NASA’s Juno spacecraft finds deep winds and patterned cyclones on Jupiter

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The world of Jupiter is entering a clearer focus for scientists, as new data from NASA reveal how the fluids of the planet are stirred and mixed, both on the surface and in the depths of the interior. All these chaotic movements reveal that Jupiter is even more complex than expected.
One surprise is that the winds that flow on Jupiter's surface extend deep into the planet's interior, causing strange variations in the gravitational field of the world, the researchers found. Even deeper inside the planet, a gaseous core rotates as if it were a solid and rigid body. Meanwhile, on the surface, gigantic cyclones dot the poles, where they form strange flower-like patterns, although scientists do not know exactly how.
the winds that flow on the surface of Jupiter extend deep into the interior of the planet
These new details, reported today in four Nature documents, come from NASA's Juno spacecraft, which has been in orbit around Jupiter since mid-2016. Juno is in a highly elliptical orbit, a path that carries the probe near the surface of Jupiter once every 53 days. It is during these nearby passes that Juno is located 2,600 miles from Jupiter's clouds, which allows its instruments to collect data more closely than any previous spacecraft.
"Never before have we been so close to this giant planet with an orbiter," Tristan Guillot, a planetary scientist at the French Riviera University in France and the lead author of one of the newspapers, tells The Verge. "And although it's going really fast … it's still capable of making these precise measurements."
These are some of the greatest discoveries:
The winds run deep
Juno has been studying Jupiter's gravitational field, or to what extent the gravitational influence of the planet extends into space. Now, the probe has revealed that the planet's gravity is not uniform at all. In fact, it is unexpectedly asymmetric.
Jupiter is basically a giant ball of fluid gas, and the researchers thought that everything would rotate mostly at the same speed. If that were the case, the gravitational field would be more or less symmetric. "The north and the south should be the same worldwide," says Guillot. "Therefore, the fact that we detect these differences in the gravitational field north and south means that there is something different in the two hemispheres."

Jet streams of Jupiter. Image: NASA

That something is deep wind, according to one of Nature's documents. Jupiter has wind bands and jet streams that crisscross the surface of the planet and spin at different speeds, sometimes with a difference of up to 220 miles per hour (100 meters per second). Many thought that these currents could exist on the outside of the planet, a bit like the winds on Earth. But now, researchers believe that jet streams actually extend deep into the planet: about 1,800 miles (or 3,000 kilometers) down, depending on the models. The deep jet streams would really change the way parts of the interior of the planet rotate. And since the winds are different in the northern and southern hemispheres, it explains why gravitational fields are different for each half of the planet.
"Now we definitely know that the surface winds are quite deep and what we're really seeing is how [fluids move] inside," says Jonathan Fortney, a planetary scientist at the University of California at Santa Cruz, who did not participate in this study. research, but reviewed the Nature documents.
A fluid core that acts solid
Juno's Jupiter measurements also indicate something much deeper than the jet streams of the planet: a fluid core that rotates like a solid. The scientists mapped Jupiter's global gravitational field and then used that information to model the interior of the planet. These models suggest that the nucleus of Jupiter, which is composed mainly of hydrogen and helium, rotates like a rigid body, although it is all fluid.
"Jupiter has a large magnetic field and is dragging the flow everywhere."
Guillot believes that it may be because the gases inside the nucleus are electrically charged or ionized. This causes the fluid core to rotate at the same rate as Jupiter's magnetosphere, a large field of magnetism that surrounds the planet and that is generated by electric currents inside Jupiter. The magnetic field manipulates how the particles move around Jupiter, and also inside. "Jupiter has a large magnetic field and is dragging the flow everywhere," says Guillot. "That's why the deep interior is spinning evenly."
Cyclones surrounding cyclones
Juno has already revealed that cyclones, some as wide as Earth, dot the north and south poles of Jupiter. But new images taken with infrared light show that cyclones actually form a strange pattern. In the north pole, five cyclones surround a cyclone, like petals on a flower. And at the south pole, a cyclone is surrounded by eight.
The cyclones have persisted in this pattern basically since Juno arrived at Jupiter. "We did not see any very big change in the position of the cyclones," Alberto Adriani, a scientist at Italy's National Institute of Astrophysics and lead author of one of the newspapers, told The Verge. "The structure is very stable."

A mosaic of the south pole of Jupiter, seen in infrared from Juno. Image: NASA / SWRI / JPL / ASI / INAF / IAPS

Adriani believes that the cyclones formed due to a combination of the speed with which the planet turns and the heat in the polar regions of the north and south. However, there are still many unknowns: it is not clear if the cyclones were formed exactly where they are, and how they stay in that flower pattern without merging. "So far it's hard to say because these are the first observations we have," says Adriani.
Fortunately, Juno will remain in orbit around Jupiter for a couple more years at least, so we will learn more about this soon. "We are trying to get the most complete information we can about this planet," says Adriani.


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