A huge asteroid crashing into the Earth and killing all life may be a pretty far-fetched scenario — but it's far from impossible. As such, agencies like NASA and the UN have spent time envisioning ways to mitigate the threat, with nuclear weapons becoming an increasingly popular choice. Last September, the US and Russia entered into an agreement to collaborate and investigate how nuclear weapons could be used to defend the planet against rogue asteroids, but now it seems the US is actively stockpiling weapons to be used if needed.
As noticed by The Wall Street Journal, a 67-page Government Accountability Office report on the National Nuclear Security Administration (NNSA) said that some US nuclear warhead components that were scheduled to be disassembled by next year are in fact being kept whole to be used to defend the Earth against a potential asteroid impact. The report specifically states that some warheads "are being retained in an indeterminate state pending a senior-level government evaluation of their use in planetary defense against earthbound asteroids."
The threat of a direct asteroid impact has gotten more attention in recent months after a huge meteor exploded over Russia in February 2013, injuring hundreds with its debris. Last year, NASA said that the Earth was sitting in the path of over 1,400 asteroids that could cause potentially significant damage, but said that none seemed likely to hit the planet — at least for the next 100 years or so. And even those asteroids coming "close" to the Earth are millions of miles away, but that isn't stopping the US from being prepared. Whether or not these nuclear weapons are kept to battle asteroids remains to be seen, but it's at least something the government is keeping in its back pocket in case of an Armageddon scenario.