WASHINGTON,
May 8 (Xinhua) -- Scientists have discovered a wavepattern, or oscillation, in
Saturn's atmosphere only visible from Earth every 15 years, according to two
studies published Thursday in journal Nature.
The discovery is the result of a 22-year campaign
observing Saturn from Earth, 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.
Glenn Orton of NASA's Jet Propulsion Laboratory 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.
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 are: 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, 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."
