It’s not a matter of if but when another giant asteroid or comet strikes the Earth. It’s happened all throughout history, and our mere presence on this planet won’t protect it. Although, we are the only species in the history of Earth with rockets and explosives (that we know of). Uncountable sci-fi movies have told us that explosions are the answer to an impending strike, but a new analysis from Johns Hopkins University suggests that asteroids are probably considerably harder to damage than we thought, and even if you blow one up, it could simply reform.
The physics involved in an asteroid collision are well understood, but it’s difficult to apply them on such a grand scale. There are numerous processes that affect an object the size of a city when you pump massive amounts of energy into it. Based on work in the early 2000s, researchers believed that a 15-mile wide asteroid could be obliterated by a 0.6-mile object hitting it at a velocity of 3 miles per second (or equivalent energy from a weapon). That’s a lot of energy, but it’s a place to start.
Now, the Johns Hopkins team has created a new model that takes into account more detailed, small-scale processes at work inside a fracturing asteroid. The analysis focused on both short-term and long-term effects from attempting to blow up an asteroid. In the short-term, millions of cracks formed on the simulated asteroid, causing parts of the surface to flow like water. However, there’s a limit to how fast those cracks can propagate, and much of the overall structure would remain intact.
As for the long-term effects, shooting an asteroid might leave you with… an asteroid. A large clump of rock and metal doesn’t fracture evenly, so you’ll be left with a large unbroken core. The gravity from the core holds the fractured crust together and even pulls in pieces that may have broken free.
Blowing up an asteroid has always been seen as a last resort, and the new findings just underscore that. Scientists have proposed other methods of protecting Earth from impacts like slowly altering its orbit over the course of months with solar sails. Then there’s the HAMMER spacecraft, which could use a small explosion to deflect it immediately. This is all still hypothetical — hopefully, we don’t have to put these ideas into practice any time soon.