WASHINGTON, July 3: Planet Earth early on Sunday fired its first ever shot at a passing comet in the hope of peeking into its core. It will be known on Monday at 0552 GMT whether it was a hit or miss.

Scientists insisted that although the experiment was somewhat reminiscent of the 1998 movie Deep Impact , in which a US spaceship attacks a monster comet with nuclear weapons to ward off its collision with Earth, the real-life attack on comet Tempel 1 was in pursuit of exclusively scientific goals.

“The impact simply will not appreciably modify the comet’s orbital path,” Don Yeomans, a mission scientist with NASA’s Jet Propulsion Laboratory, told reporters. “Comet Tempel 1 poses no threat to the Earth now or in the foreseeable future.”

The 333-million-dollar cosmic sniper shot, in which both the target and the projectile move at least 20 times faster than bullets, is expected to provide a glimpse beneath the surface of the comet and offer new clues to the origins of the solar system.

The projectile, the size of an oil drum, was fired at 2:07am by US spacecraft Deep Impact that had undertaken a 172-day, 431-million-kilometer (268-million-mile) journey to get closer to the comet, which is about as large as half Manhattan Island.

Twelve minutes after the release, a camera-equipped probe began peeling off from the projectile and set on a separate path that will get it as close as 500 kilometres (310 miles) to Tempel 1 shortly after the copper-laden impactor slams into it.

Radio contact between the two craft has been confirmed, according to JPL officials.

The collision with the gas-spewing rock that is hurtling through in the solar system at approximately 37,100 kilometres (23,000 miles) per hour is set for 1:52am (0552 GMT) on Monday.

It will likely gouge a large crater on the surface of the comet, sending up a cloud of ice, dust and debris that researchers hope will offer a load of valuable information.

That is when the fly-by probe will swing into action. It will have approximately 13 minutes to take infrared and other images of the collision and the resulting cloud before it is swallowed by a potential blizzard of particles from the nucleus of the comet.

Images will also be snapped and beamed back to the mother spaceship by the impactor in the final minutes of its life, allowing a glimpse into a cloud of gases and dust constantly enveloping Tempel 1.—AFP