Cassini probe sights moon target

Xanadu appears as the brightest surface feature

The Cassini-Huygens mission has caught sight of Saturn's largest moon, Titan.

The first images of the object, which is believed to support oily lakes and seas, pick out broad features previously seen by Earth telescopes.

Over the next two months, the cameras on Cassini will take progressively more detailed pictures of a surface that is shrouded by a very thick atmosphere.

In January, the Huygens probe will be released and plunge down on to Titan - perhaps to splash down in a sea.

The moon is nearly the size of Mercury at 5,100km (3,200 miles) across.

The images were taken in mid-April, from a distance of more than 40m km.

Special filters

Cassini used its narrow angle camera's spectral filters specifically designed to penetrate the moon's thick atmosphere.

And although the viewing conditions were not at their best, the pictures rival anything scientists have seen before - and that includes images from the Hubble telescope.

Saturn: Getting closer all the time

Enlarge Image

Hubble had identified a large region on the moon, dubbed Xanadu, which Cassini has also now picked out as a very bright surface feature.

Scientists are unsure of the nature of Xanadu. It could be a mountain range, a giant basin, a smooth plain, or a combination of all three.

It may be dotted with hydrocarbon lakes but that is also unknown.

Over the next two months, features as small as 44km (28 miles) should become visible.

"This is our first moment of reckoning," said Dr Carolyn Porco, who leads the Cassini imaging team at the Space Science Institute in Boulder, Colorado, US.

"The mere fact that we can see the surface at all with just some rudimentary image processing, when the geometry for surface viewing is not the most favourable, says that in a very short time, we can rightfully expect to see sights on Titan that have never been seen before by anyone."

Cassini is headed for a four-year investigation of the Saturnian system.

Orbit insertion is set for 1 July. Just 30 hours later, the spacecraft will execute a flyby of Titan, passing at a distance of 350,000km (217,500 miles).

The Cassini-Huygens mission is a joint project between the US and European space agencies (Nasa and Esa) and the Italian Space Agency.