Ammonia Bearing Species on Ceres: Implication on Origin and Evolution

Friday, 18 December 2015: 11:35
2007 (Moscone West)
Maria Cristina De Sanctis1, Eleonora Ammannito2, Andrea Raponi1, Simone Marchi3, Mauro Ciarniello1, Harry Y McSween Jr4, Thomas B McCord5, Fabrizio Capaccioni6, Maria Teresa Capria1, Filippo Giacomo Carrorro1, Andrea Longobardo1, Federico Tosi1, Sergio Fonte1, Marco Giardino1, Ernesto Palomba1, Gianfranco Magni1, Francesca Zambon1, Carle M Pieters7, Lucy A McFadden8, Carol A Raymond9 and Dawn Team, (1)IAPS-INAF, Rome, Italy, (2)University of California Los Angeles, Los Angeles, CA, United States, (3)Southwest Research Institute Boulder, Boulder, CO, United States, (4)University of Tennessee, Knoxville, TN, United States, (5)Bear Fight Institute, Winthrop, WA, United States, (6)Organization Not Listed, Washington, DC, United States, (7)Brown University, Earth, Environmental and Planetary Sciences, Providence, RI, United States, (8)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (9)Jet Propulsion Laboratory, Pasadena, CA, United States
The Visible and Infrared Mapping Spectrometer (VIR) on board the Dawn spacecraft observed Ceres’ surface acquiring spectra since January 2015. Here we report the average Ceres spectrum, including the spectral range previously precluded from telescopic measurements due to telluric atmospheric absorptions. The data indicate that the surface is very dark: average albedo of 0.090 ±0.006 at 0.55 µm, consistent with HST data (Li et al., 2006). Ceres’ average spectrum is characterized by a prominent absorption band at 2.7 micron. Weaker absorption bands are observed between 3.05-3.1, 3.3-3.4 and 3.9-4 micron; the visible and near-IR ranges lack prominent bands. We modelled the spectra of Ceres using Hapke theory. Results of the spectral modelling indicate that extensive water ice is not present in surface spectra acquired so far. The best fit is obtained with a mixture of ammoniated phyllosilicates mixed with other clays, Mg-carbonates, and dark material, like magnetite (De Sanctis et al. 2015, submitted). The presence of ammonia bearing materials across the surface has implications for the origin of Ceres and its internal structure and evolution. Higher spatial resolution spectra are being acquired to address the small scale mineralogy across this dwarf planet.


Li, et al., Photometric analysis of 1 Ceres and surface mapping from HST observations. Icarus 182, 143–160 (2006).

De Sanctis et al., Ammoniated phyllosilicates on dwarf planet Ceres reveal an outer solar system origin, Nature submitted, (2015).

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.