Baltimore Sun
Nov. 28, 2004 12:00 AM
You can learn something about a rock by looking at it. But what most geologists really want is to smack it with a hammer.
And that's just what planetary scientists will do July 4 when NASA's Deep Impact mission reaches the comet Tempel 1 after a trip of six months and 80 million miles.
If all goes well, an 820-pound copper "hammer" the size of a bathtub will separate from its mother ship and, 24 hours later, smash into the comet's icy nucleus at about 23,000 mph.
The high-speed impact will wallop the pickle-shaped comet with energy equivalent to 4.8 tons of TNT, said Michael A'Hearn, a University of Maryland astronomer and principal investigator on the $311 million mission.
Nobody's sure what will happen next. There's a small chance the impactor will blow the 2 1/2-mile-long comet to smithereens, or simply bore right through it like a bullet through a snowball. More likely, scientists say, it will blast open a crater the size of a football stadium. It all depends on what Tempel 1 is made of.
Which is exactly what scientists hope to learn.
The blast also will reveal the comet's interior chemistry and nail down more precisely what conditions were like when it formed at the solar system's birth more than 4.5 billion years ago.
The Deep Impact spacecraft is undergoing final tests at Cape Canaveral, Fla. It will blast off atop a Delta 2 rocket Dec. 30, and if all goes well, rendezvous with Tempel 1 on Independence Day.
And that's just what planetary scientists will do July 4 when NASA's Deep Impact mission reaches the comet Tempel 1 after a trip of six months and 80 million miles.
If all goes well, an 820-pound copper "hammer" the size of a bathtub will separate from its mother ship and, 24 hours later, smash into the comet's icy nucleus at about 23,000 mph.
The high-speed impact will wallop the pickle-shaped comet with energy equivalent to 4.8 tons of TNT, said Michael A'Hearn, a University of Maryland astronomer and principal investigator on the $311 million mission.
Nobody's sure what will happen next. There's a small chance the impactor will blow the 2 1/2-mile-long comet to smithereens, or simply bore right through it like a bullet through a snowball. More likely, scientists say, it will blast open a crater the size of a football stadium. It all depends on what Tempel 1 is made of.
Which is exactly what scientists hope to learn.
The blast also will reveal the comet's interior chemistry and nail down more precisely what conditions were like when it formed at the solar system's birth more than 4.5 billion years ago.
The Deep Impact spacecraft is undergoing final tests at Cape Canaveral, Fla. It will blast off atop a Delta 2 rocket Dec. 30, and if all goes well, rendezvous with Tempel 1 on Independence Day.
