P53E-2183
Albedo and Spectral Variability on Ceres from Four Decades of Observations
Friday, 18 December 2015
Poster Hall (Moscone South)
Jian-Yang Li1, Andreas Nathues2, Lucille Le Corre1, Vishnu Reddy3, Mark V Sykes4, Uri Carsenty5, Julie C Castillo6, Martin Hoffmann2, Ralf Jaumann5, Katrin Krohn5, Stefano Mottola5, Thomas H Prettyman7, Michael Schäfer2, Paul Schenk8, Stefan Schroeder9, David A Williams10, David E Smith11, Maria T Zuber12, Alexandar S. Konopliv13, Ryan S Park14, Carol A Raymond6 and Christopher Russell15, (1)Planetary Science Institute Tucson, Tucson, AZ, United States, (2)Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany, (3)Organization Not Listed, Washington, DC, United States, (4)Planetary Science Institute Tempe, Tempe, AZ, United States, (5)German Aerospace Center DLR Berlin, Berlin, Germany, (6)NASA Jet Propulsion Laboratory, Pasadena, CA, United States, (7)Planetary Science Institute, Albuquerque, NM, United States, (8)Lunar and Planetary Institute, Houston, TX, United States, (9)German Aerospace Center DLR Berlin, Institute of Planetary Research, Berlin, Germany, (10)Arizona State University, Tempe, AZ, United States, (11)Massachusetts Institute of Technology, Cambridge, MA, United States, (12)Massachusetts Inst Tech, Cambridge, MA, United States, (13)Jet Propulsion Laboratory, Pasadena, CA, United States, (14)Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States, (15)Russian Academy of Sciences, Moscow, Russia
Abstract:
Dawn Framing Camera (FC) observations of Ceres established the bright spots inside the Occator and Dantu craters as the likely sources of the intermittent and localized water vapor activity observed by Herschel Space Telescope. Recent ground-based observations of Ceres suggested possible global spectral variability that was attributed to changing amount of water ice on the surface. These observations suggest a possibly changing amount of water ice caused by outgassing on time scales of months to decades. We combined the imaging and spectral data of Ceres collected in the past three decades from ground-based telescopes, Hubble Space Telescope (HST), and Dawn FC during its approach to Ceres to search for global and local variabilities on the surface, and did not find evidence supporting changes in the albedo or spectrum of Ceres. The global albedo of Ceres remains unchanged within 3% of its geometric albedo of 0.09 over the time scale of 10 years. The spectral variability of Ceres recently reported can be mostly explained by changes in the observing geometry. By comparing the spatially resolved images from HST and Dawn FC, if water outgassing causes any variations on the albedo of its sources or changes in size of albedo markings, then such change must be smaller than 15% over 10 years. The stable surface of Ceres under water sublimation activity is consistent with the nearly unchanged albedo and spectral properties of comets, although no liquid water is expected on comets and the sublimation mechanism on comets is completely different from that on Ceres. The bright spots on Ceres thus must be built up over a long period of time. It also possible that the sublimation activity on Ceres either occurs in subsurface, or at size scales of <1 km.
