Ever wondered why Jupiter's moon, Io, is so darn volcanic? NASA thinks it just may have the answer. According to a new report from the Galileo spacecraft, Jupiter's surface is hiding "a subsurface ocean of molten or partially molten magma beneath" it. As the solar system's most volcanic object, "Io produces 100 times more lava each year than all volcanoes on Earth," the folks at NASA explain. "While Earth's volcanoes occur in localized hotspots like the 'Ring of Fire' around the Pacific Ocean, Io's volcanoes are distributed all over its surface."

Earth and its moon are believed to have once boasted similar seas of magma so, as one NASA scientist explains, "Io's volcanism informs us how volcanoes work" and can perhaps give us some insight into what our Earth and moon were like back in their hotter days. In fact, Io and Earth are the only bodies in our solar system where active magma volcanoes can be found and they share some similar types of volcanic rock. One rock detected on Io by Galileo, for example, is comparable to a rock found in Scandinavia.

Io is also super-volcanic because of its huge, gaseous parent planet Jupiter. Mike Wall at Space.com explains that Jupiter's "tidal forces pull hard on the moon, causing its rocky internal layers to rub against each other and melt from the friction-induced heat." Or as NASA puts it, the gravitational "squeezing and stretching" of the moon provides the "energy for the volcanic activity." Cool, huh?