"That's awesome! That's awesome!" shouted flight control officials after the impact was confirmed on Monday. "We hit just exactly where we wanted to."
A picture sent back to Earth by a fly-by probe showed a bright flash of light as the projectile collided with the massive comet, which is travelling through the solar system at approximately 37,100kph and is equal in size to half of Manhattan Island.
The copper-laden impactor was beaming back high-resolution pictures of the comet until a few seconds before its demise.
It showed craters, ridges and presumed glaciers on the potato-shaped celestial body that was discovered in 1867 and named Tempel 1.
"We have put a new trail for other people to follow," said Charles Elachi, director of the Jet Propulsion Laboratory, a division of the National Aeronautics and Space Administration (Nasa) that was a key partner in the experiment.
Spacecraft Deep Impact was launched from the Kennedy Space Centre in Florida in January, undertaking a 173-day, 431-million-km journey to get closer to Tempel 1.
Nasa Associate Administrator Al Diaz said the success of the experiment could be attributed to broad cooperation between scientists and researchers inside and outside the US.
"It's just absolutely stunning," he told reporters. "To be in a situation where we are here tracking a comet for this period of time and then precisely positioning a spacecraft in a way that creates that environment that is so bright... I am speechless!"
Although incoming imagery is still to be analysed, the collision was expected to gouge a large crater on the surface of the comet, sending up a cloud of ice, dust and debris that researchers hope will offer valuable information.
A separate fly-by probe took images of the resulting cloud, which scientists believe could contain particles from the comet nucleus.
An image from Nasa TV shows a
view from Deep Impact's flyby
Comets circling the sun, which are numbered in billions, are seen as leftovers from a massive cloud of gas and dust that condensed to form the sun and planets about 4.6 billion years ago.
Therefore, their geological and chemical structure is believed to contain important clues to the nature of the universe.
No movie similarities
On Saturday, Tempel 1 belched out more ice and dust, expanding the size of the cloud around it.
The outburst, the fourth in the past three weeks, was not of particular concern to Nasa scientists, said project manager Rick Grammier.
"The comet is definitely full of surprises so far and probably has a few more in store for us," he commented.
The $333-million sniper shot, in which both the target and the projectile move at least 10 times faster than bullets, was to provide a glimpse beneath the surface of the comet.
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 strike on Tempel 1 was in pursuit of exclusively scientific goals.
"Comet Tempel 1 poses no threat to the Earth now or in the foreseeable future." said Don Yeomans, a mission scientist with Nasa's Jet Propulsion Laboratory.