Last week saw a rare event where not only did we have an asteroid pass by at record distance from the earth, we also had one strike it. The effect of the impact in Russia, while it was responsible for a heavy amount of casualties, could have been a lot worse and the talk in the scientific community is back to 'How do we prevent this sort of thing from happening in the future'.
The reason why the meteor wasn't detected was on account of being too small and faint to see in the night sky. Ironically this means that we currently have to hope one of the larger meteors hits us to ensure that we know it's coming. So what can we do to prevent such wide-scale destruction?
Currently, we possess no certified technology to alter the path of the asteroid, which makes our most plausible current option to evacuate the area of impact. This means detecting the object a good few months before to ensure minimal human casualties. This however is not a brilliant option as this assumes that the meteor is small-scale to prevent mass ecological damage and also a meteor of any size striking a built up area (with or without people) will likely cause huge economical repercussions.
Humanities first option when presented with an alien threat is 'Can we Nuke it'? While this is still a grey area (many scientists believe that a controlled explosion could vaporise the majority of the asteroid, allowing for smaller debris to break up in the atmosphere) there is still the concern that we are detonating a radioactive device above our planet with no real knowledge as to what the long term effects could be.
I'm pretty sure there's also a treaty banning the use of nuclear weapons in the atmosphere therefore this currently remains a bad idea.
When nuclear weapons are not an option, we turn to normal missiles for help. While a safer method in that there's no radiation, the explosion would not be enough to detroy the meteor completely and therefore we would have to hope that our atmosphere would take care of the rest.
If North Korea's "space program" is ever successful they may become our only hope.
Fighting Fire with Fire
Newton's Third Law states that for every action there is an equal and opposite reaction therefore some believe that by launching another object into space it is possible to deflect the asteroid.
While technically a sound theory, the biggest problem would be managing to get an object that has enough mass to deflect a 1km wide asteroid into space to begin with. Although it is possible to deflect an asteroid enough to miss the earth with an object of small mass, the deflection would have to occur a long long way from earth to have any effect. Current detection techniques do not allow for this solution.
(Mind you, Futurama pulled it off therefore it has to be accurate...)
Beams and Gravity
Using the theory that by deflecting the asteroid from it's orbit, even by just a little, could prevent a catastrophic collision, scientists have been looking inventively into the use of ion beams. This would effectively push the giant rock enough that it would bypass the earth.
Similarly, other's have been using the idea of sending an object to fly along-side the asteroid and allowing the gravitational attraction (weak though it may be) to change the course of direction.
Again these methods rely heavily on us having enough warning to ensure that we can alter the asteroids path.
Who said scientists were never inventive? Other proposals also include turning the asteroid into a make-shift ship and steer it out of the way, basically recreating the movie Armageddon and an orbital defence network (which could prove useful against alien invasions).
It is worth bearing in mind that more people die in the space of a month due to war and conflict than have ever died as a result of all the meteorite impacts in recorded history. While arguably the earth has never been more populated with human life, the need for such a way to defend ourselves could be attributed to an increased sense of paranoia brought on by science fiction and in fact there is nothing to worry about.
Perhaps the need to prevent an asteroid collision is as necessary as trying to prevent an earthquake or a volcano, which is impossible to do. All we can do is set up ample detection systems to give us enough time to evacuate to safety when they strike.