Saturn's Spots Mystify Astronomers

Both of Saturn?s poles have surprising swirling hotspotsthat persist even through years of polar winter, a new study reveals.

The hotspots are localized areas in Saturn'sgaseous atmosphere over its poles that are considerably warmer than thesurrounding air — they're actually about as warm as the atmosphere at Saturn'sequator, said Leigh Fletcher of the University of Oxford.

The hotspot over the southern hemisphere wasimaged by the Keck Observatories prior to arrival of the Cassini spacecraft, but the northernhemisphere has faced away from Earth for over a decade, so its hotspot was revealedonly this year by Cassini.

Scientists had thought that solar irradiationmight be generating the hotspot in the southern hemisphere (currently in itssummer phase, facing the sun), but the existence of a similar hotspot in thenorthern hemisphere, which has been plunged in wintry darkness for many years,suggests that isn't the case.

Instead, dynamic processes in Saturn'satmosphere may create the hotspots, the new findings, detailed in the Jan. 4issue of the journal Science, suggest, Fletcher says.

Air being sucked downward at the poles may causethe hotspots, while air moving upward in the atmosphere may be creating a cold"collar" around the hotspots. These air movements could beresponsible for the raging hurricane-like stormimaged over the south pole in 2006.

As unusual as the hotspots themselves is thewarm hexagonal ring of air surrounding the cold collar of the northernhemisphere hotspot. Stranger still is the lack of such a shape around the southpole.

"The mystery is... why on earth — or why onSaturn even — do we see a hexagon around the north pole, and not around the southpole?" Fletcher told

Other missions have provided hints that Jupiterand Neptune have hotspots over their poles as well, suggesting they could be afeature of the atmospheres of all gaseous planets — even extrasolarplanets, Fletcher said.

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Andrea Thompson

Andrea Thompson is an associate editor at Scientific American, where she covers sustainability, energy and the environment. Prior to that, she was a senior writer covering climate science at Climate Central and a reporter and editor at Live Science, where she primarily covered Earth science and the environment. She holds a graduate degree in science health and environmental reporting from New York University, as well as a bachelor of science and and masters of science in atmospheric chemistry from the Georgia Institute of Technology.