New Simulations May Explain Why Saturn Has A Hexagonal Storm On Its North Pole

The Cassini spacecraft captures three magnificent sights at once: Saturn's north polar vortex, its iconic rings, and its hexagon storm. NASA/JPL-Caltech/Space Science Institute

One of the many curiosities that features on Saturn is the hexagon-shaped storm sitting on the northern pole of the planet. In a new study, complete with plenty of stunning imagery, two scientists from Harvard University have weighed in with a new model that seeks to explain how the distinctive and unique feature came to be.

The study, reported in the journal Proceedings of the National Academy of Sciences, used a new three-dimensional simulation model of Saturn's atmosphere to understand how this unnatural-looking, six-sided vortex is formed. 

"We see storms on Earth regularly and they are always spiraling, sometimes circular, but never something with hexagon segments or polygons with edges," Rakesh K Yadav, a study author who works in Bloxham's lab in Harvard's Department of Earth and Planetary Sciences, said in a statement. "That is really striking and completely unexpected. [The question on Saturn is] how did such a large system form and how can such a large system stay unchanged on this large planet?"

Most importantly, their month-long simulation revealed that the storm's shape appears to be crafted by a process of deep thermal convection, likely thousands of kilometers deep, stretching much further beneath the cloud tops of the gas giant.

A GIF of the model used to understand how Saturn got its hexagonal storm. Jeremy Bloxham and Rakesh K Yadav

The team argue that a complex interaction occurs between large and small spinning cyclones that surround a larger horizontal jet stream gushing near the planet's north pole. The smaller storms interact with the larger storms, effectively pinching the eastern jet and confining it to the top of the planet, warping the stream into a hexagon.

As brilliantly explained by Yadav: “Imagine we have a rubber band and we place a bunch of smaller rubber bands around it and then we just squeeze the entire thing from the outside. That central ring is going to be compressed by some inches and form some weird shape with a certain number of edges. That's basically the physics of what's happening.” 

“We have these smaller storms and they're basically pinching the larger storms at the polar region and since they have to coexist, they have to somehow find a space to basically house each system. By doing that, they end up making this polygonal shape," they added.

Curiously enough, the model did not actually produce a hexagonal shape, but a nine-sided polygon. The researchers aren’t too dissuaded, however, and believe the unusually straight-edged geometric shape still affirms their overall thesis on how the storm is formed.

Saturn’s hexagonal spot was first spotted (so to speak) in the 1980s when Voyager spacecrafts took a glimpse of the ringed planet on their epic journey towards the outer Solar System. The Cassini-Huygens mission also captured more data during its recent mission to Saturn and its system, which ended in September 2017.

A strange twist in the story occurred back in 2018 when scientists used data from the Cassini spacecraft and found that Saturn also has a hexagonal storm on its south pole too.

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