Saturn has a big, weird decagon around its south pole

Saturn has a new, odd weather pattern resembling a decagon near its south pole. This may have formed due to a large storm nearby, but researchers aren’t totally sure.

The pattern has clearly defined sides shaped by powerful winds, looking like a decagon – a geometric polygon with 10 sides and 10 angles – from above. It is similar to a hexagonal weather pattern first seen at the planet’s north pole more than 40 years ago.

“[But] the one at the north is a bit smaller,” says Amy Simon at NASA’s Goddard Space Flight Center in Maryland. The south pole pattern also seems to be moving a bit more with the rotation of the planet.

The feature was first spotted by amateur astronomers in 2024. Simon and her colleagues then examined images taken by the Hubble Space Telescope from 2023 to 2025. “We confirmed the existence of the decagon with absolute clarity,” says team member Agustín Sánchez-Lavega at the University of the Basque Country in Spain.

It is unclear exactly when the pattern formed, with no spacecraft having orbited Saturn since 2017. “It most certainly wasn’t expected,” says Simon. “The hexagon has been there for decades, but this is something new.”

The decagon measures about 13,000 kilometres across, slightly wider than Earth. It is thought to result from a large atmospheric wave shaped by wind from a powerful jet stream that meanders near the planet’s south pole.

Its formation may be linked to a large nearby storm, although the exact cause is a bit of a mystery. “It’s a very complicated fluid dynamics sort of thing,” says Simon. “It’s telling us something about what’s going on deeper below the clouds.”

Saturn’s rings form a giant dusty doughnut encircling the planet

The rings of Saturn are normally thought to be flat, but measurements by the Cassini spacecraft show that some of their particles fly hundreds of thousands of kilometres above and below the thin main discs

Andrew Ingersoll at the California Institute of Technology says the discovery highlights that Saturn is a dynamic, changing world. “It’s very interesting to see these features,” he says.

No similar pattern has been observed on any other planets, although Jupiter does have an arrangement of cyclones at its poles. “People didn’t really predict that such an organised, polygonal pattern would exist on another planet,” says Ingersoll.

We don’t know how long the pattern will last. Other telescopes, including the James Webb Space Telescope, are poised to study it in more detail, but many scientists are vying for access to those. “We’ll look as frequently as anyone will let us,” says Simon.

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