Fireworks on horizon as NASA targets comet

NASA will mark Independence Day in the US with an audacious mission that will blast a stadium- sized hole in a comet half the size of Manhattan.

It would give astronomers their first peek at the inside of one of these 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 - about 80 million miles away from Earth at the time of impact.