The essentials about Callisto (Jupiter’s moon)
Diameter: 4,820 km
The fourth of the Galilean moons of Jupiter is Callisto. Since it is located further from Jupiter than the other Galilean moons, it does not has to deal with tidal forces.
However, it is possible that Callisto has a liquid water subsurface, but this remains to be confirmed. It is the second largest moon of Jupiter and the third largest moon in the solar system.
Callisto is made up of about as much rock as ice and we know that its surface is mainly covered with frozen water, carbon dioxide and silicates, with some organic compounds. It has many craters on the face opposite Jupiter.
Image by NASA/JPL/DLR(German Aerospace Center) / Public domain