Saturn's South Pole Shows Off a Giant 10-Sided Cloud Pattern

Astronomers have spotted a colossal 10-sided wave pattern churning in the icy ammonia clouds above Saturn's south pole. The newly identified feature, called a decagon, appears larger and more unstable than the well-known hexagonal cloud pattern at the planet's north pole, which was first seen by NASA's Voyager spacecraft in the 1980s.

The discovery came from observations made by the Hubble Space Telescope in 2023. Earlier images of the region had shown no such structure, leading researchers to suspect the decagon formed sometime between 2017 and 2023, when Saturn's south pole was tilted away from Earth and hidden from view.

The feature is still evolving, with one side already stretching more than 10,000 miles (16,700 kilometers). The findings, published in the journal Science Advances, suggest that Saturn's unique polygonal weather patterns are not as rare as once thought.

Lead author Agustin Sanchez-Lavega of the University of the Basque Country noted that while all planets with atmospheres experience wave disturbances, only Saturn produces them in geometric shapes. The decagon sits on a jet stream, much like the hexagon, but it drifts eastward at a gentle 6 mph (10 kph), whereas the hexagon is nearly stationary.

Using the European Southern Observatory's Very Large Telescope in Chile, researchers measured winds within the decagon. Comparing the two formations at opposite poles could offer insights into the weather systems of giant gas planets, Sanchez-Lavega said.

It remains unclear whether the decagon will persist as long as the hexagon, which has been visible for over 40 years—longer than a Saturnian year of about 30 Earth years. For now, Sanchez-Lavega confirmed, "the decagon is still there."