An Asteroid Bomb?
The drawback to Lu's plan is that it would work only for asteroids up to a few hundred meters across that could be engaged far from Earth. If the rock is small, we could try hitting it with a spacecraft. When all else fails, and for large asteroids and comets, only one strategy has a chance of working: nuclear bombs.
Russian scientist Vadim Simonenko and his colleagues concluded that the best way to deflect an asteroid up to 1.5 kilometers(one mile) or so wide would be to explode a nuclear bomb nearby. The explosion would destroy smaller rocks. For larger ones, the explosion would burn a layer of rock off the asteroid's surface. The expanding gas would act as a rocket motor, pushing the asteroid onto a new course.
Apophis may pose a great challenge for world leaders. As it swings past Earth in 2029, there's a slim chance that Earth's gravity will deflect the asteroid just enough to put it on a certain collision course with our planet on the next pass, in 2036. The odds are currently estimated at one in 45,000, so a strike is very unlikely Meanwhile, astronomers will continue to track Apophis to learn if it will merely taunt us again, or actually strike.