Collision in space causes cosmic fireworks on the Fourth

By Aussiegirl

New Scientist has the story of the successful Deep Impact mission. Check out the site for some fabulous photos and a link to a movie of the approach to the comet prior to impact.
Wowee!! What an amazing feat!! Isaac Newton is probably jumping up and down in his laboratory in the sky today -- could he have dreamed all those years ago that his laws would still be in use today in order to navigate through the very heavens?

And why is it that everything in space looks like a big baked potato? (And why does all unfamiliar meat on earth taste like chicken?)

Comet Tempel 1 has smashed into the Deep Impact probe, producing a blast of light that prompted the mission control room at NASA's Jet Propulsion Laboratory in California, US, to erupt into cheers and applause.

Scientists and engineers jumped in the air, pumped their fists and hugged one another. Not only had their mission to deliberately collide with a comet for the first time succeeded perfectly, but the prospect of a damp squib - with the impactor passing right through a diffuse, rubbly comet - had fizzled away.

"Geez, and we thought it was going to be subtle," exulted JPL scientist Don Yeomans, one of the Deep Impact science team. "That was considerably brighter, and had considerably more material coming out, than I had expected," he said.

"We are just ecstatic," said JPL director Charles Elachi of the success of the $330 million mission. "It was worth every penny we spent on it."

The aim of the cosmic collision was to punch a hole in the comet's crusty surface to release material from below, revealing details about the interior of comets. These bodies of ice and dust a few kilometres across are believed to contain primordial material, preserved since the formation of the solar system in the deep-freeze of space.

One reason for the spectacular burst could be that puncturing the comet's crust released subsurface pressure, allowing a much bigger plume of ejecta to spurt out, Yeomans said.

However, it will take detailed analysis to confirm exactly what happened 83 million miles from Earth. "How a washing-machine sized impactor could produce such a large disturbance is going to take some explanation," Yeomans said.

Even before the impact itself, the twin spacecraft - the impactor itself, and the flyby craft which moved aside to observe it - were both returning images far more detailed than any previous images of a comet's nucleus. At about 28 centimetres, the maximum image resolution is almost 100 times better than the previous best comet images, taken in 2004 by the Stardust mission.

The pictures show numerous perfectly circular features, which could either be impact craters or sinkholes. They also display long linear features and a varied topography of rough areas and one smooth region - "everything a geologist would love", Yeomans said.
Unidentified spectra

Dozens of observatories on Earth, as well as four in orbit, were also watching the comet at the time of impact, during which the comet brightened to six times its pre-impact level. It will take days to collect and analyse all the measurements, says Deep Impact principal investigator Michael A'Hearn.

But it is already clear that there are some unidentified spectral features in the light reflected from the ejected material, meaning the mission's goal of learning new things about the internal composition of the comet will clearly be fulfilled.

And the amazing images returned by the probe immediately after the impact represent just 10% of the total taken, A'Hearn added: "There are many more spectacular images."