Volume 36, Issue 4 p. 501-513
Free Access

Presidential Address: Presented 2000 August 28, Chicago, Illinois, USA The eucrite/Vesta story

Michael J. DRAKE

Corresponding Author

Michael J. DRAKE

Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona 85721-0092, USA

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First published: 04 February 2010
Citations: 134

Abstract

Abstract— Many lines of evidence indicate that meteorites are derived from the asteroid belt but, in general, identifying any meteorite class with a particular asteroid has been problematical. One exception is asteroid 4 Vesta, where a strong case can be made that it is the ultimate source of the howardite-eucrite-diogenite (HED) family of basaltic achondrites. Visible and near-infrared reflectance spectra first suggested a connection between Vesta and the basaltic achondrites. Experimental petrology demonstrated that the eucrites (the relatively unaltered and unmixed basaltic achondrites) were the product of approximately a 10% melt. Studies of siderophile element partitioning suggested that this melt was the residue of an asteroidal-scale magma ocean. Mass balance considerations point to a parent body that had its surface excavated, but remains intact. Modern telescopic spectroscopy has identified kilometer-scale “Vestoids” between Vesta and the 3:1 orbit-orbit resonance with Jupiter. Dynamical simulations of impact into Vesta demonstrate the plausibility of ejecting relatively unshocked material at velocities consistent with these astronomical observations. Hubble Space Telescope images show a 460 km diameter impact basin at the south pole of Vesta. It seems that nature has provided multiple free sample return missions to a unique asteroid. Major challenges are to establish the geologic context of the HED meteorites on the surface of Vesta and to connect the remaining meteorites to specific asteroids.

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