PARIS-- Scientists piecing together
data from Europe's Huygens probe to
Saturn's moon Titan described the
hazy satellite today as an environment in which a frequent rain of liquid methane
falls through a thick smog onto hills
made of water
ice.
Methane concentrations are
replenished probably from an underground
source, they said
during a press briefing held
here.
A week's analysis of the
350 photos and other data received from
the Huygens descent
probe confirmed many of the suppositions made about Titan and whetted scientists'
appetite for a follow-on mission.
"We can now dream seriously
of sending rovers to Titan," said Huygens project manager Jean-Pierre
Lebreton of the European Space Agency
(ESA). "All we need is
the money."
It took NASA's Cassini satellite seven years to reach Saturn
orbit,
and
then release
Huygens. With no
Huygens revisits currently scheduled,
it will be at least a
decade before Huygens' data is complemented by another descent probe or
lander.
Meanwhile, the Cassini
orbiter will be using Huygens data to help in measuring Titan from orbit.
"Huygens has provided ground truth for
Cassini," Lebreton
said.
As captivated as they were
by what Huygens discovered in a 3.5-hour
descent
and landing
on
Titan on Jan. 14, Huygens scientists cautioned against generalizing about what
Huygens' surface looks like.
"We sent three spacecraft
to Mars and they all went to the most
boring places" before
other satellites discovered the most interesting features of Mars, said Toby Owen of
the Institute for Astronomy in
Honolulu. Owen is a
principle investigator for studying Huygens' atmospheric sensors. Huygens images,
he said, "come from one single place
in a very different
world."
Huygens landed on a solid
surface that post-mission analysis
suggests resembles a
sandy area covered by a thin crust, according to John C. Zarnecki, lead scientists for
Huygens' Surface Science Package
instruments.
Martin G. Tomasko of the
University of Arizona at Tucson, principal investigator for Huygens' camera
system, said the 350 images taken by
Huygens and relayed by
Cassini to Earth suggest it had rained liquid methane recently before Huygens
'arrival. The rain washes off the water-icemountain peaks of the hydrocarbon
particles that settle on them, he added.
Tomasko described the
scenes showing lighter colors on the mountain tops and darker colors in the drainage areas as "an
Earth-like process, if you like, but
with very exotic
materials."
Surface temperatures on Titan were measured at -179 degrees
Celsius (94 degrees Kelvin or -290 degrees Fahrenheit),
which is about what scientists had expected. Little sunlit
penetrates
the dense hydrocarbon atmosphere, a fact that was only partly
offset
by Huygens' 20-watt lamp, which enabled the probe to deliver
relatively
clear pictures even on the surface. Tomasko described the
process
as "taking pictures of an asphalt parking lot at dusk."