IMPACT EXCAVATION ON ASTEROID 4-VESTA - HUBBLE-SPACE-TELESCOPE RESULTS

Hubble Space Telescope images of asteroid 4 Vesta obtained during the favorable 1996 apparition show an impact crater 460 kilometers in diam eter near the south pole. Color measurements within the 13-kilometer-d eep crater are consistent with excavation deep into a high-calcium pyr oxene-rich crust or olivine upper mantle, About 1 percent of Vesta was excavated by the crater formation event, a volume sufficient to accou nt for the family of small Vesta-like asteroids that extends to dynami cal source regions for meteorites, This crater may be the site of orig in for the howardite, eucrite, and diogenite classes of basaltic achon drite meteorites.