Cassini Images Mammoth Cloud Engulfing Titan's North Pole
A giant cloud half the size of the United States has been imaged on Saturn's
moon Titan by the Cassini spacecraft. The cloud may be responsible for the material
that fills the lakes discovered last year by Cassini's radar instrument.
Cloaked by winter's shadow, this cloud has now come into view as winter turns to spring.
The cloud extends down to 60 degrees north latitude, is roughly 2,400 kilometers (1,490 miles)
in diameter and engulfs almost the entire north pole of Titan.
Image right: Cassini imaged a huge cloud system covering the north pole of Titan. Image credit: NASA/JPL/University of Arizona
+ Full image and caption
The new image was acquired on Dec. 29, 2006, by Cassini's visual and infrared mapping
spectrometer. Scientific models predicted this cloud system, but it had never been imaged in such detail before.
The cloud image is available at: http://www.nasa.gov/cassini
"We knew this cloud had to be there but were amazed at its size and structure,"
said Dr. Christophe Sotin of the University of Nantes, France, a member of the visual
and infrared mapping spectrometer team and distinguished visiting scientist at NASA's
Jet Propulsion Laboratory, Pasadena, Calif. "This cloud system may be a key element in
the global formation of organics and their interaction with the surface."
The same cloud system seen on Dec. 29, was still there two weeks later during a Jan. 13,
2007, flyby, even though observing conditions were slightly less favorable than in December.
The Cassini radar team reported last year that the lakes at the north pole are partly filled,
and some appear to have evaporated, likely contributing to this cloud formation, which is made
up of ethane, methane and other organics. These findings reinforce the idea that methane rains
down onto the surface to form lakes and then evaporates to form clouds. Scientists compare this
methane cycle to the hydrological cycle on Earth, dubbing it "methane-ologic cycle."
Ground-based observations show this Titan cloud system comes and goes with the seasons.
A season on Titan lasts approximately seven Earth years. Based on the global circulation models,
it seems that such cloud activity can last about 25 Earth years before almost vanishing for four
to five years, and then appearing again for 25 years.
Scientists expect this cloud to be around for several years. As the seasons change, scientists
expect a shift of these clouds and lakes from the north pole to the south pole. On Titan's south
pole, scientists have seen only one kidney-shaped lake with Cassini's imaging cameras.
"With 16 more flybys to come this year, we should have the opportunity to monitor the evolution
of this cloud system over time," said Dr. Stephane Le Mouelic, working with the Cassini visual
and infrared mapping spectrometer team, and also at the University of Nantes.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and
the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena,
manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington. The Cassini
orbiter was designed, developed and assembled at JPL. The visual and infrared mapping spectrometer
team is based at the University of Arizona, Tucson.
Media contact: Carolina Martinez
Jet Propulsion Laboratory, Pasadena, Calif.