December 14, 2004 8:55 PM PST
NASA to fire projectile into comet
In January, the space agency will launch Deep Impact, a rocket that will fire a projectile into Comet Tempel 1. If all goes well, a collision will take place on July 4 that will raise a dust cloud that astronomers will use to study the chemical composition of the comet, said officials at NASA and researchers at the American Geophysical Union, a conference taking place in San Francisco this week.
The collision will create a crater with a 100-meter diameter on the 4-mile wide comet, a relatively minor hit.
"We are reproducing natural processes that occur all the time," said Karen Meech, a researcher from the University of Hawaii and one of the principal investigators on the Deep Impact project. "In a sense, this is a fairly small mark on the comet."
Comets are believed to offer a glimpse of the chemical composition of the early universe, but an in-depth study has always been difficult.
Deep Impact won't be easy either. The rocket will have to launch between Jan. 8 and Jan. 28 to arrange the hit on July 4, when the comet will only be 83 million miles from Earth. The rocket overall will have to travel 268 million miles. The copper-covered projectile will be moving at 23,000 miles per hour when it hits. For the last 12 hours of the journey, it will navigate itself.
The projectile is coated in copper because copper, unlike aluminum, won't react with water and it's cheaper than gold or silver, said Michael A'Hearn, a Deep Impact principal investigator and a professor at the University of Maryland. A "flyby" spaceship will relay back data and pictures.
Comet Tempel 1 is fairly typical for comets found in the Kuiper Belt, A'Hearn said.
The mission will cost roughly $311 million, NASA officials said.
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