NASA Baffled Over Why Volcanoes on Jupiter's Moon Io are in the Wrong Place

First Posted: Apr 05, 2013 08:18 AM EDT

Jupiter's moon, Io, is one of the most volcanically actively worlds in the Solar System. Massive shoots of lava explode up to 250 miles high into its atmosphere. As impressive as that is, though, researchers have found that the volcanoes simply aren't in the right place on the moon. Concentrations of volcanic activity are significantly displaced from where they should be based on models that predict how the moon's interior is heated.

Since Jupiter is so massive, Io is caught between its gravity and the gravities of two neighboring moons. Io has a fast orbit, whipping around Jupiter more quickly than the other two moons--Europa and Ganymede. This means that Io experiences the strongest gravitational pull from its neighboring moons in the same orbital location, which means that Io's orbit is distorted into an oval shape and causes the moon itself to flex during its orbit.

How does that affect Io's volcanoes? As Io moves further away from Jupiter, the gravitational pull decreases and the moon relaxes. This flexing that the moon experiences causes tidal heating and actually warms up Io's interior.

In order to further study this flexing and the moon's volcanic activity, researchers performed a spatial analysis using a new, global geologic map of Io. The map itself provided the most comprehensive inventory of Io's volcanoes to date, which allowed the researchers to explore the patterns of volcanism. In particular, they tested a range of interior models by comparing observed locations of volcanic activity to predicted tidal heating patterns.

They found that, surprisingly, the volcanoes weren't where they should be. Instead, they discovered a systematic eastward offset between observed and predicted volcano locations. The positions couldn't even be reconciled with existing solid body tidal heating models.

That said, researchers may have a theory that could explain the offset. "Our analysis supports a global subsurface magma ocean scenario as one possible explanation for the offset between predicted and observed volcano locations on Io," said Christopher Hamilton, one of the researchers, in a press release. "However, Io's magma ocean would not be like the oceans on Earth. Instead of being a completely fluid layer, Io's magma ocean would probably be more like a sponge with at least 20 percent silicate melt within a matrix of slowly deformable rock."

The findings, while unusual, may encourage researchers to find that missing piece of the puzzle that could explain why Io's volcanoes are where they are. Currently, scientists are still unsure exactly why the volcanoes aren't where they should be.

"The interpretation for why we have the offset and other statistical patterns we observed is open, but I think we've enabled a lot of new questions, which is good," said Hamilton in a press release.

The findings are published in Earth and Planetary Science Letters.

Want to a small movie of one of Io's volcanoes spewing debris into its atmosphere? Check it out here.

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