By This Hour Science Desk
A vast 10-sided wave has emerged around Saturn’s south pole, offering astronomers an unusual new view of the giant planet’s atmosphere and a fresh question about how its polar weather systems take shape. NASA says images from the Hubble Space Telescope reveal the evolving pattern circling the pole, the first large regular-sided jet pattern reported in Saturn’s southern hemisphere.
The geometry immediately invites comparison with Saturn’s celebrated northern polar hexagon, a feature observed for more than four decades. But the newly identified southern structure has 10 sides, not six, and the researchers describe it as distinct from its northern counterpart. Its apparent recent formation makes the finding more than a striking image: scientists may be able to follow a planetary-scale atmospheric pattern while it is still changing.
NASA said the results were published in Science Advances. The work draws together Hubble observations extending back to 2023 and ground-based images that first drew attention to an undulating band near the south pole in 2024. Observations from 2025 provided stronger indications of the decagonal form, while Hubble’s archived and newer views confirmed that the feature had been present earlier than the ground-based discovery.
A southern counterpart, but not a duplicate
Saturn’s north pole is known for a long-lived six-sided atmospheric pattern. The northern hexagon has appeared whenever astronomers have looked for it for more than 40 years, NASA said. That record set a clear expectation for researchers studying Saturn’s polar circulation: if the planet’s north-south jet-stream system is broadly symmetrical, might the southern pole contain a comparable formation?
Researchers had searched Hubble images for such a southern counterpart since 1990. Images obtained by NASA’s Cassini spacecraft during its 2004 to 2017 orbit of Saturn, however, showed no sign of a long-lived southern formation, according to NASA’s account of the research. The absence of such an indication in those observations is central to why the new feature is being treated as potentially recent rather than as a structure merely overlooked for decades.
What Hubble has now found is not a southern hexagon. It is a 10-sided wave, situated in one of Saturn’s powerful jet streams and encircling the south pole. NASA describes the pattern as giant and evolving. That combination of scale, regularity and change distinguishes it from an isolated cloud feature or a one-time atmospheric disturbance in the account supplied by the mission team.
The difference in shape also limits easy conclusions. The new wave resembles the northern hexagon sufficiently to make comparison useful, but it is not evidence that the two poles necessarily operate in the same way. The researchers say further observations and computer-model analysis will be required to establish how the decagon formed, how long it could endure and how it relates to the better-known northern pattern.
Years of images turned a hint into a defined pattern
The path to the finding began with changing visibility. As Saturn’s seasons changed, its south pole gradually returned to view from Earth. That made it possible for observers using ground-based telescopes to see the relevant region more clearly and to compare images over time.
In images contributed to the Planetary Virtual Observatory Laboratory, a site managed by the University of the Basque Country, lead study author Agustín Sánchez-Lavega and amateur astronomers Trevor Barry and Jean-Paul Oger noticed a subtle wavy band around the southern polar area in 2024. The facility accepts observations of solar-system planets submitted by observers from around the world. The 2024 images did not by themselves establish a sharply defined 10-sided structure; they pointed to a feature that merited closer scrutiny.
Ground-based imagery from 2025 made the decagon interpretation more persuasive, NASA said. Researchers then used Hubble’s observations to trace the feature further back. By assembling several years of data, they found faint indications that the structure had begun to emerge in 2023 before taking on a clearer pattern.
This chronology matters because it separates when the feature was first noticed from when the available record suggests it began to appear. Ground observers identified the subtle band in 2024, then saw stronger evidence in 2025. Hubble data, examined across years, placed signs of the formation back in 2023. None of that establishes an exact start date, nor does it show why the pattern emerged when it did. It does provide a documented sequence in which a tentative visual clue became a recognizable atmospheric structure.
Hubble’s role was not simply to add another image. NASA says the telescope can obtain sharp, high-spatial-resolution observations over full rotations of Saturn without the blurring imposed by Earth’s atmosphere. That capability allowed researchers to test the suggestion from ground-based pictures and to see the broader, repeating form around the pole.
The wave appears to extend beyond the visible clouds
The new pattern is significant not only for its outline. NASA says it appears to run through several layers of Saturn’s atmosphere, indicating that it is a vertically extended structure rather than a feature confined to one cloud level. The finding places the decagon within the planet’s atmospheric circulation, rather than describing it solely as a pattern at the top of the visible cloud deck.
Different Hubble wavelengths probe different altitudes in Saturn’s atmosphere. In the observations, the decagon’s apparent position shifts slightly depending on the wavelength used. NASA attributes that shift to the different atmospheric levels being sampled, not necessarily to a contradiction in the location of a single pattern. Taken together, the views support the conclusion that the wave is present across multiple layers.
That interpretation still leaves important boundaries on what can be claimed. The supplied account does not identify a settled mechanism that drives the wave. It does not say whether the 10-sided pattern will persist, strengthen or break down. Nor does it establish that the feature has reached a stable configuration. Describing it as vertically extended is evidence about its atmospheric reach; it is not yet a full explanation of its origin or future.
Those unanswered questions are unusually important because the researchers believe the formation may be recent. A long-established atmospheric pattern can reveal its present form while obscuring the route by which it arose. A structure that appears to be strengthening, by contrast, may give scientists a chance to observe changes over time. NASA’s researchers frame that opportunity as one of the principal scientific values of the southern decagon.
Regular monitoring gives the team a continuing record
The Hubble observations used in the study came through the Outer Planet Atmospheres Legacy, or OPAL, program. NASA says OPAL has photographed the outer planets annually for more than a decade. Its purpose is inherently comparative: repeated observations can track seasonal changes, follow short-lived storms and identify atmospheric features that evolve more slowly than a single observing campaign would reveal.
That long-running record is what allowed the team to look backward after the ground-based images raised the prospect of a southern polar pattern. In this case, annual and repeated observations did not merely document Saturn’s appearance at one moment. They supplied the temporal record needed to identify preliminary signs in 2023 and compare them with the increasingly distinct form seen later.
The approach also defines a limitation. A time series can show that a structure changes, but it needs to continue before it can determine whether the change leads to persistence. The team plans further observations of Saturn to learn whether the decagon becomes a stable, long-lived arrangement resembling the northern hexagon or continues to evolve. Hubble and NASA’s James Webb Space Telescope are both identified as tools for that work.
Computer models will also be part of the effort. NASA says researchers intend to use them alongside continued telescope observations to investigate what generated the wave and what it may reveal about atmospheric dynamics on giant planets in the solar system, including possible connections to atmospheric patterns on Earth. Those are research aims, not conclusions of the current report.
The central question is why the pattern appeared now
The most consequential uncertainty is also the most direct one: why would a large regular-sided wave appear around Saturn’s south pole now, after earlier searches and the Cassini mission found no comparable long-lived feature? The researchers have not answered that question. NASA’s account presents it as the issue that future data and modeling must address.
There is also uncertainty in the feature’s lifespan. Saturn’s northern hexagon offers a compelling point of comparison because it has remained observable over decades. Yet the southern decagon’s different number of sides and apparently emerging character argue against assuming the same fate. It may settle into a durable pattern, but the supplied evidence does not permit that prediction.
For now, the strongest conclusion is narrower and more valuable: observations from space and the ground have converged on a large 10-sided wave around Saturn’s south pole, and Hubble data indicate that it reaches through more than one atmospheric layer. The record reaches back to 2023 and shows a feature that became increasingly recognizable. Continued monitoring will determine whether Saturn has added a lasting southern landmark to its atmosphere or offered a rare glimpse of a transient planetary-scale pattern in formation.
