MEASURING WINDS ON JUPITER
Using ALMA observations, our team discovered that the most remarkable jet (in red and blue) is aligned with Jupiter’s southern aurora (seen here in the south of Jupiter). Wind speeds were measured up to 400 meters per second (900 miles per hour).
Jupiter is famous for its distinctive red and white bands: swirling clouds of moving gas that astronomers traditionally use to track winds in Jupiter’s lower atmosphere. Astronomers have also seen, near Jupiter's poles, the vivid glows known as aurorae, which appear to be associated with strong winds in the planet’s upper atmosphere.
But until now, we have never been able to directly measure wind patterns in between these two atmospheric layers, in the stratosphere, mostly due to the lack of tracers of winds in that part of the atmosphere.
We found an alternative to this thanks to the 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.
By observing the light emitted from some of these molecules, we were very surprised to measured winds up to 1450 km/h in the stratosphere. Such wind speeds 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.
We think these winds are caused by the strong jet stream observed at higher altitudes, near the auroral region. These results from the interaction between Jupiter and its magnetic field. All these measurements set the stage for similar yet more extensive measurements to be made by the JUICE mission and its Submillimetre Wave Instrument.