Asteroids and nukes, they seem like the perfect match.
We've gone full circle more than once in the discussion about asteroid collision mitigation plans in recent years. The once sci-fi space rock disposal solution is becoming more sci-fact every time the ugly subject of errant space rocks is discussed. It's a “given" that if an incoming asteroid were to be spotted last-minute, we'd obviously need to launch our entire nuclear deterrent into space.
Unfortunately, there's a catch (actually, there's a few catches) with this plan:
1) What if we shot a nuke at an incoming asteroid and it was woefully weak compared to the structure of the asteroid? All we'd succeed in doing is turn the deadly asteroid into a radioactive deadly asteroid.
2) What if we shot a nuke at an incoming asteroid, the asteroid blew up, but there's enough time for the asteroid to reform under the mutual gravity of its debris? Well, that's not good either.
3) What if we shot a nuke at an incoming asteroid, the asteroid blew up, but now we have a thousand smaller chunks of the deadly asteroid racing toward us? Well, it would be like choosing between getting shot by a cosmic bullet, or cosmic buckshot. The former packs a bigger punch, while the latter blanket-bombs an entire hemisphere.
With all these “what if's" we'd be stupid to launch a nuclear weapon at an asteroid, right?
Well, despite the flaws, it turns out that going nuclear is probably still the 'best' option if we spotted an “on-target Apophis" tomorrow, and a group of scientists have been busy simulating this event.
In a January video from Los Alamos National Laboratory, New Mexico, scientists using the awesome power of 32,000 processors inside the Cielo supercomputer have simulated the impact of a 1-megaton nuclear explosion on the surface of a 500-meter wide asteroid.
Their conclusion is fabulous: Yes, a big boom can solve a big problem.
“Ultimately this 1-megaton blast will disrupt all of the rocks in the rockpile of this asteroid, and if this were an Earth-crossing asteroid, would fully mitigate the hazard represented by the initial asteroid itself," said Los Alamos scientist Bob Weaver.
Basically, by detonating this nuclear warhead on the surface of an asteroid like the one visited by the Japanese Hayabusa asteroid sample return mission, a shock wave will propagate through the “rubble pile" (the nickname given to asteroids composed of loose material clumped together via a weak gravitational field), disrupting the asteroid enough so it can be pushed out of the way or ripped apart. It may not solve the problem of getting hit by lots of smaller pieces of asteroid, but if there's enough time, this debris may be pushed out of harm's way by the blast. Humans: 1, Asteroid: zero.
Most recently, the discovery of asteroid 2012 DA14 has prompted some concern that the next asteroid to hit Earth probably won't be of extinction-level proportions, but more of city- or country-sized proportions. The 50-meter wide DA14 definitely wont hit us in 2013, but it will pass under the orbit of geosynchronous satellites, a fact that seems a little too close for comfort.