* Astronomy

This image of Titan was taken by the Cassini spaceprobe on December 12, 2006, when it was approximately 231,121 kilometres away.


Credit NASA

The image was taken using the CB3 and IRP0 filters.

This image composite contains a radar image taken during a February 2005 (T3) flyby, and overlaid are images from the visual and infrared mapping spectrometer taken on Sept. 7, 2006, (T17) and Oct. 25, 2006 (T20).


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Credit: NASA/JPL/University of Arizona

The thin strip is the infrared image taken on the inbound leg of the T20 flyby and crosses the radar image near an area with a small, crater-like feature. In the radar image a faint fan of material seems to originate at the crater, and the portion of the infrared image that crosses the faint fan shows both a large brightness contrast and very sharp boundaries. The fan-like deposit has such sharp boundaries and strong contrast with its surroundings that it supports the idea that the deposit seen in the radar images is a flow of material erupted from the small crater. This may be the strongest evidence yet of cryovolcanism on Titan. The infrared image was taken at a distance of 1,100 kilometres from the surface of Titan and resolves features as small as 400 meters. The infrared images were taken at wavelengths of 1.3 microns shown in blue, 2 microns shown in green, and 5 microns shown in red.

This set of composite images was constructed from the best Cassini radar data and visual and infrared mapping spectrometer data obtained from all the Titan flybys up to the most recent flyby on Oct 25 (T20).


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Credit: NASA/JPL/University of Arizona

The globe to the upper right is centred on 0 degrees longitude, and each of the other globes is labelled as to which longitude appears at the centre of the disk. The two rightmost images in the bottom row are of the north and south poles of Titan, respectively. The two instruments provide complementary data, all of which is required to understand the geologic processes that have shaped the surface of Titan over the age of the solar system.
The images were taken at wavelengths of 1.3 microns shown in blue, 2 microns shown in green, and 5 microns shown in red.

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 kilometres), 93 miles long (150 kilometres) and 19 miles wide (30 kilometres). 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" - Robert H. Brown , Cassini scientist, 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.


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Credit: NASA/JPL/University of Arizona

"These mountains are probably as hard as rock, made of icy materials, and are coated with different layers of organics. 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. 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" - Larry Soderblom of the U.S. Geological Survey, Flagstaff, Arizona, a Cassini interdisciplinary scientist.

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 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. With radar data alone, we identified it as a possible volcano, but the combination of radar and infrared makes it much clearer" - Rosaly Lopes, radar team member at NASA's Jet Propulsion Laboratory in Pasadena, California.

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" - Robert H. Brown.

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.

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