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Space

Jupiter's Great Red Spot is making its atmosphere hotter

By New Scientist and Press Association

27 July 2016

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Art by Dillon Yothers with Luke Moore

A mysterious hot spot in Jupiter’s upper atmosphere is caused by the planet’s most famous feature.

The Great Red Spot – a massive storm system three times wider than the Earth – is heating the atmosphere high above it to temperatures hundreds of degrees warmer than anywhere else on the planet.

Scientists made the discovery after observing Jupiter’s infrared light emissions, which allowed them to make temperature measurements.

At high altitude, some 800 kilometres above the planet’s visible cloud tops, temperatures were much greater than would be expected as a result of warming by the distant sun.

“We could see almost immediately that our maximum temperatures at high altitudes were above the Great Red Spot far below – a weird coincidence, or a major clue?” says James O’Donoghue at Boston University.

The Great Red Spot was first officially recorded in 1831, but may have been the same “permanent spot” identified by Italian astronomer Giovanni Cassini in 1665.

It consists of a hurricane-like system of gases swirling at speeds of up to 685 kilometres per hour. Because of its size, the winds can take six days to complete one revolution.

“The Great Red Spot is a terrific source of energy to heat the upper atmosphere at Jupiter,” says Luke Moore, also at Boston University. “But we had no prior evidence of its actual effects upon observed temperatures at high altitudes.”

O’Donoghue, Moore and their colleagues concluded that the Great Red Spot produces “acoustic waves” of energy – waves that vibrate in the direction of their travel, like sound waves. A similar effect on a much smaller scale has been observed over the Andes mountains on Earth.

These heat Jupiter’s upper atmosphere when they crash into a different sort of wave, called gravity waves, which move like a plucked guitar string.

Journal reference: Nature, DOI: 10.1038/nature18940

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