Ganymede, and Callisto. The Moon is non-luminous, meaning that it does not produce light. We see the Moon because it reflects light from the Sun, and half of the Moon’s surface is always ...

The four largest – Io, Europa, Ganymede and Callisto – were discovered by Galileo Galilei in 1610 when he pointed the first astronomical telescope at the Moon, Venus and the planet Jupiter in quick ...

The moon is so volcanic because of tidal forces caused by gravitational interactions with Jupiter and its other large moons, Europa and Ganymede. Using its Microwave Radiometer, Juno detected heat ...