Astronomers using the Hubble Space Telescope have spotted a giant ten-sided storm circling Saturn's south pole, a geometric twin to the famous hexagon that has ringed the planet's north for more than four decades.
The new feature, called a decagon, is roughly 104,000 miles wide. It is the first large, regular-sided jet pattern ever observed in Saturn's southern hemisphere, according to the NASA and European Space Agency team that runs the telescope.
A twin for a famous hexagon
Saturn's north pole has hosted a six-sided jet stream since at least 1981, when NASA's Voyager spacecraft first photographed it. That hexagon is one of the most unusual weather patterns in the solar system, with sides wider than Earth itself.
For years, scientists saw nothing similar at the south pole. Cassini, the spacecraft that orbited Saturn from 2004 to 2017, recorded a warm polar vortex and a cyclone there but no polygonal jet. That led many researchers to think the hexagon was a northern-only oddity.
Why it took so long to spot
Geometry hid the answer. Saturn's tilt and its long orbit around the sun mean each pole drops out of view for years at a time. From Earth, the south pole was effectively out of sight from about 2012 to 2023.
Using Hubble's Outer Planet Atmospheres Legacy program, which has tracked the giant planets since 2023, astronomers pieced together images showing the decagon slowly taking shape. The researchers suspect the pattern formed between 2017 and 2023, during the years the pole was hidden.
What the find tells scientists
The discovery, reported in the journal Science Advances, shows that Saturn's atmosphere can build stable polygonal jets at both poles, even though the two patterns differ in shape.
Researchers say studying the decagon as it evolves could reveal how the planet's fast winds interact with its deep interior. Hubble images from August 2025 show the storm still changing, giving scientists a rare chance to watch a planetary-scale weather system grow up.