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July 11, 2011 / Dave Gorham

Turbulent Saturn: The Great White Spot

The Great White Spot is not something your dry cleaner can help you with. But if you’re up on your spots, like the Great White Spot and the Great Red Spot, then you know all you really need to do is watch. Watch the Great White Spot. Sounds easy. You’ll need a fairly powerful telescope and perhaps a link to images from the Cassini spacecraft.

Saturn's Great White Spot is easy to see. Image: NASA / JPL

If you’re guessing the Great White Spot is not of this Earth, you would be correct. First noticed in December of 2010, the Great White Spot is the name given to a storm in Saturn’s northern hemisphere. And over the past seven months, the storm has been growing. Even today, the storm is “going like crazy,” according to Linda Spilker of the NASA Jet Propulsion Laboratory in Pasadena, California.

Saturn is not typically a stormy tempest like its neighbor, Jupiter. Known to be home to many violent outbreaks, Jupiter’s storms rage across the planet’s hemispheres in perpetuity. In fact, the Great Red Dot can be found on Jupiter without even knowing what you’re looking for. And it’s been raging for centuries. On the other hand, since 1876 astronomers have noted only five previous storms of such magnitude on Saturn.

What’s the outlook for the Great White Spot? I’m not sure astronomers have a clear idea. Though storms have been identified within Saturn’s southern hemisphere (10 storms noted since 2004), northern hemisphere storms are rare. One thing’s for certain, it’s like no storm on Earth! Measured by the Cassini craft, electrical activity has been calculated to be 10,000 times greater than lightning on Earth, counting up to ten lightning strikes per second in just that one storm. Then again, the storm stretches almost entirely around the planet.

Storms such as this are cyclical and seem to occur about every 27-28 years, on average, as the northern hemisphere of Saturn rotates toward the Sun. Previous cyclical spots have been noted in 1990, 1960, 1933, 1903 and 1876.

As a planet, Saturn is more calm than Jupiter. Both planets are classified as "gas giants," and both are comprised mainly of hydrogen with a rocky core. Image: Wikipedia

Fortunately, Cassini is onsite. Launched in 1997, Cassini entered Saturn’s orbit in 2004 and returns detailed images to Earth. Though Cassini’s Saturn mission has been extended twice, the craft is expected to enter Saturn’s atmosphere in 2017 which will bring the mission to its end.

Artist's conception of the Cassini spacecraft orbiting Saturn. Image: Wikipedia








Saturn is the sixth rock from the Sun (Earth is #3, Jupiter #5). Image: Wikipedia








Saturn is the second largest planet in the solar system (Jupiter is the largest). This image shows the relative size of Saturn compared to Earth. The Great White Spot would swallow our planet, the fifth largest in the solar system. Image: Wikipedia and NASA

The Great White Spot, as viewed by NASA. Recorded February 26 in false-color mosaic format. Image: NASA's Astronomy Picture of the Day (APOD).






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