THE GEOLOGY OF VESTA: INSIGHTS FROM UNBRECCIATED EUCRITES
Gaffey (1997) observed sub-hemispheric color and spectral variations across the surface of Vesta, corresponding to regions of differing mineralogies. He was able to produce a generalized lithologic map of Vesta using these results. We can build upon such work by using the HED meteorites as a spectral groundtruthing tool for DAWN in order to produce more accurate geologic maps of Vesta's surface.
This study focuses on the eucrite member of the HED family (specifically the unbrecciated eucrites), and attempts to quantify the petrologic factors that have the greatest impact upon their spectra (grain size, mineral chemistry, and texture). Eucrites are primarily composed of pigeonite and plagioclase, with varying amounts of silica and opaque phases (usually ilmenite, chromite, and sulfides). However, despite their similarities, we are able to see great petrologic variability, from quench-textured, rapidly-cooled lithologies, to coarse, exsolved, slowly-cooled, cumulate types. Such variability is also reflected within their spectra and our results show that we are able to distinguish between different types of eucrites potentially corresponding to different lithologies on the surface of Vesta - using their spectra alone.