Flyby near miss, crash in Russia, crash in Cuba, all in one week — two in one day. It’s time to get serious about asteroid defense.

Astronomers have been sounding the warning on near-earth objects for about 20 or 30 years now. They think that there are about 1,000 that pose a threat, but this week’s events show that our understanding is very incomplete. And the sad truth is, we don’t even have a manned space flight program anymore.