Astronomers have finally measured the speed of the stratospheric winds near Jupiter’s south pole. These air currents move at 1,450 kilometers (900 miles) per hour – twice as fast as the winds in Jupiter’s Great Red Spot, and almost four times faster than the fastest wind speed ever recorded on Earth.
As reported in Astronomy & Astrophysics, this measurement required the Atacama Large Millimeter/submillimeter Array (ALMA), one of the most sophisticated observatories on the planet. But this alone wasn’t enough. The observations were possible thanks to a serendipitous event: a comet colliding with Jupiter.
Back in 1994, comet Shoemaker-Levy 9 slammed into the gas giant. The event released molecules into the Jovian atmosphere that persist until today. Researchers were able to track those molecules and measure how fast they move. The stratosphere of Jupiter is cloudless, so without these molecules, researchers would have not been able to measures the winds.
The team found that the polar jets are much faster than the stratospheric winds at the equator, where they are about 600 kilometers an hour. The observations reveal the incredible extent and depth that the stratospheric jet reaches at the pole.
"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," co-author Bilal Benmahi, from the Laboratoire d'Astrophysique de Bordeaux, said in a statement.
"A vortex of this size would be a unique meteorological beast in our Solar System," added lead author Thibault Cavalié also from the Laboratoire d'Astrophysique de Bordeaux.
This study shows that there is a lot that can be learned about Jupiter from Earth. One of the most exciting things was that it took only 30 minutes of observation time from ALMA to get these results – this is a very short time when it comes to astrophysical observations.
"The high levels of detail we achieved in this short time really demonstrate the power of the ALMA observations," says Thomas Greathouse, a scientist at the Southwest Research Institute in the US and co-author of the study. "It is astounding to me to see the first direct measurement of these winds."
The European Space Agency's JUpiter ICy moons Explorer (JUICE) will be equipped with a submillimeter light instrument that will be able to do these observations up close. It is expected to launch next year and will reach Jupiter in 2029.