Saturn’s New Decagon: Hubble Reveals a Ten‑Sided Wave at the South Pole

For decades we’ve marveled at Saturn’s iconic six‑sided hexagon, a stable jet‑stream swirl perched over its north pole. Now, the Hubble Space Telescope has thrown a fresh curveball into the mix: a massive, ten‑sided atmospheric wave – a “decagon” – hugging the planet’s south pole.

The feature sits roughly at 63° S latitude, right inside one of Saturn’s most powerful jet streams. It isn’t just a superficial cloud pattern, either. By peering at the planet in different wavelengths, scientists saw the wave threading through several atmospheric layers, hinting that it’s a deep‑seated dynamical structure.

What makes this discovery especially thrilling is that the decagon appears to be changing before our eyes. Early Hubble images from 2023 showed a faint, wavy band near the southern pole. By 2024, ground‑based observers noticed a subtle undulation, and in 2025 the pattern had sharpened into a clear ten‑sided shape. In other words, we may be watching it grow and solidify in real time.

Finding a regular‑sided jet pattern in the southern hemisphere is a first. The Voyager missions first spotted the northern hexagon back in the early ’80s, and the Cassini orbiter, which lingered around Saturn for over a decade, never saw a comparable structure down south. The decagon finally fills that missing piece of the puzzle.

How did researchers pin it down? They dug through years of data collected under NASA’s Outer Planet Atmospheres Legacy (OPAL) programme, stitching together Hubble snapshots with observations from Earth‑based telescopes. The combined view gave them enough detail to trace the wave’s edges and confirm that it indeed forms a decagon rather than a random swirl.

Scientists are still scratching their heads about the decagon’s origin. Is it a nascent feature that could someday become as stable as the northern hexagon, or will it dissolve back into the surrounding chaos? And what does its evolution tell us about the interplay between jet streams and atmospheric waves on gas giants?

Answering those questions will require continued monitoring, but the payoff could be big. A better grasp of Saturn’s weather systems may illuminate the atmospheric dynamics of other giant planets – even exoplanets that orbit distant stars.

Until then, Saturn has added another geometric mystery to its already flamboyant skies, and astronomers are thrilled to have caught the shape in the act of forming.