Saturn’s south pole has drawn itself a decagon

One would think a planet made entirely of weather would have the decency to look like weather. Saturn has spent forty years wearing a hexagon at the north pole instead, and has now produced a ten-sided figure at the south.

The finding

Images from the Hubble Space Telescope show a large, evolving ten-sided atmospheric wave around Saturn’s south pole, published on 2 September 2026 in Science Advances. The work is led by Agustín Sánchez-Lavega of the University of the Basque Country, with the observations gathered under NASA’s Outer Planet Atmospheres Legacy programme.

Not a copy of the hexagon

The northern hexagon has been seen every time anyone has looked for it in more than forty years, and it has stayed much the same. The decagon has not. Amy Simon of NASA’s Goddard Space Flight Center, the OPAL principal investigator: «This feature is different — it appears to be strengthening.»

A structure that is strengthening is a great deal more interesting than a structure that is merely large. It means the thing can be watched forming, which nobody has managed with the hexagon, discovered long after it settled.

What makes a corner

The wave sits inside a polar jet: a ring of very fast wind that, when disturbed, will not wander freely but settles into a whole number of lobes. Ten lobes give ten straight edges. The structure runs through several layers of atmosphere rather than sitting in the cloud tops, which is what distinguishes a wave in the wind from a pattern in the haze.

The awkward question

Simon asks it herself: «why did it suddenly form now when we haven’t seen one before?» Saturn’s year runs to nearly thirty of ours, so the honest answer may be that the southern hemisphere has simply not been watched carefully for long enough at this point in its season.