MORE ASTEROID NEWS — drawing the proper line between realistic concern and hysteria.

This asteroid, 2004 MN, is still unlikely to strike — and it’s not big enough to produce a Lucifer’s Hammer kind of situation. It’s more of a Krakatoa-level threat, which is bad enough, but not a civilization-ender. The big lesson, though, is that this sort of threat isn’t just theoretical. Though the probability of a big hit is low, even a hit of this level — which at 1/42 can’t be called very low-probability at this point — is serious. We’re fortunate that nothing like this happened during the Cold War, when it might have triggered a nuclear exchange. But as nuclear weapons proliferate, there’s more reason to try to ensure that we’re not caught by surprise even by these smaller impacts.