How to stop killer asteroids [Spectral Lines]

In a world of endless threats, the most worrisome are those that can kill you. And a large asteroid hurtling toward a catastrophic collision with Earth tops the list. Killer asteroids are part of a category of slow-emerging existential threats, such as global climate change, that, because they reveal themselves gradually, invite the attention of engineers, who are well suited to craft solutions from materials and technologies at hand.