Asked by: Jamie Remington, Andover
It is certainly possible, but would be a difficult and expensive task. The key would be in deflecting the asteroid away from its collision course with Earth rather than shattering it into equally dangerous debris.
This could be done by impacting it with a non-destructive projectile, simply tugging the asteroid into a different orbit with a nearby high-mass spacecraft, ablating the asteroid’s surface with a high-power laser (or a nearby nuclear explosion), or by placing small rockets on the asteroid’s surface.
All of these techniques would require at least five years to achieve, which is why early warning of potential asteroid impacts is vitally important.