An experimental study on impact‐induced alterations of planetary organic simulants

1Yasuhito Sekine,2Kenya Kodama,3Takamichi Kobayashi,2Seiji Obata,1Yu Chang,4Nanako O. Ogawa,4Yoshinori Takano,4Naohiko Ohkouchi,2Koichiro Saiki,5Toshimori Sekine
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13075]
1Department of Earth and Planetary Science, The University of Tokyo, , Bunkyo, Tokyo, Japan
2Department of Complexity Science and Engineering, The University of Tokyo, Kashiwa, Chiba, Japan
3National Institute for Materials Science, Tsukuba, Ibaraki, Japan
4Department of Biogeochemistry, JAMSTEC, Yokosuka, Kanagawa, Japan
5Center for High Pressure Science and Technology Advanced Research, , Shanghai, China
Published by arrangement with John Wiley & Sons

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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