The swirling hurricanes in the turbulent atmosphere of the gas planet Jupiter look beautiful. Oceanographer Lia Siegelman was struck by something other than the beauty of the swirls. “It reminded me of the images of the turbulent ocean around Antarctica that I was examining at the time,” she says.
That observation led to a study in which Siegelman, of the University of California, and colleagues now provide the first evidence that Jupiter’s giant hurricanes are driven by the same kind of convection currents that create ocean vortices tens of times smaller on Earth. In Jupiter’s atmosphere it’s about gas flows and in the ocean about water, but from a physics perspective these are both ‘liquids’ that you can describe with the same principles of fluid dynamics, Siegelman explains in an email. Her results appeared last week in Nature Physics.
In the atmosphere of Jupiter, the largest planet in our solar system, thousands of kilometers thick, hurricanes from hundreds to thousands of kilometers in size rage with wind speeds of more than 250 kilometers per hour. At Jupiter’s north pole you will find eight of these gigantic hurricanes and at the south pole five. And they don’t just blow over. The hurricanes at the poles have been raging since they were first captured by the Juno spacecraft in 2016. How they form is still unknown, but by mapping the movements of Jupiter’s ammonia-rich clouds, Siegelman and colleagues have now shown how they are powered.
The researchers analyzed a series of infrared images from Juno that captured the eight hurricanes at Jupiter’s north pole. The infrared images, with a resolution of about ten kilometers per pixel, show the temperature of the cloud cover. In hot spots, there are thin, low-hanging clouds that allow you to see deeper into Jupiter’s hot atmosphere. Thick, high clouds cover that hot atmosphere, making it look colder there.
Up and sideways
By juxtaposing infrared images taken by Juno in quick succession, the researchers were able to track both the upward and sideways movement of the clouds. For example, they saw how fast and in which direction the hurricanes and neighboring vortices whiz around and grow.
“We saw that the hurricanes are driven by moist convection currents,” Siegelman says. Warm air with a low density rises from the deep atmosphere. Cooler air, with a higher density, sinks downwards. This creates turbulent vortices in the ammonia clouds. This provides the hurricanes with energy. The suspicion that Jupiter’s gigantic hurricanes are propelled in this way is not new. The idea has been around for some time and is supported by computer simulations. But the oceanographers’ research provides evidence for the first time.
Siegelman continues her investigation of the swirling gas giant and looks forward to new images of Juno. “Jupiter and its rich turbulence are fascinating.”
A version of this article also appeared in NRC Handelsblad on 15 January 2022
A version of this article also appeared in NRC on the morning of January 15, 2022