New Delhi, Sept. 4 -- Scientists have discovered an enormous 10-sided wave pattern in the icy ammonia clouds over Saturn's south pole.

The spinning, meandering decagon appears to be even bigger and more unstable than the hexagon of clouds around Saturn's north pole that was spied by NASA's twin Voyagers in the 1980s, the Spanish-led team reported Wednesday.

This new jet stream formation popped up in the Hubble Space Telescope's sights in 2023 after earlier observations came up empty. The researchers suspect the bizarre atmospheric phenomenon may have formed between 2017 and 2023, when Saturn's south pole was tilted away from Earth and therefore out of view.

It could still be evolving, with a single side of the decagon already exceeding...