Based on heat prediction models of Jupiter's moon Io, NASA and European Space Agency researchers say the moon's volcanoes are not where they are expected to be.

The moon's volcanic activity is 30 to 60 degrees east of where models suggest it should be.

"We performed the first rigorous statistical analysis of the distribution of volcanoes in the new global geologic map of Io," said Christopher Hamilton of the University of Maryland, College Park, who led the research, according to a NASA report. "We found a systematic eastward offset between observed and predicted volcano locations that can't be reconciled with any existing solid body tidal heating models."

With more than 400 active volcanoes, Io is the most volcanically active place in our solar system, playing host to hundreds of volcanoes that have been known to spew fountains of lava as much as 250 miles (about 400km) into the air. Other than Earth, Io is the only other place on the solar system known to have active magma volcanoes, according to the NASA report. 

Io's intense geological activity is in part due to Jupiter's powerful gravitational forces pulling the moon towards it as it orbits near the planet, then relaxing the gravitational pull as the Io moves away. This flexing from gravity causes tidal heating, creating friction in Io's interior, generating tremendous heat and contributing to the moon's volcanism.

One possible scenario to explain Io's actual volcanic activity against the incorrectly predicted centers of volcanic activity is that the moon might have an ocean of electrically conducting magma below its surface.

"Our analysis supports a global subsurface magma ocean scenario as one possible explanation for the offset between predicted and observed volcano locations on Io," says Hamilton. "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."

Much is left to be learned about Io, where the volcanism is so extensive that it gets resurfaced every million years. According to Hamilton, we must learn more about Io's interior because the moon's surface is too young to get a good record of its history.