What is powering the volcanoes on Jupiter’s moon io?
the energy source that powers io's volcanoes lies in the tides exerted by Jupiter and in the slightly elliptical orbit of the satellite. When the Voyager 1 spacecraft approached io in March 1979 the images sent back to Earth revealed that its surface appeared dotted with a multitude of volcanic centres, of which a dozen exhibited full activity with towering lava flows and plumes up to some hundred kilometres high.
under normal conditions the intense tidal forces produced by Jupiter would eventually reset the eccentricity of io's orbit in a short time, making it a perfect circumference. however, the nearby satellite Europa has an orbital period exactly twice that of io. this 1:2 resonance forces io's orbit to be slightly elliptical over time and leads the two satellites to renew their mutual position every 3.55 days – less important is another 1:4 synchronism with the orbital period of Jupiter's moon Ganymede. As a consequence the Jupiter tide causes a periodic deformation of the entire satellite which heats and melts its interior, producing intense volcanic phenomena on the surface to such an extent that io holds the record of ‘most volcanically active body of our Solar System’.
io is the closest of the Galilean moons to Jupiter