It was an asteroid 65 million years ago that hit the Earth in Russia and set up a plume of smoke that enveloped the earth. This caused years of wintry conditions. It was this episode that caused the demise of the dinosaurs and the ascendency of birds and mammals. We thus owe our evolutionary position to asteroids. However, we are at threat of losing that ascendency should another major asteroid hit the earth.
Astronomers take the threat of asteroid collision very seriously. An asteroid that hits land brings with it intense heat that will start major fires. If the asteroid hits water it can cause tsunamis up to 4 km high. Where ever it hits there is sure to be a chain reaction of earthquakes affecting many parts of the world. And then of course there is the dust that blocks out the sun.
The first thought by scientists was to meet asteroids that had a collision orbit with Earth in space and blow them apart with nuclear devices. This suggestion became the basis of the movie Armageddon. Scientists have long since discredited this idea because the asteroid would break into small parts that would still be likely to hit the earth and cause possibly irrevocable damage.
A better suggestion has been made. That is the solar collector. This would be in effect a giant reflective panel that would be sent into space to move parallel to the dangerous asteroid and direct the rays of the sun on to one spot of the rock. The asteroid would heat up and the steam given off from the burning point would send vapors into space that would change the orbit of the asteroid.
This is an ingenious idea and more sophisticated than the hung-ho approach of just nuking any threats to Earth. The technology still needs to be developed. Although NASA and the scientific community now take asteroid impact seriously politicians are forever cutting space program budgets when the economy takes a nose dive. Perhaps it is only China with its massive liquidity that can really muster the long term financial resources to ready a solar collector for the day when it is needed.