NASA's Near Earth Object program currently has 145 potentially hazardous asteroids on its list out of 1,062 objects larger than one kilometer in diameter, and 6,292 total discovered objects. What's all that mean? Well, that there's a lot of stuff out there that could potentially impact our planet -- some of it pretty big.Source Via
So instead of sending shuttle crews up at the last minute to blow an approaching asteroid up, British astronomers at the Astrophysics Research Centre are planning to build a 10-ton "gravity tractor" spacecraft that will influence the object's trajectory. The process would take some time -- a craft would have to be launched 15 years in advance to really have an effect -- but, once the tractor arrives, it'd hover close by an asteroid and gently guide it along a different path.
It's a Freaking Gravity Tractor
So, there is concern in some circles, that one day the earth will be struck by an asteroid, putting to an end our plans to do important stuff, like watching the "Office," or buying Miley Cyrus's new line of clothes at Walmart. Stupid jerk astroid! So what do we do? Build a Gravity Tractor (suck it, John Deere!) to avert certain death. Sweet.