Saturn has somehow become the only planet we know with giant geometric weather patterns at both poles.
Hubble observations have revealed an enormous 10-sided atmospheric wave, a decagon, around Saturn’s south pole, while its famous north-polar hexagon has been known for more than four decades.
This isn’t a solid structure or a perfectly drawn shape sitting on the clouds, bitch. The decagon is a huge wave embedded inside one of Saturn’s powerful jet streams, centered around 63° south latitude. Hubble observations at different wavelengths show that the pattern extends through multiple atmospheric layers, meaning it has real vertical structure rather than being just a surface cloud pattern.
And the scale is ridiculous. Researchers report that a single side of the decagon can stretch more than 16,700 kilometers, making one side alone wider than Earth. Unlike Saturn’s remarkably stable northern hexagon, the southern decagon appears more dynamic and slowly moves eastward at roughly 10 km/h.
Scientists found hints of the structure in Hubble observations from 2023, with the shape becoming increasingly obvious in later observations. That raises the fascinating possibility that we’re actually watching a giant planetary weather pattern develop in real time. Hubble’s OPAL program has been monitoring Saturn and the other outer planets annually, making this kind of long-term comparison possible.
Why Saturn produces polygon-shaped atmospheric waves remains an open question. Other planets have powerful jets, vortices and atmospheric waves, but Saturn appears uniquely good at turning them into enormous geometric patterns. Scientists now have two very different natural laboratories, a long-lived hexagon in the north and an evolving decagon in the south, to figure out why.
Source: NASA/ESA Hubble Space Telescope, STScI, Science Advances.