NASA’s Hubble Space Telescope has discovered an enormous 10-sided atmospheric wave pattern encircling Saturn’s south pole, marking the first time a large, regular-sided jet pattern has been observed in the planet’s southern hemisphere. The decagon—a geometric shape with 10 sides and 10 angles—sits within one of Saturn’s powerful jet streams and extends through multiple layers of the atmosphere, according to a study published Wednesday in Science Advances.
The discovery emerged from years of Hubble observations dating back to 2023, when researchers first spotted subtle hints of the structure beginning to form. By 2025, Hubble images captured in August and September showed the wave fully developed and clearly defined. Ground-based observers had also noticed an undulating band along the south pole in 2024 imagery, contributing to the detection.
Agustín Sánchez-Lavega, lead author of the study and a researcher at the University of the Basque Country in Spain, noted that scientists have been searching for a southern counterpart to Saturn’s famous north pole hexagon in Hubble images since 1990, but earlier observations—including data from NASA’s Cassini spacecraft, which orbited Saturn from 2004 to 2017—showed no sign of such a long-lived formation.
The feature appears remarkably similar to Saturn’s iconic hexagon at its north pole but differs in critical ways. The north pole hexagon has remained stable for over 40 years, its six sides and points consistently dark. By contrast, the new decagon shows fuzzy, variable edges across its features, suggesting it is unstable or still evolving. Amy Simon, study co-author and principal investigator of Hubble’s Outer Planet Atmospheres Legacy (OPAL) program at NASA’s Goddard Space Flight Center, described the discovery as offering “a rare opportunity to watch a giant atmospheric pattern develop.”
Why the decagon formed remains a mystery. Sánchez-Lavega said the cause could be the result of disturbances in gas flows, possibly linked to a nearby storm with a high-pressure center similar to Jupiter’s Great Red Spot. He added, “There is no single model to explain it. It may be the result of an instability in the jet stream in which it is situated, or a wave forced from deeper levels of the atmosphere.”
The decagon’s future remains uncertain. If seasonal changes over Saturn’s southern polar region play a role in its formation, Sánchez-Lavega predicted the structure may become more pronounced in coming years, potentially peaking around 2032 when solar insolation reaches its maximum at the decagon’s latitude. However, the wave’s unstable appearance suggests it could continue to evolve or eventually dissipate, unlike the robust northern hexagon.
Scientists plan to continue observing Saturn using Hubble and NASA’s James Webb Space Telescope, along with computer modeling, to determine whether the decagon will settle into a stable configuration like its northern counterpart or remain a transient phenomenon. Mike Wong, study co-author at the University of California, Berkeley, emphasized the value of sustained observation: “A lot of the discoveries we see coming from OPAL are not just based on one observation, but on years and years of data. Regular observations over time are enabling a lot of new findings.”
Sources
- NASA Science — official announcement of Hubble’s discovery, publication details, and quotes from Amy Simon and Mike Wong
- Phys.org — comprehensive details on the discovery timeline, Sánchez-Lavega’s background, and explanation of how the pattern was detected
- Scientific American — expert commentary from Agustín Sánchez-Lavega on the decagon’s formation, comparison to the hexagon, and future observations
- AP News — confirmation of the 10-sided wave discovery and details on Saturn’s south pole observations
- Science Advances — peer-reviewed publication: Agustín Sánchez-Lavega et al., “A decagon wave around Saturn’s south pole,” Science Advances 12, no. 36 (2026)
