NASA's Juno probe has provided new insights into Jupiter's volcanic moon Io, concluding that it does not possess a subsurface ocean of magma. This finding addresses longstanding questions regarding the moon's volcanic activity and its geological composition.
Data from Juno and the earlier Galileo mission indicated the possibility of a 31-mile (50-kilometer) deep magma ocean beneath Io's surface. However, recent measurements have shown that Io's interior is rigid, suggesting that the volcanic eruptions are fueled by pockets of molten rock within the mantle rather than a global magma ocean.
Io is home to approximately 400 active volcanoes, with its surface predominantly covered in lava plains. The heat required for melting rock in Io's mantle is generated by tidal heating, caused by gravitational interactions with Jupiter and other Galilean moons. As Io orbits Jupiter, the varying distance results in significant gravitational forces that heat its interior.
Juno has been orbiting Jupiter since 2016 and has conducted multiple flybys of Io, including close approaches in December 2023 and February 2024. These close encounters allowed scientists to measure Io's gravitational field and assess its internal structure.
The implications of these findings extend beyond Io, offering insights into the geological characteristics of exoplanets, particularly those in tight orbits around M-dwarf stars. If Io lacks a magma ocean, similar exoplanets may also be devoid of such features, challenging existing assumptions about their geologic activity.