NASA Spacecraft Tracks Raging Saturn Storm

Carolina Martinez 818-354-9382
Jet Propulsion Laboratory, Pasadena, Calif.
carolina.martinez@jpl.nasa.gov

Preston Dyches 720-974-5859
Space Science Institute, Boulder, Colo.
media@ciclops.org

Image Advisory: 2008-069 April 29, 2008

NASA Spacecraft Tracks Raging Saturn Storm

PASADENA, Calif. -- As a powerful electrical storm rages on Saturn with lightning bolts 10,000
times more powerful than those found on Earth, the Cassini spacecraft continues its five-month
watch over the dramatic events.

Scientists with NASA's Cassini-Huygens mission have been tracking the visibly bright,
lightning-generating storm--the longest continually observed electrical storm ever monitored by
Cassini.

Saturn's electrical storms resemble terrestrial thunderstorms, but on a much larger scale. Storms
on Saturn have diameters of several thousand kilometers (thousands of miles), and radio signals
produced by their lightning are thousands of times more powerful than those produced by
terrestrial thunderstorms.

Color images of the storm are available at: http://saturn.jpl.nasa.gov and

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

Lightning flashes within the persistent storm produce radio waves called Saturn electrostatic
discharges, which the radio and plasma wave science instrument first detected on Nov. 27, 2007.
Cassini's imaging cameras monitored the position and appearance of the storm, first spotting it
about a week later, on Dec. 6.

"The electrostatic radio outbursts have waxed and waned in intensity for five months now," said
Georg Fischer, an associate with the radio and plasma wave science team at the University of
Iowa, Iowa City. "We saw similar storms in 2004 and 2006 that each lasted for nearly a month,
but this storm is longer-lived by far. And it appeared after nearly two years during which we did
not detect any electrical storm activity from Saturn."

The new storm is located in Saturn's southern hemisphere--in a region nicknamed "Storm Alley"
by mission scientists--where the previous lightning storms were observed by Cassini.
"In order to see the storm, the imaging cameras have to be looking at the right place at the right
time, and whenever our cameras see the storm, the radio outbursts are there," said Ulyana
Dyudina, an associate of the Cassini imaging team at the California Institute of Technology in
Pasadena, Calif.

Cassini's radio plasma wave instrument detects the storm every time it rotates into view, which
happens every 10 hours and 40 minutes, the approximate length of a Saturn day. Every few
seconds the storm gives off a radio pulse lasting for about a tenth of a second, which is typical of
lightning bolts and other electrical discharges. These radio waves are detected even when the
storm is over the horizon as viewed from Cassini, a result of the bending of radio waves by the
planet's atmosphere.

Amateur astronomers have kept track of the storm over its five-month lifetime. "Since Cassini's
camera cannot track the storm every day, the amateur data are invaluable," said Fischer. "I am in
continuous contact with astronomers from around the world."

The long-lived storm will likely provide information on the processes powering Saturn's intense
lightning activity. Cassini scientists will continue to monitor Storm Alley as the seasons change,
bringing the onset of autumn to the planet's southern hemisphere.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency
and the Italian Space Agency. JPL, a division of Caltech, manages the Cassini mission for
NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard
cameras were designed, developed and assembled at JPL. The imaging team is based at the
Space Science Institute, Boulder, Colo. The radio and plasma wave science team is based at the
University of Iowa, Iowa City.

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