The Fallout Would Be Too Great
Johnson and his team have worked on various possible ways to stop an asteroid in its track. One of the most obvious tactics would be to blow the giant asteroid up with some sort of sophisticated space missile with a massive nuclear payload. Once the missile hits its target, the space rock would disintegrate. But his analysis shows that this would only cause the asteroid to break into smaller pieces and rain down destruction on Earth. Then there’s the possibility of nuclear fallout, which is too great a risk.