Nasa has revealed new details about Io, Jupiter’s third-largest moon and the most volcanic world in our solar system.
Io has over 400 active volcanoes on its surface, creating stunning lava flows and eruptions that send plumes into space.
A recent discovery by Nasa’s Juno mission has helped solve a 44-year-old mystery about the source of Io’s intense volcanic activity.
NASA posted on X: “New discoveries from our #JunoMission reveal the fiery heart of Jupiter moon Io’s rage. (Yes, that is an active volcano erupting into space.)”

What powers Io’s volcanoes?

Io’s volcanoes are likely powered by separate magma chambers instead of one large magma ocean. According to the paper titled “Io’s tidal response precludes a shallow magma ocean”, published in Nature, this phenomenon explains the moon’s intense volcanic activity.
Io’s volcanoes constantly erupt, spewing lava and plumes that shape its unique surface. Although Io was discovered in 1610, its volcanic activity was only confirmed in 1979 by Nasa scientist Linda Morabito.
“Since Morabito’s discovery, planetary scientists have wondered how the volcanoes were fed from the lava underneath the surface,” Juno principal investigator Scott Bolton was quoted as saying to Nasa. “Was there a shallow ocean of white-hot magma fueling the volcanoes, or was their source more localised? We knew data from Juno’s two very close flybys could give us some insights on how this tortured moon actually worked,” he added.

How did Nasa observe Io?

Nasa’s Voyager 1 spacecraft captured the first images of Io’s volcanic plumes in 1979. About the same size as Earth’s Moon, Io is constantly squeezed by its elliptical orbit around Jupiter. This squeezing, called tidal flexing, creates intense heat inside the moon, melting its interior and causing eruptions.
During close flybys in late 2023 and early 2024, Nasa’s Juno spacecraft used Doppler measurements to collect precise gravity data.This showed that Io doesn’t have a global magma ocean as previously thought, but instead has separate magma chambers powering its volcanoes.
“This constant flexing creates immense energy, which literally melts portions of Io’s interior,” explained Bolton.

Understanding other moons

The findings extend beyond Io. “Juno’s discovery that tidal forces do not always create global magma oceans does more than prompt us to rethink what we know about Io’s interior,” Juno co-investigator Ryan Park was quoted as saying to NASA. “It has implications for our understanding of other moons, such as Enceladus and Europa, and even exoplanets and super-Earths,” he added.

Future missions

Juno continues its mission, recently completing its 66th science flyby over Jupiter on November 24. Its next close approach, scheduled for December 27, will bring it 2,175 miles above Jupiter’s cloud tops. Since entering the planet’s orbit in 2016, Juno has travelled over 645 million miles.