Using its Microwave Radiometer (MWR) and Jovian Infrared Auroral Mapper (JIRAM), Juno captured data that supports a new model for the fast-moving jet stream encircling Jupiter's north pole. The results were presented at the European Geosciences Union General Assembly in Vienna.
"Everything about Jupiter is extreme," said Scott Bolton, Juno's principal investigator at the Southwest Research Institute. "We're getting a closer look at the immensity of energy this gas giant wields."
Juno's instruments, originally designed to peer into Jupiter, have also been turned on Io. By combining MWR readings with JIRAM infrared data, scientists detected cooling lava flows beneath Io's crust across the moon's entire surface. According to Shannon Brown of NASA's Jet Propulsion Laboratory, "We were surprised by what we saw: evidence of still-warm magma that hasn't yet solidified below Io's cooled crust."
The findings suggest that about 10% of Io's surface harbors slowly cooling lava beneath the crust. These flows act as efficient heat radiators, transporting internal heat outward, much like a car radiator. This process helps explain how Io so rapidly renews its surface.
JIRAM data also revealed that Io's most energetic volcanic eruption, initially recorded during Juno's Dec. 27, 2024 flyby, remained active into March 2025 and may still be ongoing. Another close approach is scheduled for May 6, with Juno flying within 55,300 miles (89,000 kilometers) of the moon.
Juno's 53rd orbit on Feb. 18, 2023, marked the start of radio occultation experiments aimed at measuring Jupiter's atmospheric temperature structure. By analyzing how radio waves bend while passing through the atmosphere, researchers obtained the first temperature measurements of Jupiter's north polar stratospheric cap, finding it about 11 degrees Celsius cooler than its surroundings and encircled by 100 mph (161 kph) winds.
Extended JunoCam and JIRAM data also allowed scientists to track the motion of Jupiter's polar cyclones. Observations confirmed the cyclones' gradual poleward drift due to beta drift and revealed complex interactions resembling spring-like oscillations.
"These competing forces result in the cyclones 'bouncing' off one another... stabilizing the entire configuration," said Yohai Kaspi, a Juno co-investigator from the Weizmann Institute of Science.
The new cyclone model has implications for understanding atmospheric systems on other planets, including Earth. Juno's evolving orbit continues to provide new perspectives on Jupiter's radiation belts and weather phenomena.
"It's a little scary, but we've built Juno like a tank," said Bolton. "We're learning more about this intense environment each time we go through it."
Research Report:NASA's Juno Mission Gets Under Jupiter's and Io's Surface
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