The spacecraft had a fruitful dozen years. Launched in 1999,
Stardust's first mission was to capture the debris cascading off
of the comet Wild 2 and bring it back to Earth. Wild 2 is a hunk
of dust and ice that's believed to be 4.6 billion years old, and
so scientists thought it might contain the building blocks of
the solar system. Going there to find out required Stardust to
travel three billion miles, beginning with a loop around the Sun
to slingshot itself toward the comet. Once it had sidled up to
the three-mile-wide comet, Stardust deployed its aerogel mitts
to catch the dust in the tail. In January 2006, Stardust
completed its mission by becoming the first craft to return a
comet sample to the Earth. That ancient sample held a surprise,
too. The mission scientists mostly expected to find a lot of
dust from old starshence the name "Stardust." But inside this
sample from a lonely ball of ice and rock, scientists found one
of the fundamental building blocks of life. It was glycine, a
simple amino acid th