HR: 17:35h
AN: P44A-06    [Abstracts]
TI: Saturn's Titan: The Case for Surface Activity
AU: * Nelson, R M
EM: robert.m.nelson@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, United States
AU: Team, C T
EM: rmnelson2@earthlink.net
AF: Lunar and Planetary Lab, University of Arizona, Tucson, AZ 85721, United States
AB: The Saturn orbital tour of the Cassini spacecraft has produced VIMS instrument observations of Titan's surface through spectral ‘windows' in its atmosphere where methane, the principal absorbing gas, is transmitting. We have found that the reflectance of a region on Titan's surface (latitude 26S, longitude 78W) increased twofold between July 2004 and March-April 2005. It returned to the July 2004 level by November 2005. In late December 2005 the reflectance surged upward again to a new maximum. It then declined for the next three months. Detailed analyses indicate that the brightening episodes are a surface phenomenon, making these the first changes seen on Titan's surface. The spectral differences between the region and its surroundings rule out the deposition of many ices including H2O, CO2, and CH4 as possible causes. Remarkably, the change is spectrally consistent with the deposition and removal of ammoniated materials. NH3 has been proposed as a constituent of Titan's interior but not its surface or atmosphere. This transitory NH3 spectral signature is consistent with occasional effusion events in which juvenile ammonia is brought to the surface. Its decomposition may feed nitrogen to the atmosphere. The size of the region suggests it may exceed the size of the largest active volcanic areas in the solar system. This work done at JPL/CALTECH under contract with NASA
DE: 5405 Atmospheres (0343, 1060)
DE: 5410 Composition (1060, 3672)
DE: 5422 Ices
DE: 5464 Remote sensing
DE: 5470 Surface materials and properties
SC: Planetary Sciences [P]
MN: 2007 Joint Assembly