Comets are leftovers from the creation of the solar system 4.5 billion years ago; they also delivered organic chemicals and water-the crucial building blocks of life-to the young Earth. Scientists would love to get a bit of comet into the lab for analysis. Now it looks as though they will. On Feb. 6 a remarkable space probe called Stardust is scheduled to take off for a January 2004 encounter with Comet Wild 2. With a tennis racquet size collecter, Stardust will snatch dust particles from the comet's tail as it flies by and then return to parachute its precious cargo to Earth two years later.