Meteorite to blame for the death of mammoths?

Celestial explosion as the cause of the extinction of the Gross uger 12, 000 years ago

A scanning electron micrograph of a carbon particle with extraterrestrial inclusions. © Jim Wittke
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What made the glacial mammoths die out and brought the Stone Age people of North America to the brink of extinction 13, 000 years ago? This question has been hotly debated for years. An unusual answer is now provided by American researchers in the journal Proceedings of the National Academy of Sciences: they blame the explosion of a meteorite in the earth's atmosphere.

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Mammoths and many glacial mammals are extinct today. The most probable cause is an excessive hunt by the early humans or a plague that killed these animals. An international research team, including geologists from Northern Arizona University, has now revealed evidence that 12, 900 years ago a comet or other low-density object set course for Earth and exploded in the upper atmosphere. According to the researchers, this explosion must have created a "path of destruction" through the habitats of large mammals and humans of the time.

Fire, shock and climate change

"The detonation either grilled them or the shockwave killed them, " explains Ted Bunch, professor of geology and former NASA expert on crater research. "There followed a kind of mini-nuclear winter." So far, however, no one had found a crater that could prove such an impact at this time. However, the research team assumes that the comet, which was probably four to six kilometers in diameter, exploded about 50 to 100 kilometers above the surface of the earth and therefore left no crater behind. But what followed was a strong shockwave, firestorms and a cooling of the climate in North America and Europe.

"The comet could have broken into smaller pieces as it approached Earth, exploding at various points over the two continents, " explains Bunch. The scientists see evidence of such multiple explosions in a ten centimeter thick "black mat" of carbonaceous material that extends north to Canada, Greenland and Europe and extends south to the islands off the coast of California and Carolina. display

Extraterrestrial carbon compounds

In the material of this mat, the researchers found carbon compounds, which are typical for a high heat development. In addition, there are also molecules in it which must be of extraterrestrial origin, such as fullerenes, round, 60-atom carbon compounds, which typically arise in shock events outside the Earth's atmosphere. The fullerenes contain concentrations of the helium-3 isotope that are higher than typical for the terrestrial atmosphere. Also nanodiamonds discovered the scientists in the black layer. Since these are formed only under extremely high pressure, for example in the interstellar space outside of the solar system, this is in their view a further indication for an extraterrestrial impact.

"Either these things have been registered with the impactor, or they have arisen during the explosion, " explains Bunch. The violence of the explosion must have been tremendous. "A hydrogen bomb is equivalent to about 100 to 1, 000 megatons of TNT, " said the researcher. The detonations we are talking about, however, had about ten million megatons. That is more than the total explosive power of all nuclear bombs worldwide today and in the past

Heavenly explosions more frequent than expected?

According to the researchers, these detonations have destabilized a huge ice sheet, known as the Laurentide Ice Sheet, which at that time covered much of Canada and North America. The explosion heat and firestorms had melted much of the ice and released steam into the atmosphere. In any case, the scientists found that below the deposits from that time the black mat fossils of mammoths and other large mammals, as well as the early fighters of the so - called Clovis Culture were common.

In and around this, however, every trace of such relics is missing. Cause could be the environmental boom and the destruction of the explosion. The geologists consider such events, in which celestial bodies burst in the atmosphere, to be generally more frequent than previously assumed. Probably as many as two to three of them have occurred in the last 100, 000 years alone weitere and more could follow.

(Northern Arizona University, 25.09.2007 - NPO)