Titan, Saturn's largest moon, as seen by the spaceprobe Huygens during its successful descent on January 14th 2005. The lighter features appear to be islands around which a dark liquid is flowing. Although the Huygens probe found no conclusive evidence of liquids on Titan, images like this would tend to imply that in the recent past there was liquid flowing on the surface. It is probable that it would have been liquid methane, or another hydrocarbon.