How could we defend Earth from a large asteroid or comet?

In 2013, NASA announced its “Grand Challenge” to locate any nasty asteroids heading our way and prevent their impact. Rock-stopping options include:

Nuking it: Attack the asteroid with a nuclear missile, smashing it into space dust.

Ramming it: Launch a rocket directly into the asteroid to break it in half or divert its course.

Blasting it: Target the asteroid with a space-based laser to vaporize it before it gets too close.

Redirecting it: Mount rocket engines to the asteroid’s surface to change its course so it misses Earth.

Picture Credit : Google