Methane smog enshrouds Titan, Saturn's mysterious moon. Because of that smog, researchers have surmised that liquid methane should exist on the surface, but probes had failed to find any. Recent radar imaging by the Cassini space probe, however, has now uncovered 75 lake-like areas, some spanning 70 kilometers, near the northern pole. Scientists believe these to be liquid-filled depressions, because the temperature (−179 degrees Celsius) and pressure (1.5 times that at Earth's surface) there are ripe for liquid methane and its breakdown product, ethane, to persist. The lakes may fill up either from liquid stored underground or through evaporation and subsequent hydrocarbon rain. Future flybys should reveal how the lakes vary seasonally, as well as whether lakes exist elsewhere on Titan's surface. The report appears in the January 4 Nature.
This article was originally published with the title "Titanic Lakes of Methane" in Scientific American 296, 3, 30 (March 2007)