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Mega-storm continues on Saturn

April 30, 2008
Courtesy Space Science Institute
and World Science staff

As a pow­er­ful elec­tri­cal storm rages on Sat­urn with light­ning 10,000 times more pow­er­ful than Earth’s, NASA’s Cas­si­ni space­craft con­tin­ues a five-month watch over the events.

The view be­low ap­prox­i­mates what the eye would see, and was cre­at­ed by com­bin­ing im­ages tak­en us­ing red, green and blue spec­tral fil­ters. The storm stands out more clear­ly in the sharp­ened, en­hanced col­or view above. (Cred­it: NA­SA/JPL/Space Sci­ence In­sti­tute)

Sat­urn­ian elec­tri­cal storms re­sem­ble Earth’s thun­der­storms, but much larg­er—sev­eral thou­sand kilo­me­ters or miles wide. Thus, a tem­pest as wide as the Paris-New York dis­tance would­n’t be atyp­i­cal, though for the ringed plan­et, such a size is like a thumb­print on a beach ball.

The light­ning pro­duces ra­dio waves called Sat­urn elec­tro­stat­ic dis­charges, which Cas­si­ni first de­tected on Nov. 27. These have “waxed and waned in in­tens­ity for five months now,” said Ge­org Fisch­er, a Cas­si­ni team mem­ber at the Uni­ver­s­ity of Io­wa. 

“We saw si­m­i­lar storms in 2004 and 2006 that each lasted for nearly a month, but this storm is longer-lived by far,” he added. It rages in Sat­urn’s south­ern hem­i­sphere, in a re­gion nick­named “Storm Al­ley” where the pre­vi­ous storms were seen.

Cas­si­ni’s ra­dio plas­ma wave in­stru­ment de­tects the storm eve­ry time it ro­tates in­to view, eve­ry 10 hours and 40 min­utes—the ap­prox­i­mate length of a Sat­urn day, Fisch­er said. Eve­ry few sec­onds the storm gives off a ra­dio pulse last­ing for about a tenth of a sec­ond, he added, typ­i­cal of light­ning bolts and oth­er elec­tric dis­charges. 

Am­a­teur as­tro­no­mers have al­so tracked the tem­pest 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 dis­turb­ance will likely pro­vide in­forma­t­ion on the pro­cesses pow­er­ing Sat­urn’s in­tense light­ning ac­ti­vity, Fisch­er added. 

The Cas­si­ni craft is the first to ex­plore the Sat­urn sys­tem of rings and moons from or­bit. It’s part of the Cas­si­ni-Huy­gens mis­sion, a co­op­er­a­tive proj­ect of NASA, the Eu­ro­pe­an Space Agen­cy and the Ital­ian Space Agen­cy.

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As a powerful electrical storm rages on Saturn with lightning 10,000 times more powerful than Earth’s, NASA’s Cassini spacecraft continues a five-month watch over the dramatic events. Saturnian electrical storms resemble Earth’s thunderstorms, but much larger—several thousand kilometers or miles wide. Thus, a tempest as wide as the Paris-New York distance wouldn’t be atypical, though the ringed planet, this would look smaller than a thumbprint on a beach ball. The lightning produces radio waves called Saturn electrostatic discharges, which Cassini first detected on Nov. 27. These have “waxed and waned in intensity for five months now,” said Georg Fischer, a Cassini team member at the University of Iowa. “We saw similar storms in 2004 and 2006 that each lasted for nearly a month, but this storm is longer-lived by far,” he added. It rages in Saturn’s southern hemisphere, in a region nicknamed “Storm Alley” where the previous storms were seen. Cassini’s radio plasma wave instrument detects the storm every time it rotates into view, every 10 hours and 40 minutes, the approximate length of a Saturn day, Fischer said. Every few seconds the storm gives off a radio pulse lasting for about a tenth of a second, he added, typical of lightning bolts and other electric discharges. Amateur astronomers have also tracked the tempest 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 disturbance will likely provide information on the processes powering Saturn’s intense lightning activity, Fischer added. The Cassini craft, the first to explore the Saturn system of rings and moons from orbit, is part of the Cassini-Huygens mission, is a cooperative project of NASA, the European Space Agency and the Italian Space Agency.