"It's almost impossible to resist the speculation the flat dark material is some kind of drainage channel, that we're seeing some kind of shoreline," said Martin Tomasko, the University of Arizona planetary scientist who leads the Huygens camera team.

Other instruments recording the force of the probe's touchdown suggest the 705-pound spacecraft landed on a squishy material similar to wet sand or clay and in a fog of methane.

"We don't know whether this still has liquid in it, whether the liquid has drained away, or drained into the surface," Tomasko said of the equatorial landing site. "You have the feeling this was set not so long ago and that maybe the liquid has not penetrated too far into it."

Huygens gathered readings on the chemical composition, temperature and pressure changes as well as pictures during a 2 1/2 -hour parachute descent. Huygens passed through an 11-mile-deep cloud of methane before landing.

"Presumably, there is a reservoir of methane on the surface," said Shushiel Atreya, one of the atmospheric research team members.

Launched as part of the NASA-led Cassini mission that began orbiting Saturn in late June, Huygens relied on the larger mother ship to record its findings and relay them to Earth.

One of the instruments recorded for the first time the sounds of Titan's atmosphere, a deep whooshing tone.

Though scientists characterized Huygens' brief but much anticipated mission a success, a panel of experts plans to investigate a disturbing failure of the primary communications channel. It meant Huygens gathered only half of the anticipated 750 panoramic images of Titan and lost information about wind speeds that would help explain weather and environmental changes.

The Europeans scrambled to assemble a network on 18 radio telescopes in Australia, Japan, China, the United States and Europe, where astronomers were able to track a faint signal from the probe that will permit wind speed calculations.