Cassini and Telescope See Violent Saturn Storm

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News release: 2011-150 May 19, 2011

Cassini and Telescope See Violent Saturn Storm

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2011-150&cid=release_2011-150

PASADENA, Calif. -- NASA's Cassini spacecraft and a European Southern Observatory ground-
based telescope tracked the growth of a giant early-spring storm in Saturn's northern hemisphere that
is so powerful it stretches around the entire planet. The rare storm has been wreaking havoc for
months and shooting plumes of gas high into the planet's atmosphere.

Cassini's radio and plasma wave science instrument first detected the large disturbance, and amateur
astronomers tracked its emergence in December 2010. As it rapidly expanded, its core developed into
a giant, powerful thunderstorm. The storm produced a 3,000-mile-wide (5,000-kilometer-wide) dark
vortex, possibly similar to Jupiter's Great Red Spot, within the turbulent atmosphere.

The dramatic effects of the deep plumes disturbed areas high up in Saturn's usually stable
stratosphere, generating regions of warm air that shone like bright "beacons" in the infrared. Details
are published in this week's edition of Science Magazine.

"Nothing on Earth comes close to this powerful storm," says Leigh Fletcher, the study's lead author
and a Cassini team scientist at the University of Oxford in the United Kingdom. "A storm like this is
rare. This is only the sixth one to be recorded since 1876, and the last was way back in 1990."

This is the first major storm on Saturn observed by an orbiting spacecraft and studied at thermal
infrared wavelengths, where Saturn's heat energy reveals atmospheric temperatures, winds and
composition within the disturbance.

Temperature data were provided by the Very Large Telescope (VLT) on Cerro Paranal in Chile and
Cassini's composite infrared spectrometer (CIRS), operated by NASA's Goddard Space Flight Center
in Greenbelt, Md.

"Our new observations show that the storm had a major effect on the atmosphere, transporting energy
and material over great distances, modifying the atmospheric winds -- creating meandering jet
streams and forming giant vortices -- and disrupting Saturn's slow seasonal evolution," said Glenn
Orton, a paper co-author, based at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

The violence of the storm -- the strongest disturbances ever detected in Saturn's stratosphere -- took
researchers by surprise. What started as an ordinary disturbance deep in Saturn's atmosphere punched
through the planet's serene cloud cover to roil the high layer known as the stratosphere.

"On Earth, the lower stratosphere is where commercial airplanes generally fly to avoid storms which
can cause turbulence," says Brigette Hesman, a scientist at the University of Maryland in College
Park who works on the CIRS team at Goddard and is the second author on the paper. "If you were
flying in an airplane on Saturn, this storm would reach so high up, it would probably be impossible to
avoid it."

Other indications of the storm's strength are the changes in the composition of the atmosphere
brought on by the mixing of air from different layers. CIRS found evidence of such changes by
looking at the amounts of acetylene and phosphine, both considered to be tracers of atmospheric
motion. A separate analysis using Cassini's visual and infrared mapping spectrometer, led by Kevin
Baines of JPL, confirmed the storm is very violent, dredging up larger atmospheric particles and
churning up ammonia from deep in the atmosphere in volumes several times larger than previous
storms. Other Cassini scientists are studying the evolving storm, and a more extensive picture will
emerge soon.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the
Italian Space Agency. The mission is managed by JPL for NASA's Science Mission Directorate in
Washington. The European Southern Observatory in Garching, Germany operates the VLT in Chile.
JPL is a division of the California Institute of Technology in Pasadena.

For information about Cassini, visit: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .

Jia-Rui Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.
jccook@jpl.nasa.gov

Dwayne C. Brown 202-358-1726
NASA Headquarters, Washington
dwayne.c.brown@nasa.gov

Nancy Neal-Jones/Elizabeth Zubritsky 301-286-0039/301-614-5438
Goddard Space Flight Center, Greenbelt, Md.
nancy.n.jones@nasa.gov/elizabeth.a.zubritsky@nasa.gov

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