Recent NASA/ESA Hubble Space Telescope observations have revealed a giant, evolving ten-sided atmospheric wave encircling Saturn's south pole, according to a study reported on 2 September 2026 in Science Advances. The European Space Agency says this is the first time a large regular-sided jet pattern has been observed in the planet's southern hemisphere. The feature resembles Saturn's famous northern hexagon but is also distinctly different.

By combining several years of Hubble observations dating back to 2023, taken under the Outer Planet Atmospheres Legacy programme, researchers found subtle hints of the structure emerging before it became clearly defined. Ground-based images contributed by observers first showed a faint undulating band along the southern pole in 2024, with 2025 imagery hinting more strongly at the decagon. The wave sits within one of Saturn's powerful jet streams and extends through multiple atmospheric layers, indicating it is not confined to cloud level.

Study co-author Amy Simon of NASA's Goddard Space Flight Center said the feature appears to be strengthening, offering a rare chance to watch a giant atmospheric pattern develop. Further Hubble and James Webb observations, plus computer modelling, are planned to understand how the decagon formed, how long it may last and how it compares with the long-lived northern hexagon.