One of the places on the world wide web I like sometimes to go is the Gazetteer of Planetary Nomenclature. There you will find, among much else, that the geographical feature pictured above is called Ligeia Mare, a hydrocarbon lake towards the north of the northern hemisphere of Titan, Saturn's largest moon. Ligeia Mare is about 500 km in breadth and has a sister lake, Kraken Mare; they are fed by rivers that wash down valleys whenever it rains - huge pools of methane, ethane, propane and (probably) other hydrocarbon compounds which remain liquid in the frigid Titanian temperatures. NASA's epochal probe, Cassini, has photographed sunlight flashing from Ligeia Mare (see below) and its Huygens lander in 2005 reached the surface of Titan near the equator, sending back a picture of some orange rocks; now there is proposal to land some kind of craft on, or in, one of the methane lakes. Boating on Titan . . .