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The Case for Impact Defence This work is considered exceptional by our editorial staff.

February 15th, 2013: 17-meter, 10,000-ton meteor exploded over Chelyabinsk, Russia with the power of over 30 times that of the Hiroshima nuclear bomb. The shockwave from the explosion damaged over 7,000 buildings, seriously injuring almost 1,500 people. The cost rose up to $33 million USD.

This was not the only time a cosmic object impacted the Earth. Asteroids of 4 metres hit the Earth once a year on average. Those of about 15 metres like the Chelyabinsk meteor hit once every 30 years on average. In the past 600 million years, there has been 60 impacts with asteroids larger than 5km in diameter. The most famous impact is the Cretaceous-Paleogene mass extinction event 66 million years ago with an asteroid of over 10km in diameter.

The damage is tremendous. To give some perspective, an asteroid of 5km in diameter is equivalent to 10 million megatons of TNT, while the largest nuclear weapon ever detonated is a mere 50 megatons of TNT. An impact of that magnitude would cause a global catastrophe, even leading to the extinction of the human species.

These collisions cause direct damage to the Earth’s topology, and pose a big threat to global climate and life. We have been very lucky so far; all the modern impacts have been in remote locations. However, if the Chelyabinsk meteor were to have hit New York City, it could very well have destroyed the entire island of Manhattan, killing thousands of people in a matter of seconds.

With such a high risk, it is surprising that a good number of the population remains oblivious to these impacts. It was only a few months ago when I read this from an article on debunking apocalypse theories: “Another possibility is an impact with an asteroid, but it has never occurred since the extinction of dinosaurs.” He is not alone in his ignorance; many would just as well dismiss the idea of an asteroid impact as science fiction.

The Chelyabinsk meteor served as a wake-up call for the world. Or so many scientists hoped. The same problems we faced decades ago still pervade.

Other than ignorance itself, the biggest issue with an asteroid defense system is the cost. Current efforts are estimated to catalog orbits of 90% of near-Earth objects of diameters between 140m and 1km by 2030 with a budget of $20 million. But these calculations have a very high uncertainty, and objects smaller than 140m can still cause massive damage (an impact with a 140m asteroid would destroy a better part of the North American continent). To actively catalog every harmful asteroid, there would have to be a much powerful telescope in a Venus-like orbit, away from the Earth to avoid glare from the Sun. A project like this has an estimated cost of $750 million just for construction, never mind getting it in orbit.

Cataloging is only scratching the surface. Once a dangerous asteroid has been detected, what then? Many plausible methods of impact avoidance are being discussed, such as nuclear weapon, gravity tractor, and rocket propulsion. These will cost billions of dollars to build and launch. Obama Administration's current project to send astronauts to a near-by asteroid is clocking in at $2 billion per year.

Even with the high expenses, there are even higher risks at hand. Surely, with million-dollar budget movies being made in Hollywood every year, we can afford to spend some money to save all of humanity from a global disaster? And yet, the government’s recent sequestration left NASA with an even smaller budget for asteroid defence.

There is also the political controversy over methods of impact avoidance. Most obviously, a nuclear weapon powerful enough to blast an asteroid into tiny, safe fragments could very well be used to attack an enemy. Astronomer Carl Sagan also proposed the “Deflection Dilemma”: Any method capable of deflecting asteroids away from Earth also hold the power to deflect asteroids towards a target. Considering the track record of genocidal political leaders, this is a major concern. Gravity tractors could be used to pull objects towards specific targets, even pulling it towards a specific country on Earth, turning an asteroid into a doomsday weapon.

So the big question remains: who controls the power? The power to avoid impacts seems to be too big to hand over to a single person, even a single country. Could the UN possibly handle it as they have handled climate control? Or would there need to be a stronger global force that could unite the planet as one better than a group of delegates from a select number of countries?

The answers to these questions are not clear yet, but the need for a defence system is more than clear—it is obvious and critical. Statistically, we are 15 million years overdue for a doomsday asteroid and it could come any day and without sufficient warning. We have been putting it off for decades, even as the technology to deflect an asteroid became available, but time is running out. It will take years to develop a sufficient defence system. Even with a system in place, it will require a long enough warning period, which means we will have to have telescopes in place to detect the dangerous cosmic objects before it is too late.

So let us get started. There is no better time than right now. There are maybe a dozen people working on impact avoidance; let us turn that number to hundreds. Let us live knowing that we, as a species, are protected. And most of all, let us not look back in regret later because, as Astrophysicist Neil deGrasse Tyson put it, “[we] fared no better than the proverbially pea-brained dinosaurs.” We are the most intelligent species the Earth has seen, and we have the power to choose our fate when a massive, fiery rock confronts us. So let us choose wisely.



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