Stardust mission aerogel calibration. Close-up of an aerogel sample being cut under a microscope after being blasted with a standard material at a very high velocity. This calibration process is being carried out to prepare for handling samples obtained as part of NASA's Stardust mission. This mission, launched in 1999, used an aerogel collector to sample dust while passing through the coma of comet Wild 2. The Stardust sample was returned to Earth in January 2006. Several studies have been made of the cometary and interstellar dust particles collected and returned by the Stardust mission. Photographed at NASA's Ames Research Center, California, USA.