Infrared images snapped by the orbiting Cassini reveal a 30-kilometre-wide dome that appears to be a cryovolcano, a volcanic-like vent that spews forth ice instead of lava.

Scientists theorise the volcano at one time spat out icy plumes that released methane into Titan's atmosphere.

The findings will appear in Thursday's issue of the journal Nature.

Titan is the only moon in the solar system that has a significant atmosphere made up of nitrogen and methane.

Its atmosphere is similar to that of primordial Earth and scientists believe that studying it could provide clues to how life began.

Scientists have long speculated that the organic materials in Titan's atmosphere were formed by seas or lakes of methane or ethane, but the latest Cassini images did not show any evidence that Titan is awash in pools of methane.

Methane is a highly flammable gas on Earth, but it is liquid on Titan because of the intense atmospheric pressure and cold.