Astronomers Discover 10-Sided Polygon in Saturn's Atmosphere
A decagon-shaped cloud formation has been detected near Saturn's south pole, joining a famous hexagon at the north pole.
What happened
Astronomers using the Hubble Space Telescope discovered a 10-sided polygonal atmospheric structure (decagon) near Saturn's south pole. The formation was first detected in ground-based observations, including from amateur astronomers, and became clearly visible in Hubble images from 2023; by 2025 its vertices had become well-defined. Each side of the decagon measures approximately 16,800 kilometers. A jet stream near the feature reaches speeds of 116 meters per second (260 mph), while the decagon pattern itself moves at only 2.5 meters per second. The discovery was published in Science Advances and represents the first long-lasting polygonal structure found at Saturn's south pole, complementing the hexagon observed at the north pole for the past 44 years.
Context
Saturn's atmosphere is composed entirely of clouds and gases with no solid surface; these geometric patterns are atmospheric phenomena rather than physical structures. The leading hypothesis is that atmospheric waves are confined by powerful jet streams, similar to ocean waves bounded by a beach, with the wavelengths determined by planetary rotation and wind patterns—a current that circles the planet six times could produce a hexagon, while one circulating ten times produces a decagon. The recent visibility of the southern hemisphere and improved observational technology have enabled detection of this feature after decades of searching for a southern counterpart to the famous northern hexagon. Understanding these formations bears on fundamental questions about planetary atmospheric dynamics.
What's disputed
The mechanism of polygon formation remains uncertain. The exact depth of these structures, the lifespan of the new decagon, whether its appearance is seasonal, and what triggered its formation are all unknown. Scientists plan continued observations with Hubble and the James Webb Space Telescope and advanced atmospheric modeling to address these questions.