New model explains extreme jet streams on all giant planets
For the first time, an international team of scientists led by Leiden Observatory and SRON can explain the extreme jet streams observed around the equators of all the giant planets using a single model.
Some of these planets have an eastward wind around the equator, while others have a westward jet stream. Their research has been published in the journal Science Advances.
So-called rapidly rotating convection in the atmospheres of the giant planets may play a crucial role in driving both eastward and westward jet streams. This has been discovered by a team of astronomers led by postdoctoral researcher Keren Duer-Milner from Leiden Observatory and SRON. The research has been published in the journal Science Advances.
Using global circulation models, the team found that the eastward jet streams on Jupiter and Saturn and the westward jet streams on Uranus and Neptune can be explained by differences in their atmospheric depth. The atmospheres exhibit what’s called a bifurcation: under nearly identical conditions, the atmosphere can settle into one of two stable states. This results in either an eastward or a westward equatorial jet stream. For the first time, the researchers have found a direct link between the direction of the jet streams and atmospheric depth.
Fastest Winds in the Solar System
For decades, scientists have been searching for the mechanism that drives the super-fast winds on the giant planets. These jet streams, with speeds between 500 and 2000 km/h, are the fastest atmospheric flows observed in the solar system—far exceeding the typical wind speeds on Earth.
The fact that Jupiter and Saturn have eastward jet streams, while Uranus and Neptune have westward ones, has long been puzzling. The main factors influencing the flows on these planets are thought to be quite similar: they receive little sunlight, have moderate internal heat sources, and rotate rapidly. No known forces could account for the difference in wind direction. Until now, scientists assumed that the opposite wind directions must be caused by different driving mechanisms.
Now, Duer-Milner and colleagues have discovered that rapidly rotating convection cells near the equator can act as a kind of ‘conveyor belt’ on the surface. These can drive the jet streams on different planets either eastward or westward. Convection is the process by which heat is transported within an atmosphere or fluid through circulation. It is thought to be the main process that carries heat from the interior of gas giants to their outer layers.
Atmospheres Across the Universe
‘We hoped to show that the mechanism we believe operates in the gas giants Jupiter and Saturn could also explain the equatorial jet streams on the ice giants Uranus and Neptune,’ says Duer-Milner. ‘We’re excited because we’ve finally found a simple, elegant explanation for a complex phenomenon.’ The scientists are now using measurements from the Juno spacecraft to look for evidence that the proposed mechanism exists in Jupiter’s atmosphere.
Duer-Milner hopes that their results can also be applied to planets outside our solar system. ‘Understanding these flows is crucial because it helps us grasp the fundamental processes that govern planetary atmospheres—not only in our solar system but throughout the Milky Way. This discovery gives us a new tool to understand the diversity of planetary atmospheres and climates across the universe,’ she says.