HR: 1340h
AN: P23B-1350    [Abstracts]
TI: Titan's Lake Distribution and Classification from the Cassini RADAR
AU: * Aharonson, O
EM: oa@caltech.edu
AF: Geologic and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, United States
AU: Hayes, A
EM: hayes@gps.caltech.edu
AF: Geologic and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, United States
AU: Lewis, K
EM: klewis@gps.caltech.edu
AF: Geologic and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, United States
AU: Lunine, J
EM: jlunine@lpl.arizona.edu
AF: Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, United States
AU: Lorenz, R
EM: Ralph.Lorenz@jhuapl.edu
AF: Johns Hopkins University Applied Physics Lab, 11100 Johns Hopkins Rd, Laurel, MD 20723, United States
AU: Mitchell, K
EM: Karl.L.Mitchell@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology 4800 Oak Grove Dr., Pasadena, CA 91109, United States
AU: Jannsen, M
EM: Michael.A.Janssen@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology 4800 Oak Grove Dr., Pasadena, CA 91109, United States
AU: Mitri, G
EM: Giuseppe.Mitri@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology 4800 Oak Grove Dr., Pasadena, CA 91109, United States
AU: Wall, S D
EM: Stephen.D.Wall@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology 4800 Oak Grove Dr., Pasadena, CA 91109, United States
AU: Elachi, C
EM: charles.elachi@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology 4800 Oak Grove Dr., Pasadena, CA 91109, United States
AU: Cassini RADAR Team, a
AB: A picture is emerging of surface hydrology in the north polar region of Titan. Quasi-circular, lobate to complex features, which take up 2.4% of the global coverage area (22.4% of the surface), are separated into 3 classes: dark lakes, granular lakes, and bright lakes. Dark lakes are interpreted as liquid filled while bright lakes are interpreted to be empty basins. Based on observed backscatter and geospatial position, granular lakes are inferred as transitional between dark and bright counterparts. In this work, the differences in distribution, morphology, and radiometric properties between the classes are explored using the Cassini Radar. The differences and similarities between the classes have implications for the interaction and evolution of hydrologic features on Titan. Dark lakes, which represent 84% of the mapped features, are found between 65°N and 90°N, and show a general trend of decreased off-nadir backscatter poleward. Granular lakes, which are distinguished from dark lakes by a higher backscatter cross-section relative to their surroundings, are found as low as 55°N and extend to 77°N. We have found no abrupt statistical change between dark and granular lakes, suggesting a smooth transition between the two classifications. Bright lakes, distinguished by their higher backscatter relative to their surroundings, represent ~10% of observed lakes. They are found in the same latitude range as granular lakes, often interspersed among them. Shoreline complexity, expressed as the fractal dimension, shows that bright and granular lakes are characteristically more circular than dark lakes. High resolution (~5 km) altimetry collected coincident with Synthetic Aperture Radar (SAR) images shows that bright lakes are empty basins 250-350 m in depth. Comparison between SAR images and integrated power in the altimetry waveforms shows that bright lakes have high return in both nadir and off-nadir backscatter relative to their surroundings. This allows distinguishing variations in roughness from intrinsic properties of the materials. Initial topographic measurements from stereo radar images constrain the relative elevations of nearby lakes, allowing comparison among lake classes. In cases where filled lakes lie above empty lakes, a state of disequilibrium with respect to subsurface transport is implied. In general, a single topographic contour cannot be used to separate empty and full lake positions. Combining morphology, radiometry, and topography provide complementary information on the nature of Titan's surface and sub-surface hydrocarbon hydrology.
DE: 1800 HYDROLOGY
DE: 6281 Titan
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting