Enceladus size comparison. Computer artwork of Enceladus (centre) in front of the Earth and next to Earth's moon (right), showing their comparative sizes. Enceladus is the sixth-largest of Saturn's moons with a diameter of 500 kilometres. It is one of Saturn's major satellites, however it is quite diminutive when compared with the Earth and Earth's Moon. Enceladus is one of the brightest objects in the Solar System. Its surface is covered in water ice that reflects sunlight.