Astronomers using the NASA/ESA Hubble Space Telescope have spotted a giant, 10-sided atmospheric wave circling Saturn's south pole, a feature never before seen in the planet's southern hemisphere. The discovery, published in Science Advances, marks the first time a large regular-sided jet pattern has been observed there, and it bears a striking resemblance to Saturn's famous northern hexagon, yet it is distinctly different, hinting at a new atmospheric phenomenon in the making.
A Pattern Emerges From Years of Data
The feature did not appear overnight. By analyzing Hubble observations dating back to 2023, researchers found subtle hints of the structure before it became a clearly defined pattern. These images were taken as part of Hubble's Outer Planet Atmospheres Legacy (OPAL) programme, which has photographed the outer planets annually for over a decade. The wave sits within a jet stream, and its shape is evolving, strengthening over time, giving scientists a rare chance to watch a giant atmospheric pattern develop in real time.
Ground-Based Astronomers Spot It First
The discovery was possible because Saturn's changing seasons gradually brought the south pole back into view from Earth. Amateur astronomers Trevor Barry and Jean-Paul Oger, along with researcher Agustín Sánchez-Lavega from the University of the Basque Country in Spain, first noticed a subtle undulating band in ground-based images submitted to the Planetary Virtual Observatory Laboratory in 2024. Additional 2025 imagery hinted even more strongly at the decagon structure, prompting a closer look with Hubble.
Hubble's vantage from space offers unmatched image sharpness and spatial resolution over full rotations of Saturn, without the blurring caused by Earth's atmosphere. The space telescope confirmed the feature's presence back to 2023, filling in the timeline of its emergence. The northern hexagon has been visible for more than 40 years, but this southern decagon is new, and it appears to be strengthening, offering a unique opportunity to study how such a pattern forms.
The discovery was made possible by a combination of citizen science and space-based observation. The Planetary Virtual Observatory Laboratory, managed by the University of the Basque Country, accepts ground-based images of Solar System planets from observers worldwide, and it was there that the first hints of the decagon were found. This collaboration between amateur and professional astronomers, along with Hubble's long-term monitoring, has revealed a feature that may reshape understanding of Saturn's atmosphere.
As Saturn's seasons continue to shift, the south pole will remain in view, allowing researchers to track the decagon's evolution. Whether it will become as stable as the northern hexagon or eventually dissipate remains to be seen, but the opportunity to witness the birth of such a large-scale atmospheric structure is rare. The findings underscore the value of sustained observation and the unexpected discoveries that can emerge when scientists and hobbyists look at the same planet with fresh eyes.
