Titan's atmosphere revealed by new NASA observation

Erica Hupp / Dolores Beasley
May 12, 2005
Headquarters, Washington
202/358-1237, 1753

Nancy Neal Jones
Goddard Space Flight Center, Greenbelt, Md.
301/286-0039

Release 05-20

TITAN'S ATMOSPHERE REVEALED BY NEW NASA OBSERVATION

Titan's atmospheric winds, temperature and mixing have been revealed by new
observations from the Cassini spacecraft. The thick atmosphere of Saturn's
giant moon is rich in organic compounds, whose chemistry may be similar to
that which occurred on Earth before the emergence of life.

"Titan is not just a dot in the sky; these new observations show that Titan
is a rich, complex world much like the Earth in some ways," said Dr. Michael
Flasar, the Composite Infrared Spectrometer instrument (CIRS) principal
investigator at NASA's Goddard Space Flight Center, Greenbelt, Md. Flasar is
lead author of a paper on this research published May 13 in the Journal
Science.
The CIRS science team found evidence for an isolated polar vortex similar to
one that occurs on Earth. CIRS' observations indicated that strong winds
circulating around Titan's north pole isolate the atmosphere there during
the polar night. Mixing of the polar region with the lower latitude regions
of the atmosphere is inhibited during this time. On Earth, the south polar
atmosphere is isolated for months during the long Antarctic winter allowing
the formation of polar stratospheric clouds. Normally inert chlorine
compounds (such as chlorine nitrate) undergo chemical reactions on the cloud
crystals that free molecular chlorine. In the spring, sunlight decomposes
the molecular chlorine, leading to the famous annual Antarctic "ozone hole".
Titan's atmosphere contains no ozone; however CIRS results show that a large
part of its atmosphere is isolated during the polar night, and could allow
unusual and complex chemistry to occur.

Like Earth, Titan's axis of rotation is tilted, so its poles also experience
a long night during winter. The polar winter on Titan is many Earth years
long, because Saturn orbits the sun once in almost 30 years. Currently it is
early winter in Titan's northern hemisphere. The CIRS team found significant
temperature differences between Titan's north pole and the equator. The team
used this observation to derive the speed of circumpolar winds around the
north pole. The team believes these winds are isolating the atmosphere
around Titan's north pole because the CIRS data showed that the
concentration of several heavy organic (carbon-containing) molecules is
highest there.
Heavy organic molecules form naturally in Titan's atmosphere, blanketing the
moon with an orange haze. Titan's atmosphere consists of about 98 percent
nitrogen with most of the remainder being methane. When these molecules
rise to the upper atmosphere, they are broken apart by sunlight and the
fragments form heavier organic molecules like propane, ethane, acetylene,
hydrogen cyanide, and even more complex molecules. Because the stratospheric
air over the winter pole is cold, it sinks and brings down the heavy organic
compounds that formed higher up. If the air over Titan's north pole is
isolated during the winter, the heavy organics should build up in the
stratosphere over the season. This is just what the CIRS team is seeing.

"We don't know if there are even more similarities to Earth's ozone hole
process, like polar clouds that react with molecules in the atmosphere,
simply because we haven't seen them yet," said Flasar. "But we wouldn't be
surprised to discover them, nor would we be surprised to find that Titan has
some unique twists of its own. This is what makes science so exciting.
Nature is too rich for us to predict exactly what we will find when we go
exploring."

The research was funded by NASA and the European Space Agency. The
Cassini-Huygens mission is a cooperative project of NASA, the European Space
Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a
division of the California Institute of Technology in Pasadena, manages the
Cassini-Huygens mission for NASA's Science Mission Directorate, Washington,
D.C.

For more information, go to:


http://www.nasa.gov/vision/universe/...zone_Hole.html

or

http://saturn.jpl.nasa.gov




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Jacques :-)

www.spacepatches.info