Evrim Yazgin
Cosmos science journalist
NASA’s Juno mission has peered below the surface to help scientists better understand Jupiter’s storms and its moon Io’s subsurface temperature.
Juno was launched in 2011 and has been in orbit around Jupiter since 2016. Its mission has been extended a beyond its original 5 years. It is now due to finish in September this year, or until the end of the spacecraft’s life.
NASA has provided an update of the latest findings from Juno.
The mission team used the spacecraft’s microwave radiometer (MWR) to look at Io – one of Jupiter’s 4 largest moons, together known as the Galilean satellites because they were first observed by Galileo Galilei in 1610.
The MWR instrument was originally designed to peer beneath Jupiter’s clouds.
“The Juno science team loves to combine very different datasets from very different instruments and see what we can learn,” says Juno scientist Shannon Brown, from NASA’s Jet Propulsion Laboratory in Southern California.
“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,” Brown says.
About 10% of the moon’s surface has these remnants of cooling lava.
“Io’s volcanos, 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 adds.
Juno has also been measuring Jupiter’s atmospheric temperature since 2023. The first ever measurement of the gas giant’s north polar cap revealed the region is about 11°C cooler than surrounding areas. The north polar cap is also encircled by winds exceeding 160 km/h.
The spacecraft has also tracked the cyclones in Jupiter’s north. Unlike tropical cyclones or hurricanes on Earth, Jupiter’s cyclones do not occur in isolation.
Jupiter has a massive northern polar cyclone which has a diameter of 3,000 km (nearly as big as Earth’s Moon) and the 8 smaller cyclones which encircle it, each with diameters of 2,400 to 2,800 km (larger than Pluto).
Tracking the cyclones’ movements revealed that each storm gradually drifts toward the pole. This is similar to how cyclones on Earth migrate, but on our planet they break up before reaching the poles due to the lack of warm, moist air that fuels them.
When Jupiter’s cyclones get close to each other, they interact.
“These competing forces result in the cyclones ‘bouncing’ off one another in a manner reminiscent of springs in a mechanical system,” says Juno co-investigator Yohai Kaspi, from the Weizmann Institute of Science in Israel. “This interaction not only stabilises the entire configuration, but also causes the cyclones to oscillate around their central positions, as they slowly drift westward, clockwise, around the pole.”
“Everything about Jupiter is extreme,” says Juno mission principal investigator Scott Bolton, from the Southwest Research Institute in the US. “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.”
