What would happen if a significantly large asteroid was discovered to be on a collision course with the earth? If nothing could be done to stop it, the results would be devastating.
In days of old, the disappearance of the dinosaurs was a mystery, but now it is believed that an asteroid about 10 kilometers (6.2 miles) in diameter hit the planet some 65 million years ago to wipe this species out. The impact created the Chicxulub Crater in present-day Mexico, and it is estimated that this gigantic chunk of rock hit land at a speed of about 30 kilometers per second. That's 54000 kilometers, or if you prefer, over 33000 miles per hour! In such a collision, the impact with either the earth's crust or water surface would finally stop the asteroid. The energy created by such action would vaporize the asteroid and a big chunk of the area it hits. The fragments of this asteroid would then fly back into the atmosphere. Some would escape into space and assume an orbit, but most of the debris would fall back to earth. Because of the asteroid's initial size and velocity, this would occur all over the planet, and it would heat the atmosphere up so much that virtually everything on the planet's surface would fry. The dust from the impact itself, as well as the soot from massive forest fires, would block out sunlight for over a year, killing most plant life. This in turn would result in species of animals (including humans today) dependent on food to die off in a relatively short timespan.
To conclude, this is something one doesn't want to happen, to say the least. Fortunately, an occurence of such a catastrophic event is estimated to only happen once every 50 million to 100 million years. But again, what if a gigantic asteroid was headed this way despite those odds? Could anything be done to avoid the ensuing disaster?
Scientists believe the answer to this question is yes. The most popular theory behind this hypothetical scenario involves the use of nuclear warheads. Physicists at the Los Alamos Laboratory in New Mexico have utilized the latest Cray supercomputer to predict the effect of a nuclear blast on an incoming asteroid. Robert Weaver, a research and development scientist at Los Alamos, believes that asteroids are merely constructed of clumps of rock held together by gravity, and thus one atomic detonation would be sufficient enough to shatter such an object into harmless space dust. It should be noted, however, that the model Weaver came up with involved a much smaller asteroid with a diameter of some 500 meters, or about 1/20 the size of the one believed to have killed off the dinosaurs.
This poses a problem if the asteroid in question happened to be the size of Texas, as it was in the 1998 science-fiction film Armageddon. Four physics students in England have estimated that to successfully blast apart an asteroid of that magnitude, a nuclear explosion some 2 billion times more powerful than anything ever detonated on earth would have to take place. Then again, the odds that a Texas-sized asteroid will ever head in the earth's direction would make the 50 million to 100 million year chances of a 10 kilometer rock doing likewise seem like a daily occurence, so this probably isn't something worth losing sleep over.
The other main theory to thwart potential asteroid collisions involves changing the object's path by means of gravitational manipulation. For example, an unmanned probe could be sent to fly alongside such an asteroid. It is believed that even the modest gravitational pull of such a craft would eventually exert a tug on the asteroid and change its course. The main problem with this idea is that the asteroid would have to be detected many years in advance so this slow and gradual correction would have adequate time to materialize. It has also been suggested that a quicker way to divert an asteroid's path would involve deliberately slamming such a spacecraft into its surface, thereby relying on brute force, but it wouldn't be as accurate as the aforementioned method of riding along. In fact, this forceful method could very well serve as a quite risky leap of faith. If that impact took place in the wrong location or at the wrong time, disaster could very well be unavoidable.
Thankfully, science has evolved and one can be thankful that plans are being drawn to prevent such a catastrophe. Those who lived in the countless preceding centuries would have had no hope of avoiding such a collision at all. An event like this may only happen every 50 million to 100 million years, but it's certainly nice to realize that, at least on paper, something can be done about it.