Among the few apocalypses worse than nuclear annihilation, asteroid impact has got to be near the top of the list—at least if Hollywood's depictions are any indication. Luckily, the American public has at least one agency defending it against errant space rocks: the exact same agency that's supposed to be protecting us from thermonuclear war in the first place.
The Government Accountability Office (GAO)—a federal agency tasked with maintaining operational transparencies and government reporting—recently examined efforts of the National Nuclear Security Agency (NNSA), which is responsible for decommissioning old weapons and generally managing America's stockpiles of nukes. While the overall numbers of these weapons has declined since the end of the Cold War thanks to a variety of international disarmament treaties (more than 12,000 since the Iron Curtain fell), the GAO discovered that the nuclear agency was lagging behind its goal of dismantling all nuclear weapons retired from service before 2009 by 2022. Not only that, the GAO found that the NNSA had actively halted the destruction of a small number of nukes "pending a senior-level government evaluation of their use in planetary defense against earthbound asteroids." That is, until someone has evaluated their ability to blow up planet-killing asteroids.
As the NNSA explained in the GAO report,
For potential use in planetary defense against earthbound asteroids. NNSA officials told us that CSAs associated with a certain warhead indicated as excess in the 2012 Production and Planning Directive are being retained in an indeterminate state pending a senior-level government evaluation of their use in planetary defense against earthbound asteroids. While NNSA has declared these CSAs to be excess and, until March 2013, had scheduled them for disassembly beginning in fiscal year 2015, the national labs' retention letter has also characterized the CSA associated with this warhead as an "irreplaceable national asset." The WDD program is coordinating NNSA's evaluation of their use in planetary defense with the support of LLNL, LANL, and Y-12.
This actually isn't that far fetched. Our planet is covered in evidence of asteroid strikes, one of the largest of which constitutes the Gulf of Mexico. Now, that was generated by a multi-kilometer wide rock that also killed the dinosaurs but even single-kilometer-wide asteroids hit Earth once every hundred years or so. And should a rock that size hit, say downtown DC, the impact "could wipe out everything inside the Beltway," Lindley Johnson, a program executive at the National Aeronautics and Space Administration, told the WSJ.
Though nothing that big is expected to venture into our danger zone in the near future, the planet is routinely peppered with smaller space rocks like the 20 meter-wide one that exploded over Russia last winter and injured thousands in the region. in fact, NASA estimates that close to 100 tons of asteroid debris collides with the planet every day, though most all of it burns up in the atmosphere before hitting the surface.
These extraterrestrial threats aren't big enough to land a ragtag team of oil drilling misfits on, but they could very well be nudged off a collision course with the Earth with the help of these nuclear warheads. What's more, once the warheads are decommissioned, they can't simply be reassembled into working weapons. They are, therefore, a non-renewable resource, hence the NNSA's reluctance to destroy them without clearance from officials higher in the federal food chain.
This isn't the only reason the NNSA is dragging its feet, mind you. he agency is also lobbying to hold onto some of the old subassemblies for use in next-generation W78 standoff missiles, or as a tactical reserve of enriched uranium. This would be a means of balancing the workload among its various decommissioning sites since weapons before and after the year 2009 must be handled differently according to the various disarmament treaties. However, regardless of whether this subset of retired weapons are spared or not, the GAO is not bullish on the NNSA's chances of finishing its required work by the 2022 deadline. [WSJ - GAO - Defense One]
Image: Urszula Lysionek