Hubble Spots New Decagon Wave at Saturn's South Pole

A giant, evolving 10-sided atmospheric wave now circles Saturn's south pole, the first such structure seen there and a companion to the long-famous northern hexagon.

NASA's Hubble Space Telescope has revealed a giant, evolving, 10-sided atmospheric wave encircling Saturn's south pole, described in a study published Wednesday in the journal Science Advances. It is the first time a large, regular-sided jet pattern has been observed in the planet's southern hemisphere, and it appears remarkably similar to — yet distinctly different from — the famous hexagon at Saturn's north pole, suggesting scientists may be witnessing a new atmospheric phenomenon develop.

For decades, Saturn's hexagon — a cloud pattern first identified in 1988 in Voyager data — was thought to be unique. According to space.com, the newly found decagon is even larger, about 104,250 miles (167,820 kilometers) wide, with each of its 10 sides measuring roughly 10,425 miles long. Lead author Agustín Sánchez-Lavega told space.com that the find "tells us that the hexagon is not a unique, singular feature, as was previously thought."

By piecing together several years of Hubble observations from the OPAL program dating back to 2023, researchers found subtle hints of the structure emerging before it became a clearly defined pattern. According to sci.news, Hubble's October 2023 images showed a faint 10-vertex polygon near 63°S, which sharpened by August 2024 and appeared fully formed by August–September 2025. Sánchez-Lavega said images from the Cassini spacecraft, which orbited Saturn between 2004 and 2017, showed no inkling of a long-lived formation.

The discovery traces to ground-based images contributed to the University of the Basque Country's Planetary Virtual Observatory Laboratory, where Sánchez-Lavega and amateur astronomers Trevor Barry and Jean-Paul Oger noticed a subtle undulating band along the southern pole in 2024. Hubble's view from space then offered unmatched sharpness over full rotations of Saturn, confirming the feature.

The wave sits within one of Saturn's powerful jet streams and extends through multiple layers of the atmosphere, indicating it is not just a cloud-level feature but a vertically extended structure. According to the Associated Press via the Bozeman Daily Chronicle, the decagon migrates eastward at about 6 mph, unlike the practically stationary hexagon. Associated Press reporting adds that a single side already exceeds 10,000 miles, and that the formation likely arose between 2017 and 2023 while the pole was out of view.

Researchers say further study from Hubble and the James Webb Space Telescope, plus computer modeling, is needed to understand how the decagon formed, how long it may last, and how it compares to the long-lived northern hexagon. According to Scientific American, some decagon lines appear fuzzy, suggesting the wave is unstable or still evolving, and Sánchez-Lavega believes it may become more pronounced as solar insolation peaks near 60°S around 2032. The team plans continued observations to determine whether it settles into a stable configuration.