Galileo Sees Io Erupt

NASA’s Galileo spacecraft captured this image of a volcanic eruption on Io in 1997. Io is the most volcanically active world in the solar system, thanks to constant flexing brought on by the gravitational push and pull from Jupiter as well as fellow moons Ganymede and Europa. The extreme tidal forces generate a tremendous amount of heat within Io, keeping much of its subsurface crust in liquid form seeking any available escape route to the surface to relieve the pressure. Hundreds of huge volcanoes cover a surface only slightly larger than the Moon, with erupting lava fountains reaching dozens of miles high.