Jupiter’s moon, Io, is best known for its volcanoes. Thanks to NASA’s Juno spacecraft, it’s now back in the spotlight. New findings from Juno’s infrared instrument, JIRAM, have provided the most detailed picture yet of Io’s volcanic activity, including the surprising prevalence of vast lava lakes.
Io has captivated astronomers since its discovery by Galileo Galilei in 1610. Since then, spacecraft like Voyager 1 have captured eruptions in progress, and scientists believe Io is the most volcanically active body in our solar system. However, the details of these eruptions have remained a mystery.
Recent Juno flybys skimmed just over 8,000 miles from Io’s surface. JIRAM, designed to study Jupiter’s atmosphere, was surprisingly effective in peering through Io’s volcanic haze. The instrument’s high-resolution infrared images revealed a startling fact: Io’s surface may be dominated by vast calderas, massive volcanic depressions, filled with molten lava lakes.
“The high spatial resolution of JIRAM’s infrared images, combined with the favorable position of Juno during the flybys, revealed that the whole surface of Io is covered by lava lakes contained in caldera-like features,” Alessandro Mura, a Juno co-investigator from the National Institute for Astrophysics in Rome, said in a statement. “In the region of Io’s surface in which we have the most complete data, we estimate about 3% of it is covered by one of these molten lava lakes.” (A caldera is a large depression formed when a volcano erupts and collapses.)
The JIRAM data also offers clues about the behavior of these fiery lakes. Images show a characteristic “ring” of lava around the perimeter, suggesting a cycle of upwelling magma and crust formation.
“We now have an idea of what is the most frequent type of volcanism on Io: enormous lakes of lava where magma goes up and down,” Mura added. “The lava crust is forced to break against the walls of the lake, forming the typical lava ring seen in Hawaiian lava lakes. The walls are likely hundreds of meters high, which explains why magma is generally not observed spilling out of the paterae” — bowl-shaped features created by volcanism — “and moving across the moon’s surface.”
“We are just starting to wade into the JIRAM results from the close flybys of Io in December 2023 and February 2024,” said Scott Bolton, principal investigator for Juno at the Southwest Research Institute in San Antonio.
“The observations show fascinating new information on Io’s volcanic processes. Combining these new results with Juno’s longer-term campaign to monitor and map the volcanoes on Io’s never-before-seen north and south poles, JIRAM is turning out to be one of the most valuable tools to learn how this tortured world works.”
[via Space.com; image credits: Image data: NASA/JPL-Caltech/SwRI/MSSS, Image processing by Andrea Luck (CC BY)]
