Sunday, June 12, 2005

NASA plans some big fireworks of its own for the Fourth of July.

The space agency announced Friday that it would crash a copper-clad “impactor” probe the size of a wine cask into a comet about half the size of Manhattan, all in the name of planetary science and at a cost of $333 million.

“We are really threading the needle with this one. In our quest of a great scientific payoff, we are attempting something never done before at speeds and distances that are truly out of this world,” said project manager Rick Grammier of NASA’s Jet Propulsion Laboratory in California.

Indeed. The cosmic crunch will occur at 1:52 a.m. EDT on July 4, about 83 million miles from Earth, with comet and impactor each clocking in at 23,000 mph.

Launched in early January, the bold mission is called “Deep Impact.” But is it courting disaster, as told in the 1998 comet-hits-Earth film of the same name?

“The impact simply will not appreciably modify the comet’s orbital path. Comet Tempel 1 poses no threat to the Earth,” said Don Yeomins, a mission scientist.

Nevertheless, there’s human culture onboard, and sci-fi drama, too. The little probe carries a compact disc bearing the names of 500,000 space enthusiasts, which will “melt, vaporize and essentially be obliterated — along with everything else aboard the impactor” — during the explosive collision, NASA says.

That explosion could yield some hubbub — “19 gigajoules” worth, or the equivalent of 5 tons of TNT. Scientists estimate the resulting crater could be 20-feet to 140-feet deep and as large as a football field, with a blizzard of ice and dust ejected.

NASA is quick to point out that no comets were hurt in the making of this mission, comparing the collision to a 767 airliner hitting a mosquito. The comet is, after all, about 9 miles long and weighs a billion tons; the impactor is a yard across and 820 pounds.

In addition, NASA’s official “planetary protection officer” noted that Tempel 1 will not be “contaminated by Earth-origin micro-organisms,” and that research benefits outweigh “concerns about the fate of the comet itself,” according to mission documents.

“The last 24 hours of the impactor’s life should provide the most spectacular data in the history of cometary science,” said lead investigator Michael A’Hearn, an astronomer with the University of Maryland. “It’s a whole new ballgame.”

New data could offer insight into the origins of the solar system, life on Earth and the mysterious makeup of comets in general.

The collision will be anything but private. Cameras rolling, an accompanying spacecraft will fly in tandem with the impactor probe for 14 minutes, eventually passing within 300 miles of the comet. Shields up, the craft will enter the “dust-impact hazard zone” and send back information for a month.

All of this will be monitored by NASA, six of the biggest telescopes on the planet, the Hubble Space Telescope, three other spacecraft and an army of amateur astronomers.

Curious earthlings will not be left out. Live images of the mission will be available at the agency’s Web site,

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