Sep 3, 2026

Hubble Has Spotted a Decagon Forming at Saturn's South Pole

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Saturn has just gained a new geometric shape on the map. NASA announced on September 2, 2026 that recent Hubble Space Telescope images revealed a giant 10-sided atmospheric wave circling the planet's south pole. The result, published in Science Advances, marks the first detection of a regular pattern of this kind in Saturn's southern hemisphere.

The discovery immediately invites comparison with the famous northern hexagon, observed for more than 40 years since the Voyager flybys. But this new decagon does not look like a simple copy with more sides. According to NASA and ESA, the structure appears to be strengthening, has been confirmed in Hubble data as far back as 2023, and extends through multiple layers of the atmosphere rather than sitting only in a visible cloud band.

Two Hubble views of Saturn's south pole showing the decagon-shaped atmospheric wave
Hubble revealed a 10-sided wave at Saturn's south pole, visible across images taken at different wavelengths. Image: NASA, ESA, STScI, Agustín Sánchez-Lavega, Amy Simon, Michael Wong; processing by Alyssa Pagan

The path to the announcement began outside space. Agustín Sánchez-Lavega of the University of the Basque Country and amateur observers connected to the Planetary Virtual Observatory Laboratory identified a subtle undulating band in ground-based Saturn images in 2024. Additional 2025 observations made the suspicion stronger. Hubble then acted as the judge: without the blurring of Earth's atmosphere and with enough resolution to follow full rotations of the planet, it confirmed that the shape already appeared in 2023 data.

The physical detail is what makes the story more than a curious picture. The wave is embedded in one of Saturn's powerful atmospheric jet streams, around 63 degrees south latitude, and its apparent position shifts slightly depending on the wavelength observed. That points to a vertical structure crossing different altitudes. The scientific paper describes an evolving phenomenon: vertices and sides have gained contrast over the years, the pattern drifts slowly eastward, and it may result from a dynamical instability in the jet, possibly influenced by a nearby dark vortex.

Single-filter Hubble image with the decagon labeled at Saturn's south pole
In a single filter, the decagon geometry appears more clearly; the X marks an area where Hubble did not capture data. Image: NASA, ESA, STScI, Agustín Sánchez-Lavega, Amy Simon, Michael Wong; processing by Alyssa Pagan

For anyone following space science, the importance lies in the long clock. Cassini orbited Saturn from 2004 to 2017 and saw no stable formation like this in the south. Then the planet's seasons changed: the south pole gradually became better oriented toward Earth, and Hubble's annual OPAL program gave researchers a comparable sequence of images. That patience is exactly what lets scientists separate a passing storm from atmospheric architecture in formation.

What changes now is the question. For decades, the northern hexagon looked like an almost solitary anomaly, a long-lived quirk of Saturnian weather. A southern decagon does not make the phenomenon ordinary, but it weakens the idea that there was only one special case. If both poles can organize jet streams into giant polygons, fluid models for gas giants need to explain when a wave becomes trapped, how long it survives, and why certain side counts appear.

The team wants to keep observing Saturn with Hubble and, if possible, with James Webb, while also testing numerical simulations. Nobody yet knows whether the decagon will stabilize for decades like the northern hexagon or fade as the season changes. For now, that is the fascinating part: we are not only looking at a strange shape. We are watching planetary weather happen in real time, on a world where a storm can be larger than Earth and a wave can draw geometry in the sky.

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