Io: Why so much sulfur?

Question

Io is the only body in the Solar System whose crust is dominated by sulfur and its compounds. Carbon and nitrogen are also very common in the universe but we don't see them or their compounds in Io's crust. Why not?

Answer 1

The composition of natural satellites usually reflects the ratios of local particulates from which they condensed. The reason we know the moon formed from debris around the Earth is exactly this. Planetary formation models are extremely complex and depend heavily on starting variables, but I suspect a localized elevation in sulfuric compounds would be associated with the collision/condensation that produced Io.