Saturn Does the Wave in Upper Atmosphere

Feature May 7, 2008


Saturn Does the Wave in Upper Atmosphere

Two decades of scrutinizing Saturn are finally paying off, as scientists have discovered a wave
pattern, or oscillation, in Saturn's atmosphere only visible from Earth every 15 years.

The discovery of the wave pattern is the result of a 22-year campaign observing Saturn from
Earth (the longest study of temperature outside Earth ever recorded), and the Cassini spacecraft's
observations of temperature changes in the giant planet's atmosphere over time.

The Cassini infrared results, which appear in the same issue of Nature as the data from the 22-
year ground-based observing campaign, indicate that Saturn's wave pattern is similar to a pattern
found in Earth's upper atmosphere. The earthly oscillation takes about two years. A similar
pattern on Jupiter takes more than four Earth years. The new Saturn findings add a common link
to the three planets.

Just as scientists have been studying climate changes in Earth's atmosphere for long periods of
time, NASA scientists have been studying changes in Saturn's atmosphere. Glenn Orton of
NASA's Jet Propulsion Laboratory in Pasadena, Calif., says patience is the key to studying
changes over the course of a Saturnian year, the equivalent of about 30 Earth years.

"You could only make this discovery by observing Saturn over a long period of time," said Orton,
lead author of the ground-based study. "It's like putting together 22 years worth of puzzle pieces,
collected by a hugely rewarding collaboration of students and scientists from around the world
on various telescopes."

The wave pattern is called an atmospheric oscillation. It ripples back and forth within Saturn's
upper atmosphere. In this region, temperatures switch from one altitude to the next in a candy
cane-like, striped, hot-cold pattern. These varying temperatures force the wind in the region to
keep changing direction from east to west, jumping back and forth. As a result, the entire region
oscillates like a wave.

A "snapshot" of the hot-cold temperature patterns in Saturn's atmosphere was captured by the
Cassini Composite Infrared Spectrometer. Along with Earth-based data, the "snapshot" also
uncovered other interesting phenomena. Among them: the temperature at Saturn's equator
switches from hot to cold, and temperatures on either side of the equator switch from cold to hot
every Saturn half-year.

Mike Flasar, co-author of the Cassini paper, and principal investigator for Cassini's Composite
Infrared Spectrometer at NASA's Goddard Space Flight Center, Greenbelt, Md., said that Cassini
helped define this oscillation in combination with the ground observation campaign.

"It's this great synergy of using ground-based data over time, and then getting up close and
personal with the oscillation in Saturn's atmosphere through Cassini," said Flasar. "Without
Cassini, we might never have seen the structure of the oscillation in detail."

Cassini scientists hope to find out why this phenomenon on Saturn changes with the seasons, and
why the temperature switchover happens when the sun is directly over Saturn's equator.

More information on the Cassini-Huygens mission can be found at: http://saturn.jpl.nasa.gov,

and http://www.nasa.gov/cassini.

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 mission for NASA's Science Mission Directorate, Washington,
D.C. The Cassini orbiter was designed, developed and assembled at JPL. The Composite
Infrared Spectrometer team is based at NASA's Goddard Space Flight Center, Greenbelt, Md.

-- Written by Diya Chacko

Media Contact:
Diya Chacko/ Carolina Martinez 818-393-5464/354-9382

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