What Goes Around Comes Around

Among the strategies regarding the possibility of preventing a catastrophic event, such as Earth colliding with a large asteroid or comet, we can find early detection, asteroid deflection or possibly the destruction of the object intersecting Earth's orbit. Some of these precautions could rise more problems than solving any of them.

The early detection of Near Earth Objects was initiated some decades ago, in the effort to map and track all the objects in the near vicinity of Earth that could pose serious security problems, if such an object chose to enter the atmosphere.

The Near Earth Objects or NEO has so far mapped all the large objects that could pose a threat, however there are still a lot of smaller objects in space. As a result of the observations, NASA's NEO announced that the biggest threat of an object smashing into Earth's surface is the asteroid Apophis, which has a probability of 3 percent of intersecting our orbit. This has been revised lately to zero probability, due to new observations, thus there is no possibility for a large object to collide with Earth in the near future.

Asteroid deflection strategies suggest several valid ideas of how an object could be thrown of its orbit, such as a gravitational tractor. This would probably be the best alternative to the explosive deflection, and consists of sending a unnamed massive spacecraft, that would create a strong enough gravitational field that will pull the object slowly away from its trajectory over a long period of time.

But deflection techniques have one major flaw in their design. All objects present in the solar system, follow trajectories that orbit the Sun. Temporarily deflecting an asteroid off its track would only offer the guarantee of safety until the next time the object comes near the planet. Asteroids deflected through gravitational tractors or powerful nuclear explosions could become more dangerous if they somehow pass through a gravitational keyhole which would bring them back right onto a collision course and this involves another deflection procedure.

In the last year NASA has been severely criticized by a number of people in the astronomic community for not doing enough to keep track of the smaller asteroids. The U.S. Congress has recently pulled the plug of a number of programs run by the agency for not being able to extend its mission to detect objects smaller than 140 meters across.