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NASA's Juno probe reveals secrets of Jupiter's atmosphere in 3D

A NASA spacecraft is giving the best-ever 3D model of the largest planet of our solar system.

The Juno mission is using its second extended phase to peer far into the clouds of Jupiter, using a polar-orbiting view that no previous spacecraft was able to access.

The results in the early phase of the extension — which started this year and will go to 2025, if the spacecraft outlasts the intense radiation — have been rich so far, investigators said in a news conference Thursday (Oct. 28). 

In photos: NASA's Juno Mission to Jupiter

This composite image shows views of Jupiter in infrared (left) and visible light (right) taken by the Gemini North telescope and NASA's Hubble Space Telescope, respectively. (Image credit: International Gemini Observatory/NOIRLab/NSF/AURA/NASA/ESA, M.H. Wong and I. de Pater (UC Berkeley) et al.)

So far the spacecraft revealed new information on how water behaves far down in the clouds, and why the cyclones at the poles appear so stable. "This is going to tell us a lot about how giant planets are throughout the galaxy," Juno principal investigator Scott Bolton told reporters at the news conference.

The dominating result was learning that the Great Red Spot is far deeper than investigators thought, with the famous storm going as deep as 310 miles (500 kilometers) beneath Jupiter's cloud tops. But the new insight on deep atmospheric processes at Jupiter goes far beyond this single hurricane.

Juno's approach used gravity techniques to uncover the extent of the atmospheric belts and zones at the giant planet, which are detectable thousands of miles or kilometers below the cloud tops, Bolton said. "Gravity represents one of the main techniques that we [use to] open up the planet and look inside."

Measuring the magnetic field has also been useful, because partway down the huge planet's gas envelope, hydrogen starts to behave like a fluid rather than as a gas, which influences the behavior of the greater atmosphere. 

And a microwave instrument, "invented literally for this mission", is showing a weird inversion deep in at least one huge storm at Jupiter, where the temperature suddenly flips from warm to cold, Bolton said.

"It flips somewhere near about 50 miles [80 km] down," Bolton added, noting that is not too far below where water clouds are predicted to form in the atmosphere. 

"What we're seeing is that this storm's roots go down past the water clouds, past where sunlight penetrates," Bolton said, which is far different than at Earth where our atmosphere is affected by water, condensation and sunlight. "It also is indication that the ammonia and water are being moved up and down," he added.

This illustration combines an image of Jupiter from JunoCam with a composite image of Earth to depict the size and depth of Jupiter's Great Red Spot.

This illustration combines an image of Jupiter from JunoCam with a composite image of Earth to depict the size and depth of Jupiter's Great Red Spot. (Image credit: NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill)

This transition zone has been dubbed the "Jovicline", partially after a term first invented by science fiction author Arthur C. Clarke. He discussed this boundary in a 1971 short story, "A Meeting With Medusa," which described the voyage of a balloon moving towards this zone. 

But there's also an Earthly analogy that Clarke was borrowing from, which is the "thermocline" — a spot where seawater suddenly transitions from warm to cold. The results from Juno, which Bolton said were unexpected, imply a process moving the ammonia around on Jupiter. It might be large circulation cells, or it might be some other "meteorological phenomenon."

The circulation cells are also newly investigated and came from scientists tracing the path of ammonia in Jupiter's atmosphere. Ammonia is only available in relatively small amounts, but it pointed the way to circulation cells in the north and south hemispheres that appear to behave similarly to "Ferrel cells" on Earth that dominate our own planet's circulation.

"The Jovian cells begin at the cloud levels and extend to at least 200 miles [322 km], and probably much deeper than that. This means that the cells on Jupiter are at least 30 times deeper than the equivalent cells on Earth," said Keren Duer, a graduate student from the Weizmann Institute of Science in Israel, at the news conference. Duer is lead author of a Geophysical Research Letters paper published this week, describing the phenomenon.

More insight also came concerning persistent cyclones observed at the poles of Jupiter, using infrared or heat-seeking wavelengths. "In the infrared, just like in the spy movies, you can see your enemies in the dark," joked Alessandro Mura, a Juno co-investigator at the National Institute for Astrophysics in Rome, at the event.

Mura pointed to previously known Texas-sized storms at the north and south poles, with eight in an octagonal pattern in the north and five in a pentagonal pattern in the south. The symmetry was not an accident, scientists suspected, as they embarked on a deeper study of the storms. 

"Anytime you see something symmetrical, you think that it should be something hidden below ... it is some kind of force, or hidden mechanism or law, which you want to discover," Mura said.

In this case, a team led by Mura found that the cyclones have oscillations that affect each other and that allow what would be an otherwise unstable storm to stay in place for longer than expected. Moreover, this stability indicates deep roots in the atmosphere, even beyond what Juno can see. The peer-reviewed results were published in July in Geophysical Research Letters.

The symmetry only briefly broke in 2019, when the southern pentagon briefly was joined by a sixth storm. The "intruder" only lasted two months and disappeared without merging with the other five storms, Mura said. Why is poorly understood, but the team plans more observations to learn more.

"The five cycles are probably in a configuration where they leave some kind of free space for an intruder to get in," Mura added, but said that the persistence of an "intruder" may depend on the size of the storms. "Maybe you need a very big cyclone to get to the sixth place" permanently in the configuration around the pole, he said. 

Bolton said the extended investigation will continue the probe of Jupiter's deep atmosphere, with questions such as how far down the roots are to these various storms, particularly in the north pole as the spacecraft's path takes it closer to this region. The spacecraft will also zoom by Europa in the coming year, allowing scientists an unprecedented close-up view of the moon's north pole ahead of other missions that will visit the world in the 2030s.

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Elizabeth Howell

Elizabeth Howell is a contributing writer for Space.com who is one of the few Canadian journalists to report regularly on space exploration. She is the author or co-author of several books on space exploration. Elizabeth holds a Ph.D. from the University of North Dakota in Space Studies, and an M.Sc. from the same department. She also holds a bachelor of journalism degree from Carleton University in Canada, where she began her space-writing career in 2004. Besides writing, Elizabeth teaches communications at the university and community college level, and for government training schools. To see her latest projects, follow Elizabeth on Twitter at @howellspace.