Japanese May Lose Hayabusa Spacecraft

Like Earth, Titan has a nitrogen-rich atmosphere, but there is no atmospheric oxygen, and its surface temperature is 291 degrees Fahrenheit below zero. Its weather is based on methane, which seeps from the moon's interior in some as yet unexplained way to cloak Titan in a blanket of smog.

"It is a humid atmosphere," said Francois Raulin of the University of Paris, in which "liquid methane is playing the role of water," rising as gas to create clouds, then falling as rain to etch rivers in Titan's icy ridges.

Scientists have not seen the methane "oceans" that were expected before Huygens landed, nor have large methane cloudbanks been observed in several Cassini flybys. Still, said Denis Bogan, NASA headquarters project scientist for Cassini/Huygens, "there is little doubt" of a methane-based meteorology. Cassini, he suggested, just has not seen it yet.

Huygens did, however, confirm that methane rising high in Titan's atmosphere breaks apart and recombines into more complex hydrocarbons that fall to the surface, depositing a layer of organic dust that can be as much as 0.6 miles thick.

Huygens landed in this "granular, unconsolidated material," which is "like clay or wet sand," said John Zarnecki of Britain's Open University. "I'm not saying that's the composition, but that's the consistency."

At Mars, meanwhile, the ESA's orbiting Mars Express spacecraft has been using its Mars Advanced Radar for Subsurface and Ionosphere Sounding to collect the first-ever profiles of what lies below the Red Planet's desert landscape.

In findings published yesterday in the journal Science, researchers reported that a layer of ice near the Martian north pole was exceptionally pure and about a mile deep. "There was no zone of melt," however, at the bottom of the ice layer, as there is with Earth's glaciers, said Jeffrey Plaut, of NASA's Jet Propulsion Laboratory.

Plaut, speaking at ESA's Paris news conference, said the radar had so far found "no convincing evidence of subsurface liquid water" on Mars but would begin a serious search for it next spring. "We can certainly say however, that we have observed significant amounts of water in the form of ice," he added.