Jupiter’s moon Io is covered in hundreds of volcanoes, spewing fountains of lava that regularly fill craters in their place with hot molten pools. The latest discovery of extreme volcanic activity on a Jovian moon surpasses any eruptions previously detected on Io, proving that this chaotic world has no boundaries.
NASA’s Juno mission has discovered a volcanic hot spot on the southern half of Jupiter’s moon, marking the most powerful eruption ever found on Io or anywhere else in the solar system beyond Earth. combined.
“This is the most powerful volcanic event ever recorded on the most volcanic world in our solar system — so that’s saying something,” Scott Bolton, a researcher at the Southwest Research Institute in San Antonio and principal investigator of the Juno mission, said in a statement.
Details of the discovery were recently published in the Journal of Geophysical Research: Planets.
Credit: NASA/JPL-Caltech/SwRI/ASI/INAF/JIRAM
A lava fountain
Juno has been orbiting Jupiter for about ten years. The spacecraft’s extended mission, which began in 2021, allowed scientists to explore Jupiter’s moons Io, Europa, Ganymede, and Callisto.
Juno flies by the same area of Io once every two orbits. During the latest flyby on December 27, 2024, the spacecraft flew within about 46,200 miles (74,400 kilometers) of the moon and focused its infrared instrument on the southern hemisphere.
Using Juno’s Jovian Infrared Auroral Mapper (JIRAM) instrument, donated by the Italian Space Agency, scientists discovered the phenomenon of extreme infrared light. The total radiant energy of the new hot spot has been measured at over 80 billion watts.
“What makes the event even more surprising is that it did not involve a single volcano, but many active sources that shone at the same time, increasing its brightness more than a thousand times compared to normal levels,” Alessandro Mura, a researcher at the Italian National Institute for Astrophysics (INAF), and lead author of the paper, said in an emailed statement. “This good agreement suggests that it was a single large explosive event, spreading over hundreds of kilometers underground.”
The data not only suggests that this is the most powerful volcanic eruption ever recorded on Io, it also indicates that there is a large chamber system of interconnected magma reservoirs beneath the moon’s surface. This woven system can be activated simultaneously to produce a single, planet-wide energy release. “We have evidence that there are several hot spots coming out at the same time,” said Mura.
JunoCam, the spacecraft’s visible light camera, also captured the event. The team compared images taken by JunoCam from the mission’s last two flybys of Io in April and October of 2024 and the most recent one taken in December 2024, and found significant changes in surface area counts where the hot spot was found.
A troubled world
Io’s volcanic activity is the result of the gravitational pull between Jupiter’s gravitational pull on the moon and the precisely timed pull from neighboring moons Ganymede and Europa. The battered moon is experiencing massive tidal forces, causing its surface to move up and down 100 meters at a time, according to NASA.
The ocean’s energy generates tremendous heat inside Io, thus causing its liquid subsurface to seek relief from the pressure by escaping to the surface. Io’s surface is constantly renewed, as molten lava refills the moon’s craters, coating the moon with liquid rock.
The newly discovered explosion will likely leave a long-lasting impact on Io. The team behind Juno will use the mission’s upcoming flyby of the moon on March 3 to observe the hot spot and note any changes in the environment.
“While it’s always great to see events that rewrite the record books, this new hot spot could do even more,” Bolton said. “An interesting feature could improve our understanding of volcanism not only on Io but also on other planets.”
