The fifth planet outward from the sun, Jupiter is the exploration target of the Juno mission. Jupiter has more than twice the mass of all the other planets in the solar system combined. A gas-giant planet, Jupiter is composed like a star. It did not, however, grow big enough to ignite the core nuclear fusion that makes stars shine. With an enormous magnetic field, the planet has a kind of miniature solar system with dozens moons. Its swirling cloud stripes are punctuated by massive storms such as the Great Red Spot, which has raged for hundreds of years.