This colorized map from NASA's Dawn mission shows the distribution of minerals across the surface of Vesta. It was made from spectra –- data collected in different wavelengths of radiation –- obtained by Dawn's visible and infrared mapping spectrometer. The spectrometer data were then laid over a mosaic created by Dawn's framing camera.
The map indicates that the Vesta surface is not uniform, with a sharp contrast between the northern and southern regions. The visible and infrared mapping spectrometer detected a type of mineral known as diogenite that is typical of Vesta's lower crust. The upper crust, however, has more eucritic material. Diogenites are silicate rocks with more magnesium than the eucrites, which are richer in iron. These data suggest that the region around the Rheasilvia basin is richer in diogenites than the equatorial regions.
The north-south variation in minerals indicates that the deep crust exposed in the southern Rheasilvia region is dominated by pyroxene-rich, diogenitic material while the equatorial region seems to retain the most ancient eucrite-rich mineralogy.
In this image, blue shows a richer concentration of diogenite minerals and yellow shows a richer concentration of eucrite minerals. Credit: NASA/JPL-Caltech/UCLA/INAF/MPS/DLR/IDA
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