New data from NASA’s Juno mission, which has been orbiting Jupiter since 2016, has provided scientists with insight into the extreme winds and cyclones present within the gas giant’s atmosphere. The data allowed scientists to develop a model that better represents the fast jet stream circling Jupiter’s north pole, which is cluttered with many cyclones.
What’s more, data from Juno’s Io flybys has revealed the subsurface temperature profile of Io, the innermost of the four Galilean moons and the most geologically active world in our solar system. The new temperature profile features new information on Io’s inner structure and the extent of its immense volcanic activity.
“Everything about Jupiter is extreme. The planet is home to gigantic polar cyclones bigger than Australia, fierce jet streams, the most volcanic body in our solar system, the most powerful aurora, and the harshest radiation belts. As Juno’s orbit takes us to new regions of Jupiter’s complex system, we’re getting a closer look at the immensity of energy this gas giant wields,” said Juno’s principal investigator, Scott Bolton of the Southwest Research Institute in San Antonio, Texas.
JunoCam image of Io, taken on April 9, 2024. (Credit: NASA/JPL-Caltech/SwRI/MSSS/Gerald Eichstädt/Thomas Thomopoulos)
To collect the data, Juno’s team used the spacecraft’s Microwave Radiometer (MWR) instrument. MWR is trained to peer through the thick atmospheric clouds of Jupiter and study the planet’s deep atmosphere. However, during its development, Juno’s team also trained and tested the instrument on Io, and since arriving at Jupiter, the team has combined data from MWR and the Jovian Infrared Auroral Mapper (JIRAM) instrument to learn more about Io.
Juno has completed several flybys of Io during its extended mission, coming within 1,500 km of the moon’s surface on two flybys. MWR, JIRAM, and a variety of other Juno instruments were used during these flybys, as well as other close encounters with Io, to collect the data featured in the new study.
“The Juno science team loves to combine very different datasets from very different instruments and see what we can learn. When we incorporated the MWR data with JIRAM’s infrared imagery, we were surprised by what we saw: evidence of still-warm magma that hasn’t yet solidified below Io’s cooled crust. At every latitude and longitude, there were cooling lava flows,” said Juno scientist Shannon Brown of NASA’s Jet Propulsion Laboratory in California.
Video: Imagery of Io’s south polar region collected by JIRAM. The bright spots are areas of volcanic activity. (Credit: NASA/JPL/SwRI/ASI/JIRAM)
The results of Juno’s investigation of Io show that approximately 10% of Io’s surface is comprised of this subsurface still-warm magma. While further analysis of Juno’s data and future study by the spacecraft are needed, these initial results provide insight into Io’s surface renewal process and how heat travels from within the moon to its surface.
“Io’s volcanoes, lava fields, and subterranean lava flows act like a car radiator, efficiently moving heat from the interior to the surface, cooling itself down in the vacuum of space,” Brown explained.
Furthermore, JIRAM data from Juno’s Dec. 27, 2024, flyby of the moon revealed that lava and ash were still being ejected from the site of the most energetic eruption in Io’s geologic history. Scientists confirmed that the site was still active as recently as March 2, and will get another look at the site on May 6, when Juno flies past Io at a distance of 89,000 km.
Infrared JIRAM image of Io, where bright spots of volcanic activity can be seen. The large bright spot is the most powerful volcanic eruption ever observed on Io. (Credit: NASA/JPL-Caltech/SwRI/ASI/INAF/JIRAM)
Juno hasn’t just been investigating Io, however. The spacecraft has continued to make groundbreaking observations of Jupiter and its activity.
Starting on Feb. 18, 2023, Juno began performing radio occultation experiments to further explore and understand the atmospheric temperature structure of Jupiter. These radio occultation experiments involve teams on Earth beaming a radio signal to Juno while the spacecraft is either behind or close to Jupiter. The radio signal must first travel through Jupiter’s atmosphere in order to reach Juno, and then travel through the atmosphere again when Juno sends the signal back to Earth.
Jupiter’s thick atmospheric layers bend the radio waves within the signal, and scientists can measure and analyze these bends to learn more about atmospheric temperature and density. To date, Juno has completed 26 radio occultation experiments, and scientists have already begun making exciting discoveries from the analysis of the experiments.
One such discovery was the first-ever temperature measurement of the stratospheric cap within Jupiter’s north polar region. The results from the temperature measurement revealed that the stratospheric cap is approximately 11 degrees Celsius cooler than the surrounding atmosphere, which features winds blowing at speeds greater than 161 km/h.
Image of small cyclones located near Jupiter’s north pole. (Credit: NASA/JPL-Caltech/SwRI/MSSS/Brian Swift)
Littering Jupiter’s north pole are nine cyclones that Juno has continuously studied since its arrival at the planet in 2016, with Juno’s JunoCam visible light imager instrument regularly imaging the cyclones. After collecting nearly a decade’s worth of imagery, scientists can accurately track the long-term movements of the main northern polar cyclone and the eight smaller cyclones that surround it. Interestingly, these large cyclones are only found in Jupiter’s polar regions.
Analysis of the images shows that across multiple Juno orbits, the cyclones drift closer and closer to the Jovian north pole. This drift is known as “beta drift,” a phenomenon that results from the interaction between Jupiter’s Coriolis force and the irregular wind patterns of each cyclone.
Beta drift is similar to how tropical cyclones move on Earth. However, Earth cyclones are confined to the tropical and sub-tropical regions of Earth’s oceans, as they run out of the warm, moist air that fuels them when they move toward polar latitudes. Furthermore, Earth’s Coriolis force weakens near the north and south poles.
Jupiter’s northern polar cyclones, seen in infrared by Juno. (Credit: NASA/JPL-Caltech/SwRI/MSSS)
Imagery also showed that the cyclones cluster together and begin interacting with one another as they approach the pole.
“These competing forces result in the cyclones ‘bouncing’ off one another in a manner reminiscent of springs in a mechanical system. This interaction not only stabilizes the entire configuration, but also causes the cyclones to oscillate around their central positions, as they slowly drift westward, clockwise, around the pole,” said Juno co-investigator Yohai Kaspi of the Weizmann Institute of Science in Israel.
While there are stark differences between the cyclones on Earth and those on Jupiter, the new observations of Jupiter’s polar cyclones will help scientists gain a deeper understanding of cyclonic motion. A new atmospheric model has already been developed and is expected to be applied not only to Jupiter but also to Earth, Saturn, and other planets that host cyclones.
NASA's #JunoMission gets under Io's skin: New data from our Jovian orbiter reveals volcanic action on Jupiter's moon Io (seen here in infrared) and also sheds light on the fierce winds and cyclones of Jupiter's atmosphere. https://t.co/kmKvWzEhaf pic.twitter.com/Qcm2LPUUA5
— NASA Solar System (@NASASolarSystem) April 29, 2025
“One of the great things about Juno is its orbit is ever-changing, which means we get a new vantage point each time as we perform a science flyby. In the extended mission, that means we’re continuing to go where no spacecraft has gone before, including spending more time in the strongest planetary radiation belts in the solar system. It’s a little scary, but we’ve built Juno like a tank and are learning more about this intense environment each time we go through it,” Bolton said.
Juno’s team presented their new results at the European Geosciences Union General Assembly on April 29.
(Lead image: JunoCam image of Jupiter’s northern latitudes. Credit: NASA/JPL-Caltech/SwRI/MSSS/Jackie Branc)