Saturn moon 'like Australia'
2006-05-05 19:51
Washington - Huge regions of Saturn's moon Titan are covered with dunes, possibly made out of ice crystals, sand or some other unknown material, said international space scientists on Thursday.
The researchers said images of Titan, beamed back to earth from the joint United States-European Cassini mission, look very much like sand dunes in the Sahara desert, Namibia, Saudi Arabia and Australia.
"It's bizarre," said Ralph Lorenz of the American University of Arizona. "These images from a moon of Saturn look just like radar images of Namibia or Arabia.
"Titan's atmosphere is thicker than Earth's, its gravity is lower, its sand is certainly different - everything is different except for the physical process that forms the dunes and resulting landscape."
The Cassini craft was launched in 1997 and reached Saturn in 2004 after an interplanetary cruise that took it past Venus and Jupiter.
Scientists thought dark patches were seas
The latest radar images show the dunes are up to 150m high and hundreds of kilometres long.
Scientists had initially thought the dark patches on Titan, the largest of Saturn's 47 moons, were seas. Now these patches appear to be largely made up of these dunes.
Titan's flat surface is very cold, with a temperature of minus 180 degrees Celsius. Scientists believe its thick atmosphere may occasionally rain methane.
The existence of pristine dunes, piled over other geological features, shows that wind recently blew fine grains of some material around, said the researchers wrote in their report, published in the journal Science.
They said it could be sand, ice or "something else".
The scientists said the presence of the dunes was "comforting", because at least the processes that lead to their formation could be studied on Earth.
Movie shows what the probe 'saw'
Also on Thursday, the European Space Agency released new movies of the descent of its Huygens probe to Titan's surface.
The probe is piggybacked onto the Cassini spacecraft.
The four-hour movie shows what the probe actually "saw" within the few hours of the descent, and the eventual landing.
"At first the Huygens camera just saw haze over the distant surface," said Erich Karkoschka of the University of Arizona, who created the movies.
Then the moon's sandy surface comes into view. The films can be viewd at http://saturn.esa.int or http://www.lpl.arizona.edu/DISR/.