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Long-Lived Lightning Storm Rages on Saturn

April 29, 2008

A monster
storm spawning bolts of lightning 10,000 times more powerful than any seen on
Earth is raging on the ringed planet Saturn.

The
powerful electrical storm cropped up in Saturn’s southern hemisphere five
months ago, when it was first spotted by NASA’s
Cassini spacecraft
, and has persevered to become the planet’s longest continuously
recorded tempest to date.

“We
saw similar
storms
in 2004 and 2006 that each lasted for nearly a month, but this storm
is longer-lived by far,” said Georg Fischer, an associate with Cassini’s radio
and plasma wave science team at the University of Iowa, Iowa City, in a
statement. “And it appeared after nearly two years during which we did not
detect any electrical storm activity from Saturn.”

Cassini’s
radio and plasma wave science instrument first picked up signals from the storm’s
lightning bursts on Nov. 27, 2007, with the probe’s cameras catching their
first visual glimpse on Dec. 6. Images of the storm show it as a smudge on
Saturn’s otherwise creamy cloud bands.

“The
electrostatic radio outbursts have waxed and waned in intensity for five months
now,” Fischer said.

Electrical
storms on Saturn are similar to thunderstorms on Earth, but much larger. They
can span thousands of miles and generate radio bursts from
lightning that can be thousands of times more powerful than Earthly lightning bolts,
said mission scientists, who named a massive lightning storm in 2004 “Dragon.”

The current
electrical tempest is mired in a region of Saturn that mission scientists have dubbed
“Storm Alley” because of its frequent and intense storms. Every few seconds the
storm belches intense radio pulses consistent with lightning that can be
detected even when the weather itself is over the horizon and out of direct
view from Cassini.

Researchers
hope that by tracking the Saturnian weather, they may gain new insights into
the processes behind the planet’s lightning, as well as how it changes as the
seasons shift from summer to autumn in Saturn’s southern hemisphere.

“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, a Cassini imaging team associate at the
California Institute of Technology in Pasadena, Calif.

Cassini’s
onboard instruments have tracked the storm every 10 hours and 40 minutes, when
Saturn’s rotation brings it into view, though amateur astronomers are also
watching over the tempest from Earth.

“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.”

Launched in
1997, Cassini arrived at Saturn in 2004 and has spotted a series of odd storms
while studying the ringed planet and its many moons. The probe has captured views of a hurricane-like
storm
near the south pole of Saturn and recorded a massive
lightning storm
about 2,175 miles wide (3,500 kilometers) wide in 2006.

Earlier
this year, managers for the international Cassini-Huygens mission, which
includes NASA, and the European and Italian space agencies, extended the probe’s
$3.27 billion expedition by two additional years to 2010.


Source: imaginova



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