NASA's Cassini spacecraft spent three hours on Oct

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Hurricane-Like Storm Churning on Saturn

Irene Klotz

Discovery News

10 Nov 2006

Nov. 10, 2006 — Saturn has cooked up a sizeable storm that is the first in the solar system besides Earth to feature a hurricane-like eye and well-formed towers of clouds.

Though smaller than the famed Great Red Spot churning away on Saturn's giant neighbor, Jupiter, the Saturn storm is still formidable. It sprawls for about two-thirds the diameter of Earth across Saturn's southern pole.

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

NASA's Cassini spacecraft spent three hours on Oct. 11 observing the beast and clocked its winds at 350 mph — twice as strong as Hurricane Katrina was at its peak. The spacecraft also imaged a shadow cast by clouds stacked above and ringed around the south pole, as well as two spiral arms of clouds protruding from the central ring.

Scientists estimate the tower of clouds spans 20- to 45 miles above the clouds in the center. That's between two and five times taller than the clouds that surround the eye of a hurricane on Earth.

The Saturn storm can grow much taller because the planet's hydrogen-helium atmosphere is much less dense than Earth's at comparable pressures.

Also, unlike hurricanes on Earth, the storm is not moving around, but appears locked at Saturn's south pole. And with a temperature of around minus 270 degrees Fahrenheit, there is no ocean, nor warm tropical water to pump its strength.

At the base of the eye, scientists can discern, but not explain, dark clouds. They do know Saturn's south pole is warmer than the rest of the planet.

"The winds decrease with height and the atmosphere is sinking, compressing and heating over the [planet's] south pole," said Richard Achterberg of NASA's Goddard Spaceflight Center in Greenbelt, Md.

Additional observations are planned as the seasons change on Saturn and the south pole transitions from summer to fall.

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