Mineralogic mapping of the Av-9 Numisia quadrangle of Vesta

In the this manuscript we present the mineralogic mapping of the Av-9 Numisia quadrangle of Vesta. The Numisia region in Vesta’s equatorial zone (22 south to 22 north, 218 to 288 east, in Claudia coordinate system) takes its name from the impact crater Numisia. The main feature wich dominates the quadrangle is the Vestalia Terra plateau, a topographic high about 10 km above the surrounding areas. At south, this region fades into the Rheasilvia basin while at north it is bounded by the steep scarp of Postumia basin. The Visible and Infrared mapping spectrometer VIR onboard NASA/Dawn provided the main data source for this work. In particular we are using spectral parameters synthesizing characteristics of the whole spectra into a single value. Pyroxene-related spectral parameters allow to detect lower/crust or mantle material (diogenites) and upper crust material (eucrites). The combined analysis of albedo from the Framing Camera, the geologic map and the spectroscopic data offer an interesting opportunity to understand the surface features of this region of Vesta. Over Vestalia Terra there are the main craters of the area Numisia, Cornelia, Fabia, Teia and Drusilla, which are rich in features as bright and dark material outcrops and pitted terrains. Mineralogic analysis of those feature is presented along their geologic interpretation recently published. Using the spectral parameters we demonstrate that Vestalia Terra material is mainly howarditic, as shown by materials excavated by Cornelia and Fabia, and the composition of the slope north of Vestalia Terra. This agrees with the strong Bouguer Anomaly observed by Raymond et al., indicating an higher density in relation with the surrounding areas. Beside the recently published works based on gravimetric modeling and geologic interpretation, the mineralogic mapping presented herein gives an additional contribution to depict a more complete geologic history of Numisia.