Cassini Maps Global Pattern of Titan's Dunes

Carolina Martinez 818-354-9382
Jet Propulsion Laboratory, Pasadena, Calif.
carolina.martinez@jpl.nasa.gov

Image advisory: 2009-032 Feb. 26, 2009

Cassini Maps Global Pattern of Titan's Dunes

Titan's vast dune fields, which may act like weather vanes to determine general wind
direction on Saturn's biggest moon, have been mapped by scientists who compiled four
years of radar data collected by the Cassini spacecraft.

Titan's rippled dunes are generally oriented east-west. Surprisingly, their orientation
and characteristics indicate that near the surface, Titan's winds blow toward the east
instead of toward the west. This means that Titan's surface winds blow opposite the
direction suggested by previous global circulation models of Titan.

"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 Applied Physics Laboratory in Laurel, Md. "Think of the dunes sort
of like a weather vane, pointing us to the direction the winds are blowing." A paper
based on these findings appeared in the Feb. 11 issue of Geophysical Research
Letters.

"Titan's dunes are young, dynamic features that interact with topographic obstacles and
give us clues about the wind regimes," said Jani Radebaugh, Brigham Young
University, Provo,
Utah. "Winds come at these dunes from at least a couple of different directions, but
then combine to create the overall dune orientation."

The new map, based on all the high-resolution radar data collected during a four-year
period, is now available at: http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini .

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.

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.

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. JPL manages the Cassini-Huygens mission for
NASA's Science Mission Directorate. 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.

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