http://www.jpl.nasa.gov/news/news.cfm?release=2009-032

Cassini Maps Global Pattern of Titan's Dunes
Jet Propulsion Laboratory
February 26, 2009

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.

Media contact: Carolina Martinez 818-354-9382
Jet Propulsion Laboratory, Pasadena, Calif.
carolina.martinez{at}jpl.nasa.gov

2009-032
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