What’s the News: Jupiter’s moon Io is more volcanically active than any other object in our solar system, releasing 30 times more heat than Earth through volcanism. It’s thought that Jupiter’s gravity pulls so hard on the moon and causes so much friction that the resulting thermal energy melts a huge amount of underground rock, feeding Io’s 400 active volcanoes.

For years, astronomers have debated whether Io’s spewing lava comes from isolated pockets of magma or a layer that spans the entire moon. Astronomers have now peered into Io’s interior for the first time, discovering that it has a global sea of magma roughly 30 miles thick. “It turns out Io was continually giving off a ‘sounding signal’ in Jupiter’s … magnetic field that matched what would be expected from molten or partially molten rocks deep beneath the surface,” lead researcher Krishan Khurana told Wired.

How the Heck:

As NASA’s Galileo spacecraft flew by Jupiter nearly a decade ago, it detected distortions in the planet’s magnetic field. “Just like the waves beamed from an airport metal detector bounce off ...