Hubble Space Telescope images captured on 2025-08-29 show a 10-sided atmospheric jet, called a decagon, circling Saturn's south pole. ^[1] Scientists discovered a decagon-shaped wave in Saturn's southern atmosphere, a 10-sided phenomenon that appears to have formed recently over the planet's south pole. ^[2] Agustín Sánchez-Lavega, lead author of the study, said there is no single model to explain the wave, and it may result from an instability in the jet stream or a wave forced from deeper levels of Saturn's atmosphere. ^[3] NASA's Cassini mission, which studied Saturn for more than 13 years, never observed a similar polygonal jet in the planet's southern hemisphere. ^[4] Older imaging from the Hubble Space Telescope and NASA's Cassini probe showed no such structure, and Hubble photographs from 2023 first showed the wave taking shape, becoming fully developed in images taken in August and September 2025. ^[5] Planetary scientist Agustín Sánchez-Lavega of the University of the Basque Country in Bilbao, Spain, said on 2025-09-02 that the decagon's discovery suggests the north pole's hexagon is not as extraordinary as previously thought. ^[6] The decagon was first apparent in Hubble images from autumn 2024, and astronomers later confirmed it was visible in observations from as early as 2023, though less defined. ^[7] The wave is described in a study published on 2026-09-02 in the journal Science Advances, led by Agustín Sánchez-Lavega, a physicist at Spain's Bilbao School of Engineering. ^[8]