Professors Discover Means to Test ‘Big Freeze’ Theory

September 10, 2013
Comet-Impact

Researchers have argued for the last six years about whether a comet impact 13,000 years ago triggered the so-called “Big Freeze” that killed the North American mammoths and other large mammals changing life forever on Earth. This idea, referred to as the Younger Dryas impact hypothesis, is still very controversial. Now MNU assistant professor Drew Overholt, PhD, and University of Kansas professor Adrian Mellott, PhD, have found a definitive way to test this hypothesis.

Overholt completed his doctorate at KU last spring and part of his dissertation examined rare isotopes that are hard to create on Earth. These Cosmogenic nuclides are produced more abundantly deep in space from cosmic rays. For this reason, comets and other extraterrestrial objects tend to contain these nuclides. Therefore, Overholt theorized, ice core samples can be tested for these nuclides, providing evidence of past impacts.

“Scientists have never had a before-the-fact test for the Younger Dryas impact hypothesis,” Overholt says. “We have found such a test and it will work for other large impacts as well. It is especially good for long-period comet impacts--the comets that only come around every million or more years.”

The ramifications of such tests are of great interest to scientists. While they cannot predict future events, the test could tell researchers how often these impacts have occurred, which could help scientists determine what threat these events pose. Overholt’s paper was published in “Earth and Planetary Science Letters” in September. His work continues through the KU Astrobiophysics Working Group which includes scientists from Kansas and West Virginia. Overholt says the debate over Younger Dryas is a popular topic now with National Geographic and other news sites covering the varied theories.

In an article on the University of Kansas website, Brendan Lynch quotes Overholt saying the test could find “the smoking gun researchers have been seeking for the Younger Dryas impact hypothesis.”

Overholt’s research website contains additional information on Cosmogenic nuclides at: http://kusmos.phsx.ku.edu/~melott/Overholt.htm.