There’s a hexagon of cloud at Saturn’s north pole. It surrounds the pole at 77 degrees north latitude, making it wider than two Earths. First discovered by Voyager in the early 1980s, it was still there in 2009, nearly 30 years later.

“The longevity of the hexagon makes this something special, given that weather on Earth lasts on the order of weeks,” said Caltech astronomer Kunio Sayanagi. “It’s a mystery on par with the strange weather conditions that give rise to the long-lived Great Red Spot of Jupiter.”

No one knows what causes the hexagon or how it has remained organized for so long. JPL atmospheric scientist Kevin Baines called it “one of the most bizarre things we’ve ever seen in the solar system.”