Cassini Spacecraft Captures Images and Sounds of Big Saturn Storm

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Jia-Rui Cook 818-354-0850
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Dwayne C. Brown 202-358-1726
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News release: 2011-203 July 6, 2011

Cassini Spacecraft Captures Images and Sounds of Big Saturn Storm

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2011-203&cid=release_2011-203

PASADENA, Calif. – Scientists analyzing data from NASA's Cassini spacecraft now have the first-
ever, up-close details of a Saturn storm that is eight times the surface area of Earth.

On Dec. 5, 2010, Cassini first detected the storm that has been raging ever since. It appears at
approximately 35 degrees north latitude on Saturn. Pictures from Cassini's imaging cameras show the
storm wrapping around the entire planet covering approximately 1.5 billion square miles (4 billion
square kilometers).

The storm is about 500 times larger than the biggest storm previously seen by Cassini during several
months from 2009 to 2010. Scientists studied the sounds of the new storm's lightning strikes and
analyzed images taken between December 2010 and February 2011. Data from Cassini's radio and
plasma wave science instrument showed the lightning flash rate as much as 10 times more frequent
than during other storms monitored since Cassini's arrival to Saturn in 2004. The data appear in a
paper published this week in the journal Nature.

"Cassini shows us that Saturn is bipolar," said Andrew Ingersoll, an author of the study and a Cassini
imaging team member at the California Institute of Technology in Pasadena, Calif. "Saturn is not like
Earth and Jupiter, where storms are fairly frequent. Weather on Saturn appears to hum along placidly
for years and then erupt violently. I'm excited we saw weather so spectacular on our watch."

At its most intense, the storm generated more than 10 lightning flashes per second. Even with
millisecond resolution, the spacecraft's radio and plasma wave instrument had difficulty separating
individual signals during the most intense period. Scientists created a sound file from data obtained
on March 15 at a slightly lower intensity period.

Cassini has detected 10 lightning storms on Saturn since the spacecraft entered the planet's orbit and
its southern hemisphere was experiencing summer, with full solar illumination not shadowed by the
rings. Those storms rolled through an area in the southern hemisphere dubbed "Storm Alley." But the
sun's illumination on the hemispheres flipped around August 2009, when the northern hemisphere
began experiencing spring.

"This storm is thrilling because it shows how shifting seasons and solar illumination can dramatically
stir up the weather on Saturn," said Georg Fischer, the paper's lead author and a radio and plasma
wave science team member at the Austrian Academy of Sciences in Graz. "We have been observing
storms on Saturn for almost seven years, so tracking a storm so different from the others has put us at
the edge of our seats."

The storm's results are the first activities of a new "Saturn Storm Watch" campaign. During this
effort, Cassini looks at likely storm locations on Saturn in between its scheduled observations. On the
same day that the radio and plasma wave instrument detected the first lightning, Cassini's cameras
happened to be pointed at the right location as part of the campaign and captured an image of a small,
bright cloud. Because analysis on that image was not completed immediately, Fischer sent out a
notice to the worldwide amateur astronomy community to collect more images. A flood of amateur
images helped scientists track the storm as it grew rapidly, wrapping around the planet by late
January 2011.

The new details about this storm complement atmospheric disturbances described recently by
scientists using Cassini's composite infrared spectrometer and the European Southern Observatory's
Very Large Telescope. The storm is the biggest observed by spacecraft orbiting or flying by Saturn.
NASA's Hubble Space Telescope captured images in 1990 of an equally large storm.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the
Italian Space Agency. NASA's Jet Propulsion Laboratory in Pasadena manages the mission for the
agency's Science Mission Directorate in Washington. The radio and plasma wave science team is
based at the University of Iowa, Iowa City, where the instrument was built. The imaging team is
based at the Space Science Institute in Boulder, Colo. JPL is a division of the California Institute of
Technology, Pasadena.

For images and an audio file of the storm, visit: http://www.nasa.gov/cassini and
http://saturn.jpl.nasa.gov .

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