Emily Lakdawalla has been monitoring the return of Hayabusa feverishly, and tweeted a link to this amazing video of the Japanese space probe's fiery return: Wow! In this footage obtained from a DC-8 flying over Australia, you can see the probe breaking up, with individual pieces falling off and burning up as they ram through the Earth's atmosphere at several kilometers per second. The last little piece you can see at the end is, I think, the hardened component that contains samples of the asteroid Itokawa, obtained when Hayabusa landed on its surface.
As I mentioned in an earlier post, Itokawa is a 500-meter-long potato-shaped rubble pile, an asteroid that is not a solid rock like a boulder or mountain, but probably an assemblage of rubble held together by its own gravity. If one of these things were headed straight for us, we could lob nukes at it, even slam it with space probes at high speed to try to push it out of the way, and it would laugh at us. We need to understand these objects much better than we currently do if the time ever comes that we need to keep one from smacking into us. The sample of Itokawa contained inside that tiny glowing dot you saw in that video may just give us some of the answers we need to do that. Science! It makes the world better, but it also just might save it, too.