Io's Misplaced Volcano Mystery Solved with Subsurface Ocean of Molten Rock

Could Io have an underground magma ocean? Tides flowing in a subsurface ocean of molten rock could explain why Jupiter's moon appears to have its volcanoes in the "wrong" place, according to a new study.

"This is the first time the amount and distribution of heat produced by fluid tides in a subterranean magna ocean on Io has been studied in detail," said Robert Tyler, one of the researchers, in a news release. "We found that the pattern of tidal heating predicted by our fluid-tide model is able to produce the surface heat patterns that are actually observed on Io."

Io is the most volcanically active world in the entire solar system. It has hundreds of erupting volcanoes that blast fountains of lava up to 250 miles high. The intense geological activity is due to the heat produced by a gravitational tug-of-war between Jupiter's massive gravity and smaller, but precise pulls from its neighbor in the same orbital location, which distorts Io's orbit into an oval shape. This modified orbit causes Io to flex as it moves around Jupiter, causing material within Io to shift position and generate heat by friction, just as rubbing your hands together briskly makes them warmer.

The researchers actually compared computer models using assumptions to a map of the actual volcano locations on Io. This revealed that most of the volcanoes were offset 30 to 60 degrees to the East of where the models predicted they'd be.

So why were the volcanoes misplaced? The researchers believe that a combination of fluid and solid tital heat effects may best explain all the volcanic activity observed on Io.

"The fluid tidal heating component of the hybrid model best explains the equatorial preference of volcanic activity and the eastward shift in volcano concentrations, while simultaneous solid-body tidal heating in the deep-mantle could explain the existence of volcanoes at high latitudes," said Wade Henning, one of the researchers. "Both solid and fluid tidal activity generate conditions that favor each other's existence, such that previous studies might have been only half the story for Io."

The findings reveal a bit more about this world, and show why these volcanoes are slightly shifted to one side or the other.

The findings are published in the journal Astrophysical Journal Supplement Series.

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