Possible shoreline revealed in first Titan picture

PASADENA, California - The world has had its first look at the surface of the Saturnian moon Titan after pictures from the European space probe Huygens showed a possibly rocky surface with "drainage channels" for liquids.

The first picture from a height of about 16km, as Huygens descended before landing on the surface, showed what scientists said appeared to be a shoreline. They speculated the channels might feed into canyons on the surface.

"I think none of us would have expected ... this kind of unveiling, but it is pretty consistent with the surprises we've seen before," said Al Diaz, Nasa's associate administrator for science.

The US$3 billion ($4.30 billion) Cassini-Huygens mission, a joint project of Nasa and the European and Italian space agencies, was launched in 1997 from Cape Canaveral, Florida, to study Saturn, its rings, moons and magnetosphere.

In December, the Saturn explorer Cassini dropped off Huygens for a three-week journey toward Titan, culminating in the probe's parachute-slowed plunge to the moon's surface.

The photos were beamed from the European Space Agency's headquarters in Germany.

Officials there said it appeared that Huygens landed on some sort of solid surface rather than in liquid. They did not offer any speculation on where the "drainage channels" in the photo might lead or how they were formed.

Titan is believed to have liquid methane and ethane on its surface, but the moon's heavy fog blanket made it unclear what Huygens would encounter when it reached its landing site.

Scientists said there had been problems retrieving data from one wind experiment but held out hopes they could get the information from a different study.

"We can say this afternoon we have ... a scientific success," said Jean-Jacques Dordain, director-general of the European Space Agency, in a press conference from its operations centre in Germany monitored on Nasa TV.

Cassini, which acted as the relay station for Huygens, sent back signals showing it had finished retrieving and had turned toward Earth to begin transmission of a likely three hours of data.

Given the sensitive nature of the mission, the Saturn orbiter Cassini recorded the data from Huygens on four systems.

The 320kg probe made its two-hour descent through Titan's atmosphere to the surface after a seven-year journey piggybacked on Cassini and a final one-way trip of about three weeks on its own.

Scientists expect to spend years poring over the results.

"It's got to be unravelled, got to be put together and then scientists being scientists are going to argue about what it means as we piece together our place in the universe and how we came to be," said David Southwood, ESA's director of scientific programmes.

Scientists believe the organic chemical reactions taking place on Titan resemble the processes that gave rise to life on Earth 4 billion years ago. Its atmosphere is mostly nitrogen, like Earth's, but its surface temperatures of about minus 180degC make it inhospitable to life.

The saucer-shaped probe was designed to rotate on its way down, taking high-definition, panoramic images of Titan's thick, smoggy atmosphere and its landscape.

Along with its six scientific instruments that measure the components of Titan's atmosphere, Huygens carries a sound recorder and a lamp to look for signs of surface liquid.

Titan, believed to be the only moon in the solar system with an atmosphere, is larger than Mercury and Pluto.

"Huygens is the most distant controlled descent and landing ever attempted in the solar system," said Simon Green, of the Open University, at a London news conference.

"It (Titan) is a great laboratory to go searching for the past history of what happened on Earth," he added.

Some science team members monitoring the flight have waited decades to see the first of 750 planned images and other scientific readings from the yellow-skied moon.

Huygens was named for the Dutch scientist who discovered Titan in 1655, Nasa officials said.

- REUTERS