SURFACE COMPOSITION OF CERES QUADRANGLE AC-4 INVESTIGATED BY THE DAWN MISSION
The albedo calculated from images acquired by the Framing Camera (FC) is a very uniform within this quadrangle, with a few exceptions: 1) Low-albedo materials that are likely ejecta from the northern rim of Occator and from other small craters including one inside Ezinu, 2) Small areas with albedo higher than average including the southern rim of Ezinu and one fresh crater (unnamed) at 61.4°N, 221.5°E.
The Visible and InfraRed mapping spectrometer (VIR) is sensitive to absorption bands due to OH in phyllosilicates at 2.7 µm and ammoniated phyllosilicates at 3.06 µm . The most extreme variations are observed in Occator ejecta (where the two absorption bands are strong) in contrast with the floor of Occator. Generally, fresh craters exhibit materials that have relatively weak phyllosilicate absorption bands, such as the southern rim of Ezinu and the unnamed crater at 61.4°N, 221.5°E. In addition, that particular crater contains H2O-rich materials  that are associated to mass-wasting.
We plan to focus on the following topics.
1- Perform an analysis of the composition of fresh craters in order to detect possible variations between the craters and to determine whether the composition of fresh craters is representative of the rest of the surface.
2- Investigate whether the H2O-rich area is associated to a distinctive mineralogy, and make comparisons with Oxo, where H2O has also been found ?
3- Measure the extent of ejecta from Occator and compare the results with those from geological mapping .
1. Russell C. T. et al., 2011, SSR 163
2. De Sanctis M.C. et al.,2011, SSR 163
3. De Sanctis et al., 2015, Nature 528.
4. Combe J-Ph. et al., 2016, GSA (this meeting)
5. Combe J-Ph. et al., 2016, LPSC #1820
6. Scully et al., Icarus, submitted