Date: 4 Sep 1997
NASA's Hubble Space Telescope revealed a giant impact crater on the asteroid Vesta. The crater is a link in a chain of events thought responsible for forming a distinctive class of tiny asteroids as well as some meteorites that have reached the Earth.
The giant crater is 285 miles across, which is nearly equal to Vesta's 330 mile diameter. If Earth had a crater of proportional size, it would fill the Pacific Ocean basin. Astronomers had predicted the existence of one or more large craters, reasoning that if Vesta is the true parent body of some smaller asteroids then it should have the wound of a major impact that was catastrophic enough to knock off big chunks. The observations are described in the 5 September issue of Science Magazine.
The top left image is a Hubble image of Vesta taken in May 1996 when the asteroid was 110 million miles from Earth. The asymmetry of the asteroid and "nub" and the south pole is suggestive that it suffered a large impact event. The image was digitally restored to yield an effective scale of six miles per pixel (picture element).
The center image is a color-encoded elevation map of Vesta which clearly shows the giant 285-mile diameter impact basin and "bull's-eye" central peak. The map was constructed from 78 Wide Field Planetary Camera 2 pictures. Surface topography was estimated by noting irregularities along the limb and at the terminator (day/night boundary) where shadows are enhanced by the low sun angle. The elevation map here has been tilted with respect to the left and right images to make the crater and central peak bulls-eye more prominent.
The upper right image is a 3-D computer model of the asteroid Vesta synthesized from Hubble topographic data. The crater's 8-mile high central peak can clearly be seen near the pole. The surface texture on the model is artificial, and is not representative of the true brightness variations on the asteroid. Elevation features have not been exaggerated.
Last Update: 12 Apr 2011 (AMB)
Credit: Ben Zellner (Georgia Southern University), Peter Thomas (Cornell University) and NASA