NASA's Deep Impact probe has just completed  an extraordinary feat: A fly-by at only 400 miles range of a comet. It's all about the science, of course, and the spirit of discovery. But the photos will make your brain pop.
The 10-foot long spacecraft, launched in 2005 and already far surpassing its original mission parameters, completed part of a new mission dubbed EPOXI (Extrasolar Planet Observation and Deep Impact Extended Investigation), which involved a close fly-by of a comet. The plan had been to observe comet Boethin in December 2008, but as it became time to maneuver for the rendezvous, astronomers couldn't find the comet. It may have broken up, or become too faint to see.
A quick re-think resulted in today's encounter with comet Hartley 2 , a weird lump of rock about a mile wide, which wanders our solar system up to five times as far away from the Sun as the Earth.
The rendezvous was a complete success, with the spacecraft getting as close as 435 miles from Comet Hartley 2, and observing it with its sensor suite. Among the pile of data are clues as to the formation of the comet, and hints about the prehistory of our Solar System (and how planets across the galaxy form).
But the many photos that came from Deep Impact's imaging cameras tell the best story. Check them out at NASA's site. 
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