IO

IO is a moon of Jupiter. Io is the most volcanically active body in the solar system. Volcanic plumes rise 300 km (190 miles) above the surface, with material shooting out at nearly half the required escape velocity. An interesting point is that Enceladus has plumes that shoot out ice and water vapor (with organic compounds), and IO has plumes that shoot out lava like material. Both moons have tidal friction that cause these plume eruptions and also generate heat.

Io's orbit, keeping it at more or less a cozy 422,000 km (262,000 miles) from Jupiter, cuts across the planet's powerful magnetic lines of force, thus turning Io into a electric generator. Io can develop 400,000 volts across itself and create an electric current of 3 million amperes. This current takes the path of least resistance along Jupiter's magnetic field lines to the planet's surface, creating lightning in Jupiter's upper atmosphere.

** Image of IO is from NASA, the source of the material.