Planetary Science Seminar

During its year of operations at Vesta, Dawn acquired high quality spectra from 0.2 to 5 microns in the 864 spectral channels of the Visible and Infrared Mapping Spectrometer. These data were used to characterize and map the distribution of minerals on Vesta. VIR spectra are dominated by pyroxene absorptions at 0.9 and 1.9 µm indicating the ubiquitous presence of this family of minerals on the surface and confirming the hypothesis that Vesta is a differentiated body. Since olivine is a major component of the mantles of differentiated bodies, much effort has been dedicated to the identification of the possible presence of olivine on Vesta's surface especially within Rheasilvia basin in the South Pole where, according to numerical models, the impact(s) could have exposed the mantle. While in the southern regions there is so far no evidence of olivine, it has been detected mainly in the northern hemisphere. The identification of olivine-rich lithologies on Vesta can constrain different petrologic scenarios, each of which predicts different abundances and distributions of olivine. The compositional context of the olivine sites suggests a mantle source, where the geographical location jeopardizes this conclusion. Thus while the early Dawn observations concluded that Vesta was similar to predictions, our later compositional analysis suggests a complex evolutionary history for Vesta not adequately described by the current models.