Io facts :
Discovery:Jan 7, 1610 by Galileo Galilei
Mean Distance from Jupiter (km):421,600
Mean Distance from Sun (AU):5.20
Revolution period : 1d 18h 27.6m
Io is one of Jupiter’s moons, discovered by the famous astronomer, Galileo. Io is unique in the numerous volcanoes that cover its surface.
Deep within its surface, Io is made up of iron and iron sulfide. Io generates a lot of heat from beneath its surface. This heat emerges to the surface in the form of hot sulfur spewing geysers and volcanic lava. Io has the most volcanically active surface in all of the solar system. The first volcano discovered on Io and also the largest volcano has been called Pele. Some of Io's volcanic plumes are over 300 km, the material being ejected from the surface at approximately one kilometer per second. Due to such extensive volcanic activity the surface of Io is very colorful, mottled with red, yellow, white and orange black markings.
The surface of Io is mostly molten rock and crust, with deposits of frozen sulfur dioxide – a result of so much volcanic activity A doughnut shaped cloud of ions on Io, glow when ultraviolet rays fall on it. Io has no mountains on its surface. The only mountain peak is about 9 km high.
Io has a thin atmosphere of sodium gas along with sulfur, potassium and oxygen atoms – seen clearly even from Earth. The temperature on Io's surface is about -143° C (-230° F); except areas where there is volcanic activity.