Best-yet images of Titan disappoint

Researchers struggle to revise their theories

July 04, 2004|By Thomas H. Maugh II | Thomas H. Maugh II,LOS ANGELES TIMES

The first pictures of Saturn's moon Titan returned by NASA's Cassini spacecraft after its initial fly-by were not nearly as good as researchers had hoped, but they were good enough to overturn several theories about the moon, scientists said yesterday.

The Jet Propulsion Laboratory team's efforts to peer through the dense, smoggy haze that surrounds Saturn's largest moon revealed only fuzzy details of the surface, but those details left team members puzzled and confused.

The images, surprisingly, did not show the large bodies of liquid on the surface that astronomers had expected to find. The oceans of liquid methane or ethane that had been predicted would have shown up very brightly in the images obtained so far, said imaging team member Bob West of JPL.

"If there are oceans, we should have seen them by now," he said.

"That's a little disappointing," added team member Kevin Baines.

Researchers had previously thought, moreover, that the lighter areas on the surface of Titan were water ice and that the darker areas were other materials. But spectroscopic data from Cassini's infrared spectrometer "has turned those theories on their heads," said deputy project scientist Elizabeth Turtle of the University of Arizona. "The story has changed completely in the last 10 hours."

Viewing the preliminary data, she said, the team now knows that the dark areas are almost pure water ice, while the brighter areas are mixtures of water ice "and other things," she said, probably hydrocarbons. "This is a truly strange place."

The images do show one very bright area over the moon's south pole, about the size of the state of Arizona, that the team believes is composed of methane clouds. The clouds are probably the equivalent of light, fluffy cumulus clouds on Earth, Turtle said.

The team sees evidence that Titan's atmosphere is being swept up into the clouds by a geographical feature such as a mountain, much as humid air is swept up into storm clouds over mountains. The team was disappointed, however, to see no traces of lightning in the clouds.

Turtle noted that the images were taken from 200,000 miles away from Titan and that Cassini will get much closer to the moon on many of the 45 fly-bys yet to come.

The spacecraft will also launch the Huygens probe to explore Titan on Christmas Eve. Three weeks later, Huygens will parachute to the surface of the sphere, transmitting data throughout the trip.

The Los Angeles Times is a Tribune Publishing newspaper.

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