Astronomers using the NASA Hubble Space Telescope have discovered a newly formed 10-sided atmospheric wave, or decagon, encircling Saturn’s south pole. Published in the journal Science Advances, the findings reveal a vertically extended structure moving through multiple atmospheric layers of the gas giant, marking the first time a regular-sided jet pattern has been observed in Saturn’s southern hemisphere.
How the Decagon Formed at Saturn’s South Pole
According to researchers, the decagon sits within one of Saturn’s powerful jet streams. Unlike ephemeral cloud formations, this wave extends deep through multiple layers of the atmosphere. The structure shifts slightly in apparent position depending on the wavelength captured by Hubble, which probes varying altitudes. While Saturn’s northern pole has hosted a famous, long-lived hexagon for over 40 years, no such formation was recorded in the south by NASA’s Cassini spacecraft during its mission from 2004 to 2017. Data analyzed by the research team confirms the southern decagon began emerging recently, with subtle hints visible in Hubble observations dating back to 2023.
Ground-Based Observers and Hubble Observations
The discovery originated from collaborative ground-based imaging. Agustín Sánchez-Lavega, lead author of the study and a researcher at the University of the Basque Country in Spain, noted that amateur astronomers Trevor Barry and Jean-Paul Oger first spotted a subtle undulating band near the southern pole in 2024 images. These contributions were submitted to the Planetary Virtual Observatory Laboratory, a website managed by the University of the Basque Country. Subsequent 2025 ground-based imagery strengthened the evidence of a decagon structure, prompting researchers to pull high-resolution data from Hubble’s Outer Planet Atmospheres Legacy (OPAL) program.
Insights from Planetary Scientists
“We’ve never seen anything quite like this in Saturn’s southern hemisphere,” said Amy Simon, study co-author and OPAL principal investigator at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Simon pointed out that while the northern hexagon has persisted for decades, the southern decagon offers a rare live view of a giant atmospheric pattern actively developing. Sánchez-Lavega added that given Saturn’s symmetrical north-south jet stream system, researchers had searched for a southern counterpart to the northern hexagon in Hubble images since 1990 before finally capturing its emergence.
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