Saturn is famous for many things: its spectacular rings, enormous size, and powerful storms. But now, scientists have discovered something completely unexpected at the planet’s south pole—a giant atmospheric wave forming a striking 10-sided shape.
Recent observations from NASA’s Hubble Space Telescope have revealed a huge, evolving atmospheric pattern known as a decagon around Saturn’s south pole. The discovery is particularly exciting because Saturn already has a famous geometric atmospheric feature at its north pole: a long-lasting six-sided jet-stream pattern known as the northern hexagon.
However, the newly discovered southern structure is not simply a copy of the northern hexagon. It appears to be developing and strengthening over time, giving scientists a rare opportunity to watch a giant atmospheric pattern form on another planet.
The findings have been published in the journal Science Advances.
A Strange Pattern Appears at Saturn’s South Pole
Saturn’s atmosphere is constantly moving. Powerful winds, jet streams, storms, and temperature differences create complex patterns that can change over time.
For decades, scientists have known about Saturn’s northern hexagon. This enormous six-sided atmospheric structure has remained remarkably stable since it was first observed by spacecraft and telescopes.
Scientists have long wondered whether a similar structure could exist around Saturn’s south pole.
Now, they may finally have an answer.
The newly detected feature is a large, undulating wave embedded within Saturn’s southern jet stream. Instead of six sides, however, the pattern appears to have approximately 10 sides, giving it the appearance of a giant decagon.
Even more surprising is that scientists did not simply discover an old structure that had been hidden from view. Evidence suggests that the feature was beginning to emerge relatively recently.
“We've never seen anything quite like this in Saturn's southern hemisphere,” said Amy Simon, study co-author and principal investigator of NASA's Outer Planet Atmospheres Legacy (OPAL) program.
Unlike the northern hexagon, which has remained visible for decades, the southern structure appears to be strengthening and evolving.
That makes it scientifically valuable.
How Did Scientists Find It?
The discovery was the result of years of observations rather than a single photograph.
Saturn takes about 29 Earth years to orbit the Sun. Because of this long orbital period, its seasons change slowly. As Saturn's southern hemisphere gradually became more visible from Earth, astronomers were able to study its south polar region in greater detail.
The first clues came from observations made by astronomers using ground-based telescopes.
Agustín Sánchez-Lavega, the lead author of the study from the University of the Basque Country in Spain, and amateur astronomers Trevor Barry and Jean-Paul Oger noticed something unusual in images of Saturn taken in 2024.
The images showed a subtle, wavy band around the planet's south pole.
At first, it was difficult to determine exactly what the feature was. But additional observations made from Earth in 2025 provided stronger evidence that the waves were forming a large, regular-sided pattern.
Then researchers turned to Hubble.
Hubble Reveals the Hidden Structure
NASA's Hubble Space Telescope has a major advantage over telescopes on Earth: it observes Saturn from above Earth's atmosphere.
Earth's atmosphere can distort astronomical images, making it difficult to see small or subtle details. Hubble avoids this problem and can produce extremely sharp images of Saturn.
Researchers examined Hubble observations collected through NASA's Outer Planet Atmospheres Legacy (OPAL) program.
OPAL has been observing the outer planets—including Jupiter, Saturn, Uranus, and Neptune—on a regular basis for more than a decade.
When scientists went back through Hubble's Saturn observations, they found evidence that the southern structure was already present as far back as 2023.
This was an important discovery.
It meant that astronomers were not looking at a completely established atmospheric feature. Instead, they were seeing what appears to be a structure developing over time.
Sánchez-Lavega noted that researchers had been searching for a southern counterpart to Saturn's northern hexagon for decades. Even observations from NASA's Cassini spacecraft, which explored Saturn from 2004 to 2017, did not reveal evidence of a long-lived southern structure like this.
A Wave That Reaches Through Saturn's Atmosphere
One of the most interesting aspects of the discovery is that the decagon does not appear to be simply a pattern painted across Saturn's visible clouds.
