Chuck Bednar for redOrbit.com – Your Universe Online
Researchers from the University of California, Davis have found new evidence discrediting a controversial theory that a cosmic impact caused a thousand-year period of cold that coincided with the extinction of mammoths and other massive creatures.
Peter Thy, a project scientist in the UC Davis Department of Earth and Planetary Sciences, and his colleagues studied rock soil droplets from northern Syria and found that they were probably formed by Stone Age house fires and not from a nearly 13,000 year old cosmic impact.
Some scientists believe that the Younger Dryas cold period, which took place 10,800 BC and 9,500 BC, was caused when a comet or meteorite struck North America. However, in research published online in the Journal of Archaeological Science, Thy and his fellow researchers found evidence that contradicted an impact-related theory for this prolonged period of cold climate.
The researchers analyzed siliceous scoria droplets, porous granules typically associated with melting, from four different locations in northern Syria that date back at least 10,000 years ago. They then compared those findings to similar scoria droplets previously believed to have resulted from the aforementioned cosmic impact at the very beginning of the Younger Dryas.
They found that the composition of the droplets was related to the local soil, and not to soil from other continents, as would have been expected from an intercontinental impact. Furthermore, the texture of the droplets, thermodynamic modeling and other analyses revealed that the scoria was formed by short-lived heating events of modest temperatures.
If those droplets had been caused by a large impact event, they would have been formed in temperatures that were intensely high. Finally, the samples collected from various archaeological sites spanned a period of 3,000 years. Had a comet or asteroid impact been responsible, the scoria droplets would have been connected by a single date, according to Thy.
“There is no evidence to suggest that siliceous scoria droplets result from very high temperature melting of soil and are the result of a cosmic event,” the study authors wrote. In a statement, Thy added that the impact catalyst theory “is out… there’s no way that can be done.”
House fires were the actual source of the scoria droplets, the researchers said. The region of Syria where the soil originated was associated with early agricultural settlements along the coast of the Euphrates River. Most of the sites included mud-brick structures, and some of those show signs of intense fire and melting, indicating that they formed when fires burned buildings made out of local soil and straw.
While the research indicates that a cosmic impact what not responsible for killing off the mammoths, it does not explain what the catalyst for that event and the prolonged period of frigid conditions that followed might actually be, said Science World Report. That will require additional research, the website added.