Io may be close to thermal equilibrium, according to a study published this week in Nature. And if the new findings are correct, the volcanically wild moon could one day break free of Jupiter’s hold — and lose its rare, volcanic splendor.
Io is Jupiter’s innermost moon, and is the most volcanically active body in the Solar System. Its geological activity is thought to be the result of tidal heating from friction generated by the pull of Jupiter’s gravity. But it’s not known whether this internally generated tidal heat is high enough to generate the heat flow observed on Io’s surface.
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Using astronomic observations made between 1891 and 2007, Valery Lainey, of the Observatoire de Paris in France, and colleagues have estimated the dissipation of tidal energy in Io by tracking its effect on the orbital motions of the innermost Galilean moons. For Io, the value is in good agreement with the observed surface heat flow and suggests that Io is close to thermal equilibrium. Jupiter’s tidal dissipation is close to the upper bound of its average value, as would be expected from the long-term evolution of the system.
“The measured secular accelerations indicate that Io is evolving inwards, towards Jupiter,” Lainey and her colleagues add, “and that the three innermost Galilean moons (Io, Europa and Ganymede) are evolving out of the exact Laplace resonance.”
In an accompanying editorial, Gerald Schubert of the University of California in Los Angeles, writes that “Io’s orbital imprisonment is the cause of its spectacular volcanism.”
“If it eventually breaks free, the most volcanically active object in our Solar System will become dormant.”