On January 15, 2006, a capsule hit Earth's atmosphere at 12.9 kilometers per second, the fastest reentry of any human-made object, protected by an ablative heat shield that burned away at over 2,900 degrees Celsius. Inside was about one milligram of comet dust. This episode explores NASA's Stardust mission, born from the Discovery Program after the cancellation of the Comet Rendezvous Asteroid Flyby, and its target Comet Wild 2, which Jupiter flung into the inner solar system in 1974 with its primordial material still pristine.

We explain how aerogel, a silica solid that is 99.8 percent empty space, captured hypervelocity grains without vaporizing them, how Whipple shields turned incoming debris into harmless gas, and why a 450 meters-per-second impact shock sterilized any microbes. We follow the 1999 launch, the Earth gravity assist, the A ...