Why did Io lose its initial water content while Europa retained substantial ice?

Answer

Intense radiation from Jupiter blasted lighter molecules away early in history

As the innermost Galilean moon, Io received significant radiative energy from Jupiter, which stripped it of lighter, volatile materials like water and hydrogen over billions of years.

Why did Io lose its initial water content while Europa retained substantial ice?
GeologyJupitermoonsVolcanismTidal heatingIogeological activity