A Cassini RADAR swath across Titan's north polar regions passed over numerous methane-ethane lakes and river channels that feed them. There is not any evidence that any of the channels were actually running with flowing liquid when Cassini took the image; it's more likely that they are dry washes like those in Earth's deserts, and that they appear dark because a layer of fine sediment is deposited along their bottoms. The data are from flyby T28, April 10, 2007.

NASA / JPL