CAMBRIDGE, U.K.--A trip to Titan would be the ultimate hiking experience, according to new data from the European Huygens lander. Three-dimensional views of the surface of Saturn's large moon reveal extremely steep valleys topped with looming ice cliffs. Temperatures never rise above minus 180 degrees Celsius. "It's quite dramatic," says planetary scientist Jonathan Lunine of the University of Arizona's Lunar and Planetary Laboratory in Tucson, who presented the images here on Thursday at the 37th meeting of the Division of Planetary Sciences of the American Astronomical Society. "You would need an ice axe to scale the 30 degree slopes."
Huygens touched down on Titan on 14 January. During its descent by parachute, it continuously took snapshots of the panorama beneath. These have now been combined into a 3D-image of a 1-by-3-kilometer swath of terrain, showing valleys carved out by "methane monsoons". Taking Titan's atmospheric properties, seasons, and solar insolation into account, Lunine's colleague Ralph Lorenz estimates that the "monsoons" will happen every few centuries and last for months. They're like the episodic rainstorms in the Arizona desert, but on a longer timescale, he says.
Intrepid Titan hikers would also have to watch out for volcanic outbursts that would help to continuously replenish the methane in Titan's atmosphere from below. Radar images of the moon's surface obtained by NASA's Cassini spacecraft show evidence of volcanic domes, craters, and lavalike flows, probably from a frigid mixture of water and ammonia. Some of these resemble flows on the slopes of Mauna Loa, Hawaii. "There's major resurfacing going on," says volcanologist Rosaly Lopes of NASA's Jet Propulsion Laboratory in Pasadena, California.
Meanwhile, ideas about Titan's surface have also changed a bit since January. During touchdown, a measuring device on the bottom of the Huygens lander first encountered much resistance, and then went through softer material, leading scientists to conclude that Titan was like crFme brvlTe, with a thin, crust of brittle rock. Now, John Zarnecki of the Open University at Milton Keynes, United Kingdom, who heads one of Huygens's instrument teams and discussed the results at a press conference here, thinks it's more likely that the sticklike device hit one of the many ice pebbles that are also seen in Huyges's surface pictures.
It will be a while before outdoor travel organizations will offer trips to Titan, but Jean-Pierre Lebreton, Huygens's project scientist at the European Space Agency, hopes to go back soon, at least vicariously. "Huygens has paved the way for future missions to the surface of Titan," he says.