Astronomers have discovered a giant, evolving 10-sided atmospheric wave encircling Saturn’s south pole, according to findings published in Science Advances. The spinning, meandering decagon sits within one of Saturn’s powerful eastward jet streams in the icy ammonia clouds over the planet’s southern hemisphere, providing a striking geometric counterpart to the famous six-sided northern hexagon discovered by NASA’s Voyager probes in the 1980s.
Astronomers Discover 10-Sided Atmospheric Wave at Saturn’s South Pole
The research was led by Agustín Sánchez-Lavega, a planetary scientist at the University of the Basque Country in Spain. Co-authors include Amy Simon, principal investigator of the Outer Planet Atmospheres Legacy (OPAL) program at NASA’s Goddard Space Flight Center, and Michael Wong of the University of California, Berkeley, alongside other colleagues. Leigh Fletcher of the University of Leicester also contributed to the study by measuring wind speeds in the decagon using the European Southern Observatory’s Very Large Telescope in Chile.
Detection and Timeline of the Decagon
For decades, researchers had searched for a southern counterpart to Saturn’s northern hexagon. Neither images captured by NASA’s Cassini spacecraft—which orbited the ringed gas giant between 2004 and 2017—nor earlier observations showed any sign of a long-lived formation.
The breakthrough came as Saturn’s changing seasons gradually brought its south pole back into view from Earth. Ground-based observers first noticed a subtle undulating band near the south pole in 2024, and additional imagery in 2025 hinted further at the structure. By piecing together several years of data, researchers using the Hubble Space Telescope traced the pattern back to 2023, revealing that the structure had begun emerging before becoming a clearly defined decagon. Scientists suspect the phenomenon may have formed between 2017 and 2023 while the south pole was tilted away from Earth.
Characteristics and Comparison to the Northern Hexagon
Centered around 60 degrees south, the decagon appears larger and more unstable than its northern counterpart. While the northern hexagon is practically stationary, the southern decagon migrates eastward at a tame pace of 6 mph (10 kph). Meanwhile, the jet stream itself races around the planet at roughly 260 miles (420 kilometers) per hour. A single side of the newly discovered decagon already exceeds 10,000 miles (16,700 kilometers).
Observations across multiple wavelengths show that the decagon extends through multiple layers of the atmosphere rather than remaining confined to a single cloud-top level. The structure appears most pronounced near the vortex and least distinct on the opposite side of the planet.
Broader Implications for Planetary Weather
The discovery demonstrates that polygonal waves can form in both polar regions of Saturn, suggesting the planet has a propensity for geometric shapes bounded by straight lines. Although all solar system planets with atmospheres feature wave-spawning disturbances, polygonal shapes appear unique to Saturn.
Researchers are investigating what creates the decagon and whether it will eventually settle into a stable configuration or fade away. While the northern hexagon has remained visible for more than 40 years—longer than a 30-Earth-year Saturnian year—scientists currently confirm only that the decagon is still active as they continue utilizing Hubble, ground observations, James Webb Space Telescope data, and atmospheric computer models to solve the mystery.
