So, the tether on your tether-and-ballast system got tangled. The gravity tractor wasn't built Ford-tough. What do you do now about that killer asteroid barreling toward Earth? Well, if you tried one of the mitigation strategies just mentioned, the asteroid is most likely (a) big and (b) far away. That gives you some time to prepare for impact, although you won't have any historical precedent to provide best practices.
In fact, many astronomers point to fictional accounts -- "On the Beach" by Nevil Shute, for example -- as the best source material about what we might do and how we might fare in a true global cataclysm. Clearly, astronomers would try to pinpoint where the asteroid would hit so ground-zero areas could be evacuated, and governments would try to build underground bunkers, store food and water, collect animal and plant species, and shore up the global financial, electronic, social and law-enforcement infrastructures. The impact of a smaller asteroid -- say, one about 984 feet (300 meters) wide -- could devastate a region the size of small nation.But a rock bigger than 0.621 miles (1 kilometer) wide would affect the whole world. A rock larger than 1.86 miles (3 kilometers) would end civilization [source: Chapman].
Tsunamis, firestorms and earthquakes might cause additional damage. Either way -- impact in the ocean or land -- public officials might only have days or hours to evacuate heavily populated areas. Millions of lives would likely be lost.
Given these scenarios, you can see why governments around the world are so interested in keeping asteroids far from our biosphere. You can also see why dollars don't always drive decisions -- because the cost of failure far exceeds the cost of even the most elaborate deflection concept.
Author's Note: 10 Ways to Stop a Killer Asteroid
A few years back, I saw a TV program about the increased contact occurring between humans and sharks. There was one amazing shot that stuck with me: It showed an aerial view of swimmers just off the coast of Nags Head, and, unbeknownst to them, hundreds of sharks swam nearby. You could see their shadows among the bathers, dark and sinister. Had the people in the water known what was lurking nearby, they would have been on the beach in seconds. I feel the same way about NASA's NEO detection program. Are we better off knowing all those rocks are out there, circling us like sharks? Sometimes it seems better to be the oblivious bodysurfer who swims in ignorant bliss.
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- Chapman, Clark R. "How a Near-Earth Object Impact Might Affect Society." Commissioned by the Global Science Forum, OECD, for "Workshop on Near Earth Objects: Risks, Policies, and Actions." January 2003.
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- NASA. "Deep Impact's Impactor." Deep Impact: Mission to a Comet. (March 11, 2012) http://www.nasa.gov/mission_pages/deepimpact/spacecraft/impactor.html
- NASA. "How many near-Earth objects have been discovered so far?" Near Earth Object Program FAQs. March 18, 2012. (March 18, 2012) http://neo.jpl.nasa.gov/faq/
- Plait, Phil. "Death by meteorite." Bad Astronomy, Discover Magazine. Oct. 13, 2008. (March 11, 2012) http://blogs.discovermagazine.com/badastronomy/2008/10/13/death-by-meteorite/
- Schweickart, Russell, Edward T. Lu, Piet Hut and Clark R. Chapman. "The Asteroid Tugboat." Scientific American. November 2003.
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