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Science 2 June 2006:
Vol. 312. no. 5778, pp. 1330 - 1334
DOI: 10.1126/science.1125841
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Reports

The Rubble-Pile Asteroid Itokawa as Observed by Hayabusa

A. Fujiwara,1* J. Kawaguchi,1 D. K. Yeomans,2 M. Abe,1 T. Mukai,3 T. Okada,1 J. Saito,1 H. Yano,1 M. Yoshikawa,1 D. J. Scheeres,4 O. Barnouin-Jha,5 A. F. Cheng,5 H. Demura,6 R. W. Gaskell,2 N. Hirata,3 H. Ikeda,1 T. Kominato,7 H. Miyamoto,8 A. M. Nakamura,3 R. Nakamura,9 S. Sasaki,10 K. Uesugi1

During the interval from September through early December 2005, the Hayabusa spacecraft was in close proximity to near-Earth asteroid 25143 Itokawa, and a variety of data were taken on its shape, mass, and surface topography as well as its mineralogic and elemental abundances. The asteroid's orthogonal axes are 535, 294, and 209 meters, the mass is 3.51 x 1010 kilograms, and the estimated bulk density is 1.9 ± 0.13 grams per cubic centimeter. The correspondence between the smooth areas on the surface (Muses Sea and Sagamihara) and the gravitationally low regions suggests mass movement and an effective resurfacing process by impact jolting. Itokawa is considered to be a rubble-pile body because of its low bulk density, high porosity, boulder-rich appearance, and shape. The existence of very large boulders and pillars suggests an early collisional breakup of a preexisting parent asteroid followed by a re-agglomeration into a rubble-pile object.

1 Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan.
2 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.
3 Graduate School of Science and Technology, Kobe University, 1-1 Rokkodai-cho, Nada, Kobe, Hyogo 657-8501, Japan.
4 Department of Aerospace Engineering, University of Michigan, Ann Arbor, MI 48109–2140, USA.
5 Applied Physics Laboratory, Johns Hopkins University, Laurel, MD 20723, USA.
6 School of Computer Science and Engineering, Aizu University, Ikki-machi, Aizu, Fukushima 965-8580, Japan.
7 NEC Aerospace Systems Limited, 4206 Ikebe, Tsuzuki, Yokohama, Kanagawa, 224-0053, Japan.
8 Department of Geosystem Engineering, University of Tokyo, Tokyo 113-8656, Japan.
9 Grid Technology Research Center (GTRC), National Institute of Advanced Industrial Science and Technology (AIST), Umezono 1-1-1, Tsukuba 305-8568, Japan.
10 Mizusawa Astrodynamics Observatory, National Astronomical Observatory of Japan, 2-12 Hoshigaoka, Mizusawa, Iwate 023-0861, Japan.

* To whom correspondence should be addressed. E-mail: fujiwara{at}planeta.sci.isas.jaxa.jp

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
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B. E. Schmidt, P. C. Thomas, J. M. Bauer, J.-Y. Li, L. A. McFadden, M. J. Mutchler, S. C. Radcliffe, A. S. Rivkin, C. T. Russell, J. Wm. Parker, et al. (2009)
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Regolith Migration and Sorting on Asteroid Itokawa.
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Science 316, 1011-1014
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Dynamical Configuration of Binary Near-Earth Asteroid (66391) 1999 KW4.
D. J. Scheeres, E. G. Fahnestock, S. J. Ostro, J.-L. Margot, L. A. M. Benner, S. B. Broschart, J. Bellerose, J. D. Giorgini, M. C. Nolan, C. Magri, et al. (2006)
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Adventures in near-Earth object exploration..
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X-ray fluorescence spectrometry of asteroid Itokawa by Hayabusa..
T. Okada, K. Shirai, Y. Yamamoto, T. Arai, K. Ogawa, K. Hosono, and M. Kato (2006)
Science 312, 1338-1341
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Detailed images of asteroid 25143 Itokawa from Hayabusa..
J. Saito, H. Miyamoto, R. Nakamura, M. Ishiguro, T. Michikami, A. M. Nakamura, H. Demura, S. Sasaki, N. Hirata, C. Honda, et al. (2006)
Science 312, 1341-1344
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Mass and local topography measurements of Itokawa by Hayabusa..
S. Abe, T. Mukai, N. Hirata, O. S. Barnouin-Jha, A. F. Cheng, H. Demura, R. W. Gaskell, T. Hashimoto, K. Hiraoka, T. Honda, et al. (2006)
Science 312, 1344-1347
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Pole and global shape of 25143 Itokawa..
H. Demura, S. Kobayashi, E. Nemoto, N. Matsumoto, M. Furuya, A. Yukishita, N. Muranaka, H. Morita, K. Shirakawa, M. Maruya, et al. (2006)
Science 312, 1347-1349
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Touchdown of the Hayabusa spacecraft at the Muses Sea on Itokawa..
H. Yano, T. Kubota, H. Miyamoto, T. Okada, D. Scheeres, Y. Takagi, K. Yoshida, M. Abe, S. Abe, O. Barnouin-Jha, et al. (2006)
Science 312, 1350-1353
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