Jupiter's Io -The Volcano Center of the Solar System

These images of Jupiter's intensely volcanic moon, Io, taken five months apart, show the results of a titanic eruption, 400-kilometers (250 miles) across over Pillan Patera. The ability to monitor such changes over a period of years was one of the Galileo Spacecraft's important scientific contributions.

Orbiting the giant planet Jupiter is the fascinating moon, Io, one of four moons discovered by Galileo in 1610. One look at Io and it is obvious that something unusual is going on there. Its mottled surface is a collage of colors-yellow, orange, red, and blackish browns - which make it look somewhat like a gigantic pizza. The explanation for this remarkable color palette is found down on the surface. Io is literally bursting with volcanic activity. Volcanoes spew out vast amounts of sulfurous material which cover Io's Iandscape, which reflects the various colors that sulfur takes on at different temperatures.

Intense radiation from Jupiter's atmosphere over the course of the Galileo mission severely damaged the craft's computer circuitry and resulted in failure of the computer systems. In order to prevent the possibility of the crippled spacecraft contaminating the environment of Io's neighboring moon, Europa, which may harbor a liquid water ocean beneath its surface, the spacecraft was plunged into the atmosphere of Jupiter on September 21, 2003.

Io is the most volcanically active body in the solar system. Volcanic plumes rise 300 kilometers (190 miles) above the surface, with material spewing out at nearly half the required escape velocity.

A bit larger than Earth's moon, Io is the third largest of Jupiter's moons, and the fifth one in distance from the planet.

in its widely varying distances from Jupiter, Io is subjected to tremendous tidal forces. These forces cause Io's surface to bulge up and down (or in and out) by as much as 100 meters (330 feet). On Earth, in the place where tides are highest, the difference between low and high tides is only 18 meters (60 feet), and this is for water, not solid ground.

This tidal pumping generates 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. Thus, the surface of Io is constantly renewing itself, filling in any impact craters with molten lava lakes and spreading smooth new floodplains of liquid rock. The composition of this material is not yet entirely clear, but theories suggest that it is largely molten sulfur and its compounds (which would account for the coloring differentals) or silicate rock (which would better account for the apparent temperatures, which may be too hot to be sulfur). Sulfur dioxide is the primary constituent of a thin atmosphere on Io. It has no water to speak of, unlike the other, colder Galilean moons. Data from the Galileo spacecraft indicates that an iron core may form Io's center, thus giving Io its own magnetic field.

Io's orbit, keeping it at more or less a cozy 422,000 kilometers (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.

Posted by Casey Kazan. Adapted from NASA documents.

Source:

http://solarsystem.nasa.gov/planets/profile.cfm?Object=Io