Dinosaur Extinction by Asteroid Impact
One of the most popular theories about end of the dinosaur’s reign on earth is the asteroid collision theory. It was in 1980 that this theory was put forward by Walter Alvares, a professor in the Earth and Planetary Science department at the University of California, Berkeley.
According to the theory, around 65 million years ago, at the end of the Cretaceous period, an asteroid collided with the earth at the Yucatan Peninsula in New Mexico. Walter and his father Louis Alvarez were the promoters of this theory. The evidence they put forward showed increased iridium levels on the clay layers of the period. They claimed that the bolide asteroid that hit the earth, created a massive Chicxulub crater, which is now buried underneath the surface. Scientists are not certain whether the Dinosaurs were already on a decline at that time.
The scientists differ when it comes to the actual impact results. They have different opinions and theories about how the Dinosaurs died after the impact. Some supports the theory that there was an intense heat wave right after impact and some suggests that the earth’s atmospheric temperature dropped dramatically after the impact. There are others who say that after the collision, the atmosphere heated up and later the matter ejected from the crater caused a cooling down.
In September 2007, a group of scientists from the Southwest Research Institute in Boulder, Colorado and Czech scientists led by William Bottke analyzed the probabilities of Dinosaur extinction due to an asteroid impact. They used computer simulations to find out the origins of the Chicxulub crater. Their study revealed that about 160 million years ago, a giant asteroid named Baptistina, that lies between Mars and Jupiter was hit by a smaller unnamed asteroid, creating a cluster of shattered small asteroids. The scientists came to the conclusion that some of the left over pieces in these cluster were hurtling towards the earth’s orbit from time to time and that one of these asteroids hit the Yucatan Peninsula 65 million years ago. But, later discoveries and analysis of computer models suggested that the collision of asteroids take tens of millions of years and it is highly improbable that an asteroid from the Baptistina family could have created the Chicxulub crater.
Another intriguing and controversial theory suggests that the passing of the star Nemesis through the Oort Comet cloud could trigger a comet shower on the earth. But, there is no evidence to suggest that this theory is true.