The causes for the extermination of dinosaurs millions of years ago have long been a bone of contention.
Some scientists believe a collision of two asteroids in the solar system that sent enormous chunks of rocks hurtling towards the Earth spelled the demise of the magnificent creatures. The impact is thought to have unleashed monstrous tsunamis, raging wildfires and sandstorms, triggering an Armageddon that wiped the dinosaurs off the Earth.
The impact on the Earth of possible cosmic collisions between comets and asteroids has worried scientists so much that a lot of resources and manpower have been devoted to the study of Near-Earth Objects (NEOs). NEOs are comets and asteroids that have been pulled by the gravitational force of nearby planets into trajectories that bring them close to the Earth's orbit.
Scientists have calculated that an asteroid which has a diameter of more than a mile might hit the Earth once every 100,000 to one million years.
In spite of their infrequent nature, scientists argue that the magnitude of such cosmic disasters is much greater than other natural calamities. The havoc that could be wrought would be enough to cause the instant extinction of a majority of species on the planet.
Over the past century, our Earth did have a couple of close shaves with asteroids. On June 30, 1908, a large asteroid with a diameter of 50 metres hurtled through the atmosphere at 11 kilometres per second and exploded 6 to 9km above the ground in Siberia. The wayward rock exploded with a force of 20 million tonnes of TNT (the equivalent of 1,000 Hiroshima bombs), felling 60 million trees over an area of 2,200 sq km and decimating thousands of animals.
A couple of other near-misses also sent chills down the spines of scientists.