Powerful Stratospheric Winds On Jupiter’s Measured With ALMA For The First Time

Eddie Gonzales Jr. – MessageToEagle.com – Using the Atacama Large Millimeter/submillimeter Array (ALMA), in which the European Southern Observatory (ESO) is a partner, a team of astronomers has directly measured winds in Jupiter’s middle atmosphere for the first time.

By analyzing the aftermath of a comet collision from the 1990s, the researchers have revealed incredibly powerful winds, with speeds of up to 1450 kilometers an hour, near Jupiter’s poles. They could represent what the team have described as a “unique meteorological beast in our solar system.”

An artist’s impression of winds in Jupiter’s stratosphere near the planet’s south pole, with the blue lines representing wind speeds. These lines are superimposed on a real image of Jupiter, taken by the JunoCam imager aboard NASA’s Juno spacecraft. Jupiter’s famous bands of clouds are located in the lower atmosphere, where winds have previously been measured. But tracking winds right above this atmospheric layer, in the stratosphere, is much harder since no clouds exist there. By analysing the aftermath of a comet collision from the 1990s and using the ALMA telescope, in which ESO is a partner, researchers have been able to reveal incredibly powerful stratospheric winds, with speeds of up to 1450 kilometres an hour, near Jupiter’s poles. Credit: ESO/L. Calçada & NASA/JPL-Caltech/SwRI/MSSS

Measuring wind speeds in Jupiter’s stratosphere using cloud-tracking techniques is impossible because of the absence of clouds in this part of the atmosphere. However, astronomers used an alternative measuring aid in the form of comet Shoemaker-Levy 9, which collided with the gas giant in spectacular fashion in 1994.

This impact produced new molecules in Jupiter’s stratosphere, where they have been moving with the winds ever since.

“The most spectacular result is the presence of strong jets, with speeds of up to 400 meters per second, which are located under the aurorae near the poles,” says Thibault Cavalié of the Laboratoire d’Astrophysique de Bordeaux in France, in a press release.

These wind speeds, equivalent to about 1450 kilometers an hour, are more than twice the maximum storm speeds reached in Jupiter’s Great Red Spot and over three times the wind speed measured on Earth’s strongest tornadoes.

“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 kilometers in height,” explains co-author Bilal Benmahi, also of the Laboratoire d’Astrophysique de Bordeaux. “A vortex of this size would be a unique meteorological beast in our solar system. The new ALMA data tell us the contrary,” says Cavalié, adding that finding these strong stratospheric winds near Jupiter’s poles was a “real surprise.”

The ALMA data allowed them to measure the Doppler shift—tiny changes in the frequency of the radiation emitted by the molecules—caused by the winds in this region of the planet.

“By measuring this shift, we were able to deduce the speed of the winds much like one could deduce the speed of a passing train by the change in the frequency of the train whistle,” explains study co-author Vincent Hue, a planetary scientist at the Southwest Research Institute in the US.

In addition to the surprising polar winds, the team also used ALMA to confirm the existence of strong stratospheric winds around the planet’s equator, by directly measuring their speed, also for the first time. The jets spotted in this part of the planet have average speeds of about 600 kilometers an hour.

“These ALMA results open a new window for the study of Jupiter’s auroral regions, which was really unexpected just a few months back,” says Cavalié. “They also set the stage for similar yet more extensive measurements to be made by the JUICE mission and its Submillimetre Wave Instrument,” Greathouse adds, referring to the European Space Agency’s JUpiter ICy moons Explorer, which is expected to launch into space next year.

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Written by Eddie Gonzales Jr. – MessageToEagle.com Staff