September 2, 20262 min read Add Us On GoogleAdd SciAmThe strange structure appears to have formed recently, but nobody can explain exactly whyBy Adam Kovac edited by Claire CameronA polar projection of Saturn’s southern hemisphere at a red wavelengths at 763 nanometers that was obtained by the Hubble Space Telescope on August 29, 2025. NASA/ESA/A. Sánchez-Lavega/Basque Country University (EHU)Scientists are baffled after discovering a weird decagon-shaped wave in the atmosphere of the planet Saturn. The 10-sided phenomenon appears to have formed over the planet’s south pole recently, but no one is quite sure why.Nothing in Earth’s atmosphere compares to this wave, says Agustín Sánchez-Lavega, a physicist at Spain’s Bilbao School of Engineering. Why it has formed around Saturn’s south pole is an enigma, but it could be the result of disturbances in gas flows, possibly linked to a nearby storm with a high pressure center similar to Jupiter’s Great Red Spot.“We do not yet know for certain,” Sánchez-Lavega says. “There is no single model to explain it. It may be the result of an instability in the jet stream in which it is situated or a wave forced from deeper levels of the atmosphere.”On supporting science journalismIf you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.The wave is described in a new study that was published on Wednesday in Science Advances.This isn’t the first unusual wave scientists have seen in Saturn’s atmosphere. In the 1980s, astronomers detected an hexagonal wave—a six-sided shape—over the planet’s north pole. While it was theorized that a similar wave may be present over the south pole, the decagon seems to have formed more recently. Older imaging by the Hubble Space Telescope and NASA’s Cassini probe don’t show any such structure.In fact, it wasn’t until 2023 that Hubble photographs showed the wave taking shape. It became more and more defined until it appeared fully developed in images taken in August and September 2025, according to the new research.Polar projections of Saturn’s southern hemisphere at two wavelengths: red at 763 nm and a methane absorption filter at 889 nm. The decagon is indicated by a yellow arrow. The dashed lines show the circles of latitude in blue, with their values indicated. The images were obtained the Hubble Space Telescope on August 29, 2025.NASA/ESA/A. Sánchez-Lavega/Basque Country University (EHU)“If the seasonal insolation cycle over the southern polar region plays a role in the formation of this structure, it may well become more pronounced in the coming years, when insolation reaches its peak at the latitude of the decagon around the year 2032,” says Sánchez-Lavega, who is lead author of the new study.Whatever the wave is, it is likely to change. Looking closely at the images, some of the lines of the decagon appear quite fuzzy, which leads Sánchez-Lavega to believe the wave is unstable or still evolving. An added enigma is why such features have only been spotted on Saturn and not on Jupiter, another large, gaseous planet that is known for its stormy weather.“What causes one hemisphere to have six sides and the other 10—perhaps this is related to the difference in latitude between the two cases,” he says. “There are many unanswered questions, which we hope future observations and models will help to clarify.”Subscribe to Support Independent JournalismGreat science journalism requires human expertise, time, effort and creativity. And it costs money. That’s why I and the journalists here at Scientific American hope you’ll join our community.When you subscribe, you are supporting staff and freelance journalists who are passionate about telling science stories that are true, important and compelling. Our editors and reporters are often experts in their fields, which means they understand the nuances of big discoveries and can untangle the breakthroughs from the hype. With a subscription, you are also supporting rigorous fact-checking to ensure the words we publish are precise and accurate. And you’re supporting original illustrations, graphics and photos that bring you closer to an advanced laboratory, an ice sheet in Antarctica or a space mission in orbit. You’re helping us craft other types of high-quality journalism as well: Our newsletters are carefully written, edited and curated by staffers you have or will come to know and love. Our Science Quickly podcast is based on original reporting, collaboration with editors and scientists and exacting production.Subscriptions keep this engine running so we can continue to deliver thoughtful, rigorous and independent science journalism to you. In an era of viral misinformation, this work is crucial. If you value what we do, I hope you’ll consider joining us as a subscriber