To Catch A Comet

This week, after 10 years aflight, the unmanned spacecraft Rosetta caught up with its target: the comet 67P/Churyumov-Gerasimenko. A European Space Agency product, the Rosetta is the first spacecraft ever to rendezvous with a comet. In November it will attempt to "harpoon" 67P and land on its surface.


Why such interest in a frozen ball of dirt? Comets are thought to be primitive building blocks of the solar system as well as leftovers from our solar system's formation. They trap gases in their icy, dusty interiors, then slam into planets with such impact that new molecules are generated. The heat of the collision transforms the molecules into amino acids, essentially seeding planets with protein precursors, water and potentially life itself. In fact, the simplest amino acid, glycine, was recently discovered in samples from a different comet -- 81P/Wild-2 -- collected by NASA's Stardust spacecraft.