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Published Online April 19, 2007
Science DOI: 10.1126/science.1134390

Reports

Submitted on August 28, 2006
Accepted on April 2, 2007

Regolith Migration and Sorting on Asteroid Itokawa

Hideaki Miyamoto 1*, Hajime Yano 2, Daniel J. Scheeres 3, Shinsuke Abe 4, Olivier Barnouin-Jha 5, Andrew F. Cheng 5, Hirohide Demura 6, Robert W. Gaskell 7, Naru Hirata 6, Masateru Ishiguro 8, Tatsuhiro Michikami 9, Akiko M. Nakamura 4, Ryosuke Nakamura 10, Jun Saito 11, Sho Sasaki 12

1 Department of Museum Collection Utilization Studies, The University Museum, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan; Department of Earth and Planetary Science, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan; Department of Geosystem Engineering, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656, Japan; Planetary Science Institute, 1700E Fort Lowell, Suite 106, Tucson AZ 85719, USA.
2 Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan.
3 Department of Aerospace Engineering, University of Michigan, Ann Arbor, MI 48109, USA.
4 Graduate School of Science and Technology, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe, 657-8501, Japan.
5 The Johns Hopkins University Applied Physics Laboratory, Laurel MD 20723, USA.
6 Department of Computer Software, University of Aizu, Ikki-machi, Aizu-Wakamatsu City, Fukushima 965-8580, Japan.
7 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.
8 Astronomy Department, Seoul National University, Seoul 151-747, Korea.
9 Fukushima National College of Technology, Iwaki 970-8034, Japan.
10 National Institute of Advanced Industrial Science and Technology, Tsukuba 306-8568, Japan.
11 Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan; School of Engineering, Tokai University, Hiratsuka, Kanagawa 259-1292, Japan.
12 RISE Project Office, National Astronomical Observatory of Japan, 2-12 Hoshigaoka, Mizusawa, Oshu, 023-0861, Japan.

* To whom correspondence should be addressed.
Hideaki Miyamoto , E-mail: hm{at}um.u-tokyo.ac.jp

High-resolution images of the surface of asteroid Itokawa from the Hayabusa mission reveal it to be covered with unconsolidated millimeter-sized and larger gravels. Locations and morphologic characteristics of this gravel indicate that Itokawa has experienced considerable vibrations, which have triggered global-scale granular processes in its dry, vacuum, microgravity environment. These processes likely include granular convection, landslide-like granular migrations, and particle sorting, resulting in the segregation of the fine gravels into areas of potential lows. Granular processes become major resurfacing processes because of Itokawa's small size, implying that they can occur on other small asteroids should they have regolith.




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Science. ISSN 0036-8075 (print), 1095-9203 (online)