We observed the near-Earth ASTEROID 2008 EV5 with the Arecibo and Goldstone planetary radars and the Very Long Baseline Array during December 2008. EV5 rotates retrograde and its overall shape is a 400 ± 50 m oblate spheroid. The most prominent surface feature is a ridge parallel to the asteroid's equator that is broken by a concavity about 150. m in diameter. Otherwise the asteroid's surface is notably smooth on decameter scales. EV5's radar and optical albedos are consistent with either rocky or stony-iron composition. The equatorial ridge is similar to structure seen on the rubble-pile near-Earth asteroid (66391) 1999 KW4 and is consistent with YORP spin-up reconfiguring the asteroid in the past. We interpret the concavity as an impact crater. Shaking during the impact and later regolith redistribution may have erased smaller features, explaining the general lack of decameter-scale surface structure.
Bibliographical noteFunding Information:
The Goldstone Solar System Radar, Arecibo Observatory, and NRAO Socorro & Green Bank staff helped to obtain the data presented here. We thank A. Galad, B.W. Koehn, M.D. Hicks, and V. Reddy for providing EV5’s rotation period and spectral type from their optical and infrared observations in advance of publication. The Arecibo Observatory is part of the National Astronomy and Ionosphere Center, which is operated by Cornell University under a cooperative agreement with the National Science Foundation. The NRAO is run by Associated Universities, Inc. for the National Science Foundation. Some of this work was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA). This paper is based in part on work funded by NASA under the Science Mission Directorate Research and Analysis Programs. M.W. Busch was supported by the Hertz Foundation. Our observations of EV5 are dedicated to the memory of Steven Ostro.
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- Asteroids, Dynamics
- Asteroids, Surfaces
- Radar observations