Callisto is the outermost of the Galilean satellites and the third largest satellite in the Solar System. Callisto is also the most heavily cratered object in the Solar System.


Callisto has shown no signs of resurfacing since first impacts have molded its surface. Therefore, it has the oldest landscape in the Solar System, with a surface age of about 4 billion years.

Four largest moons of Jupiter: The Galilean moons