In a development that will surely delight geometry enthusiasts and mildly confuse the rest of us, NASA's Hubble Space Telescope has spotted a giant, evolving, 10-sided atmospheric wave encircling Saturn's south pole. This marks the first time a large, regular-sided jet pattern has been observed in the planet's southern hemisphere - and it's giving the famous northern hexagon a run for its money in the polygon department.
The findings, published Wednesday in the journal Science Advances, reveal that the feature is remarkably similar to Saturn's northern hexagon yet distinctly different, suggesting scientists may be witnessing a brand-new atmospheric phenomenon on the iconic gas giant. Because one six-sided storm wasn't enough, apparently.
Researchers pieced together several years of Hubble observations dating back to 2023, finding subtle hints of the structure before it blossomed into a clearly defined pattern. Those observations were taken as part of Hubble's Outer Planet Atmospheres Legacy (OPAL) program, which has been photographing the outer planets annually for over a decade. Because nothing says 'legacy' like a decade of planetary yearbook photos.
"We've never seen anything quite like this in Saturn's southern hemisphere," said Amy Simon, study co-author and OPAL principal investigator at NASA's Goddard Space Flight Center in Greenbelt, Maryland, in a statement that suggests she's seen a lot of things in Saturn's southern hemisphere. "The northern hexagon has been there every time we've looked for more than 40 years. This feature is different - it appears to be strengthening, giving us the rare opportunity to watch a giant atmospheric pattern develop."
The discovery was made possible because Saturn's changing seasons gradually brought the south pole back into view from Earth, where ground-based astronomers first identified it. Agustín Sánchez-Lavega, lead author of the study from the University of the Basque Country in Spain, manages the Planetary Virtual Observatory Laboratory, which collects ground-based images of solar system planets from observers worldwide. In those images, first in 2024, Sánchez-Lavega and amateur astronomers Trevor Barry and Jean-Paul Oger noticed a subtle undulating band along the southern pole. Additional 2025 imagery hinted even more strongly at this decagon structure.
Then Hubble stepped in to provide the sharp, unblurred view that only a space telescope can offer. "Given Saturn's symmetry in its north-south jet stream system, we have been searching for a counterpart to Saturn's northern hexagon on the south pole in Hubble images since 1990," Sánchez-Lavega said. "Images from NASA's Cassini spacecraft, which orbited Saturn between 2004 and 2017, showed no inkling of a long-lived formation, either. The Hubble data confirmed the feature's presence back to 2023."
The wave sits within one of Saturn's powerful jet streams and extends through multiple atmospheric layers, indicating it's not just a cloud-level feature but a vertically extended structure. Its apparent position shifts slightly because Hubble captures images at different wavelengths, probing different altitudes - because even atmospheric waves deserve a multi-angle approach.
"The most intriguing part to me is that this seems to have just formed recently," said Simon. "The question is, why did it suddenly form now when we haven't seen one before?"
Indeed, why now? Perhaps Saturn decided to switch up its style after 40 years of the same old hexagon. The authors say further study is needed from Hubble and NASA's James Webb Space Telescope, as well as computer models, to understand how the decagon formed, how long it might last, and how it compares to its well-established northern counterpart.
Hubble's longevity has been a boon for tracking changes over time in solar system planets. The OPAL program allows scientists to follow seasonal changes, track short-lived storms, and identify slowly evolving atmospheric features. "When we started the OPAL program, we expected compelling surprises, but we didn't know what to expect specifically," said Mike Wong, study co-author from the University of California, Berkeley. "A lot of the discoveries we see coming from OPAL are not just based on one observation, but on years and years of data. Regular observations over time are enabling a lot of new findings."
The team plans to continue observing Saturn to determine whether the decagon settles into a long-lived, stable configuration or keeps evolving. Future observations could help scientists understand what drives the wave, what it reveals about atmospheric dynamics of giant planets across the solar system, and how these relate to Earth's own weather patterns - because apparently, we can't even have a storm without it being compared to something on Earth.
Hubble, a joint project of NASA and the European Space Agency (ESA), has been operating for over three decades. NASA's Goddard Space Flight Center manages the telescope and mission operations, with support from Lockheed Martin Space. The Space Telescope Science Institute in Baltimore, operated by the Association of Universities for Research in Astronomy, conducts science operations for NASA. And there you have it - another groundbreaking discovery, all thanks to a space telescope that refuses to retire.