Hubble images ten-sided storm at Saturn’s south pole

New Hubble images show Saturn’s south pole looking jagged rather than round: A ten-sided storm encircles the polar region. The space telescope provided the final confirmation and the best images yet of a structure first spotted by Agustín Sánchez-Lavega of the University of the Basque Country in Bilbao in an amateur observation.

NASA describes the decagon as an atmospheric wave. It sits in a powerful jet stream and extends across different layers of Saturn’s atmosphere — an indication that it is probably not simply a cloud formation. Exactly how such waves take on an angular shape remains unclear, as does the question of why this pattern formed now.

The comparison with the north pole makes the observation particularly interesting. The famous hexagon was discovered more than 40 years ago and has been visible for decades. The decagon, by contrast, only formed from 2023 onward. A similar pattern occurs in Earth’s jet streams, but obstacles at the surface prevent comparable stability there. Saturn lacks such obstacles, which is why at least the hexagon can persist for decades or even centuries.

The decisive clue came from the Planetary Virtual Observatory and Laboratory program at the university in Bilbao. People who do not work professionally in astronomy can also submit observations there. Sánchez-Lavega and two amateur astronomers initially found a barely perceptible, wave-shaped band along the south pole. A year later, it was more clearly visible, but only Hubble could capture the entire structure from Earth orbit.

Specifically, the discovery shows that amateur observations can provide the first clue to a difficult-to-see phenomenon. The research team plans to continue monitoring the storm: The key questions now are whether the decagon will stabilize and how it formed. Its cause and possible lifespan remain unknown.