The cloud-forming weather layer creates Jupiter's banded appearance. This composite image shows Jupiter's visible and infrared light views taken by NASA's Hubble Space Telescope and NASA’s Gemini North telescope. Credit: International Gemini Observatory/NOIRLab/NSF/AURA/NASA/ESA, M.H. Wong and I. de Pater (UC Berkeley) et al.
NASA's Juno probe orbiting Jupiter has revealed new details about how Jupiter's unique and vibrant atmospheric features provide clues to the unobserved processes beneath its clouds. These results reveal the inner workings, including the zones and belts of clouds that surround Jupiter. They also highlight its polar cyclones as well as the Great Red Spot.
Today, scientists published several papers about Juno's atmospheric discoveries in Science and the Journal of Geophysical Research. Two issues of Geophysical Research Letters have also published additional papers.
Lori Glaze, NASA's director of planetary science at its headquarters in Washington, stated that Juno's new observations open up a treasure trove of new information about Jupiter. "Each paper sheds light on different aspects of the planet's atmospheric processesa wonderful example of how our internationally-diverse science teams strengthen understanding of our solar system."
Juno was placed in Jupiter's orbit by the spacecraft in 2016. A specialized suite has scanned below the turbulent cloud deck of Jupiter's planet during each of its 37 orbits.
"Previously, Juno shocked us with hints, that phenomena in Jupiter’s atmosphere went deeper than we expected," Scott Bolton, principal investigator at Juno, San Antonio Southwest Research Institute, and lead author on Science journal paper about the depth of Jupiter’s vortices, said. "Now we are putting all the pieces together and getting a real understanding of Jupiter's violent and beautiful atmosphere in 3D."
This illustration shows the Great Red Spot's size and depth. It is a combination of a JunoCam image of Jupiter taken aboard NASA's Juno spacecraft. Credit: JunoCam Image dаta: NASA/JPL-Caltech/SwRI/MSSSJunoCam Image processing by Kevin M. Gill (CC BY)Earth Image: NASA
Juno's microwave radiometer allows mission scientists to see beneath Jupiter's cloud tops, and examine the structure of its vortex storms. The Great Red Spot is the most well-known of these storms. This crimson vortex, which is larger than Earth, has fascinated scientists since its discovery nearly two centuries ago.
New results have shown that cyclones are more warm at the top with lower atmospheric densities. However, they are cooler at the bottom with higher atmospheric densities. Anticyclones which rotate in the opposite direction are warmer at the bottom but colder at the top.
These storms also appear to be much taller than anticipated. Some are 60 miles (100 km) lower than the cloud tops, while others, such as the Great Red Spot which extends over 200 miles (335 kilometers), are higher. This surprising discovery shows that vortices extend beyond regions where water condenses or clouds form to areas below the level at which sunlight warms the atmosphere.
Instruments studying Jupiter's gravity field could detect the Great Red Spot's height and size. Juno flew by Jupiter's most iconic spot twice, providing the opportunity to search the storm's gravity signature as well as the MWR data on its depth.
Juno was hovering low above Jupiter's cloud deck at 130,000 mph (209,000 km/h). Juno scientists were able measure velocity changes of 0.01 millimeters per second with a NASA Deep Space Network tracking antenna. This was from a distance greater than 400 million miles (650,000,000 kilometers). The team was able to limit the Great Red Spot's depth to 300 miles (500 km) below the cloud tops.
Marzia Parisi is a Juno scientist at NASA's Jet Propulsion Laboratory, Southern California. She was the lead author of a Science paper on gravity overflights to the Great Red Spot. "We are confident that future gravity experiments at Jupiter can be complemented by MWR's discovery on the depth.
The JunoCam imager's data and the microwave radiometer from a flyover at the Great Red Spot on July 11, 2017, provide a glimpse into the inner workings of Jupiter’s most famous anticyclone. Credit: NASA/JPL-Caltech/SwRI/MSSSImage processing: Kevin Gill CC BY
Belts and Zones
Jupiter is also known for its unique belts and zoneswhite-reddish clouds that wrap around it. The bands are separated by strong east-west winds that blow in opposite directions. Juno discovered previously that jet streams (or winds) can reach depths of approximately 2,000 miles (3,200 km). Scientists are still trying to figure out how jet streams form. Juno's MWR data from multiple passes have revealed one clue: the ammonia gas in the atmosphere travels up and downstream in astonishing alignment with the jet streams.
Keren Duer, a graduate student at the Weizmann Institute of Science, Israel, and the lead author of the Science journal paper about Ferrel-like Jupiter cells, said that "By following ammonia we found circulation cells both in the north and southhemispheres which are similar in nature as 'Ferrel cell', which controls much of our climate here in Earth." "Earth has only one Ferrel cell per half-sphere. Jupiter has at least eighteen.
Juno's MWR data shows that the zones and belts undergo a transition at 40 miles (65 km) below Jupiter's water clouds. Jupiter's belts shine brighter in microwave light at shallow depths than their neighboring zones. However, at deeper levels below the water clouds, it is the reverse. This reveals a similarity with our oceans.
"We call this level the Jovicline in analogy with a transitional layer in Earth's oceans known as the thermocline," stated Leigh Fletcher (Juno participant scientist) and lead author of the Journal of Geophysical Research, Planets paper highlighting Juno’s microwave observations of Jupiter’s temperate belts.
Mission scientists carried out an experiment to measure minute velocity changes in Juno's spacecraft during a Jupiter flyby in July 2019. This was due to the gravity field at the Great Red Spot. Credit: NASA/JPL-Caltech/SwRI
Polar Cyclones
Juno had previously found polygonal arrangements at Jupiter's poleseight of giant cyclonic thunderstorms. Five were arranged in an octagonal arrangement in the north, and five in a pentagonal arrangement in the south. Five years later, mission scientists have confirmed that these atmospheric phenomena remain in the same place, thanks to observations made by JIRAM's Jovian Infrared Auroral Mapper.
Alessandro Mura is a Juno coinvestigator at The National Institute for Astrophysics (Rome) and the lead author of a paper in Geophysical Research Letters about oscillations in Jupiter's Polar Cyclones. These slow oscillations suggest that they have deep roots.
JIRAM data also shows that these cyclones, much like hurricanes, want to move in the opposite direction from Earth's. However, cyclones at each pole push them back. This balance explains the location of cyclones and the numbers at each pole.
Further exploration of Clouds on Jupiter rising above the surrounding atmosphere
