Nov. 9, 2004 — Radar images taken during the Cassini spacecraft's first flyby of Titan, the largest moon of Saturn, show tantalizing features of what may turn out to be some sort of liquid on the moon's face.

Scientists have long theorized that Titan's thick atmosphere — Titan is the only moon in the solar system to sport such a well-formed and pronounced gaseous cushion — may rain down on the moon's surface and possibly form pools of organic material.

Though just one percent of the moon was mapped by radar during Cassini's close approach on Oct. 26, scientists already have determined that the moon's surface is relatively young, with few fresh crater impacts.

The radar, which unlike optical wavelength cameras can pierce through Titan's thick clouds, revealed one strikingly bright feature that may have been a flow from a volcano, which due to Titan's frigid temperatures would spew not molten rock, but ice.

"It looks very much like it's something that oozed across the surface," said Cassini radar team member Ralph Lorenz of the University of Arizona. "It may be some sort of 'cryovolcanic' flow."

The surface feature just as well may have been carved by erosion or some other processes, he added. "It's too early to tell."

The probe was flying about 1,550 miles, or 2,494 kilometers, above Titan's surface when it caught sight of the bright surface feature within a 1,200-mile long by 75-mile wide (1,960 by 120 kilometers) swath of terrain in Titan's northern hemisphere.

The radar works by bouncing radio signals off the surface of the moon and timing their return to the spacecraft. Areas that appear bright in radar images have returned more of the signals than darker areas, which may contain materials that absorb the radar signals or which may be sloped away from the direction of illumination.

"Radar has provided the first evidence for possible young cryovolcanism on Titan's surface," said Cassini scientist Jonathan Lunine, also with the University of Arizona. "Now our challenge is to find out what is flowing, how it works, and the implications for Titan's evolution."

Also this week, the Cassini science team released a dazzling new image of density patterns in Saturn's A ring and a picture of Saturn's wreck of a moon Rhea, the second largest satellite after Titan. The image shows large craters covering the moon's surface and what may be exposed icy material.

Cassini arrived at Saturn in July for a four-year mission.