Jupiter, the largest planet in our solar system, has over 79 known moons. The four largest, known as the Galilean moons, are Io, Europa, Ganymede, and Callisto. These moons were discovered by Galileo Galilei in 1610 and are significant for their unique geological features and potential for hosting life. Io is the most volcanically active body in the solar system, while Europa has a subsurface ocean that may harbor life. Ganymede is the largest moon, even bigger than the planet Mercury, and Callisto is heavily cratered, indicating a long history of impacts.