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Published September 9, 1994 | metadata_only
Journal Article

First Images of Asteroid 243 Ida


The first images of the asteroid 243 Ida from Galileo show an irregular object measuring 56-kilometers by 24 kilometers by 21 kilometers. Its surface is rich in geologic features, including systems of grooves, blocks, chutes, albedo features, crater chains, and a full range of crater morphologies. The largest blocks may be distributed nonuniformly across the surface; lineaments and dark-floored craters also have preferential locations. Ida is interpreted to have a substantial regolith. The high crater density and size-frequency distribution (–3 differential power-law index) indicate a surface in equilibrium with saturated cratering. A minimum model crater age for Ida—and therefore for the Koronis family to which Ida belongs—is estimated at 1 billion years, older than expected.

Additional Information

© 1994 American Association for the Advancement of Science. We thank the Galileo project and the National Aeronautics and Space Administration (NASA) for support; in particular, the Galileo Flight Team, led by W. O'Neil, N. Ausman, M. Landano, and O. Adams. The Ida mosaic was constructed by L. Wainio's group and we wish to recognize H. Mortensen. We also acknowledge D. J. Tholen, R. P. Binzel, P. Magnusson, A. Barucci, S. Mottola, R. Sullivan, R. Pappalardo, P. Geissler, J. -M. Petit, J. Moore, W. F. Bottke, M. Nolan, E. Ryan, W. Merline, B. E. A. Mueller, E. Ashphaug, B. Carcich, P. Lee, D. Simonelli, R. Wagner, P. J. Guske, J. Yoshimizu, and R. Hasegawa. A portion of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. The National Optical Astronomy Observatories are operated by the Association of Universities for Research in Astronomy, Inc. (AURA), under cooperative agreement with the National Science Foundation.

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August 22, 2023
August 22, 2023