Great Red Spot makes Jupiter hot, study suggests

Scientists havelong wondered why Jupiter's upper atmosphere has temperaturessimilar to those of Earth, even though the biggest planet in thesolar system is five times farther away from the sun.

The answer may be The Great Red Spot, an enormous storm bigenough to swallow three Earths that has been raging on Jupiterfor at least three centuries, a study showed on Wednesday.

Using an infrared telescope at Hawaii's Mauna KeaObservatory, scientists discovered that the upper atmosphere
above the Great Red Spot the largest storm in the solar systemis hundreds of degrees hotter than anywhere else on theplanet.

It could be a coincidence or a major clue, said BostonUniversity physicist James O'Donoghue, lead scientist of the
study published in the journal Nature.

The storm spans 22,000 kilometresby12,000 kilometres(13,670 miles by 7,456 miles) and is located in Jupiter's lower atmosphere. The topof its clouds reach altitudes of about 50 kilometres(31 miles).

By a process of elimination, the newly found hot spot mustbe heated from below, the study concluded.

Heat transfer method unknown

The finding provides a strong link between Jupiter's upperand lower atmosphere, though the exact process by which heat istransferred remains unknown. The most-likely energy source isacoustic waves that provide heat from below, the study said.

Scientists also are unsure why the storm is brick red, norwhy it has changed color over time. In a 1900 report in the
Seattle Post-Intelligencer, scientists described the oval stormas salmon pink. Recent images from the Hubble Space Telescopeshow it has become orange tinged and more circular.

Like a hurricane on Earth, the Spot's center is relativelycalm, but farther out winds reach 430 kilometres per hourto680 kilometres per hour (270 mph to 425 mph). Because there is no land on Jupiter, which is madealmost entirely of hydrogen and helium, the storm can never makelandfall and dissipate.

"The Great Red Spot is like a wheel that's wedged betweentwo conveyor belts running in opposite directions," said
planetary scientist Glenn Orton, with NASA's Jet PropulsionLaboratory in Pasadena, Calif.

"One is adding momentum to it at the top, and another isadding momentum at the bottom. Together, they feed the vortexand essentially keep it alive."

But the storm may not be alive much longer. It has beenshrinking for the last 100 years, Orton said.

More information is expected from NASA's Juno spacecraft,which arrived at Jupiter on July 4.

• Space rock smashing into Jupiter captured by amateur astronomers