The reason why asteroids are a reminder that we need to be working on our space program is twofold. First, with an advanced space program we can spot them in time to change their trajectories — or, unless they’re so big there’s no point, evacuate the impact zone. (Asteroids 3,000 feet across, or about 20 times as wide as 2012 DA14, which gave us a near-miss on Friday, would strike the Earth with an impact of 40,000 megatons, which would kill most everybody and likely end human civilization). And second, if our civilization spreads beyond the Earth — whether to the Moon, Mars, orbital colonies, or even to large asteroids themselves — then it’s much less likely that any single cause could destroy humanity at one blow.

Just last week, British Astronomer Royal Martin Rees and former astronaut Ed Lu wrote in the Wall Street Journal that we need to take precautions against future asteroid strikes. The first step is comparatively easy: Scan the skies for objects that cross the Earth’s orbit (there are more than you might think.) This can be done from Earth and from space — in fact, Canada is launching an asteroid-hunting satellite next month — and after a while you’ll have a pretty good idea of what’s out there.

The next step is to be able to move the asteroids when you find them. Luckily, we’re beginning to develop that capability through the private sector, with asteroid-mining startups like Planetary Resources and Deep Space, Inc. appearing on the scene. Being able to move them, however, pretty much depends on finding them early, as it’s much easier to give them a gentle nudge way in advance than to try to deflect something massing millions of tons on short notice. The other nice thing about asteroid mining, of course, is that we pay to develop those capabilities by also developing the ability to gather valuable resources from outer space. It’s win-win. (And using space resources in space makes the idea of moon bases or orbital colonies much more practical).