Astronomers Discover Mysterious 10-Sided Cloud Structure at Saturn’s South Pole
Astronomers have discovered a giant and unusual 10-sided atmospheric structure at Saturn’s south pole, adding a new mystery to the weather system of the Solar System’s second-largest planet.
The feature, known as a decagon, was detected through observations from the NASA/ESA Hubble Space Telescope. Scientists say the structure is a large, evolving atmospheric wave embedded within one of Saturn’s powerful jet streams and extends through multiple layers of the planet’s atmosphere.
The discovery is particularly striking because Saturn is already famous for another geometric atmospheric phenomenon: the long-known six-sided hexagon at its north pole. The newly observed southern structure, however, has 10 sides, suggesting that Saturn’s two polar regions may be shaped by more complex atmospheric processes than scientists previously understood.
What Did Astronomers Discover on Saturn?
The newly identified feature is not a solid structure or an artificial object. It is a massive atmospheric wave pattern formed within Saturn’s clouds and winds.
NASA describes it as a giant, evolving 10-sided wave encircling the planet’s south pole. Observations collected over several years suggest that subtle signs of the structure were visible from 2023 before it became a more clearly defined pattern.
The decagon is centred around approximately 63 degrees south latitude and appears within one of Saturn’s powerful jet streams. Different observations at different wavelengths allow scientists to study the feature at different atmospheric altitudes, revealing that it is not simply a pattern on the visible cloud tops.
That makes the discovery especially important. Scientists are effectively observing a three-dimensional atmospheric phenomenon rather than an ordinary cloud formation.
Why Is Saturn's 10-Sided Structure So Unusual?
Planetary atmospheres are full of waves, storms and jet streams. Earth, Jupiter, Neptune and other planets all have complex weather systems.
What makes Saturn unusual is its ability to produce large, organised polygonal patterns.
Saturn's north pole has been home to a famous hexagonal jet-stream pattern for decades. The hexagon has persisted for an extraordinarily long period, surviving for more than one Saturnian year—roughly 30 Earth years.
Until now, however, scientists had not identified a similar large regular-sided pattern in Saturn's southern hemisphere.
The new discovery changes that picture.
But there is an important difference: the southern pattern is a decagon rather than another hexagon. It also appears to be evolving, which could mean astronomers are witnessing a relatively new atmospheric phenomenon rather than a structure that has already reached long-term stability.
Hubble Observations Reveal a Developing Atmospheric Phenomenon
The discovery became possible as Saturn's southern hemisphere became increasingly visible from Earth.
Researchers combined observations dating back to 2023 as part of Hubble's Outer Planet Atmospheres Legacy (OPAL) programme, which has monitored the outer planets over many years. The observations indicate that the pattern has become increasingly distinct over time.
Additional observations from ground-based telescopes and infrared measurements have helped scientists examine the thermal structure of the region and study how wind speeds change with altitude.
This multi-layered approach matters because Saturn does not have a solid surface where researchers can directly observe weather patterns in the same way meteorologists study storms on Earth.
Instead, scientists must use different wavelengths of light and infrared observations to understand what is happening inside the planet's deep atmosphere.
How Does the Southern Decagon Compare With Saturn's Famous Hexagon?
The discovery naturally raises comparisons with Saturn's north-polar hexagon.
Both features are associated with powerful atmospheric jet streams and demonstrate how rapidly moving gases can organise themselves into surprisingly geometric shapes. But the southern decagon is not simply a copy of the northern hexagon.
NASA and ESA describe the southern feature as similar in appearance but distinctly different, potentially indicating a new atmospheric phenomenon.
The difference in shape could provide scientists with valuable clues.
A polygonal atmospheric wave depends on factors such as:
- Wind speed and direction
- Atmospheric depth
- Temperature differences
- Changes in wind speed at different altitudes
- The interaction between jet streams and planetary rotation
Even small differences in these conditions can potentially produce very different atmospheric patterns.
That means the contrast between a six-sided northern structure and a 10-sided southern structure may help researchers test and improve models of atmospheric dynamics on giant planets.
Why Saturn's South Pole Is Becoming a Major Research Target
Saturn's atmosphere remains one of the most fascinating weather laboratories in the Solar System.
The planet rotates rapidly and contains powerful jet streams, enormous storms and atmospheric layers that interact in ways that are still not fully understood. Unlike Earth, Saturn's atmosphere is dominated by gases and extends deep below the visible cloud layers.
The newly discovered decagon provides scientists with an opportunity to watch a large-scale atmospheric structure as it develops.
Researchers do not yet have a complete explanation for why the structure has 10 sides or whether it will eventually stabilise, change shape or disappear. That uncertainty is one of the most scientifically valuable aspects of the discovery.
Instead of studying only a long-established atmospheric feature, scientists may be able to monitor an evolving one over time.
The findings were published in the journal Science Advances, while NASA and ESA released new Hubble observations of the phenomenon on September 2, 2026.
What Happens Next?
The next major question is whether Saturn's decagon will become a permanent feature of the planet's atmosphere.
Continued observations could reveal whether the pattern strengthens, weakens or transforms into another shape. Scientists will also compare future observations across different wavelengths to better understand how the structure behaves at different atmospheric levels.
Ground-based telescopes and future space-based observations could further improve measurements of Saturn's temperature and wind patterns.
The discovery may also help researchers studying other giant planets. Jupiter, for example, has its own complex polar storms, while atmospheric waves and jet streams exist throughout the Solar System.
Understanding why Saturn can create such remarkably geometric structures could therefore improve broader models of planetary weather.
A New Mystery in Saturn's Atmosphere
The discovery of a 10-sided atmospheric wave at Saturn's south pole is more than an unusual image from space.
It gives scientists a rare opportunity to study a large-scale planetary weather pattern that appears to be evolving in real time. Saturn's famous northern hexagon has puzzled researchers for decades, and the newly observed southern decagon adds another layer to that mystery.
For now, scientists do not have a final explanation for why the structure has formed with 10 distinct sides. What is confirmed is that the feature is associated with Saturn's powerful atmospheric circulation and extends across multiple layers of the planet's atmosphere.
As astronomers continue monitoring Saturn, the mysterious decagon could reveal new clues about how giant planets generate some of the most extraordinary weather patterns in the Solar System.
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