For decades, Saturn’s spinning north pole “hexagon” has mystified scientists. Now, NASA’s Hubble Space Telescope has discovered yet another enigmatic feature: a “giant” 10-sided atmospheric wave encircling Saturn’s south pole.
“This discovery marks the first time a large, regular-sided jet pattern has been observed in the planet’s southern hemisphere,” said NASA in a press release earlier this month. “The feature appears remarkably similar to Saturn’s famous hexagon at its northern pole, but is also distinctly different, suggesting scientists may be witnessing a new atmospheric phenomenon develop on the iconic gas giant.”
Before we explore the new findings published in the Science Advances journal, let’s cover some of the basics. First, Saturn is the sixth planet from the sun and the second largest in our solar system after Jupiter. It is made mostly of hydrogen and helium, it is surrounded by rings made of ice and rocks, and it is the farthest planet from Earth that can be discovered by the unaided human eye.
Jet streams refer to bands of strong wind, per the National Environmental Satellite, Data, and Information Service. According to the European Space Agency, research from the Cassini probe “suggests that eddies, or giant rotating storms, are the ‘engine’ powering Saturn's jet stream winds.”
Then, there’s that “monstrous” hexagon (in NASA’s words) that is twice the size of Earth. Cassini Visual and Infrared Mapping Spectrometer (VIMS) instrument (VIMS) scientist Kevin Baines calls it “the belly button of Saturn.”
It is actually a hurricane-like vortex with an eye 50 times larger than a typical Earth hurricane, plus a maximum wind speed about double that of the strongest cyclones on our planet. Baines explained that, unlike our Earthly hurricanes, Saturn’s belly button does not feed and water and heat. However, it does have the structure of a hurricane.
Another obvious difference from Earth storms is its hexagon shape. On Earth, jet streams don’t have such rigid patterns and symmetry, NASA said. Earth has different conditions than Saturn, such as mountains poking into its atmospheric flow.
Still, Baines said Saturn’s hexagon is “one of the biggest mysteries of the dynamics of Saturn.”
Agustín Sánchez-Lavega, a researcher at the University of the Basque Country in Spain and lead author of the new study, said scientists been searching for a counterpart to the hexagon on the south pole in Hubble images since 1990, according to the press release about the new 10-sided atmospheric wave. He explained that Saturn has a very symmetrical north-south jet stream, leading researchers to believe there might be a similar feature at the planet’s opposite pole.
“We’ve never seen anything quite like this in Saturn’s southern hemisphere,” said Amy Simon, study co-author and Hubble’s Outer Planet Atmospheres Legacy (OPAL) program principal investigator, NASA’s Goddard Space Flight Center in Greenbelt, Md., said of the 10-sided wave. “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.”
University of the Basque Country manages the Planetary Virtual Observatory Laboratory, accepts ground-based images of solar system planets contributed by observers all over the world. In 2024 Sánchez-Lavega and amateur astronomers Trevor Barry and Jean-Paul Oger noticed a subtle undulating band along the southern pole in some of those images. Then, additional 2025 imagery taken from the ground “hinted even more strongly toward this decagon structure.”
“That’s when the Hubble observations come into the picture,” said NASA. “Hubble’s view from space offers unmatched image sharpness and spatial resolution over full rotations of Saturn, without smearing by Earth’s atmosphere.”
According to NASA, several years of Hubble observations dating back to 2023 revealed “subtle hints of the structure beginning to emerge before it became a clearly defined pattern.” These observations were possible because of Saturn’s changing seasons, the space agency added.
Atmospheres are full of waves, according to a 2016 piece published by the Planetary Society. In fact, the hexagon on Saturn itself is caused by waves. What sets the south pole wave in one of Saturn’s powerful jet streams apart is that it “extends through multiple layers of the atmosphere, indicating it is not just a cloud-level feature, but a vertically extended atmospheric structure,” said NASA.
“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?”
More study is needed, Simon and the other authors said. Data from the Hubble and NASA’s James Webb Space Telescope, as well as analysis of computer models, could help researchers understand “how the decagon formed, how long it may last, and how it compares to the long-lived hexagon in the north,” NASA explained.
Going forward, the team plans to continue observing Saturn. They want to see if the decagon settles into a long-lived feature like the “belly button” or if it continues to evolve.
“Future observations also could help scientists determine what drives the wave, what it reveals about the atmospheric dynamics of giant planets throughout the solar system, and how they may relate to those we see here on Earth,” NASA added.
