At Saturn’s north pole, a jet stream traces a shape that looks drawn with a ruler.
The feature is an enormous atmospheric current, not a solid hexagon. NASA’s Cassini spacecraft revealed its six-sided outline in detail: the jet stream is roughly 30,000 kilometers across, with winds around 500 kilometers per hour, circling a vortex at the pole. Scientists have seen the pattern persist for decades, across observations by different spacecraft.
A rotating-fluid experiment in a laboratory can make similar polygonal shapes, helping explain how orderly forms can emerge in moving air or water. Yet Saturn’s exact hexagon is still puzzling. Researchers do not know why the north has this long-lived shape while the south does not, or precisely what keeps it stable.