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Strange location of Io’s volcanoes leaves astronomers puzzled

Proving that the galaxy never ceases to surprise us, a study published in January’s Earth and Planetary Science Letters claims that hundreds of volcanoes on the surface of Jupiter’s moon Io have somehow shifted.

Conducted by NASA and the ESA, the study was spearheaded by Christopher Hamilton, who serves as an Earth and planetary scientist for NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Having studied how patterns of volcanoes aid in the exploration of a planet or moon’s internal design, Hamilton sought to apply the same idea to Io by mapping the moon’s surface with data from the Voyager and Galileo spacecraft. The results were unexpected.

“Our analysis supports the prevailing view that most of the heat is generated in the asthenosphere, but we found that volcanic activity is located 30 to 60 degrees East from where we expect it to be,” said Hamilton.

This eastward shift, which can represent a displacement of 600 to 1,200 miles at the equator, threw off assumptions concerning the placement of the volcanoes. Regardless, the result was welcome.

“The unexpected eastward offset of the volcano locations is a clue that something is missing in our understanding of Io,” explained Hamilton. “In a way, that’s our most important result. Our understanding of tidal heat production and its relationship to surface volcanism is incomplete.”

The shift was unanticipated due to Io’s unique relationship with both Jupiter and two of its fellow moons, Gannymede and Europa. Existing information would maintain that Io, tugged between the planet and the moons, would experience internal heating due to the friction created by the opposing gravitational pulls. The 400 volcanoes, however, are east of the most dramatically heated area instead of on top of it. According to Hamilton, their location “can’t be reconciled with any existing solid body tidal heating models.”

The reasons for the shift remain elusive. Hamilton has some theories, including that Io is rotating faster than believed and thus causing the shifts, or that a magma ocean lay nestled somewhere within the moon. Further study is necessary, but Hamilton is excited.

“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,” he said.

Io remains the most volcanic body in the solar system, with eruptions of sulfur and other elements reaching heights of 250 miles above the moon’s surface. The activity is extensive that it is completely resurfaced every million years or so.