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Shock Discovery On Saturn's Biggest Moon
Scientists have made the surprise discovery of a methane-rich lake near the equator of Saturn's largest moon.
Lakes have previously been spotted near Titan's polar regions but it was thought that bodies of liquid could not exist near the tropics because they would evaporate.
"This discovery was completely unexpected because lakes are not stable at tropical latitudes," said planetary scientist Caitlin Griffith of the University of Arizona, who led the discovery team.
It suggests that there may be an underground source of methane that periodically vents to the surface, and could explain why the chemical is abundant in Titan's atmosphere.
"Titan may have oases," Ms Griffith added.
The research and its findings are detailed in the Nature science journal.
By measuring reflected sunlight from Titan's surface and atmosphere, the international Cassini spacecraft detected a dark region near the landing site of Huygens, a probe that parachuted to Titan's equator in 2005.
Scientists said analysis of the dark area suggests the presence of a 927-square-mile hydrocarbon lake, more than 150 times larger than Windermere, Britain's biggest natural lake.
Near the tropical lake were hints of four shallow ponds similar in size and depth to marshes on Earth.
Titan is among the few bodies in the solar system with a dense atmosphere.
The methane gas there is constantly broken up by sunlight and falls to the surface where it is transported back to the poles, condensing to form lakes.
Scientists do not believe this process created the lakes and ponds at the equator, and are now examining the possibility of a subterranean source.