At NASA's recent budget hearing, during talk of moon missions and telescope funding, U.S. Rep. Dana Rohrabacher of California brought up the risks of asteroid impacts.
"There's a big threat to these kids. There's a big threat to the people of the world. ... And that is at any time, there could be an asteroid or a near-Earth object that could come and wipe out half the world if not the entire planet," Rohrabacher said. "That is not something that's likely to happen. But it could happen. And if it does happen, it'll mean your entire generation is wiped out."
Planet-killers almost never strike Earth, but there is always some risk. For every nine space rocks we know about, there's one we don't. The good news is asteroid detection technology is getting better.
NASA's aptly named Planetary Defense Coordination Office watches for nearby asteroids with a whole network of ground- and space-based telescopes. It's tracked down most of the near-Earth asteroids larger than 1 kilometer, and it also knows where most of the smaller ones are.
"We've increased the budget to do more observations," said acting NASA Administrator Robert Lightfoot. "We've also funded a mission called DART, which is going to be a mission that goes out and determines whether we can deflect an asteroid or not."
The European Space Agency is designing a joint mission to measure how well NASA's deflection test works. And the United Nations supports a global effort to track potential threats and help governments plan a response in case a large asteroid does hit Earth.