U.S. Water News Online
HOUSTON -- Many of the same processes that helped shape the
Earth are in effect today on Saturn's smoggy moon Titan, a team of
international scientists has revealed.
Relying on data gathered directly from the atmosphere and surface
of Titan by the European Space Agency's Huygens space probe, the
scientists said they were able to conclude that a regular pattern of
precipitation and erosion is carving out streambeds and leaving
behind a layer of "dirt" on the giant moon.
"There is liquid that is flowing on the surface of Titan," said
planetary scientist Toby Owen, of the Institute for Astronomy, during
an ESA-sponsored press conference. "It's not water -- it's too cold
-- but liquid methane. And it flows in the same way it does on
Scientists around the globe have been especially interested in
Titan ever since 1980 when the Voyager space probe discovered that
the moon is the only other body in our solar system, besides the
Earth, to have a nitrogen-rich atmosphere. Though scientists don't
believe there is life on Titan, they do believe that the moon can
help them understand what processes might have shaped the Earth
billions of years ago.
Images taken by the Huygens probe, which on Jan 14. became the
first known spacecraft to descend through Titan's murky atmosphere,
show dark, ribbon-like lines leading into larger channels that
eventually end in huge, dark pools. The scientists believe these
markings are the sure signs of rivers, deltas and lakes, though they
seem to be dry at the moment. The dark material at the bottom of the
channels is most likely silt that has washed off peaks and ridges
during heavy rains, much as it does on Earth, the scientists said.
Owen noted that the apparent lack of liquid in the channels does
not mean that Titan no longer experiences wet weather. Rather,
Huygens likely landed during a dry period.
"It did not rain yesterday on Titan, but it will probably rain
tomorrow," said Owen.
But the scientists cautioned that, despite its similarities with
Earth, Titan is still a cold and toxic place. For instance, the rain
that falls on the moon is not composed of water, but liquid methane,
also known as liquid natural gas. It would be highly flammable if
only there were oxygen to burn it with -- but scientists haven't
detected any oxygen on Titan.
Because Titan is 900 million miles away from the sun -- about nine
times farther away than the Earth -- temperatures on the surface of
the moon tend to be in the range of minus-290 degrees F. At this
temperature, all water is tied up in the form of ice. Scientists
believe some of the white streaks seen in photographs taken by
Huygens are ridges of ice that were exposed when they were washed
clean of the dark, organic silt that regularly falls from the
As for what it would feel like to walk on Titan, it's possible
that a human laden with gear would quickly crunch through a thin
crust of frozen chemicals or ice and then sink several centimeters
into a mud-like substance. That's what seemed to happen to the
700-pound Huygens when it finally plopped down on the moon's surface
after a two-and-a-half hour parachute ride through its atmosphere.
Still, there's hope that Titan could one day become a habitable
body -- in about 4 to 5 billion years. That's when the sun is
expected to exhaust its supply of hydrogen and grow into a "red
giant" star. The giant would destroy life on Earth but would warm
Titan enough to release its store of water, and therefore its oxygen.
"Actually, for a brief time, Titan might be a very good place for
life," said mission investigator John Zarnecki, of the Open
University at Milton Keynes in England.
The Huygens space probe is part of the $3.3 billion
Cassini-Huygens mission to study Saturn, its rings and its moons. The
two conjoined spacecraft were launched on Oct. 15, 1997 and traveled
through more than 2 billion miles of space before being separated on
Dec. 24, 2004.
Huygens then completed its mission by descending through Titan's
atmosphere and landing on its surface on Jan 14. NASA's Cassini
orbiter will continue to study the Saturn system for nearly four more
Huygens mission investigators say they, too, may be working for
that long just to analyze all the data from the space probe.
"Of course, we have a lot more work to do," said Owen. "We're not
going to be out of work for the next few years for sure."
The ESA may even launch more missions to Titan in the future,
according to Huygens mission manager Jean-Pierre Lebreton. Such
missions could include balloon-powered spacecraft that remain in
Titan's atmosphere or ground-based robots, like the NASA rovers
currently exploring Mars.
The agency is ready to explore, said Lebreton. "We just need the
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