Scientists have mapped vast dune fields on Titan that may align with the wind on Saturn’s biggest moon — flowing opposite the way climate models had predicted.
The maps, as above, represent four years of radar data collected by the Cassini spacecraft. They reveal rippled dunes that are generally oriented east-west, which means Titan’s winds probably blow toward the east instead of the west. If so, Titan’s surface winds blow opposite the direction suggested by previous global circulation models. On the example above, the arrows indicate the general wind direction. The dark areas without arrows might have dunes but have not yet been imaged.
“At Titan there are very few clouds, so determining which way the wind blows is not an easy thing, but by tracking the direction in which Titan’s sand dunes form, we get some insight into the global wind pattern,” says Ralph Lorenz, Cassini radar scientist at Johns Hopkins University in Maryland. “Think of the dunes sort of like a weather vane, pointing us to the direction the winds are blowing.”
Titan’s dunes are believed to be made up of hydrocarbon sand grains likely derived from organic chemicals in Titan’s smoggy skies. The dunes wrap around high terrain, which provides some idea of their height. They accumulate near the equator, and may pile up there because drier conditions allow for easy transport of the particles by the wind. Titan’s higher latitudes contain lakes and may be “wetter” with more liquid hydrocarbons, not ideal conditions for creating dunes.
“Titan’s dunes are young, dynamic features that interact with topographic obstacles and give us clues about the wind regimes,” said Jani Radebaugh, from Brigham Young University in Utah. “Winds come at these dunes from at least a couple of different directions, but then combine to create the overall dune orientation.”
Researchers say the wind pattern is important for planning future Titan explorations that might involve balloon-borne experiments. Some 16,000 dune segments were mapped out from about 20 radar images, digitized and combined to produce the new map, which is available at http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini. A paper based on the new findings appeared in the Feb. 11 issue of Geophysical Research Letters.
Cassini, which launched in 1997 and is now in extended mission operations, continues to blaze its trail around the Saturn system and will visit Titan again on March 27. Seventeen Titan flybys are planned this year.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA’s Jet propulsion Laboratory (JPL) in Pasadena, California manages the Cassini-Huygens mission. The Cassini orbiter was designed, developed and assembled at JPL. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the United States and several European countries. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.
LEAD IMAGE CREDIT: NASA/JPL/Space Science Institute (Boulder, Colorado)