Hubble Space Telescope images of asteroid 4 Vesta obtained during the favorable 1996 apparition show an impact crater 460 kilometers in diameter near the south pole. Color measurements within the 13-kilometer-deep crater are consistent with excavation deep into a high-calcium pyroxensrich crust or olivine upper mantle. About 1 percent 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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The reflectance spectra of powdered samples of selected minerals, meteorites9 lunar materials and frosts are presented a s an aid in the interpretation of present and future remote sensing data of solar system ob jects. Spectra obtained in separate wavelength regions have been combined and normalized, yielding coverage from 92 to 1800 nm. Spectral features include relfectance maxima in the far UV region produced by valence-conduction interband transitions, and reflectance minima in the near UV, visible and near IF? regions, produced by charge transfer and crystal field transitions.Specific maxima and minima are diagnostic of mineral type and compostioni additionally, the minerals present in mixtures such a s meteorites and lunar samples can be determined.