The Mystery of Saturn’s Earth-sized Cyclone, Solved

The spinning vortex of Saturn's north polar storm resembles a deep red rose of giant proportions surrounded by green foliage in this false-color image from NASA's Cassini spacecraft. Measurements have sized the eye at a staggering 1,250 miles (2,000 kilometers) across with cloud speeds as fast as 330 miles per hour (150 meters per second). This image is among the first sunlit views of Saturn's north pole captured by Cassini's imaging cameras. When the spacecraft arrived in the Saturnian system in 2004, it was northern winter and the north pole was in darkness. Saturn's north pole was last imaged under sunlight by NASA's Voyager 2 in 1981; however, the observation geometry did not allow for detailed views of the poles. Consequently, it is not known how long this newly discovered north-polar hurricane has been active. The images were taken with the Cassini spacecraft narrow-angle camera on Nov. 27, 2012, using a combination of spectral filters sensitive to wavelengths of near-infrared light. The images filtered at 890 nanometers are projected as blue. The images filtered at 728 nanometers are projected as green, and images filtered at 752 nanometers are projected as red. In this scheme, red indicates low clouds and green indicates high ones. The view was acquired at a distance of approximately 261,000 miles (419,000 kilometers) from Saturn and at a sun-Saturn-spacecraft, or phase, angle of 94 degrees. Image scale is 1 mile (2 kilometers) per pixel. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.
The spinning vortex of Saturn’s north polar storm resembles a deep red rose of giant proportions surrounded by green foliage in this false-color image from NASA’s Cassini spacecraft. Measurements have sized the eye at a staggering 1,250 miles (2,000 kilometers) across with cloud speeds as fast as 330 miles per hour (150 meters per second).

There’s one big difference between Earth and Saturn—OK, there are a lot of big differences between Earth and Saturn, including size, chemistry, temperature, distance from the sun and number of moons (one for Earth, up to 62 for Saturn). But the difference that may be most important concerns their atmospheres: Earth has one, Saturn essentially is one, part of the solar system’s quartet of gas giants that also includes Jupiter, Uranus and Neptune.

With a vastly larger atmosphere than Earth’s, Saturn also has vastly larger storms—and none is as impressive as the huge cyclones that spin at its north pole, each as big around as the entire Earth, with winds that whip at 300 mph (483 k/h). The storms, first photographed by the Cassini spacecraft, which has been orbiting Saturn since 2004, have always been a mystery. But now, a paper published in Nature Geoscience by a team of researchers headed by planetary scientist Morgan O’Neill of MIT may explain things.

One thing O’Neill and her colleagues knew was that understanding cyclones on Earth would provide only limited help in understanding them on Saturn. The Earthly storms can’t form without a fixed surface beneath them—especially a wet, fixed surface, which provides the friction that allows winds to drag and converge and the warm water that serves as the storms’ rocket fuel.

To understand how things work on Saturn, the researchers had to develop a computer model that recreated the planet’s gassier, drier, deeper and more turbulent atmosphere. They then ran hundreds of simulations over the course of days to try to see how cyclones could form at all and why they would converge into one super storm at the top of the planet. The computer delivered the goods.

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SOURCE: TIME, Jeffrey Kluger