A team of astronomers has discovered a decagon-shaped atmospheric structure near Saturn’s south pole, adding a second polygonal feature to the ringed planet’s inventory. The findings, published recently in Science Advances, are based on images captured by the Hubble Space Telescope. This discovery joins the famous hexagon observed at Saturn’s north pole 44 years ago.
These formations are not solid geological structures, as Saturn lacks a defined solid surface. Instead, they are complex patterns created by clouds within the planet’s deepening atmosphere. Each side of the newly identified decagon spans approximately 16,800 kilometers, a distance that exceeds Earth’s diameter.
While a jet stream near the feature reaches speeds of 116 meters per second—nearly 260 miles per hour, surpassing Category 5 hurricane winds—the decagon pattern itself shifts slowly at just 2.5 meters per second. Scientists note that despite the swift rotation of the jet stream, the polygonal shape remains relatively stable.
The identification of the south pole feature concluded a decades-long quest for an equivalent to the northern hexagon. Prior observations from major planetary missions failed to locate a similar persistent structure, a difficulty compounded by Saturn’s axial tilt, which obscured the southern hemisphere from Earth for many years.
Initial hints of the decagon emerged from ground-based telescopes, including those operated by amateur astronomers. Analysis of Hubble data allowed researchers to trace the pattern back to 2023, with the ten vertices becoming distinctly defined by 2025. The precise mechanism behind these geometric shapes remains a subject of scientific debate.
One prevailing hypothesis suggests that the polygons are visible manifestations of massive atmospheric waves trapped by powerful jet streams. In this model, the jet stream acts like the boundary of a beach, confining waves of atmospheric gas in a circular path around the planet.
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