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That sounds relatively easy, but it's all still in the drawing-board stage. If 2012 DA14 had been headed straight for us, the single year we had to prepare would have been spent evacuating the likely impact site and hoping our trajectory calculations were correct. "You need 10 to 20 years to design and build and launch," says Yeomans. "If you're at less than 20 years, you're talking civil defense." Even if an intercept spacecraft had been in the hangar and ready to go, the rock would have had to be spotted much earlier--when it was years away--in order to be reliably deflected.
For now, the best the U.S.'s space defenders can do is keep practicing their skills and watching the skies. In 2016 the Osiris-Rex mission will fly to a well-charted near-Earth asteroid, land on it, collect a sample and return home, which should help NASA sharpen its flying skills. The Near Earth Object Office, meantime, is funded at a steady $20 million per year, which is robust enough to keep the telescopes pointed skyward and the observatories staffed. Trajectory software allows the orbit of any asteroid to be plotted a reassuring century in advance--a round figure chosen mostly because it's more than the average human lifetime. Johnson says he is cautiously optimistic that if an asteroid were spotted today that was going to strike us in Yeoman's 20-year time frame, we'd probably have the wherewithal to knock it out--provided we hustle.
But probably isn't definitely, and when the fate of the planet is at stake, we're going to have to do a better job. Any one lifetime might be a fleeting thing, but asteroids are forever. Our defenses must be too.