Hubble captures storm on the equator of Saturn

Giant white spot is "a burp" on planet

A giant white spot hurtling around the equator of Saturn and recently photographed by the Hubble Space Telescope may be the result of a rare "burp" of gas from the ringed planet's interior into its frigid upper atmosphere, scientists said Tuesday.

The rapidly changing spot - 6,000 miles wide, hundreds of miles thick and propelled by an eastbound jet stream at more than 1,000 mph - shows similarities to Jupiter's Great Red Spot, a massive, hurricane-type storm that has raged uninterrupted for at least 300 years.

But the white spot on Saturn, which appeared in late September, may dissipate within months as it continues to spread out along the equator, said Andrew Ingersoll, a professor at the California Institute of Technology in Pasadena, Calif.

"The last time Saturn did anything of this magnitude was in 1933," he said, "and that one only hung around for a month or two."

The spot's evolution is still uncertain, but scientists know that Saturn, second-largest of the solar system's nine planets, is fluid to its core, a bubbling cauldron of hydrogen, helium and trace compounds.

"If you like, Saturn burped" and sent a huge geyser of gases high into the atmosphere, Ingersoll said. The white spot is "probably a high-altitude cloud of ammonia ice crystals" that formed as the gases cooled and spread in the fierce winds.

Although the intervals between "burps" are a mystery, Ingersoll suggested that seasonal heating effects on the planet during its 30-year orbit of the sun could be the cause.

Although Hubble's main mirror contains a flaw that blurs its vision, bright objects such as planets can be effectively photographed and the data enhanced by computer to equal or surpass that from the biggest telescopes on Earth.