Neutron activation analysis of a particle returned from asteroid Itokawa

M. Ebihara, S. Sekimoto, N. Shirai, Y. Hamajima, M. Yamamoto, K. Kumagai, Y. Oura, T. R. Ireland, F. Kitajima, K. Nagao, T. Nakamura, H. Naraoka, T. Noguchi, R. Okazaki, A. Tsuchiyama, M. Uesugi, H. Yurimoto, M. E. Zolensky, M. Abe, A. FujimuraT. Mukai, Y. Yada

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Abstract

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.

Original languageEnglish
Pages (from-to)1119-1121
Number of pages3
JournalScience
Volume333
Issue number6046
DOIs
Publication statusPublished - 2011 Aug 26

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Ebihara, M., Sekimoto, S., Shirai, N., Hamajima, Y., Yamamoto, M., Kumagai, K., Oura, Y., Ireland, T. R., Kitajima, F., Nagao, K., Nakamura, T., Naraoka, H., Noguchi, T., Okazaki, R., Tsuchiyama, A., Uesugi, M., Yurimoto, H., Zolensky, M. E., Abe, M., ... Yada, Y. (2011). Neutron activation analysis of a particle returned from asteroid Itokawa. Science, 333(6046), 1119-1121. https://doi.org/10.1126/science.1207865