by Playfuls Staff |
13th December 2006
The infrared-sensitive camera on
NASA's Cassini spacecraft has photographed the tallest mountains ever seen on
Saturn's moon, Titan. The mountain chain is nearly a mile high (1.5
kilometers), 93 miles long [more] (150 kilometers) and 19 miles wide (30
kilometers). The mountains are topped by bright, white material which may be
methane or other organic (carbon-containing) "snow."
"We see a massive mountain
range that reminds me of the Sierra Nevada in the western United States," said Cassini scientist
Robert H. Brown of the University of Arizona Lunar and Planetary Laboratory in Tucson. Brown is head of
Cassini's visual and infrared mapping spectrometer (VIMS), which imaged the
mountains in Titan's southern hemisphere during the Oct. 25, 2006 flyby.
The camera took its highest-resolution
infrared views of Titan ever during this flyby, resolving surface features as
small as 400 meters, or about 440 yards. Other features seen in the
high-resolution VIMS images include fields of dunes and a deposit that
resembles a volcanic flow.
If Titan were Earth, the
mountains would be at latitudes near New Zealand. They probably formed
as mid-ocean ridges form on Earth: The surface crust pulls apart, and material
beneath the crust wells up through the crack, creating a ridge.
"These mountains are
probably as hard as rock, made of icy materials, and are coated with different
layers of organics," said Larry Soderblom of the U.S. Geological Survey,
Flagstaff, Ariz., a Cassini interdisciplinary scientist.
"There seem to be layers and
layers of various coats of organic 'paint' on top of each other on these
mountain tops, almost like a painter laying the background on a canvas,"
Soderblom said. "Some of this organic gunk falls out of the atmosphere as
rain, dust or smog onto the valley floors and mountain tops, which are coated
with dark spots that appear to be brushed, washed, scoured and moved around the
surface."
Cassini scientists combined the
new infrared data with radar data from previous flybys to better understand the
height and composition of Titan's geologic features. The shadows of the
mountains are seen in the infrared images, for example, while the shapes of the
mountains are seen in radar. Combining these different kinds of data is
essential for scientists studying Titan's geologic processes.
The Oct. 25 infrared images also
reveal a fan-shaped feature, which Brown said is probably a remnant of a
volcanic flow. Cassini radar imaged this fan-shaped feature, and also a large,
circular feature that appears to be the source of the flow, in less detail on a
previous flyby.
"The evidence is mounting
that this circular feature is a volcano," said Rosaly Lopes, radar team
member at NASA's Jet Propulsion Laboratory in Pasadena, Calif.
"With radar data alone, we identified it as a possible volcano, but the
combination of radar and infrared makes it much clearer."
Clouds lie near the wrinkled,
mountainous terrain in Titan's southern mid-latitudes. Their source has baffled
scientists. "These clouds are probably methane droplets and may form when
the air on Titan cools as it is pushed over the mountains by the Titanian
winds," Brown said.
The new infrared images also
clarify the composition of dunes that run across much of Titan. The dunes,
built on water-ice bedrock, seem to consist of sand grains made of organics,
Brown said.
