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Science: NASA to Study Interior of Comet

Posted on: Wednesday, 13 October 2004, 06:00 CDT

The space agency's Deep Impact project will shoot the comet with an 800-pound copper bullet.

BOULDER, Colo. -- The last time NASA went beyond observing major celestial events and actually created one of its own was about 30 years ago, when Apollo astronauts dropped a spent rocket and an old lunar module onto the moon's surface.

The impact made the moon bounce slightly, and by studying that seismic event scientists began to understand the moon's innards.

Next July 4, NASA will again get to see things go boom. The space agency's Deep Impact mission will slam an 800-pound copper bullet deep into a comet.

The planned wallop, expected to take place 80 million miles from Earth and just outside Mars' orbit, will generate a shower of dust. Researchers hope the experiment will illuminate the history of the solar system, the birth of its planets and even the origin of life, said Monte Henderson, a manager for Ball Aerospace of Boulder, which built the spacecraft.

Hidden inside of comets, comprised generally of rock and ice, are thought to be the ingredients of our primitive solar system. Scientists hope to detect water and rock dust from the cosmic collision.

"These are the materials that were around when Earth formed" 4 billion years ago, Henderson said. "By pulling out the pristine material, we can see how Earth was seeded with the elements necessary for the formation of life."

Knowing the exact composition of comets also will help to understand what would happen if, someday, one were to strike our planet, said Alan Stern, director of the Southwest Research Institute in Boulder.

"Imagine Longs Peak (a 14,000 foot mountain in Rocky Mountain National Park in Colorado) going 100,000 miles per hour" hitting Earth, he said. "That would be a bad day."

Deep Impact is one of many recent NASA missions seeking answers to the solar system's birth and development. Others include Stardust, set to send a sample back to Earth in 2006, and Genesis, which slammed into the Utah desert last month. Last week, scientists said they expect to salvage much of Genesis' collected solar dust.

Ball's team, some 330 employees, built the $300 million spacecraft for NASA. It will be shipped to Florida later this month for a Dec. 30 launch.

Six months after taking flight, the SUV-sized craft will release its copper bullet into the path of the comet Tempel 1. The two will collide at nearly 25,000 mph, said Mike A'Hearn, Deep Impact science team leader at the University of Maryland.

No one is exactly sure what will happen next, A'Hearn conceded. Some models show the impact blasting a football-stadium sized crater into the comet, which has a 3-mile diameter. But the hole could be smaller or larger, depending on the comet's makeup.

On another level, there's the "huge challenge" of hitting Tempel 1's sweet spot, the side illuminated by the sun, Henderson said. If the bullet strikes in deep shadows, researchers will only be able to witness the splash of dust, not the crater itself.

Henderson remains optimistic. "We've been through five years of development and testing," he said. "We have over a 90 percent probability of hitting in that illuminated area."

For Stern, any risk of failure seems worth the potential payoff.

"We've hit bigger objects, like the moon, back in the 1960s," said Stern, who, while not a member of the team, counts himself as an informed spectator. "This is harder than hitting the moon, but putting landers and rovers on Mars is much harder."

If everything goes as planned, researchers on Earth will watch the action through photos sent back from the craft and images taken by the Hubble and Spitzer space telescopes.

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