Itokawa dust particles: a direct link between S-type asteroids and ordinary chondrites |
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Authors: | Nakamura Tomoki Noguchi Takaaki Tanaka Masahiko Zolensky Michael E Kimura Makoto Tsuchiyama Akira Nakato Aiko Ogami Toshihiro Ishida Hatsumi Uesugi Masayuki Yada Toru Shirai Kei Fujimura Akio Okazaki Ryuji Sandford Scott A Ishibashi Yukihiro Abe Masanao Okada Tatsuaki Ueno Munetaka Mukai Toshifumi Yoshikawa Makoto Kawaguchi Junichiro |
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Institution: | Department of Earth and Planetary Material Sciences, Faculty of Science, Tohoku University, Aoba, Sendai, Miyagi 980-8578, Japan. tomoki@m.tohoku.ac.jp |
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Abstract: | The Hayabusa spacecraft successfully recovered dust particles from the surface of near-Earth asteroid 25143 Itokawa. Synchrotron-radiation x-ray diffraction and transmission and scanning electron microscope analyses indicate that the mineralogy and mineral chemistry of the Itokawa dust particles are identical to those of thermally metamorphosed LL chondrites, consistent with spectroscopic observations made from Earth and by the Hayabusa spacecraft. Our results directly demonstrate that ordinary chondrites, the most abundant meteorites found on Earth, come from S-type asteroids. Mineral chemistry indicates that the majority of regolith surface particles suffered long-term thermal annealing and subsequent impact shock, suggesting that Itokawa is an asteroid made of reassembled pieces of the interior portions of a once larger asteroid. |
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