March 28, 2013
Newly Discovered Evidence Supports Ancient Asteroid Impact Theory
redOrbit Staff & Wire Reports - Your Universe Online
Researchers from the University of Colorado claim to have uncovered new evidence supporting the notion that a Manhattan-sized asteroid collided with the Earth some 66 million years ago, triggering a global firestorm that would have led to the extinction of 80 percent of the planet´s species.
According to Douglas Robertson of the Cooperative Institute for Research in Environmental Sciences (CIRES) and colleagues, the firestorm caused by the asteroid believed to have slammed into Mexico's Yucatan Peninsula would also have had a tremendous impact on the environment as well.
It would have caused every twig, tree and bug around the world to burn, and would also have vaporized massive amounts of rock, blowing it high above the Earth´s atmosphere. When that material re-entered the atmosphere, it would have heated the upper levels to temperatures of approximately 2,700 degrees Fahrenheit. The extreme heat would have killed every creature not sheltered underwater or beneath the ground.
While attempting to explain why little charcoal is found at the Cretaceous-Paleogene (K-Pg) boundary at the time when the asteroid made impact and the fires are believed to have occurred, Robertson´s team discovered that researchers who had previously studied the subject corrected their data for changing sedimentation rates.
When those same corrections were applied to the charcoal data, they displayed an excess of the substance rather than a deficiency.
“Our data show the conditions back then are consistent with widespread fires across the planet,” Robertson, a research scientist at CIRES, explained in a statement. “Those conditions resulted in 100 percent extinction rates for about 80 percent of all life on Earth.”
Those findings are consistent with geological evidence which indicates that the asteroid struck the Earth approximately 66 million years ago, carving the 110-mile diameter Chicxulub crater in Mexico in the process. In addition, a 2010 report issued by experts representing 33 different international institutions concluded that the impact resulted in mass extinctions of several species, including dinosaurs, at the K-Pg boundary.
“The conditions leading to the global firestorm were set up by the vaporization of rock following the impact, which condensed into sand-grain-sized spheres as they rose above the atmosphere,” CIRES explained. “As the ejected material re-entered Earth's atmosphere, it dumped enough heat in the upper atmosphere to trigger an infrared ℠heat pulse´ so hot it caused the sky to glow red for several hours,” even though some of the infrared radiation was blocked from the planet´s surface due to the falling debris.
However, enough of the radiation would have reached the surface to have created the firestorm, igniting dead leaves and other types of tinder. So much heat would have been generated that it would have felt like spending two to three hours sitting in a broiler, and the amount of energy created on the day of the collision would have been equal to “a 1 megaton bomb exploding every four miles over the entire Earth,” Robinson said.
In addition, while some scientists have claimed that a layer of soot found at the K-Pg boundary layer shortly after the impact was caused directly by the asteroid´s collision, Robertson and his colleagues believe that is not the case. They report that the soot levels were too high to have been created during the impact event itself, and were more consistent with something that would have resulted from global fires.
Co-authors on the study include CIRES Interim Director William Lewis, University of Colorado Professor Brian Toon of the Laboratory for Atmospheric and Space Physics (LASP), and Peter Sheehan of the Milwaukee Public Museum in Wisconsin.
Their findings have been published online in the Journal of Geophysical Research-Biogeosciences, a publication of the American Geophysical Union.