Scientists may at last have uncovered the truth behind a mystery that is 65 million years old. According to findings presented at the 44th Lunar and Planetary Science Conference in Texas, a research team from Dartmouth College in New Hampshire claims that the dinosaurs, and about 70 percent of all other species on Earth, were wiped out by a piece of a comet.
It has long been suspected that a cataclysmic event occurred about 65 million years ago in what is now the Yucatan Peninsula of Mexico. The region’s 180 kilometer-wide Chicxulub crater - first discovered in 1978 by an oil company geologist - has been identified since 1990 as the site of a devastating impact, but scientists have not been in agreement over what kind of space rock might have caused it.
Drill samples taken from a thin layer of the rock strata known as the K- Pg boundary have given scientists a good idea about the size of the pre-historic explosion, and the most common theory to date has been that this worldwide layer of iridium and osmium-rich sediment was created by an asteroid about 13 kilometers across.
However, the Dartmouth College team argues that the layer was caused by a smaller, but faster moving object, or in other words, a comet. A new analysis of the data suggests that an asteroid of the size proposed by previous studies would have deposited more iridium in the layer. According to researcher Jason Moore, “You'd need an asteroid of about 5km diameter to contribute that much iridium and osmium. But an asteroid that size would not make a 200km-diameter crater. So we said: how do we get something that has enough energy to generate that size of crater, but has much less rocky material? That brings us to comets.”
The secret is that comets move much faster than the vast majority of asteroids, and an impact from one about half the size of an asteroid would have produced the same size explosion.
The findings have sparked a great deal of interest from the scientific community. Dr Gareth Collins, an expert on impact craters from London’s Imperial College, has described the research as “thought-provoking”. He is sceptical, however, that the size of the impactor can be accurately gauged from geochemistry. Dr Collins maintains that it is impossible to tell how much of the impact material was scattered globally and not ejected back into space or deposited close to the crater.
Nevertheless, these new proposals offer a compelling explanation for the cause of worldwide natural disasters – including fires, earthquakes and tsunamis – that must have ended the reign of the dinosaurs. It is also a cautionary tale for everyone currently living on Earth. The Cosmos is a busy place, and what happened 65 million years ago could one day happen again.