Sunday, July 3 2005 15:19 Hrs (IST) - World Time -

Pasadena (California): A NASA spacecraft with a Hollywood name released a probe early today (July 3, 2005) on a collision course with a speeding comet, an ambitious mission that scientists hope will offer the first peek inside one of these icy bodies.

Deep Impact released its barrel-sized "impactor" at 1137 hrs (IST) on a suicide journey that is expected to climax 24 hours later when the comet Tempel 1 smashes into it. The high-speed crash should be visible from parts of the Western Hemisphere.

Comets contain the frozen primordial ingredients of the solar system and studying them could provide clues to how the sun and planets were formed.

NASA says an impact will not significantly change the comet's orbital path around the sun, so the $333 million experiment poses no danger to Earth.

The 372-kg copper probe successfully separated from the mothership to set the stage for the collision with the comet, according to mission control at NASA's Jet Propulsion Lab in Pasadena. Electrical wires connecting the spacecraft broke, springing free the probe.

Scientists are counting on the collision to carve a stadium-sized crater in Tempel 1, a pickle-shaped comet half the size of Manhattan now about 130 million kms from Earth.

No explosives are needed since the energy from the impact will be similar to detonating nearly 5 tons of TNT.

It is the first attempt by the US space agency to catch a glimpse of the pristine core of a comet.

In what scientists say is a coincidence, the spacecraft shares the same name as the 1998 movie about a comet that hurtles toward Earth.