One of the most bizarre weather patterns in the solar system has been photographed at Saturn, where astronomers have spotted a huge, six-sided feature circling the north pole.

Rather than the normally sinuous cloud structures seen on all planets that have atmospheres, this thing is a hexagon.

The honeycomb feature has been seen before. NASA's Voyager 1 and 2 spacecraft imaged it more than two decades ago. Now, having spotted it with the Cassini spacecraft, scientists conclude it is a long-lasting oddity.

"This is a very strange feature, lying in a precise geometric fashion with six nearly equally straight sides," Kevin Baines, atmospheric expert and member of Cassini's visual and infrared mapping spectrometer team at NASA's Jet Propulsion Laboratory, said Tuesday in an image advisory. "We've never seen anything like this on any other planet. Indeed, Saturn's thick atmosphere, where circularly shaped waves and convective cells dominate, is perhaps the last place you'd expect to see such a six-sided geometric figure, yet there it is."

The hexagon is nearly 15,000 miles (25,000 kilometers) across. Nearly four Earths could fit inside it. The thermal imagery shows that the hexagon extends about 60 miles (100 kilometers) down into the clouds.

At Saturn's south pole, Cassini recently spotted a freaky eyelike feature that resembles a hurricane.

"It's amazing to see such striking differences on opposite ends of Saturn's poles," said Bob Brown, team leader of the Cassini visual and infrared mapping spectrometer at the University of Arizona. "At the south pole we have what appears to be a hurricane with a giant eye, and at the north pole of Saturn we have this geometric feature, which is completely different."