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Science 2 June 2006:
Vol. 312. no. 5778, pp. 1344 - 1347
DOI: 10.1126/science.1126272
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Reports

Mass and Local Topography Measurements of Itokawa by Hayabusa

Shinsuke Abe,1* Tadashi Mukai,1 Naru Hirata,1,3 Olivier S. Barnouin-Jha,2 Andrew F. Cheng,2 Hirohide Demura,3 Robert W. Gaskell,4 Tatsuaki Hashimoto,5 Kensuke Hiraoka,1 Takayuki Honda,1 Takashi Kubota,5 Masatoshi Matsuoka,6 Takahide Mizuno,5 Ryosuke Nakamura,7 Daniel J. Scheeres,8 Makoto Yoshikawa5

The ranging instrument aboard the Hayabusa spacecraft measured the surface topography of asteroid 25143 Itokawa and its mass. A typical rough area is similar in roughness to debris located on the interior wall of a large crater on asteroid 433 Eros, which suggests a surface structure on Itokawa similar to crater ejecta on Eros. The mass of Itokawa was estimated as (3.58 ± 0.18) x 1010 kilograms, implying a bulk density of (1.95 ± 0.14) grams per cubic centimeter for a volume of (1.84 ± 0.09) x 107 cubic meters and a bulk porosity of ~40%, which is similar to that of angular sands, when assuming an LL (low iron chondritic) meteorite composition. Combined with surface observations, these data indicate that Itokawa is the first subkilometer-sized small asteroid showing a rubble-pile body rather than a solid monolithic asteroid.

1 Graduate School of Science and Technology, Kobe University, Nada, Kobe 657-8501, Japan.
2 Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723–6099, USA.
3 Department of Computer Software, University of Aizu, Aizuwakamatsu, Fukushima 965-8580, Japan.
4 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.
5 Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan.
6 NEC Aerospace Systems Co. Ltd., Fuchu, Tokyo 181-8551, Japan.
7 National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8568, Japan.
8 Department of Aerospace Engineering, University of Michigan, Ann Arbor, MI 48109–2140, USA.

* To whom correspondence should be addressed. E-mail: avell{at}kobe-u.ac.jp

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Regolith Migration and Sorting on Asteroid Itokawa.
H. Miyamoto, H. Yano, D. J. Scheeres, S. Abe, O. Barnouin-Jha, A. F. Cheng, H. Demura, R. W. Gaskell, N. Hirata, M. Ishiguro, et al. (2007)
Science 316, 1011-1014
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Radar Imaging of Binary Near-Earth Asteroid (66391) 1999 KW4.
Steven. J. Ostro, J.-L. Margot, L. A. M. Benner, J. D. Giorgini, D. J. Scheeres, E. G. Fahnestock, S. B. Broschart, J. Bellerose, M. C. Nolan, C. Magri, et al. (2006)
Science 314, 1276-1280
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Adventures in near-Earth object exploration..
E. Asphaug (2006)
Science 312, 1328-1329
   Abstract »    Full Text »    PDF »
The rubble-pile asteroid Itokawa as observed by Hayabusa..
A. Fujiwara, J. Kawaguchi, D. K. Yeomans, M. Abe, T. Mukai, T. Okada, J. Saito, H. Yano, M. Yoshikawa, D. J. Scheeres, et al. (2006)
Science 312, 1330-1334
   Abstract »    Full Text »    PDF »


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