Size and Shape of Saturn's Moon Titan
Howard A. Zebker,1,*
Bryan Stiles,2
Scott Hensley,2
Ralph Lorenz,3
Randolph L. Kirk,4
Jonathan Lunine5
Cassini observations show that Saturn’s moon Titan is
slightly oblate. A fourth-order spherical harmonic expansion
yields north polar, south polar, and mean equatorial radii of
2574.32 ± 0.05 kilometers (km), 2574.36 ± 0.03
km, and 2574.91 ± 0.11 km, respectively; its mean radius
is 2574.73 ± 0.09 km. Titan’s shape approximates
a hydrostatic, synchronously rotating triaxial ellipsoid but
is best fit by such a body orbiting closer to Saturn than Titan
presently does. Titan’s lack of high relief implies that
most—but not all—of the surface features observed
with the Cassini imaging subsystem and synthetic aperture radar
are uncorrelated with topography and elevation. Titan’s
depressed polar radii suggest that a constant geopotential hydrocarbon
table could explain the confinement of the hydrocarbon lakes
to high latitudes.
2 Jet Propulsion Laboratory (JPL), California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA.
3 Applied Physics Laboratory, Johns Hopkins University, 11100 Johns Hopkins Road, Laurel, MD 20723, USA.
4 U.S. Geological Survey, 2255 North Gemini Drive, Flagstaff, AZ 86001, USA.
5 Departments of Planetary Science and Physics, University of Arizona, Tucson, AZ 85721, USA.
* To whom correspondence should be addressed. E-mail: zebker{at}stanford.edu
