Spring on Titan Brings Sunshine and Patchy Clouds

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE 818-354-5011
http://www.jpl.nasa.gov

Jia-Rui C. Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.
jia-rui.c.cook@jpl.nasa.gov

Anita Heward 011-44-7756-034243
European Planetary Science Congress, Rome, Italy
anita.heward@europlanet-eu.org

Spring on Titan Brings Sunshine and Patchy Clouds

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2010-308&cid=release_2010-308

The northern hemisphere of Saturn's moon Titan is set for mainly fine spring weather, with
polar skies clearing since the equinox in August last year. The visual and infrared mapping
spectrometer (VIMS) aboard NASA's Cassini spacecraft has been monitoring clouds on Titan
regularly since the spacecraft entered orbit around Saturn in 2004. Now, a group led by
Sébastien Rodriguez, a Cassini VIMS team collaborator based at Université Paris Diderot,
France, has analyzed more than 2,000 VIMS images to create the first long-term study of
Titan's weather using observational data that also includes the equinox. Equinox, when the
sun shone directly over the equator, occurred in August 2009.

Rodriguez is presenting the results and new images at the European Planetary Science
Congress in Rome on Sept. 22.

Though Titan's surface is far colder and lacks liquid water, this moon is a kind of "sister
world" to Earth because it has a surface covered with organic material and an atmosphere
whose chemical composition harkens back to an early Earth. Titan has a hydrological cycle
similar to Earth's, though Titan's cycle depends on methane and ethane rather than water.

A season on Titan lasts about seven Earth years. Rodriguez and colleagues observed
significant atmospheric changes between July 2004 (early summer in Titan's southern
hemisphere) and April 2010 (the very start of northern spring). The images showed that cloud
activity has recently decreased near both of Titan's poles. These regions had been heavily
overcast during the late southern summer until 2008, a few months before the equinox.

Over the past six years, the scientists found that clouds clustered in three distinct latitude
regions of Titan: large clouds at the north pole, patchy clouds at the south pole and a narrow
belt around 40 degrees south. "However, we are now seeing evidence of a seasonal
circulation turnover on Titan -- the clouds at the south pole completely disappeared just before
the equinox and the clouds in the north are thinning out," Rodriguez said. "This agrees with
predictions from models and we are expecting to see cloud activity reverse from one
hemisphere to another in the coming decade as southern winter approaches."

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency
and the Italian Space Agency. JPL manages the mission for NASA's Science Mission
Directorate, Washington, D.C. The visual and infrared mapping spectrometer team is based at
the University of Arizona, Tucson.

For a full version of this release, go to: http://www.europlanet-
eu.org/outreach/index.php?option=com_content&task=view&id=288&Itemid=41

For more information about Cassini, go to: http://www.nasa.gov/cassini and
http://saturn.jpl.nasa.gov .

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