Can We Stop an Asteroid Impact?

A giant comet, asteroid or similar projectile hitting the Earth from Outer Space has long been the subject of bad science fiction films and a few good books on the matter. (Arthur C. Clarke even threw his hat in the arena.) The long, drawn out and emotional film Deep Impact and the more action oriented film Armageddon both dealt with the issue, although Deep Impact's portrayal contained greater scientific accuracy.

While a meteor impact may be a popular target for summer blockbusters filled with special effects, even, as in the case of both Deep Impact and Armageddon the story was not that great, the Earth has been hit by meteors and comets in the past and will likely be struck by these celestial objects again. It is one possibly explanation for the periodic mass extinctions that are found in the fossil record.

Standing back and just letting a rock from outer space hit us with forces far larger than that of the atomic bombs that were dropped on Hiroshima and Nagasaki does not seem like a good idea, but it may seem like the forces involved are too great for humanity to combat.

Astronomers sweeping the sky have found one such rock that could possibly pose a threat to all life on this pale blue dot in the year 2029, but closer observation from ground based telescopes revealed that the risk from that asteroid was non-existent, but another possible one could occur in 2036.
That does not mean that astronomers are sweeping the sky to predict when doomsday will occur, it just means that they are cataloging potential dangers. Various types of shield to knock asteroids off course have been proposed. The question is, how would such a feat occur?

One such suggestion for deflecting a catastrophic asteroid impact is building a space tractor. A space tractor is simply an object large enough that the gravity of the "tractor" itself will cause the meteor's orbit to shift a small few thousand miles or so. Arthur C. Clarke's book Lucifer's Hammer suggests using a powerful ship and its engines as a mass driver, although the space tractor would not expend fuel once placed near the deadly object.

The best known solution to a catastrophic asteroid impact involves the use of nuclear weapons. Cynics might suggest this is just so the war hawks have something to hold on to, but causing a nuclear explosion near or on an asteroid would not destroy th object. The goal is once again to knock the celestial object off its course. The explosive force of materials near the surface should cause the object getting close to earth to alter its course.

Most people need not worry about this. Impacts such as the one that kill the dinosaurs occur relatively infrequently in our planet and unlike the dinosaurs, humans have the technology and a dedicated team of astronomers watching the unfriendly skies.

Sources:

http://news.bbc.co.uk/2/hi/science/nature/6971216.stm

http://cosmiclog.msnbc.msn.com/archive/2007/02/16/58617.aspx

http://www.guardian.co.uk/science/2007/mar/07/spaceexploration.frontpagenews