When Asteroids Attack

“Noise proves nothing. Often a hen who has merely laid an egg cackles as if she laid an asteroid.” - Mark Twain

An article at NewScientist.com, Asteroid attack: Putting Earth's defences to the test, describes a day-long test by the US Air Force in December of last year to test its readiness in the case of an asteroid impact. The US Air Force brought together scientists, military officers and emergency-response officials for the first time to assess the nation's ability to cope with an asteroid striking the Earth in just three days. The exercise was a wake-up call for the Air Force: there is no plan for what to do, the early-warning systems are woefully inadequate, and was no formal coordination between major parties like the Air Force, Homeland Security and NASA.

So it is not unreasonable to ask, should we panic? The answer is no. The best known impact in modern times was a comet 30 to 50 meters across that exploded over Tunguska, Siberia, in 1908, flattening trees for dozens of kilometres all around. The chance of a similar impact is about 1 in 500 each year, or a 10% chance of an impact in the next 50 years. The odds of a dinosaur killing, giant asteroid are much, much lower. But let’s assume you beat the odds and the next small comet or asteroid hits in your lifetime. Well the earth is a very big place with 70% of it covered in water. NASA used to fear that an ocean impact would create giant city-swamping tidal waves but recent research shows that the waves will lose energy before hitting land. (Unless the comet hits close to shore.)

What would an asteroid impact look like? A lot like an atom bomb. The heat of entry will cause the rock or comet to explode in a bright flash of light with a huge pressure and heat wave 30 seconds after. The only difference will be a lack of radiation. Since an asteroid and nuclear bomb are so similar, NASA warned the world when it calculated that a car sized asteroid would hit somewhere in the Middle East last year. They did not want a World War started because an Arab nation thought it had been nuked. Fortunately 2008 TC3 exploded over an unpopulated desert area of northern Sudan and never reached the ground.

Bottom Line

To its credit NASA was able to predict where and to the minute when the 2008 TC3 asteroid hit. To our shame, we had just 20 hours warning of this particular asteroid. And we were lucky to have spotted it at all. Our telescopes are blind to objects moving at us from the direction of the sun or even the moon. Two of the world's three leading asteroid detecting telescopes are based in Arizona, a region that clouds over between July and September.