Saturn's moon 'is alive'
2004-10-29 07:54
California - The Cassini spacecraft is sending back evidence that Saturn's planet-size moon Titan is geologically alive, possibly with liquids moving on its surface, scientists said on Thursday.
Images made from radar beams bounced off Titan during Cassini's close flyby this week revealed such surface details as a round basin, narrow miles-long linear "streaks", and a cat-shaped region of what could be the moon's theorised lakes of liquid methane and ethane.
Scientists had been reluctant to draw conclusions about surface features from pictures taken through Titan's hazy atmosphere.
But they sounded more confident after radar data arrived late on Wednesday and was processed into images depicting terrain in shades of black and white.
"We are seeing much higher resolution here ... and we are seeing detailed features," said Charles Elachi, JPL's director and team leader for Cassini's radar instrument, which imaged a swath of Titan about 121 kilometres wide and 1 995 kilometres long.
Elachi said there was "high confidence" in the evidence of geologic activity, noting the long linear features as an example.
The possible region of lakes was depicted as very dark, which in radar data is a characteristic of a signal bouncing off a very smooth surface like a liquid. The region was named "Si-Si the Cat", for a scientist's young daughter who noticed the region resembled a "Halloween cat", Elachi said.
Cassini reached Saturn this summer on a $3.3bn international mission to study the planet's system for four years.
Unlike the airless moons and space rocks that Nasa can photograph with startling clarity, Titan, hundreds of millions of miles from earth, has long stymied scientists because its surface is shrouded by a thick atmosphere of nitrogen and methane.
That has forced scientists to create theories about the surface from observations of the hydrocarbon-laced atmosphere. Scientists believe seas or lakes of methane could form as organic compounds fall out of the atmosphere and collect on the surface.
Imaging team member Alfred McEwen of the University of Arizona presented information from optical pictures taken during Cassini's dash past Titan showing streaks in the atmosphere over the north polar region and east-to-west streaks on the surface.
The surface streaks are believed to be from movement of material, and given their consistency over a large scale, wind is believed to be the primary cause, McEwen said.
"What Cassini has shown us this week ... (is that) Titan is an extremely dynamic and active place, not simply in its atmosphere but on its surface as well," said Jonathan Lunine, an interdisciplinary scientist.
On the net:
www.jpl.nasa.gov
- AP