Jupiter: Astonishingly different

Surprisingly deep currents and "solid" liquids inside the gas giant

The striking cords of bangs reach deep into Jupiter's interior unexpectedly - that's just one of the surprising results of the Juno Gravity Experiment. © NASA / JPL-Caltech / SwRI / MSSS / Kevin M. Gill
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The gas giant Jupiter again provides surprises. Because data from the NASA spacecraft Juno reveal that the planet has an unexpectedly asymmetric gravity field. This reveals that Jupiter's interior behaves differently than thought. This is how the striking cords stretch to 3, 000 kilometers. Surprising, too: The gases liquefied by the enormous pressure below behave like a solid instead of a liquid, as researchers report in the journal "Nature".

Jupiter is not only the largest planet in our solar system, it still holds many secrets. For what is going on under the raging storms and turbulent cloud bands of the gas giant is only partially known. It is unclear, for example, how far the storms reach into the depths and where they get their energy from. So far, researchers have only been able to speculate about the behavior of hydrogen and helium deep inside the gas planet.

But since July 2016, planetary scientists have a new "spy" on Jupiter: The NASA spacecraft Juno orbits the gas giant in elliptical orbits and always comes very close to him. This is the perfect opportunity to gather detailed data - including the magnetic field, auroras, and the Great Red Spot of Jupiter.

Jupiter's gravity field is asymmetrical

However, the recent insights do not come from a measuring instrument, but from the behavior of the spacecraft itself. In the context of the Juno Gravity experiment, Luciano Iess of the Sapienza University of Rome and his colleagues have used the probe's changing flight speed to be the magnet of Jupiter and so on Gravity field to measure. For this they determined whether and how much a radio signal sent to the probe and back was distorted by the Doppler effect.

The surprising result: Contrary to expectations, the gravitational field of Jupiter is not completely symmetrical. Instead, the Juno data reveal differences between the northern and southern hemispheres. As the researchers explain, such an asymmetry is rather unusual for a fast-rotating gas planet like Jupiter. It suggests that there must be dynamic and diverging currents well below the surface. display

Glimpse into the inner workings of Jupiter NASA

Up to 3, 000 kilometers deep

What's up with the deep currents of Jupiter has been researched by two other research teams. Yohai Kaspi of the Weizmann Institute of Science in Rehovot and his colleagues analyzed certain features in Juno's asymmetric gravity field data that can reveal how deep the raging wind currents reach into the gas pocket of Jupiter,

Their analyzes showed that the stormy windbreaks of Jupiter are not a purely superficial phenomenon, but have very deep roots: "The jet streams extend from the top of the cloud cover to a depth of around 3, 000 kilometers ", The researchers report. About one percent of the massive mass of Jupiter is therefore constantly in motion and racing in the storm strikes around the planet.

"By contrast, the Earth's atmosphere is less than one millionth of the Earth's total mass, " says Kaspi. The fact that in Jupiter such a massive region rotates in separate east-west bands is definitely a surprise. "

"Solid" liquids

But what lies under this deep-reaching storm zone? This is what Tristan Guillot from the Côte d'Azur University in Nice and his colleagues found out when evaluating the symmetric component of the Juno gravity field data. Thus, at 3, 000 kilometers, the zone begins where hydrogen and helium become liquid due to the normal pressure in the interior of Jupiter.

The surprising thing about it: although these gases are liquefied, they behave like a solid in the interior of Jupiter. Instead of swirling around, the hydrogen and helium mixture rotates like a single solid block. "That's a really fantastic result!" Says Guillot. "Future measurements by Juno will help us to understand how the transition between the weather zone and the solid body runs underneath."

The reason for the "solid" behavior of liquid hydrogen and helium is assumed by the researchers in the electromagnetic properties of these liquefied gases: "At this depth, the conductivity and the resulting magnetic braking effect become so strong, that they force the fluid movement into a solid-body rotation, "explain Guillot and his colleagues.

Infrared view of the tightly packed cyclones at the north pole of Jupiter NASA / JPL-Caltech / SwRI / ASI / INAF / JIRAM

Sealed storm vortex

Another surprise brought new footage and data from the gas giant's poles. Because they confirm that there are numerous eddy currents packed close together. At the North Pole, a central cyclone is surrounded by eight other storm vortexes - each of them between 4, 000 and 6, 000 gros. At the S dpol, even up to 7, 000 kilometers of cyclones surround the central cyclone.

"The big question is why these storms do not merge, " says Alberto Adriani of the Institute for Planetary Research in Rome. Because the polar cyclones of Jupiter are so close together that touch their spiral arms. Despite the enormous wind speeds of 350 kilometers per hour that prevail in them, they hardly seem to bother. There is nothing comparable in the solar system, "says Adriani.

Always new surprises

These new insights into the inner life of Jupiter throw a whole new light on the processes inside gas giants. This is not only important and exciting to better understand the gas planets in our own solar system. It also helps in exploring the many gas giants that revolve around strange stars.

"These amazing results are another example of Jupiter's surprises, " says Juno Mission Chief Scientist Scott Bolton of the Southwest Research Institute. "Juno has completed only a third of her mission, and we already see Jupiter in a whole new light." (Nature, 2018; doi: 10.1038 / nature25776, doi: 10.1038 / nature25793, doi: 10.1038 / nature25775, doi: 10.1038 / nature25491 )

(Nature / NASA, 08.03.2018 - NPO)