  Vesta, the second largest Main Belt asteroid, will be the first to be
explored in 2011 by NASA's Dawn mission. It is a dry, likely differentiated
body with spectrum suggesting that is has been resurfaced by basaltic lava
flows, not too different from the lunar maria.
  Here we present the first disk-resolved spectroscopic observations of an
asteroid from the ground. We observed (4) Vesta with the ESO-VLT adaptive
optics equipped integral-field near-infrared spectrograph SINFONI, as part of
its science verification campaign. The highest spatial resolution of ~90 km on
Vesta's surface was obtained during excellent seeing conditions (0.5") in
October 2004.
  We observe spectral variations across Vesta's surface that can be interpreted
as variations of either the pyroxene composition, or the effect of surface
aging. We compare Vesta's 2 micron absorption band to that of
howardite-eucrite-diogenite (HED) meteorites that are thought to originate from
Vesta, and establish particular links between specific regions and HED
subclasses. The overallcomposition is found to be mostly compatible with
howardite meteorites, although a small area around 180 deg. East longitude
could be attributed to a diogenite-rich spot. We finally focus our spectral
analysis on the characteristics of Vesta's bright and dark regions as seen from
Hubble Space Telescope's visible and Keck-II's near-infrared images.

Earth and Planetary Astrophysics