Decagon on Saturn’s South Pole, Formation, Movement, Significance

NASA’s Hubble Space Telescope has detected a giant 10-sided pattern of clouds and winds around Saturn’s south pole, known as the Decagon on Saturn’s South Pole. Scientists have identified it as a large atmospheric wave that is still evolving.

The discovery was led by Agustín Sánchez-Lavega of the University of the Basque Country, and the findings were published in Science Advances.

What is the Decagon on Saturn’s South?

The decagon is a large, 10-sided wave in Saturn’s atmosphere near its south pole. It is not a solid structure or a shape on the planet’s surface.

Saturn’s atmosphere has very strong winds that flow around its poles. In some places, these winds can form large waves. Under certain conditions, these waves can develop into unusual shapes. The newly observed southern wave has taken on a roughly 10-sided shape.

• The decagon is located around 63° south latitude, close to Saturn’s south pole.
• It is embedded in a powerful jet stream, where winds can reach about 400 km/h.
• Hubble observed the decagon at different heights in Saturn’s atmosphere, helping scientists study how the wave extends through its cloud layers.
• The feature was already visible in Hubble images from 2023 and became clearer and more pronounced in observations made in 2024 and 2025.

Saturn has a similar but much older atmospheric feature at its north pole. Known as the northern hexagon, it is a six-sided pattern formed by a fast-moving jet stream around the north pole. Scientists have observed this hexagonal pattern for more than 40 years.

The newly observed southern decagon is different because it appears to be more recent and still changing, while the northern hexagon has remained remarkably stable for decades.

What Makes Saturn’s Decagon Unique?

The unusual part of the discovery is not just that the southern wave has 10 sides. Scientists are particularly interested in how the shape moves and changes.

• The 10 corners of the decagon, called vertices, move back and forth in an oscillating pattern that repeats roughly every 32 days. This type of movement has not been observed in Saturn’s northern hexagon.
• Although the surrounding jet stream can reach about 400 km/h, the decagon itself moves at about 10 km/h relative to Saturn’s rotation.
• The 10 sides are not equally clear. Some vertices are weaker than others, suggesting that the structure may still be developing and could be less stable than the northern hexagon.
• Observations using different wavelengths of light show changes at different heights in Saturn’s atmosphere, helping scientists study the structure of the wave.

The feature was also tracked with the help of amateur astronomers, whose ground-based observations helped scientists follow changes in its shape and movement.

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Significance of Decagon on Saturn’s South Pole

The decagon is important because it allows scientists to study a large atmospheric feature while it is still evolving.

• Studying the decagon can improve our understanding of jet streams, winds and atmospheric waves on giant planets.
• Comparing the southern decagon with the long-lived northern hexagon may help explain why Saturn’s two poles develop different atmospheric patterns.
• The observations can be used to test computer models that try to explain how such unusual polygon-shaped waves form.
• Continued observations will show whether the decagon eventually becomes a stable feature like the northern hexagon or continues to change.

The discovery therefore provides a new opportunity to understand the dynamic atmosphere of Saturn, one of the Solar System’s giant planets.