Nasa scientists said the seas on Titan were likely filled with liquid methane or ethane, compounds abundant in clouds in Titan's atmosphere.
They said the discovery reinforced current thinking that Titan's surface must be resupplying methane to its atmosphere.
Although there was no proof that the seas contained liquid, their shape and dark appearance on radar indicates smoothness, the scientists added.
Titan is the second-largest moon in the solar system, after Jupiter's Ganymede, and is about 50 per cent larger than the Earth's moon.
|One of the "seas" on Titan is larger than any of the |
Great Lakes of North America [Nasa]
Because of the new images, the Cassini mission team is repositioning the spacecraft's radar instruments during a May fly-by so that it can pass directly over the dark areas seen by the cameras.
Cassini was launched in October 1997 and entered into orbit around Saturn in July 2004.
The mission is a project between Nasa, the European Space Agency and the Italian Space Agency.
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