Stardust is the first mission to return samples from a comet.
Aerogel (right), the material used to capture comet samples, has been certified by Guinness World Records as the world's lightest solid.
Aerogel is made of the same basic material as glass, but it is much lighter because it is 99.8 percent air.
Scientists discovered glycine, a fundamental building block of life, in samples of comet Wild 2 returned by the Stardust spacecraft.
The particles were traveling at about 6 km per second -- six times the speed of a bullet -- when they were captured by Stardust's sample collector.
