The Cassini spacecraft pierced the haze enveloping Titan, Saturn?s largest moon, to reveal surface details that already have shattered theories about its composition, scientists said on Saturday. Cassini, launched nearly seven years ago by an international team of scientists, became the first spacecraft to orbit Saturn and its rings and moons during an ?orbit insertion? manoeuvre on Wednesday.

The space probe performed so flawlessly during its 3.5 billion-km journey to Saturn that scientists scrapped an orbit correction planned for Saturday. On its first trip past Titan on Thursday, the robotic probe snapped infrared images that left scientists puzzled. ?This is the best view of the surface yet and we don?t know what to make of it,? scientist Elizabeth Turtle said at the Jet Propulsion Laboratory in Pasadena, California.

Black-and-white photos taken at 340,000 km above Titan?s surface show a murky landscape that Turtle likened to a ?melting ice cream sundae? with some fuzzy linear structures that could be mountains, rivers or fault lines. That scientists were able to discern features other than circular impact craters suggests Titan has geologic activity similar to that of Earth.

Scientists will get a better shot at Titan in October, when Cassini descends to 1,200 km to snap close-ups of the moon, whose atmosphere and soil resemble those of primordial Earth and may contain the building blocks of life. Scientists had believed bright patches on Titan?s surface seen in earlier observations were pure water ice.

But the first infrared images taken by Cassini revealed water ice as dark patches because it is mixed with ?flotsam and jetsam? that may be organic material that rained onto the surface, scientist Kevin Baines said. The infrared mapping of some 2 percent of Titan?s surface did not reveal what scientists hope to see during the four-year principal mission ? bright flashes denoting liquid on Titan?s otherwise frozen surface, Baines said.

The infrared map did show a mass of clouds the size of Arizona in Titan?s southern hemisphere that may rain down liquid methane and could be linked to storms or an upthrust on the moon?s surface, Baines said.

The 80,000-km-wide gas cloud follows Titan in its orbit around Saturn and is evidence that the moon?s upper atmosphere is breaking down, scientist Stamatios Krimigis said. ?Titan is gradually losing material from the top of its atmosphere which is being dragged around Saturn,? he said.

The spacecraft also returned data that showed it has survived some 100,000 impacts with space dust particles the size of smoke as it flew through Saturn?s ring planes during the orbit insertion manoeuvre, scientist Don Gurnett said. The $3 billion Cassini mission, a joint project of NASA, and the European and Italian space agencies, is hailed as a model of international cooperation, with scientists from 17 countries participating.

<B>Gina KEATING</B>