Mineralogy and petrography of C asteroid regolith: The Sutter's Mill CM meteorite |
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| Authors: | Michael Zolensky Takashi Mikouchi Marc Fries Robert Bodnar Peter Jenniskens Qing‐zhu Yin Kenji Hagiya Kazumasa Ohsumi Mutsumi Komatsu Matthew Colbert Romy Hanna Jessie Maisano Richard Ketcham Yoko Kebukawa Tomoki Nakamura Moe Matsuoka Sho Sasaki Akira Tsuchiyama Matthieu Gounelle Loan Le James Martinez Kent Ross Zia Rahman |
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| Institution: | 1. ARES, NASA Johnson Space Center, , Houston, Texas, 77058 USA;2. Department of Earth and Planetary Science, University of Tokyo, , Bunkyo‐ku, Tokyo, 113‐0033 Japan;3. Department of Geosciences, Virginia Tech, , Blacksburg, Virginia, 24061 USA;4. SETI Institute, , Mountain View, California, 94043 USA;5. Department of Earth and Planetary Sciences, University of California Davis, , Davis, California, 95616 USA;6. Graduate School of Life Sciences, University of Hyogo, , Kamigori‐cho, Hyogo, 678‐1297 Japan;7. JASRI, , Sayo‐cho, Hyogo, 679‐5198 Japan;8. Waseda University, , Shinjuku, Tokyo, 169‐8050 Japan;9. High‐Resolution X‐ray CT Facility, University of Texas, , Austin, Texas, 78712 USA;10. Hokkaido University, , Sapporo, 060‐0810 Japan;11. Graduate School of Science, Tohoku University, , Sendai, 980‐8578 Japan;12. Graduate School of Science, Osaka University, , Toyonaka, 560‐0043 Japan;13. Division of Earth and Planetary Sciences, Kyoto University, , Sakyo‐ku, Kyoto, 606‐8502 Japan;14. Muséum National d'Histoire Naturelle, , Paris, 70005 France;15. ESCG Jacobs, , Houston, Texas, 77058 USA |
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| Abstract: | Based upon our characterization of three separate stones by electron and X‐ray beam analyses, computed X‐ray microtomography, Raman microspectrometry, and visible‐IR spectrometry, Sutter's Mill is a unique regolith breccia consisting mainly of various CM lithologies. Most samples resemble existing available CM2 chondrites, consisting of chondrules and calcium‐aluminum‐rich inclusion (CAI) set within phyllosilicate‐dominated matrix (mainly serpentine), pyrrhotite, pentlandite, tochilinite, and variable amounts of Ca‐Mg‐Fe carbonates. Some lithologies have witnessed sufficient thermal metamorphism to transform phyllosilicates into fine‐grained olivine, tochilinite into troilite, and destroy carbonates. One finely comminuted lithology contains xenolithic materials (enstatite, Fe‐Cr phosphides) suggesting impact of a reduced asteroid (E or M class) onto the main Sutter's Mill parent asteroid, which was probably a C class asteroid. One can use Sutter's Mill to help predict what will be found on the surfaces of C class asteroids such as Ceres and the target asteroids of the OSIRIS‐REx and Hayabusa 2 sample return missions (which will visit predominantly primitive asteroids). C class asteroid regolith may well contain a mixture of hydrated and thermally dehydrated indigenous materials as well as a significant admixture of exogenous material would be essential to the successful interpretation of mineralogical and bulk compositional data. |
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