But scientists were able to conclude the areas were liquid after studying data from a Cassini instrument able to distinguish chemically different materials based on the way they absorb and reflect infrared light.

The visual and mapping instrument spotted a lake, Ontario Lacus, in Titan's south polar region during a flyby in December, NASA said. The lake is roughly 7,800 square miles, slightly bigger North America's Lake Ontario.

"Detection of liquid ethane confirms a long-held idea that lakes and seas filled with methane and ethane exist on Titan," said Larry Soderblom, a scientist with the US Geological Survey in Flagstaff, Arizona.

"The fact we could detect the ethane spectral signatures of the lake even when it was so dimly illuminated, and at a slanted viewing path through Titan's atmosphere, raises expectations for exciting future lake discoveries by our instrument."

Scientists ruled out the presence of water ice, ammonia, ammonia hydrate and carbon dioxide in Ontario