A space ship launches from Earth and travels millions of kilometers in pursuit of a comet that circles the sun every five-and-a-half years. Once in its sights, the spaceship releases an impactor in the comet's path, and when they collide, a massive hole is blasted in the streaking cosmic dust ball.
The explosion of rocks, ice and dust that follows creates a type of heavenly fireworks that burst into space on US Independence Day.
It sounds like the script of a new science fiction film, but it's not. NASA is preparing the mission for real; only its name has been borrowed from Hollywood: Deep Impact. The 1988 movie was about a comet headed for a nasty impact with Earth.
NASA's Deep Impact mission may not be quite as dramatic, but it will far exceed the movie on technical and scientific merit. The US$285 million mission is scheduled to launch from Cape Canaveral, Florida today at 1:48pm. It will culminate -- if all goes according to plan -- with a chunk being blown out of the comet Tempel 1 on July 4.
NASA hopes the mission will provide clues to the origin of the solar system.
"We're actually going to go smash a big piece of copper into a comet's nucleus and see what happens, see what's inside," said Rick Grammier, NASA's Deep Impact project manager, at a recent media briefing.
The six-month mission will begin with today's launch of a Delta rocket carrying the "Deep Impact" probe and a refrigerator-size, 370kg "bullet" or "impactor" made of copper. After the probe reaches the Tempel 1 beyond Earth's orbit, it will release the impactor, which will position itself in the comet's path while the probe manoeuvres itself away from the impact area.
The impactor and comet will collide at 10.2km per second, releasing the energy equivalent of 4.4 tonnes of exploding TNT. The impact will blast a hole in the comet the size of a football stadium, NASA officials say.
NASA will film and observe the impact from various vantage points, including the impactor, the probe and the Hubble Space Telescope.