What is the implication of Io's composition being primarily rock and sulfur?

Answer

It formed in a region too hot for significant water ice to condense and survive.

Io's location closest to the young Jupiter meant temperatures prevented the condensation of volatiles like water ice, leaving behind refractory material like rock and sulfur.

What is the implication of Io's composition being primarily rock and sulfur?
SpaceOriginJupiterGalilean moonsmoons