The chances of a large asteroid striking the Earth are remote, but because the consequences of such an impact are potentially catastrophic, NASA takes the possibility very seriously. To help counter the most likely potential threat, called Near-Earth Objects (NEO), the agency has released a 20-page multi-agency report outlining steps the US federal government needs to take over the next decade to respond to such an eventuality.
On February 15, 2013, an asteroid 20 m (66 ft) in diameter exploded over Chelyabinsk in Russia with a force of up to 30 times that of the first atomic bomb dropped on Hiroshima. Despite detonating at high altitude, the shockwave damaged buildings and thousands of people were injured by flying glass. That may seem nasty enough, but in 1908, another object 40 to 60 m (131 to 197 ft) wide blew up over Tunguska, Russia with a force of five to 10 megatons – flattening 2,000 km² (772 mi²) of forest.
What worries some space scientists and disaster relief planners is that these events aren't anywhere near the top end of the scale. According to NASA, an asteroid 140 m (459 ft) in diameter would have an explosive force of 60 megatons if it hit the Earth. As to the upper limit, ask your local dinosaurs what the effect could be.
As part of a program to study the problem, in 2005 the US Congress instructed NASA to conduct a survey to find 90 percent of the NEOs that are at least in the 140-m range or larger. An NEO is an asteroid or comet that is on a trajectory that crosses the Earth's orbit. Unfortunately, by 2017, the agency hasn't been as successful as first hoped and will only find half the 140-m objects by 2033.
To help improve things, NASA, in coordination with the Office of Science and Technology Policy, the Federal Emergency Management Agency, and other federal agencies, has issued its report, "The National Near-Earth Object Preparedness Strategy and Action Plan." Its purpose is to outline priorities to address over the next decade to best ensure an effective response to the threat posed by an asteroid impact is possible.
The plan will concentrate on five areas. These include:
Enhancing the detection and tracking of NEOs, starting with the larger ones and then working down to the smaller. This will include radar and spectrographic analysis, development of new technologies and analysis techniques, and collaboration with other institutions.
Improving the modeling of asteroids and their orbits to better predict the probability of an Earth impact, the site of the impact, the extent of the damage, and the options for preventing or mitigating the strike.
Developing new technologies and techniques for deflecting NEOs if they are far enough away or to destroy them if deflection isn't possible.
Improve international cooperation in dealing with NEOs by building awareness of the threat, increased cooperation on observation infrastructure and modeling, and international planning on how to respond to a potential impact event.
Developing emergency procedures and protocols for dealing with an asteroid strike if one occurs. This includes better communications, decision making, space-based evaluation, and mitigation plans.
"The nation already has significant scientific, technical and operation capabilities that are relevant to asteroid impact prevention," says Lindley Johnson, NASA's planetary defense officer. "Implementing the National Near-Earth Object Preparedness Strategy and Action Plan will greatly increase our nation's readiness and work with international partners to effectively respond should a new potential asteroid impact be detected."
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