“We see a massive mountain range that kind of reminds me of the Sierra Nevada mountains in the western United States. This mountain range is continuous and is nearly 100 miles long,” said Dr. Bob Brown, team leader of the Cassini visual and infrared mapping spectrometer at the University of Arizona, Tucson.
During an October 25th flyby designed to obtain the highest resolution infrared views of Titan yet, Cassini resolved surface features as small as 400 meters (1,300 feet). The images reveal a large mountain range, dunes, and a deposit of material that resembles a volcanic flow. These data, together with radar data from previous flybys, provide new information on the height and composition of geologic features on Titan.
UK Cassini scientist Professor Michele Dougherty from Imperial College London, said, “What I found most exciting about the infrared observations was the discoveries they revealed on such different scales, from the largest mountain range (nearly 100 miles in length) yet seen on the surface of Titan down to detailed resolution of sand dunes and a volcanic lava flow.”
If Titan were Earth, these mountains would lie south of the equator, somewhere in New Zealand. The range is about 150 kilometers long (93 miles) and 30 kilometers (19 miles) wide and about 1.5 kilometers (nearly a mile) high. Deposits of bright, white material, which may be methane “snow” or exposures of some other organic material, lie at the top of the mountain ridges.
“These mountains are probably as hard as rock, made of icy materials, and are coated with different layers of organics,” said Dr. Larry Soderblom, Cassini interdisciplinary scientist at the U.S. Geological Survey, Flagstaff, Ariz.
He added, “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.”
The mountains probably formed when material welled up from below to fill the gaps opened when tectonic plates pull apart, similar to the way mid-ocean ridges are formed on Earth.
Separately, the radar and infrared data are difficult to interpret, but together they are a powerful combination. In the infrared images, one can see the shadows of the mountains, and in radar, one can see their shape. But when combined, scientists begin to see variations on the mountains, which is essential to unraveling the mysteries of the geologic processes on Titan.
Professor Dougherty adds, “These discoveries show the strength of interdisciplinary science whereby combining data from different instruments onboard Cassini allows us to obtain the best understanding possible of the complex features on this enigmatic moon.”
A fan-shaped feature, possibly a remnant of a volcanic flow, is also visible in the infrared images. The radar instrument imaged this flow and a circular feature from which the flow seems to emanate on a previous flyby, but not in this level of detail.
“The evidence is mounting that this circular feature is a volcano,” said Dr. Rosaly Lopes, Cassini radar team member at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “With radar data alone, we identified it as a possible volcano, but the combination of radar and infrared makes it much clearer.”
Near the wrinkled, mountainous terrain are clouds in Titan’s southern mid latitudes whose source continues to elude scientists. These clouds are probably methane droplets that may form when the atmosphere on Titan cools as it is pushed over the mountains by winds.
The composition of dunes that run across much of Titan is also much clearer. “The dunes seem to consist of sand grains made of organics, built on water-ice bedrock, and there may also be some snow and bright deposits,” Brown said.
Commenting on these new results Professor John Zarnecki from the Open University, Lead Scientist for the Surface Science Package on the European Space Agency’s Huygens probe which descended onto surface of Titan in January 2005, said, "Titan continues to amaze us. It is incredible to think that all those kilometres away there is a moon which contains so many similar geographical features to those found here on Earth. Huygens gave us a panoramic snapshot of the surface of Titan which we continue to anaylse. When coupled with the results from Cassini's flyby's of Titan we are really beginning to build up a detailed picture of the make up of this intriguing moon."
Titan is a complex place and scientists are uncovering the secrets of the surface, one flyby at a time. Scientists hope to get more clues from the next Titan flyby, on December 12th.
For the new infrared images of the mountains visit: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov and http://wwwvims.lpl.arizona.edu .
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13.07.2018 | Technische Universität München
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12.07.2018 | University of Rochester
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