The structure exists within one of Saturn's powerful jet streams and appears to extend through multiple layers of the atmosphere.
This suggests that the feature may have significant vertical structure.
Hubble can observe Saturn at different wavelengths, and each wavelength can provide information about different atmospheric altitudes. Researchers found that the apparent position of the decagonal pattern changes slightly depending on the wavelength being observed.
That variation could provide important clues about how the structure extends through Saturn's atmosphere.
In other words, scientists may be observing something much deeper and more complex than an ordinary cloud formation.
Why Is Saturn's Northern Hexagon So Different?
The northern hexagon is one of the most extraordinary atmospheric structures in the solar system.
It is a massive six-sided jet-stream pattern surrounding Saturn's north pole. Unlike ordinary storms that appear and disappear, the hexagon has remained remarkably stable for more than 40 years of observations.
The new southern decagon is different.
Instead of appearing to have existed for decades, the evidence suggests that it has emerged and strengthened in recent years.
Scientists therefore have a fascinating natural experiment.
They can compare two enormous atmospheric patterns on the same planet:
North pole: a long-lived, stable hexagon.
South pole: a recently emerging, evolving decagon.
Understanding why the two poles behave differently could reveal important information about Saturn's atmosphere.
What Could Have Created the Decagon?
Scientists do not yet have a definitive explanation.
Saturn's atmosphere contains powerful jet streams, and these high-speed winds can interact with one another in complicated ways. Under certain conditions, waves can develop within these atmospheric currents and produce large-scale geometric patterns.
But why this particular pattern appeared now remains an open question.
Amy Simon described the timing as one of the most intriguing aspects of the discovery.
Scientists want to understand why Saturn apparently developed this enormous southern pattern when no comparable long-lived structure had previously been detected.
Computer simulations could be particularly useful.
By modeling Saturn's atmospheric winds, temperatures, pressure, and seasonal changes, researchers may be able to reproduce the decagon and determine what physical processes could have created it.
A Discovery Made Possible by Years of Patience
Perhaps the biggest lesson from this discovery is the importance of long-term observation.
If scientists had examined Saturn only once, they might have missed the early stages of the structure completely.
Instead, Hubble's repeated observations allowed researchers to compare Saturn's atmosphere across multiple years.
This is exactly what NASA's OPAL program was designed to accomplish.
Rather than taking isolated snapshots of the outer planets, OPAL creates a long-term record of their changing atmospheres. This allows scientists to track storms, seasonal changes, atmospheric waves, and other features that develop slowly.
Mike Wong, a study co-author from the University of California, Berkeley, emphasized that many OPAL discoveries become possible only after years of accumulated observations.
The southern decagon is a perfect example.
Saturn's Atmospheric Mystery Is Just Beginning
The discovery raises more questions than it answers.
Will the decagon continue to strengthen?
Will it eventually become stable?
Could it disappear after several years?
Will its shape change?
And why does Saturn have a long-lasting hexagon in the north but an apparently younger decagon in the south?
Scientists plan to continue monitoring the feature with Hubble. Future observations from NASA's James Webb Space Telescope could also provide additional information about Saturn's atmosphere at different wavelengths.
Researchers will combine these observations with computer models to investigate how the pattern formed and how long it might survive.
The discovery also has implications beyond Saturn.
Giant planets throughout the solar system have powerful atmospheres, fast-moving jet streams, and enormous storms. Studying Saturn's unusual atmospheric geometry could help scientists better understand how planetary atmospheres behave—not only on distant worlds, but also the fundamental atmospheric dynamics that shape weather and climate systems.
For now, Saturn has given scientists another spectacular mystery.
For more than four decades, its north pole has displayed a famous six-sided pattern.
Now, its south pole appears to be developing something entirely different: a giant, evolving 10-sided atmospheric wave.
And because astronomers are watching it as it changes, they may have a rare chance to witness the birth and evolution of a planetary phenomenon unlike anything seen before.
Reference:
- Agustín Sánchez-Lavega et al.
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