4 July 2005 (RFE/RL) -- A projectile released by the NASA space agency has intentionally crashed into a comet on a mission scientists hope will provide new insights into the origins of the solar system. The 372 kilogram impactor, which is about the size of a washing machine, hurtled into the Tempel 1 comet precisely on schedule at 05:50 GMT on 4 July. The impact occurred about 133 million kilometers from Earth and is expected to give scientists their first glimpse into the heart of a comet.
Scientists and engineers at the NASA Jet Propulsion Laboratory in Pasadena, California, celebrated as confirmation came through of a successful hit.
The impact was recorded from the projectile's mother ship, Deep Impact, which in turn, sent images back to Earth.
Dr. Don Yeomans, a scientist working on the $ 333 million project, could barely contain his excitement:
"The navigation was perfect," Yeomans said. "It couldn't have been any better. The impact was bigger than I expected and bigger than most of us expected."
The 14-kilometer-wide comet circles the sun every 5.5 years and much of its composition dates back to the creation of the solar system some 4.6 billion years ago.
"This is going to tell us a great deal about how this comet is put together, whether there was an interior pocket of gas that was released," Yeomans said. "We haven't had any information from the spectrometer, but it is not out of the question that the spectra after the impact will be completely different or at least a bit different from pre-impact spectra, [which would be a] suggestion that [the impact] released sub-surface materials that we haven't seen before."
Comets, likened by some scientists to dirty giant snowballs, are thought to consist of a rocky nucleus surrounded by ice but, at least until now, scientists have had little hard evidence to back their theories.
It is thought that as comets approach the sun, their icy, hydrocarbon crust begins to melt, releasing the gases and dust that produce their characteristic tails.
Astronomer Lucy-Ann McFadden, who is a member of the Deep Impact team, says the probe will make a huge contribution to our knowledge of comets and our understanding of the solar system.
"It's going to allow us to see below the surface for the first time, which is going to be really exciting," Grady told RFE/RL. "We'll be able to see how much ice is there, how much gas is there, how much dust is there, how much carbon is there in the dust. It's looking back in time."
The Deep Impact mother craft passed by the comet at a distance of some 500 kilometers, cameras rolling as the explosion sent tons of ice, dust, and rock spewing into space.
Telescopes and other equipment controlled from the probe are now beginning to send data and images back to the NASA laboratories in California, information which the scientists hope will enable them to get beneath the surface of comet Tempel 1.
It will, however, take several days for all the data from Deep Impact to download and still longer for the scientists to interpret it. But by the time they're finished, they may have shed just a little more light on the origins of the universe itself.