Deep Impact closing in

by Chris Bergin

NASA hopes to give astronomers their first peek at the inside of a comet by blasting a stadium-sized hole through one of the heavenly bodies.

If all goes as planned, the Deep Impact spacecraft will release a wine barrel-sized probe on a suicide journey, hurtling toward the comet Tempel 1, which will be about 130 million kilometres from Earth at the time of impact.
“It’s a bullet trying to hit a second bullet with a third bullet in the right place at the right time,” said Rick Grammier, project manager at Nasa’s Jet Propulsion Laboratory in Pasadena.

Scientists hope the July 4 collision will gouge a crater in the comet’s surface large enough to reveal its pristine core and perhaps yield cosmic clues to the origin of the solar system.

The comet is about 28km2.

Nasa’s fleet of space-based observatories – including the Hubble, Spitzer and Chandra telescopes – and an army of ground-based telescopes around the world are expected to record the impact and resulting crater.

The big question is: What kind of fireworks can sky-gazers expect to see from Earth?

Scientists do not know yet. But if the probe hits the bull’s-eye, the impact could temporarily light up the comet as much as 40 times brighter than normal, possibly making it visible to the naked eye in parts of the western hemisphere.

“We’re getting closer by the minute,” Andrew Dantzler, director of Nasa’s solar system division, said earlier this month. “I’m looking forward to a great encounter on the fourth of July.

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