Cassini probe reveals detailed images of Saturn's largest moon

Scientists cheered yesterday as the first detailed images emerged of Titan - the largest moon of Saturn - though they are still unsure whether its surface is liquid or solid.

Scientists cheered yesterday as the first detailed images emerged of Titan - the largest moon of Saturn - though they are still unsure whether its surface is liquid or solid.

The photos sent back from the international Cassini spacecraft were taken during a flyby which took it within 745 miles of the second largest moon in the solar system and is the only one with its own atmosphere.

As distinct dark and bright surface details became apparent, scientists at the US space agency Nasa's Jet Propulsion Laboratory declared themselves thrilled, but admitted they could only speculate about what they were seeing. Researchers need to find out if the surface is solid in advance of a lander mission next January.

"What we're looking at is the surface of Titan and that's pretty cool because it's never been done before [at such resolution]," said Carolyn Porco, an imaging scientist. "It takes a bit of [computer] processing to bring out features." That will be achieved by marrying the photos to radar data that was sent after the images.

Scientists are particularly interested to know whether Titan's hazy atmosphere conceals oceans of liquid methane and ethane. "For those of us who have been studying Titan ... it's very tantalising to say maybe those bright regions are higher icy regions that are popping up out of a dark slushy area, or maybe that's lava that's flowed and covered up some of the terrain and is forming the sharp shoreline-looking boundary," Dr Porco said.

Cassini's previous Titan flyby was at a distance of some 200,000 miles. Mission officials hoped onboard instruments would reveal new details of Titan's atmospheric density, which would be useful when Cassini launches the European Space Agency's Huygens probe mission for a descent to the surface.

The spacecraft started transmitting pictures back to Earth on Tuesday afternoon - nine hours after it had been closest to Titan.

The €2.6bn (£1.8bn) spacecraft's first flyby on 2 July disappointed researchers, who struggled to discern surface features seen through what they called "organic goo" - the hydrocarbon haze misting the moon - which has been likened to that over the Earth's biggest cities. The mission was funded by Nasa, the European Space Agency and the Italian Space Agency.