HR: 11:20h
AN: P32A-05    [Abstracts]
TI: Thermal Evolution Models for Enceladus Defining the context for the formation of the South Pole thermal anomaly
AU: * Matson, D L
EM: Dennis.L.Matson@jpl.nasa.gov
AF: Jet Propulsion Laboratory/CalTech, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AU: Castillo, J C
EM: Julie.C.Castillo@jpl.nasa.gov
AF: Jet Propulsion Laboratory/CalTech, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AU: Johnson, T V
EM: Torrence.V.Johnson@jpl.nasa.gov
AF: Jet Propulsion Laboratory/CalTech, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AU: Lunine, J I
EM: jlunine@lpl.arizona.edu
AF: Lunar and Planetary Lab., University of Arizona 1629 E University Blvd, Tucson, AZ 85721
AU: Lunine, J I
EM: jlunine@lpl.arizona.edu
AF: INTA-ISFI`, Area di Ricerca Tor Vergata, Rome, 10001 Italy
AU: McCord, T B
EM: mccordtb@aol.com
AF: Planetary Science Institute, 22 Fiddler's Road , Winthrop, WA 98862 United States
AU: Sotin, C
EM: sotin@chimie.univ-nantes.fr
AF: Jet Propulsion Laboratory/CalTech, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AU: Sotin, C
EM: sotin@chimie.univ-nantes.fr
AF: Laboratoire de Planetologie et Geodynamique, 2, rue de la Houssiniere, Nantes, 44322 France
AU: Thomas, P C
EM: thomas@baritone.astro.cornell.edu
AF: Cornell University, Department of Astronomy 422 Space Sciences Building , Ithaca, NY 14853 United States
AU: Turtle, E P
EM: turtle@pirl.lpl.arizona.edu
AF: Lunar and Planetary Lab., University of Arizona 1629 E University Blvd, Tucson, AZ 85721
AB: We have developed thermal evolution models for Enceladus as a function of time of formation (i.e., initial amount of short-lived radiogenic species available), models for the cooling of the Saturnian nebula, silicate hydration, and presence of ammonia. Differentiation of the models is mainly determined by their time of formation with respect to the formation of CAIs. For each model we identify the times when thermal conditions are suitable for significant tidal dissipation heating to be initiated and sustained until the present. This defines the context for forming the South Pole thermal anomaly detected by Cassini instruments. This anomaly has been suggested to power a geyser that might be responsible for the origin of Saturn's E-ring. However, Enceladus' nonhydrostatic shape and its old surface indicate that the overall outer layer might be thick, thus a low heat flux, except at the South Pole. We investigate different models to generate the thermal anomaly in this region. We look for mechanisms that could have locally enhanced tidal dissipation in the ice, and/or in the silicate phase (e.g., magma chamber). Models using radiogenic species and tidal dissipation can raise the core temperature to the vicinity of 1000 K. This allows the presence of a liquid layer (whose thickness remains to be modeled) at the interface between the rocky core and an icy mantle. If at the rock-ice interface water can percolate into the rock, hot water and supersaturated steam can be produced. Hot water and hot steam are useful for producing the observed hydrothermal effects and morphology. (We note that if a moderate sized silicate magma chamber is present on Enceladus, present-day tidal dissipation would be sufficient to maintain it in the molten state.) We also discuss the link between this thermal model and the observed shape and geology. This work was carried out by JPL under contract with NASA.
DE: 3616 Hydrothermal systems (0450, 1034, 3017, 4832, 8135, 8424)
DE: 5430 Interiors (8147)
DE: 5455 Origin and evolution
DE: 8424 Hydrothermal systems (0450, 1034, 3017, 3616, 4832, 8135)
SC: Planetary Sciences [P]
MN: Fall Meeting 2005