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Science 18 September 1992:
Vol. 257. no. 5077, pp. 1647 - 1652
DOI: 10.1126/science.257.5077.1647
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Articles

Galileo Encounter with 951 Gaspra: First Pictures of an Asteroid

M. J. S. Belton 1, J. Veverka 2, P. Thomas 2, P. Helfenstein 2, D. Simonelli 2, C. Chapman 3, M. E. Davies 4, R. Greeley 5, R. Greenberg 6, J. Head 7, S. Murchie 7, K. Klaasen 8, T. V. Johnson 8, A. McEwen 9, D. Morrison 10, G. Neukum 11, F. Fanale 12, C. Anger 13, M. Carr 14, and C. Pilcher 15

1 National Optical Astronomy Observatories, Tucson, AZ 85719
2 Department of Astronomy, Cornell University, Ithaca, NY 14853
3 Planetary Science Institute, Tucson, AZ 85719
4 RAND, Santa Monica, CA 90406
5 Department of Geology, Arizona State University, Tempe, AZ 85287
6 Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721
7 Department of Geology, Brown University, Providence, RI 02912
8 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109
9 U.S. Geological Survey, Flagstaff, AZ 86001
10 NASA/Ames Research Center, Moffett Field, CA 94035
11 Deutsche Forschungsanstalt für Luft und Raumfahrt, 8031 Oberpfaffenhofen, Federal Republic of Germany
12 Institute of Geophysics, University of Hawaii, Honolulu, HI 96822
13 Institute for Space and Terrestrial Science, Concord, Ontario, Canada L4K 3C8
14 U.S. Geological Survey, Menlo Park, CA 94025
15 NASA Headquarters, Washington, DC 20546

Galileo images of Gaspra reveal it to be an irregularly shaped object (19 by 12 by 11 kilometers) that appears to have been created by a catastrophic collisional disruption of a precursor parent body. The cratering age of the surface is about 200 million years. Subtle albedo and color variations appear to correlate with morphological features: Brighter materials are associated with craters especially along the crests of ridges, have a stronger 1-micrometer absorption, and may represent freshly excavated mafic materials; darker materials exhibiting a significantly weaker 1-micrometer absorption appear concentrated in interridge areas. One explanation of these patterns is that Gaspra is covered with a thin regolith and that some of this material has migrated downslope in some areas.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
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D. K. Yeomans, J. Barriot, D. W. Dunham, R. W. Farquhar, J. D. Giorgini, C. E. Helfrich, A. S. Konopliv, J. V. McAdams, J. K. Miller, W. M. Owen Jr., et al. (1997)
Science 278, 2106-2109
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Radar Images of Asteroid 4179 Toutatis.
S. J. Ostro, R. S. Hudson, R. F. Jurgens, K. D. Rosema, D. B. Campbell, D. K. Yeomans, J. F. Chandler, J. D. Giorgini, R. Winkler, R. Rose, et al. (1995)
Science 270, 80-83
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A Sharper View of Impact Craters from Clementine Data.
C. M. Pieters, C. M. Pieters, M. I. Staid, E. M. Fischer, S. Tompkins, and G. He (1994)
Science 266, 1844-1848
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First Images of Asteroid 243 Ida.
M. J. S. Belton, M. J. S. Belton, C. R. Chapman, J. Veverka, K. P. Klaasen, A. Harch, R. Greeley, R. Greenberg, J. W. Head III, A. McEwen, et al. (1994)
Science 265, 1543-1547
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Shape of Asteroid 4769 Castalia (1989 PB) from Inversion of Radar Images.
R. S. Hudson, R. S. Hudson, and S. J. Ostro (1994)
Science 263, 940-943
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Magnetic Field Signatures Near Galileo's Closest Approach to Gaspra.
M. G. Kivelson, M. G. Kivelson, L. F. Bargatze, K. K. Khurana, D. J. Southwood, R. J. Walker, and P. J. Coleman Jr. (1993)
Science 261, 331-334
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