THE THEORY THAT THE COLUMBIA WAS HIT BY A METEOR — or a piece of space debris — is not implausible, but I doubt it’s the most likely explanation. As between the two, the odds favor debris; in Low Earth Orbit there’s about twice as much manmade debris as natural meteor flux.

But assuming the impact occurred during re-entry, the Shuttle was a bit low for that. It would have had to collide with something that was re-entering (or in the case of a meteorite, just entering) the atmosphere at the same time, which is far less likely than an on-orbit collision.