Our planet has been continually bombarded by asteroids since its formation, 4.5 billion years ago. While the frequency of large impacts has decreased, many potential Near-Earth Object threats remain undiscovered, so if or when they will impact Earth remains unknown. The good news is that an asteroid impact is the only large-scale natural disaster that is, in theory, preventable. Fortunately, if an Earth-threatening asteroid is discovered in time, there are ways to mitigate or even prevent a disaster.
If an asteroid is found to be on a collision course with Earth, it can be diverted by a few different methods. For long warning times and asteroids that are not too big, a heavy “kinetic impactor” spacecraft can be used to impact the asteroid at high speeds, giving it a slight nudge so that it safely misses Earth. When warning times are short or the asteroid is large, kinetic impactors cannot provide enough momentum for the asteroid to miss Earth. In these cases, a nuclear device can be sent into space to deflect the asteroid. Very short warning time scenarios, where deflection is impossible, can be handled by using a similar device to fragment the asteroid into many small, well-dispersed pieces.
Scientists at LLNL provide computer simulations in preparation these scenarios so if the time comes where an asteroid is headed our way, we will be prepared.