Io is the most volcanically active body in the solar system, with about 100 volcanoes erupting at any one time.
Io, the innermost of Jupiter's four large moons, sports an internal ocean of magma.
The ocean of magma explains a long-standing puzzle first posed by NASA's defunct Galileo probe.
The ocean is about 20 percent liquid and 80 percent solid, similar to the consistency of crushed ice.
What's torturing Io, the Jupiter moon that holds the unfortunate distinction of the most volcanically active body in the solar system?
An underground ocean of magma, say scientists who cracked a long-standing puzzle posed by NASA's defunct Galileo probe, which orbited giant Jupiter and surveyed its moons from 1995 to 2003.
The Galileo team used the planet's strong magnetic field to look for distinct radio waves bouncing back from the Jovian moons, a technique that previously netted evidence for underground saltwater oceans on Europa, Callisto and Ganymede.
Oddly, Io, which is far too hot for liquid water, showed some distinctive footprints of liquidity as well. However, it wasn't until team members discovered new research about magnetic properties of melted rock that they were able to piece together Io's odd story Tugged by Jupiter's massive gravity, rock inside Io has melted into a molten slush that fills a cavity at least 50 kilometers (31 miles) deep.