For the first time ever NASA has set off on a collision course with a comet.
It all began with today's launch of Deep Impact. It's a copper-fortified, comet-busting spacecraft.
NASA had a single second to send Deep Impact on a 268 million-mile, six-month voyage to Comet Tempel One.
It'll be a one-way trip that NASA hopes will reach a cataclysmic end on the Fourth of July.
Scientists are counting on Deep Impact to carve out a crater that could swallow the Roman Coliseum.
It'll be humanity's first look into the heart of a comet. That's a celestial snowball still preserving the original building blocks of the sun and the planets.
Deep Impact is carrying the most powerful telescope ever sent into deep space. It'll remain with the mothership when the impactor springs free the day before the comet strike, and will observe the event from a safe 300 miles away.
The entire mission costs 330 (m) million dollars all the way through the grand finale.