Io is an eruptive mystery. Based on scientific models, the tiny Jovian moon's volcanoes flare up in the "wrong" places. How could that be? Well apparently, our models didn't account for a massive subsurface ocean of lava.
That's right: According to a new NASA study, Jupiter's moon Io may be hiding an ocean of molten rock, powered by a process known as tidal heating. Lava oceans are fascinating in their own right, but this discovery also bears important implications for the prospects of life beyond Earth. A similar heating mechanism could fuel subsurface oceans beneath the icy moons of Europa and Enceladus — two of the most promising candidates for extraterrestrial life.
Io is one of the most geologically active worlds in our solar system, with hundreds of volcanoes constantly spewing lava some 400km skyward. Planetary scientists have known for some time that Io's intense volcanic activity is the result of a gravitational tug-of-war between Jupiter and neighbouring moon Europa.
But there's a mystery in them thar space volcanoes: They're erupting in the wrong place! Usually, the volcanoes we see on Io are offset 30 to 60 degrees east of where our computer models tell us they ought to be.
According to a team of researchers including Wade Henning of NASA's Goddard Spaceflight center, the missing piece of the puzzle could be fluid dynamics. Which only makes sense if Io has a giant lava ocean beneath its surface:
The team thinks a combination of fluid and solid tidal heating effects may best explain all the volcanic activity observed on Io. "The fluid tidal heating component of a 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 Henning. "Both solid and fluid tidal activity generate conditions that favour each other's existence, such that previous studies might have been only half the story for Io."
That's pretty interesting, but also, so what? Well you see, there's another tidally-stressed moon kicking around Jupiter: Europa. You may remember that moon from every science fiction book and movie featuring alien life in our solar system ever. We've got high hopes that Europa contains a massive ocean of liquid water beneath its glacial crust. And the new insights into Io imply that subsurface oceans may be more common and longer-lasting than we realised.
Long-lasting enough for life to evolve? It's high time we rocketed over to Europa to find out.
Top: Five-frame sequence of images from the New Horizons spacecraft captures the giant plume from Io's Tvashtar volcano. Image Credit: NASA/JHU Applied Physics Laboratory/Southwest Research Institute