Infrared observations of the surface and atmosphere of Titan

Infrared photometry of Titan, Saturn, and Saturn's Rings at 3.5, 4.9, 17.8, and 18.4 microns is reported. Comparison of the albedo of Titan in the 4.9 micron 'window' with the albedo of the rings and with laboratory spectra suggests that frost, possibly water ice, could be a major constituent. If thick clouds are present they must be very dark at 4.9 microns. The 17.8 and 18.4 micron data are not consistent with a clear, dense molecular hydrogen atmosphere.