NASA's Juno space probe has revealed for the first time that Jupiter has powerful cyclones the size of Australia across its polar regions. These cyclones are unchanging and do not disperse like the cyclones on Earth.
A research group from Weizmann Institute of Science discovered which forces are at work fixing these gargantuan storms to the polar regions and why their number and locations have remained consistent over time. The research was published on Sunday in Nature Geoscience.
"We can think of Jupiter as an ideal climate laboratory," said Prof. Yohai Kaspi of Weizmann's Earth and Planetary Sciences Department. While Earth has a very diverse climate with oceans, continents, atmosphere, and the influence of humans, Jupiter is made only of gas. This makes testing hypotheses and making predictions easier.
The data for the Jupiter research was collected by the Juno probe, which was launched in 2011 and entered orbit in 2016. Prof. Kaspi, who is a co-investigator on the Juno mission, witnessed discovery of the cyclones on the planet's poles.
"If we look at older images of Jupiter taken before 2016," said Kaspi, "we see that the poles were commonly represented as large grey areas because no one knew then what they actually look like." This is because the solar system is organized on a plane that is very close to Jupiter's equator. This means that observations from Earth and earlier space missions could only capture the lower latitudes.
The Juno probe was special because it was the first probe that could capture Jupiter's poles. This allowed researchers to discover cyclones, and data gathered over the many orbits of Juno shows that the cyclones are fixed and consistent, with eight in the north pole and five in the south.
“This discovery was very surprising at the time,” says Prof. Kaspi, “because we expected the poles to be more or less symmetric.”
The tropical cyclones that form on Earth in the Atlantic and Pacific Oceans drift in circular motions toward the poles due to the planet's motion. On Jupiter Jet streams prevent cyclones from forming under 60degree latitude, so they can only forms above where the currant is weaker. The cyclones are attracted to the poles but are held off by the storm at the center of the cyclone ring.
"As long as the cyclones remain at a distance from the pole, they are attracted to it. But the nearer they venture, the more strongly they're repelled," said Nimrod Gavriel, a doctorate student from Prof. Kaspi's research team. He continued to say that latitude 84degree, where the cyclones form, is the area pole's attraction and the repulsion effect even out.
"We are trying to understand atmospheric dynamics at a large scale, and providing a successful explanation for the phenomenon of Jupiter's polar cyclones gives us the confidence that we truly know what's going on there," said Prof. Kaspi.
The discovery can be essential for weather forecasting on Earth as it will provide a greater understanding of how cyclones work. With the heating of the planet, the movement of storms across it changes, but by understanding the cyclones better, meteorologists can get better at predicting them.
For Prof. Kaspi, the discovery has added excitement. "There are no new islands to discover in the Pacific, and most planetary bodies in the solar system have already been mapped. The poles of Jupiter and the other gaseous planets are, perhaps, the last spots in the solar system that are still left to explore," he said.
The research team expects to receive more valuable data in the future, as Juno's orbit takes it closer the the polar regions of Jupiter.