Last Wednesday, NASA's Deep Impact spacecraft was launched on a one-way trip. Its target: a collision with Comet Tempel 1. The comet will be 80 million miles from Earth at the time of impact.
Made of ice, gas and dust, comets are wandering time capsules that were formed at the beginning of the solar system. Scientists believe that materials inside comets could provide clues about the system's origins, about 4.5 billion years ago.
Deep Impact has two parts: the craft itself and an "impactor." On July 4, the impactor will crash into the comet at 23,000 miles per hour. The force of the impact is expected to produce a deep crater that will expose the comet's inner material. The spacecraft's high-powered telescope and other space scopes will take a look inside the crater and send data back to scientists on Earth.