Figure 7-31 Surface Features on Titan (a) Voyager images of Titan’s smoggy atmosphere. (b) Cassini image of Titan (diameter 5150 km or 3200 mi) showing lighter highlands, called Xanadu, and dark, flat, lowlands that may be hydrocarbon seas. Resolution is 4.2 km (2.6 mi). (c) Riverbeds meandering across the Xanadu highlands of Titan. These are believed to have been formed by the flow of liquid methane and ethane. (d) Lakes filled with liquid methane and ethane. (e) The Huygens probe took this image at Titan’s surface on January 14, 2005. What appear like boulders here are actually pebbles strewn around the landscape. The biggest ones are about 15 cm (6 in.) across. (f) Our present understanding of Titan’s structure.