objects at the moment of impact -- 23,000 mph -- no explosives are needed for the job. The force of the smashup will be equivalent to 41/2 tons of TNT, creating a flash that just might be visible in the dark sky by the naked eye in one spectacular Fourth of July fireworks display.
Nothing like this has ever been attempted before.
"The most difficult and most challenging part is going to be the actual encounter because we're doing things that nobody has done before," said Jay Melosh, a planetary geologist at the University of Arizona.
Little is known about Comet Tempel 1, other than that it is an icy, rocky body about nine miles long and three miles wide. Scientists do not know whether the crust will be as hard as concrete or as flimsy as corn flakes.
"One of the scary things is that we won't actually know the shape and what it looks like until after we do the encounter," Melosh said.
The comet will be more than 80 million miles from Earth when the collision takes place. The resulting crater is expected to be anywhere from two to 14 stories deep, and perhaps 300 feet in diameter.
A jagged, cratered comet like the one headed for Earth in the 1998 movie "Deep Impact" would be difficult if not impossible to hit because of all the shadows, Melosh said. Comet Tempel 1 is believed to be smoother and easier to hit.
The scientists came up with the Deep Impact name independently of the movie studio, around the same time, neither knowing the other was choosing it, even though some members of NASA's Deep Impact team were consultants on the picture.
Deep Impact is carrying the most powerful telescope ever sent into deep space. It will 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. NASA space telescopes like the Hubble will view the collision, along with ground observatories and amateur astronomers.
The entire mission costs $330 million, all the way through the grand finale.
Hey, this mission is being carried out by the same feet/meters crowd, so let's not rule anything out.
What a bargain. Cheap at twice the price.