Mysterious polar weather on Jupiter and Saturn could be key to understanding their insides

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Scientists may finally understand why Jupiter and Saturn have very different weather conditions at their poles, despite having similar sizes and compositions. This discovery could help researchers probe deep into the interior of these giant gas planets.

Observations of both solar system the gas giants revealed that JupiterThe north pole hosts a central polar vortex surrounded by eight smaller vortices, while Saturn has a single massive, strangely hexagonal, atmospheric vortex above its north pole.

By performing complex simulations of these types of gas giant vortices, the team behind this research discovered that the difference between a single vortex configuration and a multi-vortex model depended on the “hardness” of the vortex base, that is, the weight of the gas in that region (the softer the gas, the lighter it is). This “hardness” is linked to the interior composition of the gas giant.

“Our study shows that depending on the interior properties and smoothness of the vortex bottom will influence the type of fluid pattern you see on the surface,” said research team member Wanying Kang of the Massachusetts Institute of Technology (MIT). said in a statement. “I don’t think anyone has made this connection between the configuration of surface fluids and the interior properties of these planets. One possible scenario could be that Saturn has a harder bottom than Jupiter.”

Sweeter than Saturn?

Kang and his colleagues were inspired to carry out their simulations after viewing images of Jupiter captured by the Juno spacecraft, which has been orbiting the largest planet in the solar system since 2016, and by the images of Saturn delivered by Cassini more than 13 years of observations before being deliberately plunged into the ringed planet at the end of its mission in 2017.

Juno images have revealed the immense scale of Jupiter’s polar storms, which measure about 4,800 kilometers across. For context, that’s about half the width of Earth. Cassini’s observations of Saturn, meanwhile, have shown that its single hexagonal vortex measures a staggering 18,000 miles (29,000 kilometers) wide.

Astronomers are not sure why there is such a discrepancy in size between the vortices of the two planets. “People have spent a lot of time deciphering the differences between Jupiter and Saturn,” said team leader and MIT scientist Jiaru Shi. “The planets are about the same size and are both made mostly of hydrogen and helium. It’s unclear why their polar vortices are so different.”

To answer this question, the team developed a 2D model of how the vortices at the poles of gas giants like Saturn and Jupiter would evolve over time, applying it to a range of different scenarios. This included changing characteristics such as the size of the planets, the speed of their rotation, their internal heating and the hardness of the rotating fluid in their vortices.

After ensuring that the fluid in these vortices flowed in random patterns, the scientists were ready to determine how the fluid evolved under specific conditions. This led to the discovery that a single mechanism could determine whether a single vortex or multiple vortices developed: the gentler the rotating gas at the bottom of the vortex, the smaller that vortex. This allows the formation of multiple vortices, as seen at the poles of Jupiter.

If the team is correct, this implies that Jupiter is made of softer, and therefore lighter, gas, while Saturn appears to be made of heavier gaseous material.

“What we see from the surface, the fluid pattern on Jupiter and Saturn, can tell us something about the interior, like the smoothness of the bottom, and that’s important because perhaps beneath Saturn’s surface, the interior is more enriched in metals and contains more condensable materials, allowing it to provide stronger stratification than Jupiter,” Shi concluded. “This would add to our understanding of these gas giants.”

The team’s research has been accepted for publication in the journal Proceedings of the National Academy of Sciences.