Comment »Posted on Monday 19 October 2009 at 4:02 pm by Colin Stuart
In Evolution, Space & Astronomy

Scientists in America have located what they believe to be the world’s largest crater and what’s more they are holding it responsible for the demise of the dinosaurs.

Researchers have traditionally pointed their finger at the Chicxulub crater in Yucatan, Mexico as the culprit for the extinction of T-Rex and his chums 65 million years ago, but Sankar Chatterjee and his team are turning their attention to India’s Shiva Crater.

This underwater basin measures almost 500km across, easily overshadowing Chicxulub’s measly 180km, and was most likely carved out when approximately 25km of space rock came hurtling to Earth. Dr Chatterjee and his colleagues hope to study the crater further to establish once and for all whether it was indeed caused by an impact 65 million years ago.

The underwater Shiva Crater, off the coast of India, may have caused the extinction of the dinosaurs.
The underwater Shiva Crater, off the coast of India, may have caused the extinction of the dinosaurs.

The tell-tale sign of a space-based impactor is abnormally high levels of Iridium, an element abundant in asteroids but a rarity in the Earth’s crust. Iridium levels at impact sites tend to be a hundred times greater than usual.

Whilst impacts of this size are certainly not every day, or even every millennium events, there have been five extinction level events, where over 50% of the animal population have been pole axed, in the last 540 million years. Many are attributed to asteroid and/or comet impacts, although there are other possibilities.

Subsequently the study of the position and trajectories of the asteroid and comet families has become big scientific business including NASA’s dedicated Near Earth Object program. Programs such as these led to a potential impactor being discovered in 2004 that experts rated as a 1-in-60 chance of colliding with the Earth.

Happily, they have since revised their estimations upwards. However, asteroid 99942 Apophis (2004 MN4) will still pass the Earth over 13 times nearer than the Moon, rather eerily on Friday 13th April 2029, culminating in the closest approach of such a sizeable object for a thousand years.

It is not a question of if but when a Shiva Crater causing asteroid has our name on it. Yet if Dr Chatterjee and his team are correct it will be another piece in the puzzle explaining what led to the disappearance of the dinosaurs and the advent of the mammals that would evolve to worry about a similar fate.


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