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

NASA's spacecraft has created the most detailed 3D model ever of the largest planet in our solar system.
Juno's second extended phase is being used by the Juno mission to look deep into Jupiter's clouds using a polar orbiting view that no other spacecraft has been able to reach.

Investigators stated that the initial phase of the extension, which began this year, will continue until 2025 if the spacecraft can withstand the intense radiation. The preliminary results have been very positive, they said at a Thursday news conference (Oct. 28).

Photos: NASA's Juno Mission To Jupiter

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

The spacecraft has so far provided new information about water's behavior far below the clouds and why the cyclones near the poles seem so stable. Scott Bolton, Juno's principal investigator, said that this will reveal a lot about the size of the planets in the galaxy.

The most important result was discovering that the Great Red Spot is deeper than investigators believed. Its storm sank as far as 310 miles (500 km) below Jupiter's cloud tops. The new information on Jupiter's deep atmospheric processes goes beyond the hurricane.

Bolton stated that Juno used gravity techniques to determine the extent of the atmospheric belts at the giant planet. These zones can be detected thousands of miles below the cloud tops. "Gravity is one of the main methods that we use to open up the planet and see inside."

It has been also useful to measure the magnetic field, as hydrogen begins to behave more like a fluid than a gas halfway down the enormous planet's gaseous envelope. This influences the behavior and composition of the greater atmosphere.

Bolton stated that a microwave instrument was "invented literally to this mission" and is currently showing strange inversions deep in Jupiter's storm. This means that the temperature suddenly switches from warm to cool.

Bolton said, "It flips somewhere close to about 50 miles [80km] down," adding that this is not too far from where water clouds are expected to form in the atmosphere.

Bolton stated that the storm's roots are moving down past the water clouds and past where sunlight penetrates. This is very different from Earth, where water, sunlight, and condensation affect our atmosphere. He added that it was also an indication that water and ammonia are being moved up or down.

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

Partly after Arthur C. Clarke, a science fiction author, this transition zone was named the "Jovicline". This boundary was discussed by Clarke in his 1971 short story "A Meeting With Medusa", which described the journey of a balloon towards this zone.

Clarke also borrowed an Earthly analogy from the "thermocline", which is a place where seawater suddenly changes from warm to cold. Bolton stated that Juno's results were unexpected and suggested that Jupiter was moving ammonia around. It could be large circulation cells or another "meteorological phenomenon".

Scientists who trace the ammonia's path through Jupiter's atmosphere have also recently discovered that circulation cells. Although ammonia is not readily available, it led to the discovery of circulation cells in the north hemispheres. These cells behave in a similar way to Ferrel cells on Earth which dominate the planet's circulation.

"The Jovian cells start at the cloud level and reach at least 200 miles (322 km), and possibly much further. At least 30 times deeper than Earth's equivalent cells, this means that Jupiter's cells are more advanced than Earth's," Keren Duer, a graduate student at the Weizmann Institute of Science, Israel said at the news conference. This week's Geophysical Research Letters paper, which describes the phenomenon, was led by Duer.

Persistent cyclones at Jupiter's poles were also observed using heat-seeking wavelengths or infrared. This provided more insight. Alessandro Mura (a Juno co-investigator at Rome's National Institute for Astrophysics) joked that infrared can be used to see your enemies in darkness.

Mura pointed out previously-recorded Texas-sized storms at both the north pole and south poles. Eight were in an octagonal arrangement in the north, and five in a pentagonal in the south. Scientists suspected that the symmetry was not accidental as they began to study storms more closely.

Mura stated, "Anytime you notice something symmetrical you think it should be something below... it's some kind of force or hidden mechanism or law which you want to uncover."

Mura's team discovered that cyclones can have oscillations that affect one another, which allows storms otherwise unstable to remain in place for longer periods of time than expected. This stability also indicates deep roots in Earth's atmosphere, beyond what Juno can observe. Geophysical Research Letters published the peer-reviewed results in July.

2019 was the only year that the symmetry broke. A sixth storm joined the southern pentagon for a brief moment. Mura stated that the "intruder", which lasted for two months, vanished without merging with any of the five storms. Although the reason is not well understood, the team will continue to observe more storms to find out more.

Mura said that "the five cycles are likely in a configuration that leaves some kind of open space for an intruder or a thief to get in," but added that the size and persistence of an "intruder", may depend on how strong the storms are. He suggested that "Maybe you would need a very large cyclone in order to reach the sixth place" permanently around the pole.

Bolton stated that the extended investigation will continue Jupiter's probe of its deep atmosphere. Questions such as where the roots are to these storms and especially in the north pole, as the spacecraft moves closer to this area, will be addressed by Bolton. In the next year, the spacecraft will zoom past Europa. This will allow scientists to get a close-up view at the north pole of the moon ahead of any other missions in the 2030s.

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