Rubble pile asteroids would require different mitigation techniques than solid, rocky, monolithic asteroids, but just because they’re loose aggregates doesn’t mean they can be easily broken up. “If you smacked an asteroid and it fell apart, it’s likely that given enough time, it would re-accrete unless you had a very very large offense,” says Cristina Thomas of NASA’s Goddard Space Flight Center. The tool we need to reduce the threat is more a metaphorical shovel than a hammer.
Of course, even if we successfully broke an asteroid into pieces, we’d need to make sure those pieces don’t all hit us and cause as much destruction as the original asteroid. From the science fiction films Armageddon and Deep Impact, you might get the idea that we shouldn’t close our eyes or fall asleep the best strategy is to use nuclear weapons to blow the threatening space rock to smithereens. This idea isn’t off the table completely, but it must be kept as a last resort, something to be considered only if there isn’t enough time to put together something less risky to Earth. And, somewhat surprisingly, there’s another possible use of nuclear weapons that is less risky.