- The Cassini spacecraft has sent back the best images
scientists have ever seen of Saturn's mysterious moon Titan, which is wrapped
in a thick orange atmosphere.
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- Using special equipment that can penetrate the smoggy
haze, the new images show light and dark surface details that may indicate
frozen water and possibly a crater.
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- "Although the initial images appear bland and hard
to interpret...we have indeed seen Titan's surface with unprecedented clarity,"
scientist Dennis Matson said.
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- He is one of those in charge of the four-year mission.
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- Titan will be a key focus of the Saturn mission, a joint
venture of the American and European space agencies.
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- Its thick atmosphere, made up of nitrogen, methane and
other hydrocarbons, is believed to resemble the atmosphere of planet Earth
billions of years ago. And scientists hope to gain clues about how life
might have evolved on Earth by studying this distant moon of Saturn.
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- Later in the mission, scientists intend to put a lander,
called Huygens, on its surface. But for now, they must make do with images
gathered from fly-bys of Titan as the Cassini spacecraft (with the Huygens
lander riding piggyback) orbits Saturn.
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- Using, in part, infrared observations three times as
refined as can be seen by the human eye, instruments on the Cassini spacecraft
have transmitted an evocative but confusing false-colour image of the mysterious
Earth-sized moon.
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- Mission deputy project director Elizabeth Turtle described
what has so far been seen as showing not so much a distinct surface as
"a melting ice cream sundae."
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- To give a sense of the confusion, scientists have found
indications that the dark areas they see are likely pure water ice. And
Dr. Turtle has obliquely referred to light areas as a mixture of water
and "other things."
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- While members of the U.S. and European science team that
conceived of Cassini-Huygens believe these other things are hydrocarbons,
they aren't at all confident about what they are seeing. At a press conference
on the weekend, all Dr. Turtle would surmise was that "this is a truly
strange place."
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- As for geological features on Titan's stony face itself,
Cassini does show a lined visage. "There are linear features, circular
features, curvilinear features. These suggest geological activity on Titan,
but we really don't know how to interpret them yet," said Dr. Turtle,
who is a professor of planetary science at the University of Arizona.
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- Particularly striking is a brightly lit, circular area
that may or may not be a crater formed when an asteroid collided with the
moon.
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- No one expects to find any signs of life on Titan. It
is simply too cold. Its mean surface temperature is -180 degrees. At that
point, water freezes as solid as concrete and methane gas will condense
into a liquid.
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- In fact, before the mission, some scientists had expected
to find pools of liquid methane on the surface. It would have been the
first time that scientists had observed liquid bodies on worlds beyond
Earth.
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- But so far, there's no sign of methane seas. "If
there are oceans we would have seen them by now," Robert West, a member
of NASA's Jet Propulsion Laboratory, told reporters on Saturday.
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- If the first pass of the $3.3-billion (U.S.) mission,
which took seven years and 3.5 billion kilometres to reach Saturn, seems,
in New Testament parlance, to be seeing "through a glass darkly,"
Cassini-Huygens scientists counsel patience.
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- The first pass was at a distance of 339,000 kilometres,
but over the next four years 44 more fly-bys will peer at Titan's strange
face, and the closest of them will be an astronomical hair's breath - 950
kilometres - away. At that time high-resolution radar imaging of the giant
moon's surface will be possible.
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- In January, 2005, the Huygens probe that is attached
to Cassini will descend through the atmosphere and, it is hoped, land on
Titan's surface. As it does, it will see close up whether Titan is functioning
as a sort of solar-system deep freezer, preserving many of the chemicals
thought to have formed in the processes leading to the development of life
on Earth.
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- - With a report from Associated Press and Reuters
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- © Copyright 2004 Bell Globemedia Publishing Inc.
All Rights Reserved. http://www.theglobeandmail.com/servlet/story/RTGAM
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