Callisto is one of the Galilean moons of Jupiter discovered by Galileo Galilei in 1610. Callisto is a very geologically inactive body and its surface is covered in many craters.
Callisto is the third largest moon in our solar system after Ganymede and Titan, and Jupiter’s second largest moon. It was discovered by Galileo Galilei in 1610 along with three other moons known as the Galilean moons. This discovery was important because it ultimately changed our understanding of the structure of the universe, away from a geocentric model to a heliocentric model.
Callisto has more craters than any other body in our solar system. Its entire surface is cover with evidence of impacts. The moon is also very geologically inactive, meaning these craters have remained unchanged. Callisto's composition is thought to be mainly rocky material and ice. Its atmosphere is thin and almost entirely composed of carbon dioxide.
Callisto was originally named Jupiter IV and was renamed some years later. The moon is named after a lover of the Greek god Zeus. Callisto was a nymph and the daughter of King Lycaon. All of the Galilean moons have been named after Zeus’s lovers.
The Pioneer 10 and 11 missions didn’t reveal a large amount of new information. The Voyager missions completed flybys, both in 1979. These spacecraft managed to take images of half the surface of the moon. Later, the Galileo mission, which spent eight years in orbit around Jupiter, managed to image the entire surface. Callisto has been identified as a possible location for human exploration in the future. Scientists think that the moon could be a viable option due to its lack of geological activity and that its distance from Jupiter reduces the amount of radiation from the planet.