Unified model explains extreme jet streams on all giant planets

One of the most notable properties of our solar system's giant planets—Jupiter, Saturn, Uranus, and Neptune—is the strong winds observed around their equators. While some of these planets have eastward equatorial winds, others have a westward jet stream. For the first time, an international team of scientists led by Leiden Observatory and SRON can explain the winds on all the giant planets using one model.

The so-called rapidly rotating convection in atmospheres giant planets can play a decisive role in the movement of jet streams both east and west. This is what a team of astronomers led by postdoctoral researcher Keren Duer-Milner from the Leiden Observatory and SRON discovered. The study was published in the journal Achievements of science.

Using global circulation models, the team found that differences in atmospheric depth can cause eastward jets on Jupiter and Saturn and westward jets on Uranus and Neptune. The system experiences a so-called bifurcation: under the same conditions, the atmosphere can go into one of two stable states – equatorial jets directed east or west – establishing a direct connection between the direction of the jet and the depth of the atmosphere.

Fastest wind in the solar system

For decades, scientists have been puzzled by the mechanism that produces ultra-fast winds on the giant planets, ranging from 500 to 2,000 km/h. Jet streams are the fastest winds observed in the solar system and significantly exceed typical wind speeds on Earth.

Particularly mysterious was the fact that on Jupiter and Saturn the winds are directed to the east, while the jets on Uranus and Neptune blow to the west. It is believed that the main factors that can influence the flows on these planets are similar. Planets receive little sunlight, have a moderate internal heat source, and rotate rapidly. There are no known forces that could explain the different directions of the winds. Until now, it was believed that the different directions of jet winds were due to different mechanisms that set them in motion.

Now Duer-Milner and his colleagues have discovered that rapidly rotating convection cells at the equator can act as “conveyor belt“on the surface, controlling jet streams both east and west on different planets. Convection is a process that, through circulation, can transfer heat within an atmosphere or liquid. This is believed to be the primary process by which heat from inside gas planets is transferred to the surface.

Atmosphere throughout the galaxy

“We hoped to demonstrate that the mechanism we think is at work in the gas giants Jupiter and Saturn could also explain the equatorial jets of the ice giants Uranus and Neptune,” says Duer-Milner. “We are very excited because we have finally found a simple and elegant explanation for a complex phenomenon.” Scientists are now using measurements from the Juno spacecraft to find evidence that the proposed mechanism exists in Jupiter's atmosphere.

Duer-Milner hopes their findings can be applied to planets outside our solar system. “Understanding these winds is critical because it helps us understand the fundamental processes that govern planetary atmospheres, not just ours.” solar system but throughout the galaxy. This discovery gives us a new tool for understanding diversity planetary atmospheres and climate throughout the universe,” she says.