What is the composition of Io's surface, making it fundamentally different from moons like Europa?

Answer

Hot volcanic rock and sulfur compounds

Io is completely devoid of surface water ice; its surface is composed of hot volcanic rock and sulfur compounds, whereas Europa possesses a water ice shell.

What is the composition of Io's surface, making it fundamentally different from moons like Europa?
GeologyPlanetary SciencemoonsVolcanismIo