Saturn Just Grew a Second Polygon: Hubble Spots a Huge Decagon at Its South Pole

Saturn, the planet famous for wearing a giant hexagon on its north pole, has been caught growing a matching secret on the other end of the planet. New analysis of Hubble Space Telescope data reveals a huge ten-sided atmospheric pattern — a decagon — swirling around Saturn’s south pole, a surprising counterpart to the iconic northern hexagon first spotted by the Voyager spacecraft in the 1980s.

According to researchers, the strange decagon appears to be a long-lived structure locked into the planet’s southern jet stream, much like its six-sided sibling in the north. That symmetry raises a puzzle: two massive geometric shapes at opposite poles suggest Saturn’s atmosphere organizes itself into these patterns far more readily than scientists expected.

How does a planet draw polygons?

Neither shape is drawn by anything solid — Saturn has no surface for storms to bump into. Instead, these features are standing waves in the jet streams, formed where winds moving at different speeds shear against each other. Laboratory experiments and simulations have shown that such flows can spontaneously settle into polygonal rotation, and Saturn’s deep, featureless atmosphere appears to be the perfect canvas.

The northern hexagon spans roughly 30,000 kilometers — wider than Earth is around — and has persisted for at least four decades. If the southern decagon proves equally durable, it suggests these geometric vortices are a fundamental feature of Saturn’s climate rather than a fluke.

Why it matters

Polygonal jet streams are not just a curiosity. Understanding how they form and endure helps scientists model atmospheric dynamics in general — including on Earth, where jet-stream behavior drives weather patterns. Saturn, with its hydrogen-helium atmosphere and lack of oceans or terrain, is a natural laboratory for the pure physics of rotating fluids.

Astronomers will now watch the southern pole across Saturn’s long seasons to see whether the decagon holds its shape, drifts, or eventually dissolves. Either outcome will sharpen the models of how giant planets — and perhaps climates everywhere — work.

Featured image: Saturn’s north polar hexagon, NASA/JPL/University of Arizona (public domain). Source: ScienceDaily.