The planet Jupiter, photographed by Voyager 2, 1979.
© National Aeronautics & Space Administration / Science & Society
NASA's two Voyager spacecraft were launched in 1977 to explore the planets in the outer solar system. Voyager 2 reached Jupiter in 1979 before flying on to reach Saturn in 1981, Uranus(1986) and Neptune (1989). The final phase of its mision is to cruise out of the solar system into interstellar space, continuing to return information until it loses contact with Earth. The largest planet in the solar system, Jupiter is a type of planet known as a gas giant, with an atmosphere composed mainly of hydrogen and helium. The atmosphere contains a number of large storms, the most famous of which, the Great Red Spot, is larger than the Earth and has been in existence for at least 300 years. Two of Jupiter's moons are visible in this photograph.