Callisto 1

Callisto is a moon of Jupiter. It is the third largest moon after Titan and Ganymede. It is the second largest Jovian moon. It orbits Jupiter every 17 days. Callisto could have a sub-surface ocean or layers of oceans beneath its crust. Callisto's rocky, icy surface is the oldest and most heavily cratered in our solar system. The surface is about 4 billion years old and it's been pummeled, likely by comets and asteroids.