Hundred-year storms? That's how long they last on Saturn

The largest storm in the solar system, a 10,000-mile-wide anticyclone called the Great Red Spot, has decorated Jupiter's surface for hundreds of years.
A new study now shows that Saturn—though much blander and less colorful than Jupiter—also has long-lasting megastorms with impacts deep in the that persist for centuries.

The study was conducted by astronomers from the University of California, Berkeley, and the University of Michigan, Ann Arbor, who looked at from the planet, which come from below the surface, and found long-term disruptions in the distribution of ammonia gas.
The study was published today in the journal Science Advances.

Megastorms occur approximately every 20 to 30 years on Saturn and are similar to hurricanes on Earth, although significantly larger. But unlike Earth's hurricanes, no one knows what causes megastorms in Saturn's atmosphere, which is composed mainly of hydrogen and helium with traces of methane, water and ammonia.

"Understanding the mechanisms of the largest storms in the puts the theory of hurricanes into a broader cosmic context, challenging our current knowledge and pushing the boundaries of terrestrial meteorology," said lead author Cheng Li, a former 51 Peg b Fellow at UC Berkeley who is now an assistant professor at the University of Michigan.

In the optical, Saturn's banded atmosphere appears to smoothly shift from color to color. But seen here in radio light — VLA data overlays a Cassini image of Saturn — the distinct nature of the bands is apparent. Scientists used VLA data to better understand ammonia in the gas giant's atmosphere and learned that megastorms transport the ammonia from the upper to the lower atmosphere.  Credit: S. Dagnello (NRAO/AUI/NSF), I. de Pater et al (UC Berkeley)
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Radio image of Saturn taken with the VLA in May 2015, with the brighter radio emissions from Saturn and its rings subtracted to enhance the contrast in the fainter radio emissions between the various latitudinal bands in the atmosphere. Since ammonia blocks radio waves, the bright features indicate areas where ammonia is depleted and the VLA could see deeper in the atmosphere. The broad bright band at northern latitudes is the aftermath of the 2010 storm on Saturn, which apparently depleted ammonia gas just below the ammonia-ice cloud, which is what we see with the naked eye. Credit: R. J. Sault and I. de Pater
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A huge storm dominates the rather featureless surface of Saturn in an image taken by the Cassini spacecraft on Feb. 25, 2011, about 12 weeks after the powerful storm was first detected in the planet's northern hemisphere. The megastorm is seen overtaking itself as it encircles the entire planet. Astronomers have found deep in the atmosphere the aftereffects of megastorms that occurred hundreds of years ago. The dark stripes are the shadows of Saturn's rings. Credit: NASA/JPL/Space Science Institute
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