New radar images sent back from the Cassini spacecraft have revealed an Australia-sized land mass on Saturn's moon, Titan. The continent is in a region known as Xanadu, but readers are asked to kindly refrain from any Olivia Newton-John references.

The Xanadu region had been observed before the Cassini mission. It was snapped in 1994 by the Hubble Space Telescope's infrared camera, but astronomers could only make it out as an unusually bright spot on the moon's surface.

Now it transpires that the region is riddled with geological features very reminiscent of Earth. The surface has been shaped by weather - winds, rain and a flowing liquid, most likely liquid ethane or methane.

The researchers have identified dark sand dunes, river networks, hills and valleys. The land mass has a prominent crater, which may have been caused by the impact of an asteroid, or possibly by water vulcanism. The region also boasts a range mountains reaching over 5,000 feet.

"We could only speculate about the nature of this mysterious bright country, too far from us for details to be revealed by Earth-based and space-based telescopes. Now, under Cassini's powerful radar eyes, facts are replacing speculation," said Dr Jonathan Lunine, Cassini interdisciplinary scientist at the University of Arizona, Tucson.

Most notable, though, is the absence of the organic dirt that covers most of the rest of the moon's surface.

"Xanadu has been washed clean," says Steve Wall, the Cassini radar team's deputy leader. "What is left underneath looks like very porous water ice, maybe filled with caverns."

Cassini's will next fly by Titan on Saturday 22 July. ®