An experimental study on impact-induced alterations of planetary organic simulants |
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| Authors: | Yasuhito Sekine Kenya Kodama Takamichi Kobayashi Seiji Obata Yu Chang Nanako O Ogawa Yoshinori Takano Naohiko Ohkouchi Koichiro Saiki Toshimori Sekine |
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| Affiliation: | 1. Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo, 113-0033 Japan;2. Department of Complexity Science and Engineering, The University of Tokyo, Kashiwa, Chiba, 277-8561 Japan;3. National Institute for Materials Science, Tsukuba, Ibaraki, 305-0044 Japan;4. Department of Biogeochemistry, JAMSTEC, Yokosuka, Kanagawa, 237-0061 Japan;5. Center for High Pressure Science and Technology Advanced Research, 1690 Cailun Road, Shanghai, 201203 China |
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| Abstract: | The present study systematically investigates shock-induced alteration of organic simulants of planetary bodies (OSPBs) as a function of peak shock pressure and temperature by impact experiments. Our results show that the composition and structure of OSPBs are unchanged upon impacts at peak pressures ≤~5 GPa and temperatures ≤~350 °C. On the other hand, these are dramatically changed upon impacts at >7–8 GPa and > ~400 °C, through loss of hydrogen-related bonds and concurrent carbonization, regardless of the initial compositions of OSPBs. Compared with previous results on static heating of organic matter, we suggest that shock-induced alteration cannot be distinguished from static heating only by Raman and infrared spectroscopy. Our experimental results would provide a proxy indicator for assessing degree of shock-induced alteration of organic matter contained in carbonaceous chondrites. We suggest that a remote-sensing signature of the 3.3–3.6 μm absorption due to hydrogen-related bonds on the surface of small bodies would be a promising indicator for the presence of less-thermally-altered (i.e., <350 °C) organic matter there, which will be a target for landing to collect primordial samples in sample-return spacecraft missions, such as Hayabusa2 and OSIRIS-REx. |
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