Neutron activation analysis of a particle returned from asteroid Itokawa.


A single grain (~3 micrograms) returned by the Hayabusa spacecraft was analyzed by neutron activation analysis. This grain is mainly composed of olivine with minor amounts of plagioclase, troilite, and metal. Our results establish that the Itokawa sample has similar chemical characteristics (iron/scandium and nickel/cobalt ratios) to chondrites, confirming that this grain is extraterrestrial in origin and has primitive chemical compositions. Estimated iridium/nickel and iridium/cobalt ratios for metal in the Itokawa samples are about five times lower than CI carbonaceous chondrite values. A similar depletion of iridium was observed in chondrule metals of ordinary chondrites. These metals must have condensed from the nebular where refractory siderophile elements already condensed and were segregated.

DOI: 10.1126/science.1207865

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@article{Ebihara2011NeutronAA, title={Neutron activation analysis of a particle returned from asteroid Itokawa.}, author={Mitsuru Ebihara and Shun Sekimoto and Naohito Shirai and Yasunori Hamajima and M. Yamamoto and Kenichi Kumagai and Yasuji Oura and Trevor R . Ireland and F. Kitajima and Ken Nagao and Tadashi Nakamura and Hiroshi Naraoka and Toshihide Noguchi and Ryuji Okazaki and Akira Tsuchiyama and Mayumi Uesugi and Hisayoshi Yurimoto and Michael E Zolensky and Michiaki Abe and Akio Fujimura and Takahiro Mukai and Yuichiro Yada}, journal={Science}, year={2011}, volume={333 6046}, pages={1119-21} }