New Analysis Suggests a Comet, Not an Asteroid, Killed Off Dinosaurs

Scientists say that the rocky space object that wiped out the dinosaurs 65 million years ago might not have been an asteroid, and could have instead been a comet.

The Chicxulub crater in Mexico, which measure 112-miles across, was made by the impact which caused the extinction of the dinosaurs and 70% of all species on Earth. According to a new study the crater was likely blasted out out by a faster, smaller object than originally thought.

Evidence of the object's impact is derived from a global layer of sediments that contain high levels of the element iridium, which is also known as the Cretaceous-Paleogene (K-Pg) boundary and could have have occurred on Earth naturally. The new research, which was presented last week at the 44th Lunar and Planetary Science Conference in The Woodlands, Texas.

New research suggests that the often cited iridium values are incorrect. Researchers arrived at this conclusion by comparing these valued with levels of osmium, which is another element that was delivered via the impact. Their calculations indicate that the space rock generated less debris than had previously been thought, which implies that it was a smaller object than an asteroid. For something to have created a crater so large, it would have had to have been travelling exceptionally fast.

Jason Moore, a paleoecologist at Dartmouth College in New Hampshire, 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."

Comet are balls of ice, dust and rock particles. They are differentiated from asteroids by their eccentric orbits and thin, fuzzy atmospheres known as comas or tails. The researchers say that the Chicxulub impact is more compatible with a long-period comet, which could take hundreds, thousands, or even millions of years to orbit the sun just once.

The researchers note that it is still possible that a very rapidly moving asteroid caused the impact, but contend that the fastest space objects that have been observed are mostly comets.

Not everyone, however, is convinced of the comet theory.