LYCOS RETRIEVER 
4 Vesta: Asteroids
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The most notable surface feature is a very large crater that is 460 km in diameter centered near the south pole.[10] Its width is about 80% of the entire diameter of Vesta. The floor of this crater is about 13 km below, and its rim rises 4-12 km above the surrounding area, with total surface relief of about 25 km. A central peak rises 18 km above the crater floor. It is thought that the impact responsible blew up about 1% of the entire volume of Vesta, and it is likely that a group of smaller asteroids known as the Vesta family are the remains of this collision. If this is the case, then the fact that 10 km fragments of the Vesta family have survived bombardment until the present indicates that the crater is only about 1 billion years old or younger.[15] It would ... be the original site of origin of the HED meteorites. In fact, all the known V-type asteroids taken together account for only about 6% of the ejected volume, with the rest presumably either in small fragments, ejected by approaching the 3:1 Kirkwood gap, or perturbed away by radiation pressure. Spectroscopic analyses of the Hubble images[15] have shown that this crater has penetrated deep through several distinct layers of the crust, and possibly into the mantle which is indicated by spectral signatures of olivine.
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In the future, Treiman and his colleagues plan to study other meteorites from 4 Vesta and look for similar quartz veinlets. They will ... study them for more definitive signs of water on the asteroid, such as actual water – very small droplets trapped in the quartz – or water-bearing minerals. Another approach is to look for excess hydrogen in Serra de Magé as compared to meteorites without quartz veinlets, which would indicate that water, a hydrogen-oxygen compound, may have been present. This could be done using the infrared rays produced at the NSLS vacuum ultra-violet (VUV) ring.
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The Hubble Space Telescope observed asteroid Vesta between November 28 and December 1, 1994, when Vesta was at a distance of 251 million kilometers (156 million miles) from Earth. Vesta has a diameter of 525 kilometers (326 miles) and is smaller than the state of Arizona. It rotates about its axis in 5.34 hours.
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About 1percent of Vesta was excavated by the crater formation event, a volume sufficient to account for the family of small Vesta-like asteroids that extends to dynamical source regions for meteorites. This crater may be the site of origin for the howardite, eucrite, and diogenite classes of basaltic achondrite meteorites.
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These two maps are derived from images of asteroid 4 Vesta taken between November 28 and December 1, 1994, by the Hubble Space Telescope. The mid-latitude region of Vesta, between about 16° south and 48° north, were favorably situated for viewing from Earth at the time the images were taken. The map covers a surface area of 518,000 kilometers (200,000 miles).
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News of the dent's discovery is published in an article, "Impact Excavation On Asteroid 4 Vesta: Hubble Space Telescope Results," in today's issue of Science, (Sept. 5). Co-authoring the article with Thomas was Richard P. Binzel, Massachusetts Institute of Technology, Cambridge, Mass.; Michael J. Gaffey, Rensselaer Polytechnic Institute, Troy, N.Y.; Alex D. Storrs and Eddie N. Wells, Space Telescope Science Institute, Baltimore; and Benjamin H. Zellner, Georgia Southern University, Statesboro, Ga.
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