Evidence of hydrated and/or hydroxylated minerals on the surface of asteroid 4 Vesta

Asteroid 4 Vesta is thought to be a differentiated object with intact internal structure due to its achondritic surface. In this paper, we report K‐L band spectroscopic observations of Vesta. We have detected the presence of a 3‐μm absorption feature at about the 1% level on the surface of Vesta at longitudes between 155° and 195°. This result indicates that OH and/or H 2 O‐bearing minerals are present in this region of Vesta; the sources are plausibly fragments of carbonaceous chondrite impactors or solar wind implantation. The detection of 3‐μm absorption features from Vesta, regarded as the smallest terrestrial planet, may provide clues to the origin of volatile materials on terrestrial planets.