Nasa aims at comet

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 towards the comet Tempel 1 - 130 million km away from Earth at the time of impact.

Scientists hope the July 4 collision will gouge a crater in the comet's surface large enough to reveal its pristine core.

The comet is about half the size of Manhattan - roughly 28 sq km.