Scientists said it was an "unexpected" discovery: There's a liquid methane filled lake near the equator of Saturn's moon Titan.
Scientists had seen lakes on Titan before, but they didn't expect them near the equator because they believed the intensity of the sun at those latitudes would evaporate the liquid.
"This discovery was completely unexpected because lakes are not stable at tropical latitudes," planetary scientist Caitlin Griffith of the University of Arizona, who led the discovery team, told the AP.
"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 companion probe that parachuted to Titan's equator in 2005.
"Scientists said further analysis of the dark feature suggests the presence of a 927-square-mile hydrocarbon lake — twice as big as Lake Champlain, a freshwater lake that borders upstate New York and Vermont. Near the equatorial lake were hints of four shallow ponds similar in size and depth to marshes on Earth."
The findings are published in Thursday's edition of Nature.
Space.com reports that the lake is hard to explain. The models scientists are working with suggest the methane should evaporate. Also, the fact that the lake is there during the moon's dry season is evidence the lake is not just a rain puddle.
"Instead, Griffith and her colleagues suggest this tropical lake is fed by subterranean channels, essentially making it an oasis in the desert," Space.com reports.