Saturn’s north pole has a mysterious hexagon, but Saturn’s south pole has an interesting feature, too. It’s south polar vortex, not unlike the vortices at Earth’s north and south poles, but of monstrous proportions. The dark ‘eye’ of this feature is some 5,000 miles (8,000 km) across, or about two thirds the diameter of the entire Earth. The image above is from the Cassini spacecraft in 2008. Where earlier images had shown towering clouds around the edge of this vortex, making scientists think the inside of vortex was mostly transparent, this image revealed a multitude of features deeper within Saturn’s atmosphere. ESA said recently:
Clouds are produced by convection – warm, rising gases in the atmosphere of Saturn. As they reach higher, and therefore colder, layers of the atmosphere, the gases condense and appear as clouds. At the 10 o’clock position, a stream of upwelling gas has created its own smaller vortex inside the larger one.
The image below is from Cassini in 2008, too. It’s a wider view of the vortex.
Cassini actually captured the scene above from an oblique angle, some 56 degrees below the plane of Saturn’s rings. That’s one reason the image above looks so different from the image at top, which is the view directly over Saturn’s south pole. ESA explained:
Towering eye-walls of cloud are a distinguishing feature of hurricanes on Earth. Like earthly hurricanes, the eye of this storm is composed of warmer gas than the surroundings. However, whereas hurricanes are powered by warm water and move across the surface of our planet, this vortex has no liquid ocean at its base and remains fixed to Saturn’s south pole.
Round, swirling vortices are part of the general circulation in the atmospheres of all four giant, outer planets, and Cassini has spied many mobile ones rolling through Saturn’s clouds at other latitudes. While vortices are often informally referred to as storms, scientists generally reserve that term for bright, short-lived bursts of convection that punch though the clouds, often accompanied by lightning.
Bottom line: Cassini spacecraft images of the south polar vortex of Saturn.
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.