Io is 3,630 km in diameter and is 421,600 km away from Jupiter.

Its silicate mantle and crust are under constant tidal flex from Jupiter and the three other Galilean satellites. The result of this are the constant violent eruptions of its volcanoes. It may seem strange that Europa, Ganymede and Callisto can provide a counterforce for Jupiter, but Ganymede and Callisto are larger than Io. Additional "energy" generated by Europa and Ganymede are the result of orbital resonance which is 1:2:4 - for every 1 orbit of Europa, Io orbits twice and for every 1 orbit of Ganymede, Io orbits four times. This timing sequence creates a resonance.

The face of Io has been describes as looking like a pizza. All of the dots on the face are volcanoes, and this image shows the active ones:

Close examinations by both Voyager and Galileo have images volcanoes "caught in the act."

In addition to the volcanic activity, sulfur dust is also introduced to the surface:

seen in the image above as the ring. In addition to sulfur dust, lava flows are also very common:

With all of the violet eruptions constantly spewing material upward, an atmosphere might be present - but there isn't one. The gravity of Jupiter grabs hold of the material and is put into orbit within the Io Torus:

The Torus is an area of intense electromagnetic energy and is an area of constant study. More data on the Io Torus can be found at the Io Plasma Torus links.

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