It is made from rocky materials and has an iron core and the tidal heating keeps everything from freezing. So shouldnt it have a magnetic field?
The magnetic field is from a dynamo effect of a spinning molten conductor. With most terrestrial planets it's molten iron, nickel and maybe some sulfur to lower the melting point. With planets like Jupiter, it's metallic hydrogen. It doesn't save to be chemically iron sulfide and indeed tests on Earth that simulate the dynamo use molten sodium for the lower melting point. You're missing the spin in your list of properties.
The iron seems to be chemically bound up as Fe2S3, not a magnetic material
two reasons. Io has a sesquisulfide (iron sulfide, ferric sulfide) core, which is not a metal. it's a compound. a world has to have a metallic core to generate a magnetic field. the core also doesn't spin rapidly, while the terrestrial planets' cores do (except for mars, which has a metallic liquid core that doesn't spin, and so it doesn't have a magnetic field). hope this helps! :) cedric
