37th DPS Meeting, 4-9 September 2005
Session 53 Titan III
Oral, Thursday, September 8, 2005, 4:20-6:00pm, Music Concert Hall

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[53.06] The surface of Titan: Preliminary Cassini VIMS results on roughness, albedo, and particle characteristics

B. J. Buratti (JPL/CalTech), C. Sotin (Universite de Nantes), T. B. McCord (PSI), R. H. Brown (Univ. Arizona), R. N. Clark (USGS), D. P. Cruikshank (NASA/AMES), R. Jaumann (DLR), K. Baines (JPL/CalTech), G. Bellucci (CNR), J. P. Bibring (Universite Paris-Sud), F. Capaccioni, P. Cerroni (CNR), M. Combes (Observatoire de Paris), A. Coradini (CNR), P. Drossart (Observatoire de Paris), V. Formisano (CNR), Y. Langevin (Universite Paris-Sud), D. L. Matson (JPL/CalTech), V. Mennella (CNR), R. M. Nelson (JPL/CalTech), P. D. Nicholson (Cornell University), B. Sicardy (Observatoire de Paris), J. A. Mosher (JPL/CalTech)

By the end of August 2005, the Cassini spacecraft will have accomplished 6 close, targeted flybys of Titan, ranging in distances (at closest approach) from 1025 to 2500 km. The Cassini Visual Infrared Mapping Spectrometer (VIMS) is uniquely suited to studying the surface of Titan because the thick, opaque nitrogen-methane atmosphere of Titan exhibits windows of clarity at selected atmospheric "windows" that are well distributed through the near infrared. The spectral reflectance at these windows, ranging from 0.93 to 5 microns, has been studied to derive the surface properties of the satellite, including geometric albedos, roughness, rotational light curves, and single particle phase functions. A simple empirical model has been employed to remove the haze, which adds substantial opacity even in the windows. The windows at 2 and 5 microns are particularly important because the haze opacity is lowest there. A computer code that models the surface limb-darkening behavior at a constant solar phase angle as a function of the degree of roughness has been fit to the surface intensity. Henyey-Greenstein's equation was used to derive the single particle phase function. Our results show that many areas of Titan have surface physical characteristics similar to the other icy satellites of Saturn. However, the low-albedo regions are very smooth, with a macroscopic surface roughness lower than any seen on a planetary surface. The over-all shape of the spectrum of Titan through the atmospheric windows is consistent with a mixture of water-ice and organics (tholins), although this simple picture cannot explain some details, particularly the relative reflectances in the 2.65-2.75 micron region.

Work funded by the National Aeronautics and Space Administration.

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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.