Should an approaching asteroid represent a possible collision risk to the Earth, officials say the United States could be ready to respond -- with an arsenal of nuclear weapons.
Several federal agencies are reportedly considering the feasibility of keeping some nuclear warheads that are no longer considered necessary for the national defense as possible protections against asteroids on a collision course with the Earth.
The proposal was revealed in a Government Accountability Office report on the federal agency responsible for America's nuclear weapons, the National Nuclear Security Administration, which is planning on dismantling a portion of the country's Cold War nuclear arsenal.
While that dismantling is underway there are plans to keep some warheads "pending a senior-level government evaluation of their use in planetary defense against earthbound asteroids," the GOA report said.
The possibility of an asteroid impact and its consequences has been much in the news since early last year when an asteroid exploded over the Russian city of Chelyabinsk.
The blast, estimated to be equivalent to 400,000 tons of TNT, shattered windows throughout the city, with flying glass and debris injuring hundreds of people.
Scientists estimate around 100,000 asteroids the size of the 60-foot-wide Chelyabinsk object or larger inhabit the Earth's neighborhood of the solar system.
Only about 5 percent of them have been identified and cataloged, says Lindley Johnson, who oversees NASA's efforts to locate "near-earth objects."
A 300-foot-wide asteroid hitting Washington, D.C., "could wipe out everything inside the Beltway," he says.
The U.S. government has been mulling several strategies to protect the Earth against asteroid impacts, and nuclear weapons have often been proposed as a solution.
In that scenario, a rocket armed with a nuclear warhead could be send toward the asteroids while it was still in deep space, and detonated near the object with the goal of deflecting it off of a possible collision course with the Earth.
While using nuclear warheads is a controversial proposal, some experts say it might the only solution if the asteroid is large and not discovered until well on its way toward Earth.
"When we have an impact threat warning time longer than 10-20 years, other non-nuclear options (kinetic impactors, gravity tractors) can be used," says Bong Wie, who heads the Asteroid Deflection Research Center at Iowa State University.
Such methods would require the asteroid be small enough and detected soon enough, he says.
"However, when we don't have sufficient mission lead times, all non-nuclear options are not applicable and the nuclear explosion is the only practical solution," he says.
