1. Io: Io is the brightest of Jupiter's moons due to its active volcanoes, which spew out sulfur and other materials, creating a bright, reflective surface.
2. Europa: Europa is the second brightest, with its icy surface reflecting sunlight well.
3. Ganymede: Ganymede, though the largest moon in the solar system, is the third brightest. Its surface is a mix of ice and rock, making it less reflective than Io or Europa.
4. Callisto: Callisto is the dimmest of the four Galilean moons. Its surface is heavily cratered and dark, reflecting very little light.
Therefore, the order from brightest to dimmest is: Io, Europa, Ganymede, and Callisto.
