Giant Blizzard Rages on Saturn

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A massive blizzard is raging on Saturn — a storm so large and fierce NASA astronomers and amateur skywatchers can see it from Earth.

NASA's Cassini spacecraft currently orbiting Saturn has a front row seat to the otherworldly tempest and is recording the most detailed data yet of storms on the ringed planet. But amateur astronomers back on Earth have also managed to chip in on the Saturn blizzard stormwatch.

"We were so excited to get a heads-up from the amateurs," said Cassini scientist Gordon Bjoraker, a composite infrared spectrometer team member based at NASA's Goddard Space Flight Center in Greenbelt, Md.

The data showed a large, turbulent storm, dredging up a lot of material from the deep atmosphere and covering an area at least five times larger than the biggest blizzard that hit Earth so far this year — the "Snowmageddon" storm that blanketed the Washington, D.C. area in snow in February. [Saturn's rings and moons.]

Saturn's 'storm alley'

Cassini's radio and plasma wave instrument and imaging cameras have been tracking thunder and lightning storms on Saturn for years in a region around Saturn's mid-latitudes that is nicknamed "storm alley."

But, gathering data on storms requires a tricky balancing act, since storms on Saturn can come and go on a time scale of weeks, while Cassini's imaging and spectrometer observations have to be locked in place months in advance.

Given these limitations, NASA sometimes enlists the help of amateur astronomers.

The radio and plasma wave instrument regularly picks up electrostatic discharges that are associated with the storms, so scientists have been sending periodic tips to amateurs, who can quickly go to their backyard telescopes and try to spy the bright convective storm clouds.

Amateur astronomers Anthony Wesley, Trevor Barry and Christopher Go received one of those notices in February, and were able to snap dozens of pictures over the next several weeks.

In fact, in late March, Wesley — who is based in Australia and was the first person spot the aftermath of an comet impact on Jupiter last summer — sent Cassini scientists an e-mail with a picture of the storm attached.

"I wanted to be sure that images like these were being seen by the Cassini team just in case this was something of interest to be imaged directly by Cassini or the Hubble Space Telescope," Wesley wrote.

Cassini scientists analyzed all the images in detail, including a picture from March 13 of the storm at its peak, taken by Go, who lives in the Philippines.

Saturn's storm season

Luckily, the composite infrared spectrometer happened to be targeting the latitude of the storms. The Cassini scientists had known there might be storms in that area, but were unsure when they might be active.

The Cassini spectrometer obtained data on March 25 and 26 that showed larger than expected amounts of phosphine, a gas typically found in Saturn's deep atmosphere, and an indicator that powerful currents were lifting material upward into the upper troposphere.

The spectrometer data also showed that the tropopause, which is the dividing line between the serene stratosphere and the lower churning troposphere, was about 1 degree Fahrenheit colder in the storm cell than in neighboring areas.

"A balloonist floating about 62 miles down from the bottom of Saturn's calm stratosphere would experience an ammonia-ice blizzard with the intensity of Snowmageddon," said Brigette Hesman, a composite infrared spectrometer team member and assistant research scientist at the University of Maryland.

"These blizzards appear to be powered by violent storms deeper down — perhaps another 62 to 124 miles down — where lightning has been observed and the clouds are made of water and ammonia," Hesman said.

The Cassini-Huygens mission is a joint project of NASA, the European Space Agency and the Italian Space Agency. The composite infrared spectrometer team is based at NASA's Goddard Space Flight Center in Greenbelt, Md.

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