The four Galilean satellites

Satellite Diameter km Mass kg Density g/cm Semi-major axis km 

On the surface of lo 400 active volcanoes and more than 150 mountains have been detected. There are volcanic plumes that extend up to 500 km. The tidal forces of Jupiter on lo are 6000 times stronger than those of the Moon on Earth. In addition to these forces, there are also tidal forces caused by the two other Galilean satellites Europa and Ganymede (these are comparable to the tidal force of the Moon). Furthermore, the strength of these forces varies because the orbit of lo is elliptical. The variation of the tidal forces of Jupiter due to lo s elliptical orbit is 1000 times the strength of the tidal forces of the Moon. 

On Earth, the tidal force cause deformations of the whole Earth s crust between 20 and 30 cm. On lo, the deformations can reach up to 300 m. 

As we will show later, there are several spectral signatures for the presence of ices consisting of H2O and SO2. Sulfur dioxide, SO2 has a melting point of -72.4° and a boiling point of — 10°C. It is a bent polar molecule. Due to its antimicrobial properties it is used as preservative for fruits and serves also as an antibiotic and antioxidant, protecting wine from spoilage by bacteria and oxidation.  

Water is escaping from lo which can be explained by different mechanisms  

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Io is the innermost of the four Galilean satellites and the most dense of the Jovian moons. Its density is estimated at 3.5 g/cm3. In some ways, its size, structure, and chemical composition are similar to those of our Earth s Moon. As the illustration shows, Io probably has the largest core for its size of any of the four moons. Io s surface is unusually smooth, essentially lacking in any impact craters. This evidence suggests that the moon s surface is fairly new, probably no more than about a million years old. 

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