Callisto is the outermost and second largest of the four Galilean moons that orbit the planet Jupiter. It is also the third largest moon in the solar system, surpassed in size only by Ganymede and Saturn’s moon Titan. Callisto has a surface that is made up of water ice and rocky material, and is thought to have a subsurface ocean of liquid water beneath its icy crust.
Callisto’s surface is heavily cratered, with over 100 impact craters that are over 60 kilometers (37 miles) in diameter. The craters on Callisto are some of the largest and most well-preserved impact craters in the solar system. The surface of Callisto is thought to be the oldest surface in the solar system, with an estimated age of 4 billion years.
Despite its age, Callisto’s surface is relatively smooth, with few visible mountains or other geological features. This smoothness is thought to be the result of the thick layer of water ice on the surface, which has smoothed out the roughness of the underlying rocky material.
Callisto is of great interest to scientists because of its subsurface ocean of liquid water, which may contain the necessary ingredients for life to evolve. The study of Callisto and the other Galilean moons has provided scientists with a wealth of information about the early solar system and the processes that shaped the planets and moons.
In addition to its scientific importance, Callisto is also a potential destination for future space missions. The stable, radiation-free environment on Callisto makes it a good location for a space station or other human habitation. The presence of a subsurface ocean of liquid water also makes Callisto a good target for future exploration and the search for life beyond Earth.