Big River On Titan

Cassini's radar has imaged a large river on Saturn's huge and fascinating moon, Titan.  The river flows some 250 miles and empties into the largest lake yet found on Titan, which covers an area that is five times larger than the area covered by Lake Superior.

Of course, lakes and rivers on Titan are not filled with liquid water.  On that frigid world, water freezes as hard as rock.  Instead, the liquids in that super-cold environment are ethane and methane.