Comet Wild-2. Cratered surface of Comet Wild-2, as seen by the Stardust spacecraft's navigation camera on 2 January 2004. Stardust was around 500 kilometres from the 5-kilometre-wide comet. Comets are bodies of rock and ices that periodically pass through the inner solar system. Comet Wild-2 was discovered in 1978 and has a small orbit for a comet, orbiting between Mars and Jupiter. Stardust collected cometary dust samples to be returned to Earth. It passed by the comet at a speed of six kilometres a second. Stardust, launched in 1999, took 5 years to reach Comet Wild-2. It will return to Earth in January 2006. Cometary dust is a sample of material from the early solar system.