This graph shows a spectrum, displaying the intensity of solar light reflected by the surface of Titan as a function of wavelength (colour). The red line shows the measured intensity, which is compared here with the expected intensity of hydrocarbon ice (green) and dirty water ice (blue).
In the infrared, above 1.4 nanometres, the measured intensity resembles more closely that of dirty water ice. At lower wavelengths, the fact that the expected intensity is greater than that observed suggests that the material making up the surface is darkened by impurities.
This spectrum was taken by the DISR instrument from an altitude of about 100 metres. This is the first clear measurement made of the surface of Titan and has not been contaminated by light scattered by the upper atmosphere.
The Cassini-Huygens mission is a cooperative project between NASA, ESA and Italy's ASI space agency.