Cassini Finds Titan's Clouds Hang on to Summer
- From: baalke@xxxxxxxxxxxxx
- Date: Wed, 3 Jun 2009 13:53:57 -0700 (PDT)
http://www.jpl.nasa.gov/news/news.cfm?release=2009-093
Cassini Finds Titan's Clouds Hang on to Summer
Jet Propulsion Laboratory
June 03, 2009
Cloud chasers studying Saturn's moon Titan say its clouds form and
move
much like those on Earth, but in a much slower, more lingering
fashion.
Their forecast for Titan's early autumn -- warm and wetter.
Scientists with NASA's Cassini mission have monitored Titan's
atmosphere
for three-and-a-half years, between July 2004 and December 2007, and
observed more than 200 clouds. They found that the way these clouds
are
distributed around Titan matches scientists' global circulation
models.
The only exception is timing -- clouds are still noticeable in the
southern hemisphere while fall is approaching.
"Titan's clouds don't move with the seasons exactly as we expected,"
said Sebastien Rodriguez of the University of Paris Diderot, in
collaboration with Cassini visual and infrared mapping spectrometer
team
members at the University of Nantes, France. "We see lots of clouds
during the summer in the southern hemisphere, and this summer weather
seems to last into the early fall. It looks like Indian summer on
Earth,
even if the mechanisms are radically different on Titan from those on
Earth. Titan may then experience a warmer and wetter early autumn than
forecasted by the models."
On Earth, abnormally warm, dry weather periods in late autumn occur
when
low-pressure systems are blocked in the winter hemisphere. By
contrast,
scientists think the sluggishness of temperature changes at the
surface
and low atmosphere on Titan may be responsible for its unexpected warm
and wet, hence cloudy, late summer.
The new infrared images showing the global cloud pattern are now
available at: http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini
<http://www.nasa.gov/mission_pages/cassini/main/index.html> .
As summer changes to fall at the equinox in August 2009, Titan's
clouds
are expected to disappear altogether. But, circulation models of
Titan's
weather and climate predict that clouds at the southern latitudes
don't
wait for the equinox and should have already faded out since 2005.
However, Cassini was still able to see clouds at these places late in
2007, and some of them are particularly active at mid-latitudes and
the
equator.
Titan is the only moon in our solar system with a substantial
atmosphere, and its climate shares Earth-like characteristics. Titan's
dense, nitrogen-methane atmosphere responds much more slowly than
Earth's atmosphere, as it receives about 100 times less sunlight
because
it is 10 times farther from the sun. Seasons on Titan last more than
seven Earth years.
Scientists will continue to observe the long-term changes during
Cassini's extended mission, which runs until the fall of 2010. Cassini
is set to fly by Titan on May 6.
The Cassini-Huygens mission is a cooperative project of NASA, the
European Space Agency and the Italian Space Agency. NASA's Jet
Propulsion Laboratory, Pasadena, Calif., manages the Cassini-Huygens
mission for NASA's Science Mission Directorate. The Cassini orbiter
was
designed, developed and assembled at JPL. The visual and infrared
mapping spectrometer team is based at the University of Arizona.
Media contact:
DC Agle 818-393-9011
Jet Propulsion Laboratory, Pasadena, Calif.
agle@xxxxxxxxxxxx
2009-093
.
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