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We're Getting Closer To Explaining Saturn’s Polar Hexagon Storm

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Dr. Alfredo Carpineti

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Dr. Alfredo Carpineti

Senior Staff Writer & Space Correspondent

Alfredo (he/him) has a PhD in Astrophysics on galaxy evolution and a Master's in Quantum Fields and Fundamental Forces.

Senior Staff Writer & Space Correspondent

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The North polar hexagon of Saturn, April 2, 2014. NASA/JPL-Caltech/Space Science Institute

The North Pole of Saturn has something no other planet in the Solar System has. And no, it’s not Santa. The gas giant has a strange hexagon-shaped cloud storm stretching 29,000 kilometers (18,000 miles) across that could comfortably fit more than two Earths inside. Now, a new study brings a new approach to understanding how this storm came to be.

While many studies have tried to perfectly reproduce the hexagonal vortex, this new study from Harvard University followed a different path. The researchers focused on recreating the atmosphere of Saturn with the least amount of assumptions, in an attempt to see what would arise from this approach. They found that structures similar to what we see on Saturn form spontaneously without much input.

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The simulation produced latitudinal jets of alternating directions, a large cyclone on the North Pole, as well as three smaller anticyclonic vortices and several even smaller cyclonic vortices. The effect of all these produced a polygonal jet stream.

“Our simulation, was somewhat different from the earlier attempts as we did not assume a lot of ingredients,” lead author Dr Rakesh Yadav from Harvard University told IFLScience. “We said ‘let's simulate the physics from very basic principles’ something called fluid dynamics and let's see what happens. And the exciting part about this study is that we were able to get the polygonal-shaped jets meaning that you can have storms that have multiple edges.”

As reported in Proceedings of the National Academy of Sciences, the team's main hypothesis was that the atmosphere of Saturn supports convection, the movement of material between regions of different temperatures like the currents present in a pot of boiling water. This is backed by both observations and models. The other idea is that this flow comes from deep within the Saturnian atmosphere.

Saturn's hexagonal storm as seen in 2014 (top) and a similar but larger storm with multiple edges produced in the simulation (bottom). NASA/JPL-Caltech/Space Science Institute (Top) and Rakesh K. Yadav (Bottom)

The polygonal jet generated in the simulation has nine sides but polygons with more or fewer sides can be created. Also, the circular storms produced by the model are consistent with the observations in both their numbers and speed.

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“All of these things came spontaneously out of this, out of the model. From our perspective, the most interesting part is that you can generate several observations simultaneously in a fairly simple model and from fairly basic physics,” Dr Yadav told IFLScience.

The team now plans to refine the simulation so that it will create six – and only six – sides but also making sure that the hexagonal storm is stable. This peculiar feature of Saturn was first seen by the Voyager probes almost 40 years ago and color changes with the season, it has remained a constant and stable feature.

Tracks of particles advected by the simulated flows. Rakesh K. Yadav


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