Compositional variations in the Vestan Rheasilvia basin

Abstract

We present and describe the maps of spectral parameters such as pyroxene band centers and depths, reflectance at 1.4μm and 2.8μm band depth in the Rheasilvia quadrangle. We found a broad anti-correlation between pyroxene band centers and depths while the reflectance is not correlated with the pyroxene spectral parameters. In addition, we found that the Rheasilvia quadrangle is free of OH absorption signatures. We also derived lithological maps with improvements in the spatial resolution with respect to previous lithological maps of the same region. We confirm that the central mound is dominated by eucritic/howarditic pyroxene while diogenitic lithology has been found mainly in a region delineated by Tarpeia, Severina and Mariamne craters. We found small scale variations in the composition of pyroxene. These variations identify lithological units that extend for tens of km, although small units of less than 1km have also been found. We consider this fact as an indication of a high level of compositional heterogeneity within the Vestan crust.