Piercing Titan's smoggy veil

It's "Titan or Bust" for Saturn's newest satellite, Cassini, and its 700-pound sidekick probe Huygens.

A weekend's worth of stunning images from the spacecraft as it began to orbit Saturn - including a distant flyby of a moon that one scientist terms "a deranged version of Earth" - have left scientists elated but also confused.

Saturn's rings and its moon Titan may have taken center stage. But scientists also detected an event that may hold clues to the birth and death of the rings. And the new information is whetting researchers' appetites for two more Titan encounters. During the second of these encounters, perhaps in late December, Europe's Huygens probe is slated to parachute through Titan's atmosphere and land on its surface in what promises to be a 2-1/2 hour tour de force.

In the meantime, Cassini-Huygens already has given planetary scientists an eye-opening performance.

"In one weekend, we've just turned everything we've learned from ground-based and Hubble [telescope] observations on its head," says Mark Leese, program manager for the Huygens probe's surface science package.

On Thursday, as it left Saturn's ring system, Cassini buzzed past Titan some 210,600 miles above its surface, yielding the closest look yet at the moon's surface.

Using optical cameras with special filters to pierce Titan's smoggy veil, scientists detected large patches of bright and dark surfaces that hint at its general terrain. At least one circular feature - perhaps an enormous impact crater - emerged in the images, while other features appeared as broad lines.

Referring to similar line-like forms in earlier images, "this is starting to look suspiciously like tectonic features," says Carolyn Porco, Carolyn Porco, a researcher at the Space Science Institute in Boulder, Colo., and head of Cassini's imaging team. In itself, that isn't unusual, she says; other large moons in the solar system also have them. But Titan's linear features also appear to have unique traits that set them apart from tectonic features, seen elsewhere, she adds.

Researchers caution that from a distance of more than 200,000 miles, they can't distinguish mountain ranges, seas or lakes, or other topographic standouts. That level of detail awaits closer flybys. But their cameras are revealing features that cover wide swaths of the moon's hemispheres. "The fact that we don't see a lot of circular features suggests that Titan has been geologically active," says Elizabeth Turtle, a University of Arizona planetary scientist on Cassini's optical imaging team. Such activity would erase from the surface evidence of old impacts.

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