TITAN'S SURFACE AS VIEWED FROM THE HUYGENS PROBE BY THE DESCENT IMAGER/SPECTRAL RADIOMETER

L. Soderblom, M. Tomasko, B. Archinal, T. Becker, B. Bézard, M. Bushroe, M. Combes, D. Cook, A. Coustenis, C. de Bergh, L. Dafoe, L. Doose, S. Douté, A. Eibl, S. Engel, F. Gliem, B. Grieger, T. Hare, K. Holso, A. Howington-Kraus, E. Karkoschka, H. U. Keller, R. Kirk, R. Kramm, M. Küppers, P. Lanagan, E. Lellouch, M. Lemmon, J. Lunine, E. McFarlane, J. Moores, M. Prout, B. Rizk, M. Rosiek, P. Rüffer, S. Schröder, B. Schmitt, C. See, P. Smith, N. Thomas, R. West

The Descent Imager/Spectral Radiometer (DISR) aboard the Huygens Probe characterized atmospheric radiation (350-1600 nm) and returned images and spectra of Titan's surface. The near-surface methane mole fraction is ~5% (relative humidity ~50%); making methane fog or rain at the landing site unlikely at present. Below ~8 km the eastward zonal wind dropped to <1m/s and reversed back to the west indicative of a boundary layer. Surface reflectance is ~0.08 at 531 nm, ~0.13 at 830 nm, decreasing to ~0.1 at 1500 nm consistent with dirty water ice. DISR images show brighter, higher terrains with stubby and higher-order drainage systems that border darker, lower-lying plains scoured by flow. Surface images show rounded cobbles in a dry river bed. DISR-derived topography for the drainages in the bright terrain show extremely rugged terrain with slopes as high as 30 degrees. This suggests relatively rapid erosion by flows in the river beds resulting in the deeply incised valleys.