Hopefully, everyone has heard of Deep Impact - the NASA spacecraft that crashed (intentionally) into comet Tempel 1 on July 4, 2005. If not, here's a link to the Deep Impact Mission
home page. The idea was to smash a spacecraft into a comet, and have another spacecraft watch this up close and see what happens. Conceivably, This would tell us a lot about what comets are made of. If they are pretty solid, the impacting spacecraft should make a pretty small, unexciting crater. If comets are loose aggregations of dust and ice, the impactor might plunge straight into the comet's nucleus without a trace. But if comets are something in between - as most scientists suspect - we should get a pretty exciting explosion, and a nice-sized crater.
What you probably didn't know about Deep Impact is that I did a little work on that project. In fact, I had somewhere on the order of a dozen lines of code on both the impactor and the fly-by portion of the mission. While my involvement was pretty minor, I'm still really proud to have been a part of the Deep Impact team, and this is the first time in my professional life that I can tell just about anybody what I do for work, and they have heard of the project. Awesome!
Below are a couple of pictures of the certificate of appreciation I received for participating in the mission. Way cool!