If An Earth-Killing Asteroid Comes, You Won't Have Time To Tweet About It

Earth will likely get no warning of a doomsday asteroid, NASA has admitted, crushing dreams of sending Bruce Willis into space to save humanity at the final moment. "The most likely warning today would be zero" NASA sheepishly told Forbes, given "so many of even the larger NEOs [Near Earth Objects] remain undiscovered." The surprise extinction possibility is at odds with the close flyby of asteroid Apophis this week, which astronomers spotted approaching back in 2004.

At the time, the scientists warned that there was a tiny possibility that Apophis could collide with the Earth, though that wouldn't be expected until 2029. What the asteroid's nearby orbit this week has revealed is that it is significantly larger than previously estimated – up 20-percent on the original figures – meaning, should it hit our planet, it would cause an explosion equivalent to 1,480 megatons of TNT.

Unlike movies, where teams of geologists, demolition experts, and astronauts are dispatched to safely blow up an asteroid before it can devastate Earth, NASA says that we'd likely have no warning whatsoever should an NEO be upon us. The most we'd see is a "flash of light and the shaking of the ground as it hit" the space agency says – hardly enough time to tweet "Did anybody else feel that? #doomsday"

On the other hand, if scientists spot a NEO – as was the case with Apophis – then we'd likely have decades of notice, given the predictable route they generally take. Ongoing projects like Spaceguard routinely monitor the area around Earth for potential NEOs, though exactly what we could do to prevent a subsequent collision is unclear.

While Bruce Willis used a huge bomb in the movie Armageddon, researchers last year decided that the size of the explosive would not have been sufficient to actually crack the space-rock open. In fact, more likely to succeed is an innovative system using five tons of colored paintballs, which would adjust the asteroid's path thanks to a change in solar radiation pressure.