New research on abrupt cooling of the Earth that took place about 12,900 years ago might also explain the sudden disappearance of the Clovis People, some of America's first human inhabitants. The Washington Post reports:
In just the last few years, there has arisen a controversial scientific hypothesis to explain this chain of events, and it involves an extraterrestrial calamity: a comet, broken into fragments, turning the sky ablaze, sending a shock wave across the landscape and scorching forests, creatures, people and anything exposed to the heavenly fire.
Now the proponents of this apocalyptic scenario say they have found a new line of evidence: nanodiamonds. They say they have found these tiny structures across North America in sediments from 12,900 years ago, and they argue that the diamonds had to have been formed by a high-temperature, high-pressure event, such as a cometary impact.
The comet theory was proposed in a 2007 article of New Scientist. At the time, the magazine predicted that the "findings will almost certainly stir intense controversy and debate."
The New York Times elaborates on the new evidence:
At each site the scientists looked at, the diamond layer in the rocks correlates to the date of the hypothesized impact. Within the layer, the scientists report finding a multitude of diamond particles, all encased within carbon spheres. "We've yet to find a single diamond above it," Dr. West said. "We've yet to find a single diamond below it."
Perhaps more telling, the scientists reported last month at a meeting of the American Geophysical Union in San Francisco, the carbon atoms inside some of the diamonds are lined up in a hexagonal crystal pattern instead of the usual cubic structure. The hexagonal diamonds, formed by extraordinary heat and pressure, have been found only at impact craters and within meteorites and cannot be formed in forest fires or volcanic eruptions, Dr. West said.