A list of Jupiter facts would be incomplete without mentioning the planet's rings. Unlike Saturn's more well-known rings, Jupiter's are faint and composed of dust rather than ice. These rings were too faint for astronomers to notice for centuries. Imagine how surprised everyone was when NASA's Voyager 1 spacecraft returned images of Jupiter's rings in 1979. The three-ring system begins 92,000 kilometres above Jupiter's cloud tops and extends more than 225,000 kilometres away from the planet. They range in thickness from 2,000 to 12,500 kilometres.