The most volcanic world in the Solar System: this discovery alters our understanding of Jupiter's moon.

Contrary to the prevailing beliefs about Io, the second-largest moon of Jupiter, there is no ocean of magma hidden beneath its surface, nor does it lead to the eruptions of hundreds of volcanoes. According to a study published in the journal Nature, a different mechanism is at play, as reported by Space.

Jupiter's moon Io is the world with the highest number of volcanoes in the Solar System. Previous observations of Io suggested that there was an ocean of molten magma beneath its surface, approximately 50 km deep. The surface of Io experiences eruptions from around 400 volcanoes continuously, and almost the entire surface of this moon is covered with lava plains. The lava that erupts from the volcanoes originates from the mantle.

Scientists believe that Io's volcanic activity is driven by the constant deformation of the moon due to Jupiter's gravitational influence. The reason for this is that Io has an elliptical orbit, causing it to move closer to and farther from Jupiter as it orbits the planet. This results in the moon's interior expanding and contracting, generating energy in the form of heat. Consequently, magma from the moon's interior is expelled onto the surface as lava during volcanic eruptions. In other words, the tidal energy that Io receives should be sufficient to maintain an ocean of molten magma within the moon. However, new research indicates that no such ocean of magma exists.

Researchers utilized new data from the Juno spacecraft, along with earlier observations of Jupiter's moon, concluding that volcanic eruptions do not occur due to an ocean of magma, as it is nonexistent.

If there were an ocean of magma within Io, the moon would experience significant deformation due to Jupiter's gravity. Yet, the new data reveal that Io's interior is predominantly very solid, rather than molten. This means that Io has mainly a solid mantle beneath its crust.

If there is no ocean of magma, how does it emerge from the volcanoes as lava? Scientists believe that small "pockets" of magma exist within Io's solid mantle, which rise to the surface through the volcanoes. Thus, localized areas of molten rock do exist, and they are responsible for the volcanic activity on Io.

The research findings indicate that tidal heating caused by the gravitational influence of the parent planet is insufficient to create an ocean of magma on the moon. Consequently, this discovery may also alter our understanding of other moons of Jupiter and Saturn.