Space weathered rims found on the surfaces of the Itokawa dust particles

Takaaki Noguchi, Makoto Kimura, Takahito Hashimoto, Mitsuru Konno, Tomoki Nakamura, Michael E. Zolensky, Ryuji Okazaki, Masahiko Tanaka, Akira Tsuchiyama, Aiko Nakato, Toshinori Ogami, Hatsumi Ishida, Ryosuke Sagae, Shinichi Tsujimoto, Toru Matsumoto, Junya Matsuno, Akio Fujimura, Masanao Abe, Toru Yada, Toshifumi MukaiMunetaka Ueno, Tatsuaki Okada, Kei Shirai, Yukihiro Ishibashi

研究成果: ジャーナルへの寄稿学術誌査読

99 被引用数 (Scopus)


On the basis of observations using Cs-corrected STEM, we identified three types of surface modification probably formed by space weathering on the surfaces of Itokawa particles. They are (1) redeposition rims (2-3 nm), (2) composite rims (30-60 nm), and (3) composite vesicular rims (60-80 nm). These rims are characterized by a combination of three zones. Zone I occupies the outermost part of the surface modification, which contains elements that are not included in the unchanged substrate minerals, suggesting that this zone is composed of sputter deposits and/or impact vapor deposits originating from the surrounding minerals. Redeposition rims are composed only of Zone I and directly attaches to the unchanged minerals (Zone III). Zone I of composite and composite vesicular rims often contains nanophase (Fe,Mg)S. The composite rims and the composite vesicular rims have a two-layered structure: a combination of Zone I and Zone II, below which Zone III exists. Zone II is the partially amorphized zone. Zone II of ferromagnesian silicates contains abundant nanophase Fe. Radiation-induced segregation and in situ reduction are the most plausible mechanisms to form nanophase Fe in Zone II. Their lattice fringes indicate that they contain metallic iron, which probably causes the reddening of the reflectance spectra of Itokawa. Zone II of the composite vesicular rims contains vesicles. The vesicles in Zone II were probably formed by segregation of solar wind He implanted in this zone. The textures strongly suggest that solar wind irradiation damage and implantation are the major causes of surface modification and space weathering on Itokawa.

ジャーナルMeteoritics and Planetary Science
出版ステータス出版済み - 2月 2014

!!!All Science Journal Classification (ASJC) codes

  • 地球物理学
  • 宇宙惑星科学


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