NASA's Hubble Space Telescope has spotted a giant ten-sided pattern, or decagon, circling Saturn's south pole — a structure unlike anything astronomers have seen on the planet before. The wave sits inside one of Saturn's jet streams and extends through multiple atmospheric layers, meaning it is far more than a surface cloud feature.
Saturn's north pole has hosted a persistent hexagonal jet stream for more than 40 years, first spotted by the Voyager spacecraft. The south pole showed no sign of anything similar in Cassini spacecraft data from 2004 to 2017. Faint hints of the decagon first appeared in Hubble images from 2023, with amateur astronomers Trevor Barry and Jean-Paul Oger helping confirm a wavy band by 2024, before ground-based observations solidified the finding in 2025.
"We've never seen anything quite like this in Saturn's southern hemisphere," said Amy Simon of NASA's Goddard Space Flight Center. "This feature is different — it appears to be strengthening, giving us the rare opportunity to watch a giant atmospheric pattern develop." Scientists still don't know what triggered the decagon's sudden formation or how long it will last. The findings were published September 2 in the journal Science Advances.