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This image shows the boundary between the lighter-coloured uplifted terrain, marked with what
look like rivers or streams, and darker lower areas, according to
European Space Agency scientists. The view is from about 8 kilometers (5 miles) above
the ground.
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Bumpy
ride, squishy landing
Courtesy the European Space
Agency
and World Science
After an
unexpectedly bumpy ride, the Huygens space probe landed on Titan
Jan. 12 not with a bang, a splash or a thud, astronomers say.
It was more like a splat. Huygens landed in Titanian muck, or mud,
researchers say.
Two bits of evidence suggest
this, they said: first, that the landing was so easy on the probe,
which continued operating without a glitch. Second was the fact
that its camera lens apparently accumulated some material, which
suggests the probe may have settled into the surface, although
this might have been steam that rose from the surface,
“I think the biggest surprise is that we survived landing and
that we lasted so long,” said Charles See, a member of the team
operating the camera, called the Descent Imager/Spectral
Radiometer. “That landing was a lot friendlier than we
anticipated.”
The descent was less so, the researchers said. “The ride was
bumpier than we thought it would be,” said Martin Tomasko,
principal investigator for the Descent Imager/Spectral Radiometer.
After the main parachute unfurled in the upper atmosphere, the
probe slowed to a little over 50 metres per second, researchers
said, about the speed one might drive on a roadway. In the lower
atmosphere, the probe slowed to a bit over 5 metres per second,
drifting sideways at about 1.5 metres per second, a leisurely
walking pace.
During its descent through high-altitude haze, Huygens rocked
enough that it tilted at least 10 to 20 degrees, according to the
researchers. Below the haze layer, the probe was more stable,
tilting less than 3 degrees. Tomasko and others are still
investigating the reason for the bumpy ride and are focusing on a
suspected change in wind at about 25 kilometres (16 miles) above
the ground.
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This image was returned January 14, 2005, by the European Space Agency's Huygens probe during its landing on Titan.
Initially thought to be rocks or ice blocks, the objects in the image are
now believed to be approximatly pebble-sized. The two rock-like objects just below the middle of the image are about 15 centimeters (about 6 inches) (left) and 4 centimeters (about 1.5 inches) (center) across respectively,
scientists said. They are at a distance of about 85 centimeters (about 33 inches) from Huygens.
"The surface is darker than originally expected, consisting of a mixture of water and hydrocarbon
ice," according to NASA. "There is also evidence of erosion at the base of these objects, indicating possible fluvial activity."
The image was taken with the Descent Imager/Spectral Radiometer, one of two NASA instruments on the probe.
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One of
the first, unprocessed images from the European Space Agency's Huygens
probe as it descended to Saturn's moon Titan. It was taken with the
Descent Imager/Spectral Radiometer, one of two NASA instruments on the
probe. |
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“Streams, rivers, springs and
rain”
Posted Jan. 21, 2005
Special to World Science
New
images from Saturn’s moon Titan show familiar Earth-like features including springs, rivers, streams and
rainfall – but with exotic ingredients, scientists say.
The researchers held a press conference Friday in Paris to present their first analysis of results from Huygens, a
European-built probe that landed on the smog-shrouded world a week ago.
“There are truly remarkable processes on Titan’s surface which are very similar to those occurring on
Earth today,” said Jean-Pierre Lebreton, Huygens project scientist and mission
manager for the European Space Agency.
Although researchers didn’t find any living things, they did report plenty of evidence of chemistry and processes that could be conducive to life. Titan’s chemistry is thought to be similar to the chemistry on Earth at
life’s
dawn.
Part of their analysis was based on images created by Huygens with stereo views. These are images consisting of combinations of two pictures from slightly different vantage points, which reveals
three-dimensionality better than normal images. The stereo images have not yet been made public.
In one photograph, “We see a ridge system with a peak; the ridge is about 100 meters
[109 yards] tall,” Said Martin G. Tomasko, principal investigator for the Descent Imager and Spectral Radiometer, the camera aboard Huygens. Tomasko is
with the University of Arizona in Tucson, United States.
Branching off the ridges are dark lines, which are probably evidence of rain, he said. The dark lines are riverbeds or river
channels created by rain washing off the hilltops, he explained.
“It might have rained yesterday,” said Toby Owen, Cassini Interdisciplinary Scientist for the atmospheres of Titan and Saturn, from the Institute for Astronomy, Honolulu, United States.
“This is really a very active situation.”
Another
feature of the landscape, Tomasko said, is short, stubby dark lines—in
contrast to the long ones. The short ones “I think are what you would see if you had springs, or water flowing out of the side of a hill,” he added.
The rain and the liquid in the channels, however, consists of not water but methane, a substance which on Earth is a colorless, flammable gas. Methane is also produced by the decomposition of living things. And like many other chemicals found on Titan, it is a
hydrocarbon. Hydrocarbons are chemicals composed of hydrogen and carbon, a
family of substances crucial to forming living things on Earth.
The dark material in the images is “a concentration of dirt, organic material, that lands on everything and gets washed into low regions,” Tomasko said.
“The methane rain washes the dark material off the high points and concentrates it on the bottom of these channels. They eventually flow out to these broad plains,” Tomasko said. There, the liquid settles into the ground.
“The riverbeds are dry most of the time,” however, Tomasko said. “You have pools [of liquid] that sink into the surface” shortly after it rains.
“We don’t see indications of open pools of liquid,” he added. “The liquid is just underneath the surface, as if it rained not very long ago.” However, “even in dark regions there’s plenty of evidence of fluid flow,” said Tomasko.
“We were extraordinarily lucky to come down on the boundary between this bright and dark material,” he added.
Many
of the speculations that astronomers had made about Titan before the mission
have turned out to be correct, according to the researchers.
They said they found proof of the previously hypothesized presence of methane and hydrocarbons,
using the mass spectrometer aboard Huygens. A mass spectrometer is an instrument that identifies the chemical
components of a substance by separating them according to their differing mass and electric charge.
Bigger than the planets Mercury and Pluto, Titan is one of the few moons in our solar system with its own atmosphere. It is cloaked in a thick, smog-like haze. Further study of this moon promises to reveal much about planetary formation and, perhaps, about the early days of Earth as well, scientists believe.
The probe’s landing last week was the last phase in a seven-year journey strapped to the Cassini Orbiter, a spacecraft built as a collaboration among 17 nations. Cassini, the first craft to orbit the Saturn system of rings and moons, began its orbit on June 30. Huygens was released from Cassini on Dec. 25 and later dropped through Titan’s atmosphere, collecting data as parachutes slowed it from super sonic speeds.
The probe carried six instruments designed to study the content and movements of Titan’s atmosphere and collect data and images on the surface. It sent data and images to the Cassini mothership, which
relayed them to Earth.
The probe began transmitting data to Cassini during its descent and after landing at least as long as Cassini was above Titan’s horizon. Radio telescopes on Earth continued to receive this signal well past the expected lifetime of Huygens. It was expected to last only about half an hour in the moon’s harsh climate, researchers said, but it went on working for as long as three hours.
Lebreton said future missions to Titan might include rovers and airborne devices, such as balloons.
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