Saturn has two hexagons, not one, swirling around its north pole

A vortex in the stratosphere mirrors a famous six-sided cyclone in the clouds below

Saturn hexagons

DOUBLE SIXES  Saturn’s hexagon (pictured) has a new friend. A second six-sided vortex, not visible here, has appeared hundreds of kilometers above this one.

JPL-Caltech/NASA, Space Science Institute

A new hexagon has emerged high in the skies over Saturn’s north pole.

As spring turned to summer in the planet’s northern hemisphere, a six-sided vortex appeared in the stratosphere. Surprisingly, the polar polygon seems to mirror the famous hexagonal cyclone that swirls in the clouds hundreds of kilometers below, researchers report online September 3 in Nature Communications.

When NASA’s Cassini spacecraft arrived at Saturn in 2004 — during summer in the southern hemisphere — the probe spied a similar vortex in the stratosphere over the south pole, though that one was shaped more like a plain old circle. As summer gradually turned to autumn, that vortex vanished.

Now, planetary scientist Leigh Fletcher at the University of Leicester in England and colleagues report that Cassini caught a new vortex growing in the north during the spacecraft’s final years. Relying on infrared maps of the atmosphere, the team found that from 2014 to 2017 a warm, swirling mass of air started developing over the north pole. That wasn’t surprising — but the six-sided shape came as a bit of a shock.

The shape suggests that the underlying hexagon somehow controls what happens in the stratosphere. These sorts of insights could help researchers understand how energy moves around in other planetary atmospheres.

Unfortunately, Cassini is no longer around — it dove into Saturn last year (SN: 9/2/17, p. 16). But Earth-based telescopes will keep an eye on the storm to see how it changes along with Saturn’s seasons.

Christopher Crockett is an Associate News Editor. He was formerly the astronomy writer from 2014 to 2017, and he has a Ph.D. in astronomy from the University of California, Los Angeles.

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