NASA’s Juno mission has resolved a 44-year-old mystery about Io, Jupiter’s fiery moon. New research reveals that each of Io’s volcanoes is powered by its own localized magma chamber, dismissing the long-held theory of a global magma ocean beneath the moon’s surface.
The groundbreaking discovery was unveiled in a study published in Nature on December 12 and was also a highlight of the American Geophysical Union’s annual meeting in Washington. The finding deepens our understanding of Io, the most volcanically active body in the solar system, and its role in planetary science.
Io, about the size of Earth’s Moon, hosts over 400 volcanoes that constantly spew lava and gas. While the moon was discovered by Galileo Galilei in 1610, its volcanic activity wasn’t observed until 1979, when NASA’s Voyager 1 spacecraft captured dramatic plumes erupting from its surface.
“Since Linda Morabito’s discovery in 1979, scientists have debated whether Io’s volcanoes are fueled by a global magma ocean or localized magma chambers,” said Scott Bolton, Juno’s principal investigator.
Juno’s close flybys of Io in December 2023 and February 2024 brought the spacecraft within 930 miles of the moon’s surface. These encounters allowed scientists to use NASA’s Deep Space Network to collect precise Doppler data, measuring Io’s gravitational pull on the spacecraft.
The data revealed a phenomenon known as tidal flexing, caused by the immense gravitational forces exerted by Jupiter. Io’s elliptical orbit creates relentless squeezing and stretching of its interior, generating extreme heat that melts parts of the moon’s subsurface.
“If there had been a global magma ocean, Juno would have detected a much larger tidal deformation,” said Bolton. “Instead, the findings point to magma chambers distributed beneath individual volcanoes.”
Lead author Ryan Park, a Juno co-investigator, emphasized that this discovery has far-reaching implications. “Understanding Io’s magma chambers reshapes how we think about tidal forces and their effects on planetary bodies,” he said. The findings could inform studies of other moons, such as Enceladus and Europa, and even distant exoplanets.
Juno continues to explore Jupiter and its moons. The spacecraft completed its 66th science flyby of Jupiter on November 24 and is set to make its next close pass on December 27. With each orbit, Juno advances our knowledge of the gas giant and its enigmatic moons, shedding light on the complex processes that shape planetary systems.
The Juno mission, part of NASA’s New Frontiers Program, is managed by the Jet Propulsion Laboratory and involves collaborations with international research institutions, including the Italian Space Agency. Its instruments, designed to probe Jupiter’s atmosphere, magnetic field, and satellites, are key to unlocking the secrets of our solar system’s largest planet.