Astronomers using the NASA/ESA Hubble Space Telescope have detected a giant, 10-sided atmospheric wave encircling Saturn’s south pole, ESA reported. The discovery marks the first time scientists have observed a regular polygonal jet stream pattern in the planet's southern hemisphere.
Lead author Agustín Sánchez-Lavega, a planetary scientist at the University of the Basque Country, identified the feature after amateur astronomers Trevor Barry and Jean-Paul Oger spotted an undulating band in 2024 ground-based images. Those photographs were submitted to the Planetary Virtual Observatory Laboratory, a platform managed by the university. Ground imagery captured in 2025 showed stronger evidence of the decagon pattern as Saturn's shifting seasons brought its southern polar region into view from Earth.
Hubble observations dating back to 2023 confirmed the atmospheric wave was already forming, according to the study published in Science Advances. Scientists had searched for a southern counterpart to Saturn's 40-year-old northern hexagon in Hubble data since 1990 without success. Data gathered by the Cassini spacecraft during its orbital mission from 2004 to 2017 also showed no evidence of a long-lived southern formation.
Measurements across multiple wavelengths show that the decagon sits inside a powerful jet stream and spans multiple atmospheric layers. Because different wavelengths probe distinct altitudes in Saturn's atmosphere, the wave's apparent position shifts slightly between spectral filters.
Research teams now plan to observe the wave using both Hubble and the James Webb Space Telescope to determine whether the decagon stabilizes permanently or dissipates over time. Co-author Mike Wong of the University of California, Berkeley, noted that long-term tracking under Hubble's Outer Planet Atmospheres Legacy programme remains central to documenting these evolving planetary dynamics.
