Juno launched on August 5, 2011 and successfully entered Jupiter’s orbit on July 4, 2016. During each of the spacecraft’s 37 passes of Jupiter to date, a specialized suite of instruments has peered below its turbulent cloud deck. The new results from the Juno mission highlight the inner workings of the belts and zones of clouds encircling Jupiter, as well as its polar cyclones and even the Great Red Spot. The findings appear in several papers in the journal Science, the Journal of Geophysical Research: Planets, and the journal Geophysical Research Letters.
This visible-light image of Jupiter was created from data captured on January 11, 2017 using Hubble’s Wide Field Camera 3. Near the top, a long brown feature called a ‘brown barge’ extends 72,000 km (nearly 45,000 miles) in the east-west direction. The Great Red Spot stands out prominently in the lower left, while the smaller feature nicknamed Red Spot Jr. (known to Jovian scientists as Oval BA) appears to its lower right. Image credit: NASA / ESA / NOIRLab / NSF / AURA / Wong et al. / de Pater et al. / M. Zamani.
“Previously, Juno surprised us with hints that phenomena in Jupiter’s atmosphere went deeper than expected,” said Juno principal investigator Dr. Scott Bolton, a researcher at the Southwest Research Institute.
“Now, we’re starting to put all these individual pieces together and getting our first real understanding of how Jupiter’s beautiful and violent atmosphere works — in 3D.”
Juno’s microwave radiometer (MWR) allows scientists to peer beneath Jupiter’s cloud tops and probe the structure of its numerous vortex storms. The most famous of these storms is the Great Red Spot.
The new results show that the Jovian cyclones are warmer on top, with lower atmospheric densities, while they are colder at the bottom, with higher densities.
Anticyclones, which rotate in the opposite direction, are colder at the top but warmer at the bottom.
The findings also indicate these storms are far taller than expected, with some extending 100 km (62 miles) below the cloud tops and others.
This surprise discovery demonstrates that the vortices cover regions beyond those where water condenses and clouds form, below the depth where sunlight warms the atmosphere.
The researchers examined the gravity signature of the Great Red Spot and further constrained its depth.
Within the gravity measurements taken as Juno flew above the Great Red Spot, they detected fluctuations in the planet’s gravitational field caused by the storm.
They found that, although the GRS is deeply rooted within the atmosphere, it’s far shallower than the surrounding zonal jets that power the GRS, which extend much deeper.
According to their findings, the depth of the GRS is no more than 500 km (311 miles) deep.
Jupiter’s belts and zones observed in microwave light, compared to the colors of the cloud-tops (left), and the winds at the cloud tops (right). Two wavelengths of microwave light are shown, one sensing altitudes above the water cloud, and another sensing below the water clouds. Image credit: NASA / JPL / SwRI / University of Leicester.
In addition to cyclones and anticyclones, Jupiter is known for its distinctive belts and zones — white and reddish bands of clouds that wrap around the planet. Strong east-west winds moving in opposite directions separate the bands.
Juno previously discovered that these winds, or jet streams, reach depths of about 3,200 km (1,988 miles).
Planetary researchers are still trying to solve the mystery of how the jet streams form. Data collected by Juno’s MWR during multiple passes reveal one possible clue: that the atmosphere’s ammonia gas travels up and down in remarkable alignment with the observed jet streams.
“By following the ammonia, we found circulation cells in both the north and south hemispheres that are similar in nature to ‘Ferrel cells,’ which control much of our climate here on Earth,” said Keren Duer, a graduate student at the Weizmann Institute of Science.
“While Earth has one Ferrel cell per hemisphere, Jupiter has eight — each at least 30 times larger.”
Juno’s MWR data also show that the belts and zones undergo a transition around 65 km (40 miles) beneath Jupiter’s water clouds.
At shallow depths, Jupiter’s belts are brighter in microwave light than the neighboring zones.
But at deeper levels, below the water clouds, the opposite is true — which reveals a similarity to our oceans.
“We are calling this level the ‘Jovicline’ in analogy to a transitional layer seen in Earth’s oceans, known as the thermocline — where seawater transitions sharply from being relative warm to relative cold,” said Juno team member Dr. Leigh Fletcher, a researcher at the University of Leicester.
Juno previously discovered polygonal arrangements of giant cyclonic storms at both of Jupiter’s poles — eight arranged in an octagonal pattern in the north and five arranged in a pentagonal pattern in the south.
The new data from Juno’s Jovian Infrared Auroral Mapper (JIRAM) show that these atmospheric phenomena are extremely resilient, remaining in the same location.
“Jupiter’s cyclones affect each other’s motion, causing them to oscillate about an equilibrium position,” said Juno team member Dr. Alessandro Mura, a researcher at the National Institute for Astrophysics.
“The behavior of these slow oscillations suggests that they have deep roots.”
JIRAM data also indicates that, like hurricanes on Earth, these cyclones want to move poleward, but cyclones located at the center of each pole push them back. This balance explains where the cyclones reside and the different numbers at each pole.
