Dec. 13, 2004 — There may be no strange seas of methane on Saturn's moon Titan after all, say scientists studying the latest imagery from the Cassini spacecraft.

The possibility comes as a surprise to researchers who had found compelling reasons to suspect weird liquid oceans under the orange clouds in earlier ground-based telescope studies.

What can be seen through the haze in infrared light are dark and light patches, few craters and no obvious mountains or valleys.

The dark patches have large areas of irregular coloring that don't match what would be expected if it were a flat liquid surface, said Robert Nelson of NASA's Jet Propulsion Laboratory.

There are also, so far, no glinting-type reflections that would be expected from a liquid surface.

"It's such a profound change to our thinking," said Nelson. "We've gotten much closer and what we're finding is no evidence for liquid oceans at all."

Planetary scientists will be presenting these and other very new discoveries about Titan this week at the American Geophysical Union meeting in San Francisco.

Titan's surface is beginning to look — if only to the eye — something like Earth's moon, with broad flat dark basins surrounded by brighter areas, Nelson said.

The missing seas are puzzling because there has been some pretty compelling evidence for a shiny flat, probably liquid, surface somewhere on Titan. Some of the most compelling evidence came from an experiment with the giant Arecibo Radio Telescope a few years ago.

In that study, a powerful radio signal was beamed at Titan. The reflection of that radio signal came back in the same manner that a shiny spherical Christmas tree ornament reflects a flashlight beam: as a shiny "specular" glint off a flat, shiny surface.

"We're all confused," said Titan researcher Ralph Lorenz of the University of Arizona's Lunar and Planetary Laboratory. "All of us aren't sure what we're seeing."

Cassini's radar is picking up small patches that might be small hydrocarbon lakes, Lorenze said, but it's not clear yet that they are. "That's still a reasonable conclusion," he said, especially because the vast majority of Titan's surface has yet to be seen.

Scientists expect some of the confusion to evaporate in January, when Cassini drops the Huygens probe onto Titan. They are also looking forward to February, when Cassini's visual, infrared and radar mapping and imaging systems can finally focus on the same parts of Titan's surface at the same time.

So far, images from the different instruments have been unable to see the same spots on the surface, so it's been difficult to get a complete picture.

Nelson, for his part, is not disappointed by the possibly missing seas. "I think that's the most exciting thing we've found so far," Nelson said. "Science becomes exciting when things are not what you expect."

Cassini makes another close pass by Titan on Monday.