Jupiter, the largest planet in the solar system, is a hydrogen, ammonium and helium giant. The planet has 50 moons (not including temporary ones), an immense magnetic field and if it had been about 80 times more massive it would have been a star unto itself.
Named for the most important god in Roman mythology, Jupiter takes nearly 12 years to complete its orbit around the Sun while a day on Jupiter is only about 10 hours long. Its rotation is actually the fastest in the solar system. The planet is perhaps best known for the Giant Red Spot, a storm of clouds that have been circulating since at least the 1800s.
Space-based exploration of Jupiter began in 1973 with the Pioneer 10 probe. Most data of Jupiter has come from such flyby probes, including the Saturn-focused spacecraft Cassini. Only the orbiter Galileo has studied the planet extensively, from 1995 to 2003. The spacecraft was deliberately crashed into Jupiter to avoid contaminating one of Jupiter’s moons.
Text by Noel Kirkpatrick