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The NASA/ESA Hubble Space Telescope has detected a giant ten-sided pattern of clouds and winds around Saturn's south pole, announced on 2 September 2026 and published in Science Advances.
The decagon is not a solid structure but a large atmospheric wave embedded in a jet stream at about 63 degrees south latitude, where winds reach roughly 400 km/h.
Its ten corners oscillate back and forth on a cycle of about 32 days — behaviour never seen in Saturn's long-known northern hexagon.
The feature was faintly visible in Hubble images from 2023 and grew sharper in 2024 and 2025, suggesting scientists are watching a polygonal wave form rather than a settled one.
The study was led by Agustín Sánchez-Lavega of the University of the Basque Country, with amateur astronomers contributing the ground-based tracking.
A fast ring of wind circling a pole can become unstable and buckle into a standing wave. Where the wave closes on itself in a whole number of bends, the jet traces a polygon — six bends give a hexagon, ten a decagon.
Simple Analogy: Like ripples running round the rim of a stirred cup and locking into a fixed pattern.
| Feature | Southern decagon | Northern hexagon |
|---|---|---|
| Sides | 10 | 6 |
| Latitude | About 63 degrees south | About 78 degrees north |
| First seen | Faintly in Hubble images from 2023 | Voyager images of 1980-81 |
| Stability | Still developing; some vertices weaker than others | Remarkably stable for over four decades |
| Corner motion | Vertices oscillate on a roughly 32-day cycle | No comparable oscillation observed |
A joint NASA-ESA optical and ultraviolet space telescope launched on 24 April 1990 aboard the Space Shuttle Discovery, orbiting above the atmosphere so its images escape the blurring that limits ground telescopes. Its annual programme of outer-planet monitoring produced this result
The United States civil space agency, established in 1958; its Goddard Space Flight Center contributed to this study and Hubble science operations
NASA's partner on Hubble and on the Cassini-Huygens mission to Saturn, established in 1975 with 22 member states
Pioneer 11 makes the first flyby of Saturn.
Voyager 1 and Voyager 2 fly past; their images reveal the northern hexagon.
Hubble Space Telescope launched, later used for annual outer-planet monitoring.
Cassini-Huygens orbits Saturn; the Huygens probe lands on Titan in January 2005 and Cassini ends with a controlled plunge into the planet.
Hubble images show a southern wave that sharpens into a decagon.
The decagon is announced; findings published in Science Advances.
NASA's Dragonfly rotorcraft is scheduled to launch for Titan, with arrival expected in 2034.
GS Paper 1 > Physical geography: atmospheric circulation. GS Paper 3 > Science and technology: space, awareness in new developments
General Awareness > Space science and current developments
A narrow band of very fast wind. Saturn's polar jets reach about 400 km/h, and it is the buckling of such a jet into a standing wave that produces the polygonal patterns.
One of the ten corners where the wave changes direction. At Saturn's south pole these corners oscillate back and forth on a roughly 32-day cycle, a motion absent from the northern hexagon.
A six-sided jet-stream pattern at about 78 degrees north, first seen in Voyager images of 1980-81 and stable for more than four decades — the benchmark against which the new decagon is measured.