Saturn now has a 10-sided storm: Hubble spots a rare decagon

New images from NASA’s Hubble Space Telescope show something odd at Saturn’s south pole: a decagon. That gives Saturn polygon-shaped weather systems at both poles.

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NASA says the feature was first reported in 2023, and the newer Hubble images bring it into sharper focus. What shows up is a huge 10-sided atmospheric wave, with each side stretching more than 10,000 miles (16,700 km). It’s drifting east at about 6 mph (10 km/h), and NASA thinks it may have formed sometime between 2017 and 2023. If that timing holds, the south-polar decagon is a recent arrival, and probably a less stable counterpart to Saturn’s north-polar hexagon.

That northern hexagon has a much longer track record. Voyager spotted it in the 1980s, and Cassini saw it later on. It spans about 20,000 miles (30,000 km), its winds reach nearly 300 mph (500 km/h), and it’s kept its shape for decades.

For people who follow planetary weather, this is the part that stands out. The finding hints that Saturn’s polygonal waves may be broader and more symmetrical than scientists had assumed. It also gives a clean side-by-side comparison with Jupiter’s polar cyclones, and with rotating-fluid lab experiments where geometric patterns show up on their own.

The latest Hubble observations are up on NASA’s website.

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