HR: 09:45h
AN: P11F-08    [Abstracts]
TI: No Ocean Source for Enceladus' Plumes
AU: * Schneider, N M
EM: nick.schneider@lasp.colorado.edu
AF: LASP, U Colorado, 392 UCB, Boulder, CO 80309,
AU: Burger, M H
EM: Matthew.Burger@gsfc.nasa.gov
AF: GSFC, Code 612.2 8800 Greenbelt Rd., Greenbelt, MD 20771,
AU: Johnson, R E
EM: rej@virginia.edu
AF: U. Virginia, Engineering Physics, Charlottesville, VA 22904,
AU: Kargel, J S
EM: jkargel1054@earthlink.net
AF: U. Arizona, Dept. of Hydrology & Water Resources, Tucson, AZ 85721,
AU: Schaller, E L
EM: emily@gps.caltech.edu
AF: CalTech, Dept. of Geological & Planetary Sci. 1200 E. California Blvd., Pasadena, CA 91125,
AU: Brown, M E
EM: mbrown@caltech.edu
AF: CalTech, Dept. of Geological & Planetary Sci. 1200 E. California Blvd., Pasadena, CA 91125,
AB: A groundbased telescopic search for sodium emission near Saturn's moon Enceladus places a firm upper limit on the possible amount of sodium released by eruptions there. Independent observations at the Keck and Anglo- Australian Telescopes using high resolution spectroscopy failed to detect any sodium emission near Enceladus, despite the high sensitivity of such instruments to minute amounts of sodium originating at Jupiter's moons Io and Europa. Large amounts of sodium would be expected if Enceladus' plume material were derived directly from a long-lived ocean (or more confined "sea") in contact with rocky material. Chemical models predict that sodium would dissolve into such an ocean at mixing ratios relative to water of 10^-4 to 10^-1 (Zolotov et. al, 2007). Our numerical plumes models show that such high sodium concentrations would result in a long-lived torus of sodium encircling Saturn. Our detection upper limits fall orders of magnitude below these models, leading us to conclude that the Enceladus plumes do not originate in an ocean or sea. These observations support the alternative theories that Enceladus' plumes are generated by shear heating of the icy crust - resulting in sublimation or melting - or the decomposition of clathrates. These results do not rule out the possibility that a deep ocean exists at depth that is not directly responsible for the plumes. Plume sampling by Cassini or potential future missions, however, would not be probing this potentially habitable environment. This work has been supported by NSF's Planetary Astronomy Program.
DE: 5220 Hydrothermal systems and weathering on other planets
DE: 6280 Saturnian satellites
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting