The comet Tempel 1 has a new crater this morning, the result of a fatal encounter with a NASA spacecraft.
"Right now we're minus one spacecraft - the impactor," says Rick Grammier, Deep Impact project manager at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California. "It's been totally vaporized, per planned."
This is the first time a man-made spacecraft has touched the surface of a comet.
"There is a comet up in the sky wondering what in the heck hit it," says Charles Elachi, Director of JPL.
The first medium resolution images of the impact show a starburst on the bottom half of a lumpy, potato-looking nucleus. The nucleus, which is about 5 kilometers across and 7 or 8 kilometers long, appears to already sport a large crater unrelated to this impact on its upper half.
The impactor spacecraft hit the comet on the sunlit side as hoped, allowing the Deep Impact mothership to see the impact as it occurred. The resulting spray of ejecta is now streaming from the comet, and scientists are still studying the data to determine the chemical composition of that material. Once the impact ejecta dissipates, scientists hope to get their first look at the crater their spacecraft made in the comet's surface.
"Obviously it was a very big impact; presumably we have a large crater," says principal investigator Mike A'Hearn. "Interpreting the ejecta cone is going to take a little time. There's lots of structure in it that's of interest to understanding the nature of the comet. We'll be working that out over the next half-day, and weeks and months and years. I just look forward to the wealth of data that will take me into retirement."
Earth-orbiting spacecraft like the Hubble Space Telescope and the Chandra X-Ray Observatory also witnessed the event, and gathered data about the impact. Images of the impact are now available on the Deep Impact web site.
Both the crater and the impact ejecta will indicate what lies under the comet's icy surface, helping scientists better understand how comets are constructed. This, in turn, could lead to a better understanding of the origin of the solar system. Comets formed in the outer solar system 4.5 billion years ago, at the same time that the planets were forming.
The impactor spacecraft took and relayed photos up to 3 seconds before impact, providing the closest, highest resolution images ever made of a comet nucleus.
The impactor spacecraft was released from the mothership yesterday, and it battery-powered its way over to the comet. The impactor spacecraft made self-adjustments to its position during its final two hours, ensuring it was on track to be mowed down by the comet, which was speeding toward it at 23,000 miles per hour (37,100 kilometers per hour).
The mothership, meanwhile, safely navigated its way underneath the comet. Not a single system was damaged by cometary debris.
Deep Impact originally launched on January 12, 2005, from Cape Canaveral, Florida. It traveled for nearly six months and 268 million miles to reach comet Tempel 1.
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