Surprise! Jupiter Has A New Red Spot
Red spots on Jupiter, photographed on Feb. 27, 2006.
Credit: Christopher Go via NASA

Backyard astronomers, grab your telescopes. Jupiter is growing a new red spot.

The official name of the new storm is "Oval BA," but "Red Jr." might be better. It's about half the size of the famous Great Red Spot and almost exactly the same color.

Oval BA first appeared in the year 2000 when three smaller spots collided and merged. Using Hubble and other telescopes, astronomers watched with great interest. A similar merger that happened centuries ago may have created the original Great Red Spot, a storm twice as wide as our planet and at least 300 years old.

Oval BA has been changing colors in recent months. It was white in November 2005, slowly turned brown in December and then red a few weeks ago.

Why red?

Curiously, no one knows precisely why the Great Red Spot itself is red. A favorite idea is that the storm dredges material from deep beneath Jupiter's cloudtops and lifts it to high altitudes where solar ultraviolet radiation--via some unknown chemical reaction--produces the familiar brick color.

"The Great Red Spot is the most powerful storm on Jupiter, indeed, in the whole solar system," said Glenn Orton, an astronomer at JPL who specializes in studies of storms on Jupiter and other giant planets.

"The top of the storm rises 8 km above surrounding clouds. It takes a powerful storm to lift material so high," Orton said.

Oval BA may have strengthened enough to do the same. Like the Great Red Spot, Red Jr. may be lifting material above the clouds where solar ultraviolet rays turn "chromophores" (color-changing compounds) red. If so, the deepening red is a sign that the storm is intensifying.

"Some of Jupiter's white ovals have appeared slightly reddish before, for example in late 1999, but not often and not for long," says John Rogers, author of the book "Jupiter: The Giant Planet," which recounts telescopic observations of Jupiter over the last 100 years.

"It will indeed be interesting to see if Oval BA becomes permanently red," Rogers said.

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