Mineral chemistry of MUSES-C Regio inferred from analysis of dust particles collected from the first- and second-touchdown sites on asteroid Itokawa

Tomoki Nakamura, Aiko Nakato, Hatsumi Ishida, Shigeru Wakita, Takaaki Noguchi, Michael E. Zolensky, Masahiko Tanaka, Makoto Kimura, Akira Tshuchiyama, Toshihiro Ogami, Takahito Hashimoto, Mitsuru Konno, Masayuki Uesugi, Toru Yada, Kei Shirai, Akio Fujimura, Ryuji Okazaki, Scott A. Sandford, Yukihiro Ishibashi, Masanao AbeTatsuaki Okada, Munetaka Ueno, Junichiro Kawaguchi

研究成果: Contribution to journalArticle査読

15 被引用数 (Scopus)

抄録

The mineralogy and mineral chemistry of Itokawa dust particles captured during the first and second touchdowns on the MUSES-C Regio were characterized by synchrotron-radiation X-ray diffraction and field-emission electron microprobe analysis. Olivine and low- and high-Ca pyroxene, plagioclase, and merrillite compositions of the first-touchdown particles are similar to those of the second-touchdown particles. The two touchdown sites are separated by approximately 100 meters and therefore the similarity suggests that MUSES-C Regio is covered with dust particles of uniform mineral chemistry of LL chondrites. Quantitative compositional properties of 48 dust particles, including both first- and second-touchdown samples, indicate that dust particles of MUSES-C Regio have experienced prolonged thermal metamorphism, but they are not fully equilibrated in terms of chemical composition. This suggests that MUSES-C particles were heated in a single asteroid at different temperatures. During slow cooling from a peak temperature of approximately 800 °C, chemical compositions of plagioclase and K-feldspar seem to have been modified: Ab and Or contents changed during cooling, but An did not. This compositional modification is reproduced by a numerical simulation that modeled the cooling process of a 50 km sized Itokawa parent asteroid. After cooling, some particles have been heavily impacted and heated, which resulted in heterogeneous distributions of Na and K within plagioclase crystals. Impact-induced chemical modification of plagioclase was verified by a comparison to a shock vein in the Kilabo LL6 ordinary chondrite where Na-K distributions of plagioclase have been disturbed.

本文言語英語
ページ(範囲)215-227
ページ数13
ジャーナルMeteoritics and Planetary Science
49
2
DOI
出版ステータス出版済み - 2 2014

All Science Journal Classification (ASJC) codes

  • 地球物理学
  • 宇宙惑星科学

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