Cassini mapped One-eyed Polar storm on Saturn

NASA's Cassini spacecraft has mapped something that has been never seen before on another planet, a hurricane like colossal, swirling storm, with a well-developed eye on Saturn's South Pole.

This is for the first time that a truly hurricane-like storm, ringed by towering clouds, has been detected on a planet other than Earth. The "hurricane" spans a dark area inside a thick, brighter ring of clouds, and is about 8,000 kilometers wide, or two thirds the diameter of Earth.

The images captured by Cassini's camera over a three-hour period, show winds around Saturn's South Pole blowing clockwise at 550 kilometers per hour.

After analyzing the images, sent by Cassini spacecraft, which is in orbit around Saturn exploring the planet and its moons, Andrew Ingersoll, a member of Cassini's imaging team at the California Institute of Technology, Pasadena said, "It looks like a hurricane, but it doesn't behave like a hurricane."

According to US space agency, NASA, at the center of the cauldron of storms spinning around the South Pole is the South Pole itself, which exactly appears to be the eye of this vast polar storm system.

As in a hurricane on Earth, the south polar "eye" is comparatively clear of clouds and is surrounded by a wall of towering clouds that cast shadows into the center. However, while morphologically similar, it is still ambiguous if this vortex operates in the same manner as a terrestrial hurricane.

To find out the actual status of the phenomena, Ingersoll said that "we're going to focus on the eye of this storm and find out why it's there."

The images also showed the shadow cast by a ring of spiral clouds surrounding the pole, and two towering arms of clouds extending from the central ring. These spiral clouds called eye-wall clouds, 30 to 75 kilometers above those in the center of the storm, are two to five times taller than the clouds of thunderstorms and hurricanes on Earth.

These eye-wall clouds are a distinctive feature of hurricanes on Earth. When moist air flows across an ocean's surface and then ascends vertically the clouds release rain around the eye of the storm, where the air is descending rapidly.

However, it is not certain whether such moist convection is driving Saturn's storm, still the dark "eye" at the pole, the eye-wall clouds and the spiral arms together signify a hurricane-like system.

This type of storm has never before been seen on any planet other than Earth. Even Jupiter's Great Red Spot, much larger than Saturn's polar storm, has no eye or eye-wall and is comparatively quiet at the center. That storm is large enough to fit two or three Earths, and has lasted at least 340 years and spins with a period of around six days.

There are some crucial differences between terrestrial hurricanes and Saturn's storm. For instance, it seems to be locked to its pole and does not drift like hurricanes on Earth and, as Saturn is a gaseous planet, the storm is not formed with an ocean underneath.

"The clear skies over the eye appear to extend down to a level about twice as deep as the usual cloud level observed on Saturn," said Kevin Baines of NASA's jet propulsion laboratory in California. "This gives us the deepest view yet into Saturn over a wide range of wavelengths, and reveals a mysterious set of dark clouds at the bottom of the eye."

Launched in 1997, the Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency, sent to explore Saturn and some of its moons.