Sept. 8, 2005— Scientists are anxiously awaiting results of the Cassini spacecraft's pass over Titan, in hopes of learning more about the possible existence of liquid on the surface of the massive Saturn moon.

"Every one of these flybys gives us a whole new bunch of puzzle pieces," said Trina Ray, a Cassini mission science planner at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

The flyby of Titan on Wednesday was one of the closest approaches made by Cassini since arriving at Saturn 14 months ago. The spacecraft soared about 660 miles above Titan's thick atmosphere during its eighth pass over the moon.

Data collected during the flyby was stored on Cassini's tape recorders and was to be radioed to ground stations on Earth through Friday.

The primary purpose of the flyby was to gather information by radar about the southern polar region of Titan, an area that may harbor pools of liquid methane.

Titan, the largest moon in the Saturn system, is wrapped in a thick blanket of nitrogen and methane that defies most efforts to see the surface in visible light. However, by bouncing microwave signals off the moon's surface, scientists can peer through the atmospheric stew to peek at Titan's face.

"The surface of Titan is very complex," Ray said. "No one instrument can give us all of the answers."

Scientists believe that the moon resembles primordial Earth, with the organic building blocks needed for life, as well as geologic, atmospheric and tectonic events that shape Titan's features.

The research teams are particularly interested to learn if Titan has pools of liquid on its surface.

"So far we know of one body that has liquid on the surface — that's Earth," Ray said. "It becomes a very unique situation."

Images taken from the other side of Titan's south pole reveal an unusual feature with soft, rounded edges scientists theorize may be a lake. The radar images taken during Wednesday's pass, which should be of much higher resolution than the camera, may turn up similar phenomena.

The team already is planning for Cassini's next pass by Titan on Oct. 28, when radar systems will be put to use again as the probe flies over the landing site of Europe's Huygens probe. Huygens was released by Cassini for an independent study of Titan in January.

Other researchers say there is no reason to rule out the possibility of indigenous life.

In a paper presented at the conference, scientists from the Southwest Research Institute in Colorado and Washington State University argue that Titan seems to have ingredients for life, including reservoirs of liquids, organic molecules and good sources of energy.

No one knows if life can exist in liquid methane, although some such chemical blueprints have been suggested.

"One promising location may be hot springs in contact with hydrocarbon reservoirs," said lead author David Grinspoon.