Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant composed of mostly hydrogen and helium. Its most notable features are its four Galilean moons, Europa, GANYMEDE, Callisto, and Io, as well as its Great Red Spot, a persistent anticyclonic storm. The term Jupiter is derived from the Roman god Jupiter, also known as Zeus in Greek mythology. Europa is the smallest of the four Galilean moons and is named after a Phoenician princess in Greek mythology. GANYMEDE is the largest moon in the Solar System and is named after a Trojan prince in Greek mythology. Callisto is the second-largest moon and is named after a nymph in Greek mythology. Io is the third-largest moon and is named after a priestess of Hera in Greek mythology. Finally, JOVE is another name for Jupiter, derived from the Latin Iuppiter, which is the Roman equivalent of Zeus.