The violent nature of Jupiter’s atmosphere has long been a source of fascination for scientists. NASA’s Juno spacecraft has had a ringside seat to the goings-on since it entered the orbit around the gas giant in 2016. During flybys of Jupiter, a suite of science instruments has peered below its turbulent cloud deck to uncover how the gas giant works from the inside out. One way the Juno mission learns about the planet’s interior is via radio science. Using NASA’s Deep Space Network antennas, planetary scientists track the spacecraft’s radio signal as Juno flies past Jupiter at speeds near 209,000 kph (130,000 mph), measuring tiny changes in its velocity. Those changes are caused by variations in the planet’s gravity field, and by measuring them, the mission can essentially see into Jupiter’s atmosphere. Such measurements have led to numerous discoveries, including the existence of a dilute core deep within Jupiter and the depth of the planet’s zones and belts, which extend from the cloud tops down approximately 3,000 km (1,860 miles).
This illustration depicts findings that Jupiter’s atmospheric winds penetrate the planet in a cylindrical manner and parallel to its spin axis. The most dominant jet recorded by NASA’s Juno is shown in the cutout: the jet is at 21 degrees north latitude at cloud level, but 3,000 km below that, it’s at 13 degrees north latitude. Image credit: NASA / JPL-Caltech / SSI / SWRI / MSSS / ASI / INAF / JIRAM / Björn Jónsson / CC BY 3.0.
To determine the location and cylindrical nature of the Jovian winds, Juno scientist Ryan Park and colleagues applied a mathematical technique that models gravitational variations and surface elevations of rocky planets like Earth.
At Jupiter, the technique can be used to accurately map winds at depth.
Using the high-precision Juno data, the researchers were able to generate a four-fold increase in the resolution over previous models created with data from NASA’s Jovian explorers Voyager and Galileo.
“We applied a constraining technique developed for sparse data sets on terrestrial planets to process the Juno data. This is the first time such a technique has been applied to an outer planet,” said Dr. Park, a researcher at NASA’s Jet Propulsion Laboratory.
The measurements of the gravity field matched a two-decade-old model that determined Jupiter’s powerful east-west zonal flows extend from the cloud-level white and red zones and belts inward.
But the measurements also revealed that rather than extending in every direction like a radiating sphere, the zonal flows go inward, cylindrically, and are oriented along the direction of Jupiter’s rotation axis.
How Jupiter’s deep atmospheric winds are structured has been in debated since the 1970s, and the Juno mission has now settled the debate.
“All 40 gravity coefficients measured by Juno matched our previous calculations of what we expect the gravity field to be if the winds penetrate inward on cylinders,” said Juno co-investigator Dr. Yohai Kaspi, a researcher at the Weizmann Institute of Science.
“When we realized all 40 numbers exactly match our calculations, it felt like winning the lottery.”
“Along with bettering the current understanding of Jupiter’s internal structure and origin, the new gravity model application could be used to gain more insight into other planetary atmospheres.”
“As Juno’s journey progresses, we’re achieving scientific outcomes that truly define a new Jupiter and that likely are relevant for all giant planets, both within our solar system and beyond,” said Juno principal investigator Dr. Scott Bolton, a researcher at the Southwest Research Institute.
“The resolution of the newly determined gravity field is remarkably similar to the accuracy we estimated 20 years ago.”
“It is great to see such agreement between our prediction and our results.”
The study was published in the journal Nature Astronomy.
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Y. Kaspi et al. Observational evidence for cylindrically oriented zonal flows on Jupiter. Nat Astron, published online October 26, 2023; doi: 10.1038/s41550-023-02077-8
