Between July 2011 and September 2012, NASAs Dawn spacecraft was in orbit around the asteroid Vesta. Dawn's Visible and Infrared Mapping Spectrometer team now presents a surprising finding - the signature of olivine on the asteroid s surface. Olivine is a major component of the mantle of differentiated bodies, including Earth. Vesta is large enough to have evolved an Earth-like layered structure, and the expectation was that olivine would be found in Vesta's deep, south-pole basins, which are thought to be excavated mantle rock. Yet the spectroscopic data reveal olivine-rich material close to the surface in the northern hemisphere.
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