Saturn’s South Pole Shows a Newly‑Formed Atmospheric Decagon

When you think of Saturn, the image that usually pops into mind is that glittering system of rings – the one kids point to in schoolbooks. Yet the gas giant has a lot more going on, especially at its poles, where fierce jet streams sculpt bizarre geometric shapes in the atmosphere.

Most of us have heard about the iconic hexagon that circles Saturn’s north pole, a six‑sided vortex that has been churning for decades. But a fresh look at recent Hubble Space Telescope snapshots has revealed something entirely different in the southern hemisphere: a sprawling decagon, a ten‑sided wave that seems to be marching eastward.

The discovery comes from an international collaboration that dug into images taken between 2023 and 2025. Those pictures are part of Hubble’s Outer Planet Atmospheres Legacy (OPAL) program, a long‑running effort that grabs annual photos of the outer planets to track how their clouds and storms evolve. The team also threw in data from the Calar Alto Observatory in Spain – the biggest ground‑based telescope on the continent – to fill in the gaps.

What they found is a decagon sitting snugly over Saturn’s south pole, cutting through several atmospheric layers. Unlike the static northern hexagon, which hardly shifts its position, this new structure drifts eastward, its ten corners wobbling back and forth on roughly a 32‑day cycle. In other words, the southern decagon behaves more like a rolling wave than a solid wall.

Speed‑wise, the jet streams that shape the decagon are even faster than those that forge the hexagon. While the northern feature rides winds of about 320–354 km/h (200–220 mph), the southern decagon’s winds zip along at 400–420 km/h (≈250 mph). Those speeds help explain why the southern pattern is so dynamic.

“We’ve never seen anything like this down there,” says Dr. Amy Simon, a senior planetary‑atmosphere scientist at NASA’s Goddard Space Flight Center and OPAL’s principal investigator. “The hexagon has been a constant for over 40 years; this decagon is new, it’s growing, and that gives us a rare chance to watch a giant atmospheric pattern come to life.”

Interestingly, the now‑retired Cassini probe, which orbited Saturn from 2004 to 2017, never caught a glimpse of any southern polygon. That makes the Hubble‑derived detection all the more exciting, because it opens a fresh window onto how planetary atmospheres can reorganize themselves.

Scientists think the decagon could shed light on similar mysteries elsewhere – for example, the curious arrangement of cyclones at Jupiter’s poles, where storms line up in surprisingly regular geometric patterns. By feeding the Saturn observations into computer models, researchers hope to tease out how wind shear, solar heating, and the planet’s rapid rotation conspire to sculpt these shapes.

So what’s next? With Hubble continuing its OPAL campaign and next‑generation telescopes on the horizon, we’ll be keeping a close eye on Saturn’s southern pole, watching the decagon drift, morph, and perhaps even fade. As we learn more, each new twist reminds us just how dynamic, and surprisingly orderly, giant planet atmospheres can be.

Stay curious, keep looking up, and remember: the sky still has plenty of secrets left to share.