Dawn observed a pattern of minerals exposed by deep gashes created by space rock impacts, which may support the idea the asteroid once had a subsurface magma ocean. A magma ocean occurs when a body undergoes almost complete melting, leading to layered building blocks that can form planets. Other bodies with magma oceans ended up becoming parts of Earth and other planets.
Caption of Image 1
"This image, made from data obtained by NASA's Dawn spacecraft, shows the mineral distribution in the southern hemisphere of the giant asteroid Vesta. The mineral data came from Dawn's visible and infrared mapping spectrometer, which captures different wavelengths of reflected and emitted radiation. The areas in purple have a higher proportion of diogenite minerals, and yellow areas have a higher proportion of eucrite minerals. Diogenites are silicate rocks with more magnesium than the eucrites, which are richer in iron. The mineral data lies on a mosaic obtained by Dawn's framing camera.
The small-scale variation and the fact that mixtures of diogenite and eucrite appear all over Vesta suggest a complex crust dominated by eucrite with intrusions of diogenitic materials. However, since diogenites appear in greater proportion at depth, the patterns suggest Vesta likely melted all the way through early in its evolution."
"This image shows three slices of a class of meteorites that fell to Earth that NASA’s Dawn mission has confirmed as originating from the giant asteroid Vesta. The meteorites, known as howardite, eucrite and diogenite meteorites, were viewed through a polarizing microscope, where different minerals appear in different colors. The texture of the rocks reveals that they crystallized at different rates. The image on the left comes from a meteorite named QUE 97053 (Antarctica), which is basaltic eucrite. The image in the middle comes from the Moore County (North Carolina) cumulate eucrite. The image on the right comes from a diogenite meteorite named GRA 98108 (Antarctica)."