New evidence supports the idea that a huge space rock collided with our planet about
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13,000 years ago and broke up in Earth’s atmosphere. This impact would have been powerful enough to melt the ground, and could have killed off many large mammals and humans. According to researchers it may even have set off a period of unusual cold called the Younger Dryas that began at that time. The idea that Earth experienced an asteroid or comet impact at the start of the Younger Dryas has been controversial, in part because there is no smoking-gun impact crater left behind as with other known events in our planet’s past. But researchers say it’s common for space rocks to disintegrate in the heat of a planet’s atmosphere before they can reach the ground. The scientists first reported their suspicions about the event in 2007. Now, they say, a new site in Central Mexico’s Lake Cuitzeo displays telltale signs of an impact, including melted rock formations called spherules and microscopic diamonds that could only have formed under extreme temperatures. In addition to the Mexican site, the scientists have found signs of an impact in Canada, the United States, Russia, Syria and various sites in Europe. And all of these bits of evidence were found buried in a thin layer of rock that dates to precisely 12,900 years ago. If a comet, which would have been traveling at about 30 miles per second, impacted Earth’s atmosphere, it would have created a flash of extreme heat reaching about 3,000 to 4,000 degrees Fahrenheit (1,600 to 2,200 degrees Celsius). In addition to melting the ground, such temperatures would have proven cataclysmic to many kinds of life. At the same time that the impact may have taken place, 12,900 years ago, Earth was beginning a mini ice age. It is known that many large animals, such as the mammoth and the saber-toothed cat, did not survive this age. There’s even evidence of a population decline in humans living in North America at the time, called the Clovis culture. The researchers aren’t claiming that the comet impact caused the climate changes at the time, but scientist Ted Bunch of Northern Arizona University said such an event would have had a significant effect on Earth’s climate.