The skeleton of a mammoth. Photos Lou GruberAn international team of geologists presented evidence that occurred about the same period of time the extinction of mammoths, the disappearance of Clovis culture and the start of a sharp cold snap was not associated with a comet. Until recently, the comet version was one of the most popular. The article appeared in the scientific journal Proceedings of the National Academy of Sciences, and its summary results ScienceNOW.
Approximately 14,000 years ago in the world after a long period of cold weather began Alleredskoe warming. During the warming climate in low latitudes was almost such as modern. Approximately 13,000 years ago — in the late driasovy period — warming suddenly changed sharp and rather long (1.3 thousand years) cooling. A geological event coincided with the disappearance of many in the megafauna — such as mammoths and mastodons.
At the same time in North America disappeared Clovis culture, known for a variety of artifacts. It is considered one of the first advanced cultures that emerged from the North American continent.
According to the hypothesis, formulated in 2007, all three of the above events took place after the explosion of the comet over the territory of modern Canada. This caused dramatic melting of the ice, a large amount of fresh water in the ocean currents disrupted, which in turn led to a sharp cooling and, as a consequence, the loss of Clovis and some species of megafauna.
In the new work, scientists analyzed the evidence of the comet hypothesis. One of the main pieces of evidence is the discovery in the same period of the deposits of small balls containing titanium and iridium. The last element, relatively rare on Earth, are abundantly present in the space objects like meteorites and comets.
Now researchers further analyzed the composition of the balls and found that many of the ratio of trace elements in them, as well as iridium, are characteristic of the Earth's crust. In addition, all the balls have been found in sediments characteristic of wetland. The same balls in the same sediments scientists found in Chile. According to the researchers, the explosion of a comet in Canada could not scatter the material so far south. In 2009, a similar study, researchers from the University of Wyoming found that, at the time of soil samples taken in other regions do not contain excess balls.
From this, scientists have concluded that these areas were formed, most likely the result of some natural processes. That is, the explosion of a comet 13,000 years ago over North America was not. New results have been criticized by the authors of the original study in 2007. They stated that the new work is not used for particle analysis of their formation — this surface balls are usually studied by electron microscopy.