Jupiter’s moon Io is the most volcanically active world in the whole Solar System, with hundreds of volcanoes, some erupting lava fountains up to 250 miles high. But, concentrations of volcanic activity are significantly displaced from where they are expected to be based on models that predict how the moon’s interior is heated, according to NASA and European Space Agency researchers.

Jupiter’s massive gravity and the smaller but precisely timed pulls from two neighboring moons that orbit further from Jupiter — Europa and Ganymede. Io orbits faster than these other moons, completing two orbits every time Europa finishes one, and four orbits for each one Ganymede makes. This regular timing means that Io feels the strongest gravitational pull from its neighboring moons in the same orbital location, which distorts Io’s orbit into an oval shape. This in turn causes Io to flex as it moves around Jupiter.

The flexing from gravity causes tidal heating — in the same way that you can heat up a spot on a wire coat hanger by repeatedly bending it, the flexing creates friction in Io’s interior, which generates the tremendous heat that powers the moon’s extreme volcanism.

Io’s volcanism is so extensive that it gets completely resurfaced about once every million years or so, actually quite fast compared to the 4.5-billion-year age of the solar system. So in order to know more about Io’s past, we have to understand its interior structure better, because its surface is too young to record its full history.

The research was funded by NASA, the NASA Postdoctoral Program, administered by Oak Ridge Associated Universities, and the European Space Agency……

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