3. IN INTERSTELLAR SPACE
As the atoms continue to drift through space, they cool and condense into dust grains. From there, new dust grains will float out into the cosmos, where they may collect into very small rocks, then asteroids, then planets. In July, planetary scientists announced two candidate dust particles from the Stardust spacecraft, which returned to Earth in 2006 after seven years of collecting dust samples in space. This will bring the total number of dust grains currently in human possession to three. Finding even one requires a painstaking search of Stardust's particle trap using a microscope. The first dust particle, also captured by the Stardust experiment, was announced in March. Of the three, two of the particles are magnesium-rich, while the third is carbon-based.