)/He dating has been undertaken on 21 detrital zircon grains extracted from a core sample from Ocean Drilling Project (ODP) site 1073, which is located ~390 km northeast of the center of the Chesapeake Bay impact structure. Optical and electron imaging in combination with energy dispersive X‐ray microanalysis (EDS) of zircon grains from this late Eocene sediment shows clear evidence of shock metamorphism in some zircon grains, which suggests that these shocked zircon crystals are distal ejecta from the formation of the ~40 km diameter Chesapeake Bay impact structure. (U‐Th/He) dates for zircon crystals from this sediment range from 33.49 ± 0.94 to 305.1 ± 8.6 Ma (2σ), implying crystal‐to‐crystal variability in the degree of impact‐related resetting of (U‐Th)/He systematics and a range of different possible sources. The two youngest zircon grains yield an inverse‐variance weighted mean (U‐Th)/He age of 33.99 ± 0.71 Ma (2σ uncertainties n = 2; mean square weighted deviation = 2.6; probability [P] = 11%), which is interpreted to be the (U‐Th)/He age of formation of the Chesapeake Bay impact structure. This age is in agreement with K/Ar, ⁴⁰Ar/³⁹Ar, and fission track dates for tektites from the North American strewn field, which have been interpreted as associated with the Chesapeake Bay impact event.

¹Juulia-Gabrielle Moreau,^1,2Tomas Kohout,³Kai Wünnemann,⁴Patricie Halodova,^5,6Jakub Haloda
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2019.06.004]
¹Department of Geosciences and Geography, University of Helsinki, Finland
²Institute of Geology, The Czech Academy of Sciences, Prague, Czech Republic
³Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Berlin, Germany
⁴Centrum výzkumu Řež, Husinec-Řež, Czech Republic
⁵Czech Geological Survey, Prague, Czech Republic
⁶Oxford Instruments NanoAnalysis, Bucks, United Kingdom
Copyright Elsevier

Shock-darkening, the melting of metals and iron sulfides into a network of veins within silicate grains, altering reflectance spectra of meteorites, was previously studied using shock physics mesoscale modeling. Melting of iron sulfides embedded in olivine was observed at pressures of 40–50 GPa. This pressure range is at the transition between shock stage 5 (CS5) and 6 (CS6) of the shock metamorphism classification in ordinary and enstatite chondrites. To characterize CS5 and CS6 better with a mesoscale modeling approach and assess post-shock heating and melting, we used multi-phase (i.e. olivine/enstatite, troilite, iron, pores, and plagioclase) meshes with realistic configurations of grains. We carried out a systematic study of shock compression in ordinary and enstatite chondrites at pressures between 30 and 70 GPa. To setup mesoscale sample meshes with realistic silicate, metal, iron sulfide, and open pore shapes, we converted backscattered electron microscope images of three chondrites. The resolved macroporosity in meshes was 3–6%. Transition from shock CS5 to CS6 was observed through (1) the melting of troilite above 40 GPa with melt fractions of ~0.7–0.9 at 70 GPa, (2) the melting of olivine and iron above 50 GPa with melt fraction of ~0.001 and 0.012, respectively, at 70 GPa, and (3) the melting of plagioclase above 30 GPa (melt fraction of 1, at 55 GPa). Post-shock temperatures varied from ~540 K at 30 GPa to ~1300 K at 70 GPa. We also constructed models with increased porosity up to 15% porosity, producing higher post-shock temperatures (~800 K increase) and melt fractions (~0.12 increase) in olivine. Additionally we constructed a pre-heated model to observe post-shock heating and melting during thermal metamorphism. This model presented similar results (melting) at pressures 10–15 GPa lower compared to the room temperature models. Finally, we demonstrated dependence of post-shock heating and melting on the orientation of open cracks relative to the shock wave front. In conclusion, the modeled melting and post-shock heating of individual phases were mostly consistent with the current shock classification scheme (Stöffler et al. 2018, 2019).

^1,3Xiaojia Zeng,^1,2,3 Xiongyao Li,⁴ Dayl Martin,^1,2,3Hong Tang,^1,2,3Wen Yu,^5,6 Kang Yang,^5,6Zegui Wang,⁷Shijie Wang
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2019.06.011]
¹Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
²CAS Center for Excellence in Comparative Planetology, Hefei, China
³Key Laboratory of Space Manufacturing Technology, Chinese Academy of Sciences, Beijing 100094, China
⁴European Space Agency, Fermi Avenue, Harwell Campus, Didcot, Oxfordshire OX11 0FD, United Kingdom
⁵School of Mechanics and Civil Engineering, China University of Ming and Technology, Xuzhou 221116, China
⁶State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Ming and Technology, Xuzhou 221116, China
⁷State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
Copyright Elsevier

Asteroid regolith simulants (i.e., substitute materials for asteroid surface regoliths) are useful for the preparation of asteroid landing and/or sample-return missions. In this study, we report a new Itokawa asteroid Regolith Simulant (called IRS-1) as an S-type asteroid surface analogue for China’s upcoming asteroid exploration. The IRS-1 simulant was developed from mixing terrestrial minerals with appropriate particle size distributions, based on the currently available mineralogy data of S-type asteroid 25143 Itokowa and a LL6 chondrite Sulagiri. Multiple properties of this simulant are well-characterized, including mineralogy, bulk chemistry, particle size, density, mechanical properties, reflectance spectra, thermal properties, thermogravimetry, and hygroscopicity. These results demonstrate that the IRS-1 simulant has similar mineralogy, bulk chemistry, and physical properties to the target materials (i.e., Itokowa samples and LL6 chondrite Sulagiri), making this simulant a reasonable surface analogue of S-type asteroids. Based on the investigation of mechanical properties of the IRS-1 simulant and two other prepared regolith samples (i.e., L-chondrite-like IRS-1 L and H-chondrite-like IRS1H), we found that the mineralogical variations on S-type asteroids have a relatively large influence on the mechanical properties of S-type asteroid regoliths. Our studies show that the IRS-1 simulant will be appropriate for a number of scientific and engineering-based investigations where a large amount (few kilograms to hundreds of kilograms) of sample is required (e.g., technology development, hardware testing, and drilling). This study also provides an effective production approach for the future development of asteroid regolith simulants for different types of asteroid regoliths and associated applications.