November 13, 2006—Just as people from North Carolina to the Yucatán Peninsula are heaving sighs of relief over this year's dwindling—and relatively light—Atlantic hurricane season, scientists have discovered the biggest cyclone ever seen, several worlds away.

NASA's Cassini spacecraft recently captured these images (taken in visible light [left] and infrared) of a massive hurricane-like storm at Saturn's south pole, the first such phenomenon ever spotted on another planet.

Much like an Earth-bound hurricane, the storm features a well-developed central eye and columns of towering clouds. But this cyclone could not only dwarf any Earthly storm, it could also virtually swallow the Earth itself, measuring a monstrous 5,000 miles (8,000 kilometers) across.

The cyclone is swirling over the pole at 350 miles (550 kilometers) an hour, whipping up Saturn's ammonia clouds at speeds much higher than the winds inside Jupiter's Great Red Spot.

Despite its familiar-looking eye, however, Saturn's enormous storm probably isn't a true hurricane, scientists say. Hurricanes typically drift over the warm ocean waters from which they draw their energy; the newfound storm appears to be fixed in place, and Saturn has no liquid seas.

News of the unusual discovery is stirring up a tempest among scientists, who are studying the storm to find out how it formed.

"It looks like a hurricane, but it doesn't behave like a hurricane," said Andrew Ingersoll, a member of Cassini's imaging team at the California Institute of Technology in Pasadena.

"Whatever it is, we're going to focus on the eye of this storm and find out why it's there."

—Blake de Pastino

• More Photos in the News
• Today's 15 Most Read Stories
• Free Email Newsletter: Focus on Photography