Io, which is about the size of Earth's moon and is Jupiter's closest large satellite, is covered with lava flows and dozens of active volcanoes

The heat for this activity comes from the fact that the moon travels on an elongated path around Jupiter, and therefore feels the giant planet's gravity at different strengths along its orbit.

But it will not always be so, according to a new study led by Valéry Lainey of the Paris Observatory in France.

But Lainey and colleagues have found that the moons are, in fact, moving out of their resonance – Europa and Ganymede are gradually drifting away from Jupiter, while Io is moving towards the planet.

"If this occurs on a short timescale, say [100 million] years or less, then we have been lucky to see Io in its volcanic glory, because dormancy will be the fate of Io when the resonance is broken,"

For every orbit that Ganymede makes, Europa makes two and Io four – a type of gravitational relationship called a Laplace resonance.