Ganymede (moon) (JUICE), due to launch in 2022. After flybys of all three icy Galilean moons, the probe is planned to enter orbit around Ganymede. Chinese astronomical records report that in 365 BC, Gan De detected what might have been a moon of Jupiter, probably Ganymede, with the naked eye. However, Gan De reported the color of the companion as reddish, which is puzzling since the moons are too faint for their color to be perceived with the naked eye. Shi Shen and Gan De together made fairly accurate observations of the five major planets. On January 7, 1610, Galileo Galilei observed
Rhea (moon) Rhea (moon) Rhea ( ; ) is the second-largest moon of Saturn and the ninth-largest moon in the Solar System. It is the second smallest body in the Solar System for which precise measurements have confirmed a shape consistent with hydrostatic equilibrium, after dwarf planet Ceres. It was discovered in 1672 by Giovanni Domenico Cassini. Rhea was discovered by Giovanni Domenico Cassini on 23 December 1672. It was the second moon of Saturn that Cassini discovered, and the third moon discovered around Saturn overall. Rhea is named after the Titan Rhea of Greek mythology, the "mother of the gods". It