A Newly Discovered Southern Marvel
While Saturn's six-sided northern hexagon has been known for over 40 years, the decagon is a brand-new discovery. Announced in September 2026, astronomers using the Hubble Space Telescope spotted the giant, 10-sided atmospheric wave encircling the planet's
south pole. This was the first time a large, regular-sided pattern had ever been seen in the southern hemisphere. Unlike the long-lived hexagon, data suggests this decagon only began to form in recent years, with hints of its structure appearing in observations from 2023 before becoming more distinct. This gives scientists a rare chance to watch a planetary-scale atmospheric phenomenon as it develops.
It’s a Deep, Towering Structure
The decagon is not just a superficial pattern on the cloud tops. Observations show that it is a vertically extended atmospheric structure that penetrates deep through multiple layers of Saturn's atmosphere. This is a key part of the headline's claim. When viewed through different light filters, or wavelengths, the decagon's apparent position can shift slightly. That's because different wavelengths of light probe different altitudes in the atmosphere. Seeing the pattern at various depths confirms it's a massive, three-dimensional wave, not just a flat cloud formation.
The Decagon Moves, Unlike the Hexagon
A key difference between Saturn's two geometric poles is movement. The northern hexagon is famously persistent and remains almost stationary relative to the planet's rotation. The southern decagon, however, is a wanderer. It has been observed drifting eastward. Its corners also appear to meander, meaning it doesn't maintain the same rigid, regular appearance as its northern counterpart. This contrast in behaviour suggests that different atmospheric dynamics are at play in Saturn's two hemispheres, presenting a new puzzle for planetary scientists.
It Was Found Thanks to Saturn’s Seasons
The discovery was made possible by the slow changing of seasons on Saturn, where each season lasts for more than seven Earth years. For a long time, the south pole was tilted away from Earth's view. As Saturn's orbit gradually brought its southern hemisphere back into view, astronomers on Earth, including amateur observers, began to notice a faint, wavy pattern forming in 2024. This prompted a closer look with the Hubble Space Telescope, which could capture sharper images from space and confirm the developing 10-sided shape without the blur of Earth's atmosphere.
Its Origin Is a Complete Mystery
Scientists are intrigued by why this feature formed so suddenly when nothing like it had been seen before. Images from NASA's Cassini spacecraft, which orbited Saturn from 2004 to 2017, showed no sign of such a long-lived structure. Researchers have been searching for a southern counterpart to the northern hexagon since 1990. One theory suggests that a nearby storm, or anticyclone vortex, that was first observed in 2023 and darkened significantly in 2025 may have provided the initial disturbance that triggered the formation of the persistent decagon wave. However, further studies are needed to understand how it truly formed and how long it might last.
