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Boffins get first measurements of Jupiter's stratospheric storms that show 'unique beast' dwarfing Earth's issues

Even though its Great Red Spot appears to be shrinking, the storm behind it will probably live on

Terrifying winds rip across Jupiter’s poles reaching speeds of up to 400 metres per second, or 900 miles an hour, three times as fast as the most powerful tornadoes on Earth, according to the first direct measurements of the gas giant's turbulent stratosphere.

Astronomers refer to these particularly powerful bursts as jets. “Our detection indicates that these jets could behave like a giant vortex with a diameter of up to four times that of Earth, and some 900 kilometres in height," said Bilal Benmahi, a researcher at the University of Bordeaux and co-author of a paper [PDF] published in Astronomy & Astrophysics detailing the findings.

"A vortex of this size would be a unique meteorological beast in our Solar System," Thibault Cavalié, a research scientist at Bordeaux Observatory and co-author of the paper, added this week.

Volatile gusts of winds are a well-known feature on the gas giant; massive cyclones like its Great Red Spot are visible. Scientists have previously studied Jupiter's upper atmosphere, though the latest observations made using Atacama Large Millimeter/submillimeter Array focused on its middle atmosphere.

The polar bursts are faster at 400 metres per second, and the gales around its equator are slower at about 167 metres per second (600 kilometres per hour, 370 miles per hour.)

The wind speeds were measured by tracking hydrogen cyanide molecules generated by the impact of Comet Shoemaker–Levy 9 in 1994. Using the telescope’s spectrometers, the team of researchers could detect tiny changes in the frequency of radiation the molecules emitted. These changes were the result of the winds.

Just as how you can calculate how fast, say, an ambulance is speeding from the pitch of its siren, thanks to the Doppler effect, scientists can calculate the speed of Jupiter’s gusts from the frequency of light emitted from hydrogen cyanide molecules.

Measuring Jupiter’s winds accurately is important for understanding the planet and its moons as a whole, Vincent Hue, a research scientist at the Southwest Research Institute and co-author of the paper, explained to The Register. “Jupiter and its [satellites] constantly exchange materials, like dust, molecules, and charged particles. [It] has an important influence over the system because of its important magnetic field, it is important to characterize it as best as we can.”

Studying its storms and cyclones also give astronomers a better idea of the planet’s magnetic field. “The winds we detected near Jupiter’s aurora are caused by the interaction between Jupiter’s magnetosphere and its ionosphere through a complex coupling. Initially, Jupiter and its magnetosphere exchange angular momentum which creates these very high altitude polar jets. At lower altitudes, in the stratosphere, the winds we have detected are actually a signature of these high altitude polar jets,” he added.

The next step is trying to figure out how these winds moderate the planet’s overall climate and how they might impact the chemical composition of its atmosphere.

What has been happening to the Great Red Spot?

Jupiter’s most famous storm, the Great Red Spot, has been shrinking, though a new study suggests it'll be around for a while yet.

Us Earthlings have been observing the Red Spot for more than 150 years, and it is certainly shrinking, down from 40,000 kilometres (24,850 miles) in 1879 to about 15,000 kilometres (9,320 miles) according to today's estimates. A study, published in the American Geophysical Union journal, however, reckons the storm will prevail.

The gas-giant sky watchers believe a series of smaller storms crashing into its most iconic feature has caused bits of its red clouds to disperse, making the spot look smaller. But although these opposing winds, or anticyclones, chip away at its clouds, the larger storm powering the spot swallows up these anticyclones and actually gains energy from them.

“The intense vorticity of the [Great Red Spot], together with its larger size and depth compared to the interacting vortices, guarantees its long lifetime,” said Agustín Sánchez-Lavega, lead author of the paper and a professor of applied physics at the Basque Country University. The rotational power of the cyclone might drop, but the overall energy of the storm increases.

The disruptions in the Great Red Spot are superficial, the researchers argued. The storm may appear to be getting weaker yet the depth of the winds hasn’t decreased. ®


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