"We're inclined to say that it's like a hurricane," said Ulyana Dyudina, a planetary scientist at the California Institute of Technology in Pasadena and co-author of a new study on the storm. "The similarities are remarkable, especially the shadow cast by the eye wall-just like in a Category 5 hurricane on Earth," said Timothy Dowling, who directs the Comparative Planetology Laboratory at the University of Louisville.
A Category 5 is the most powerful type of storm on the Saffir-Simpson scale. The storm also spins the same direction (clockwise) that Saturn spins on its axis-another hurricane-like trait-and its winds scream at some 350 miles an hour (550 kilometers an hour). Since 2003, the tempest doesn't appear to have changed in any way detectable by NASA's Cassini spacecraft.
Scientists aren't sure how long the storm has been raging, or how long it will last. It may be a seasonal occurrence. But because of Saturn's long orbit, the planet's year lasts 30 Earth years. The hurricane has been fall in Saturn's southern hemisphere since observations began five years ago.
Though Saturn's tempest is quite similar to hurricanes on Earth, it has its own unique features. "It's polar and it's stationary, so it doesn't move around like hurricanes on Earth," said study co-author Dyudina.
Because hurricanes draw their energy from heat evaporation over warm ocean waters, they fade away on land. "On Earth, hurricanes usually drift toward the pole and then crash into land," said Dyudina. But, Saturn has no land to interfere with the storm's power source. It also has no liquid oceans, so the storm gathers energy in a different way than Earth's hurricanes.
Scientists hope that the storm can shed light on Saturn's past-specifically, how the planet cooled. Earth's hurricanes use the evaporation of water and clouds to transfer heat away from the planet's surface.
"If we see similar things on Saturn (and the vortex) is a mechanism for how the heat gets through the clouds to space, that would raise interesting questions about the mechanisms of cooling of this planet," she said.