T282 Geology of Dwarf Planets: First Results from NASA's Dawn Mission to Ceres

Wednesday, 4 November 2015
8:00 AM - 12:00 PM
Room 344

SURFACE MINERALOGY OF CERES BY VIR ON DAWN: IMPLICATION ON ORIGIN AND EVOLUTION

Paper number: T282-3
Program: Technical Sessions
Time: 8:35 AM – 8:50 AM

Authors

Abstract

The Visual and Infrared Mapping Spectrometer -VIR- on board of Dawn observed Ceres surface acquiring spectra since January 2015. Here we report about the surface mineralogy of Ceres. On approach to Ceres, Dawn obtains images and hyperspectral data on different occasions, starting in January 2015. VIR observed Ceres from 0.4 to 5 micron, with an Istantenous Field Of View (IFOV) of 250 μrad. This spectral range includes the spectral region precluded from telescopic measurements due to the atmospheric absorptions. Ceres surface is very dark with an average albedo of 0.090 ±0.006 at 0.55 µm, consistent with HST data. The first data indicates an overall spectral homogeneity but some regions of the surface show spectral differences corresponding to different properties of the surface. The visible and near-IR range is almost flat and lacks of prominent bands, but the spectrum shows a strong phase reddening. The IR Ceres’ spectrum is characterized by a broad band in the 3 micron region. Within this broad band, several other bands are present: a prominent absorption at 2.7 micron and other smaller bands at 3.05-3.1, 3.3-3.4 and 3.9-4 micron. The Ceres spectrum is modelled using Hapke theory using different endmembers. Results of the spectral modelling indicate that the presence of extensive water ice is not consistent with surface spectra acquired so far. Also brucite does not seem a major constituent of Ceres’ surface. Other materials match better the spectrum. Here we will describe the Ceres’ surface mineralogy and its implications in terms of origin and structure.

Support by S. Marchi, T.B. McCord, H.Y. McSween, F. Capaccioni, M.T. Capria, J-P Combe, M. Formisano, A. Frigeri, G. Magni, E. Palomba, R. Jaumann, C.M. Pieters. This work is supported the Italian Space Agencies, NASA, and from the German Space Agency. Support of the Dawn Instrument, Operations, and Science Teams is acknowledged.