TERRAPUB Geochemical Journal
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Geochemical Journal, Vol. 53 (No. 1), pp. 53-67, 2019
doi:10.2343/geochemj.2.0549

STXM-XANES analyses of Murchison meteorite samples captured by aerogel after hypervelocity impacts: A potential implication of organic matter degradation for micrometeoroid collection experiments

Yoko Kebukawa,1* Kyoko Okudaira,2 Hikaru Yabuta,3 Sunao Hasegawa,4 Makoto Tabata,5 Yoshihiro Furukawa,6 Motoo Ito,7 Aiko Nakato,4 A. L. David Kilcoyne,8 Kensei Kobayashi,1 Shin-ichi Yokobori,9 Eiichi Imai,10 Yuko Kawaguchi,9 Hajime Yano4 and Akihiko Yamagishi9

1Faculty of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan
2Research Center for Advanced Information Science and Technology, University of Aizu, Tsuruga, Ikki-machi, Aizu-Wakamatsu, Fukushima 965-8580, Japan
3Department of Earth and Planetary Systems Science, Hiroshima University, 1-3-1 Kagamiyama, Hiroshima 739-8526, Japan
4Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Sagamihara, Kanagawa 252-5210, Japan
5Department of Physics, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
6Department of Earth Science, Tohoku University, 6-3 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8578, Japan
7Kochi Institute for Core Sample Research, JAMSTEC, B200 Monobe, Nankoku, Kochi 783-8502, Japan
8Advanced Light Source, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, U.S.A.
9Department of Applied Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan
10Nagaoka University of Technology, 1603-1 Kamitomiokamachi, Nagaoka, Niigata 940-2188, Japan

(Received May 13, 2018; Accepted November 6, 2018)

Abstract: The Tanpopo mission is an astrobiology space experiment at the Japanese Experiment Module (JEM) 'Kibo' on the International Space Station (ISS). One of the sub-divided themes of the Tanpopo mission is for the intact capture of organic bearing micrometeoroids in low Earth orbit using ultralow density silica aerogel (0.01 g/cm3). In order to evaluate damage to organic matter in micrometeoroids during hyper velocity impacts into the aerogel, Murchison meteorite powdered samples, analogs of organic bearing micrometeoroids, were fired into flight-grade silica aerogel (0.01 g/cm3) using a two-stage light-gas gun with velocities of 4.4 and 5.9 km/s. The recovered Murchison grains were analyzed using scanning transmission X-ray microscopy/X-ray absorption near edge structure (STXM/XANES), transmission electron microscopy (TEM) and nanoscale secondary ion mass spectrometry (NanoSIMS). TEM observation did not show significant modifications of the recovered Murchison grains. Carbon-XANES spectra, however, showed a large depletion of the organic matter after the 5.9 km/s impact, but no such effects nor any significant hydrogen isotopic fractionation were observed after the 4.4 km/s impact.
Key words: micrometeoroid, meteorite, impact, organic matter, Tanpopo mission


*Corresponding author E-mail: kebukawa@ynu.ac.jp


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