The period in question is called the Younger Dryas, an interval of abrupt cooling that lasted for about 1,000 years and occurred at the beginning of an inter-glacial warm period. Evidence for the temperature change is recorded in marine sediments and ice cores.

According to the scientists, the comet before fragmentation must have been about four kilometers across, and either exploded in the atmosphere or had fragments hit the Laurentide ice sheet in the northeastern North America.

Wildfires across the continent would have resulted from the fiery impact, killing off vegetation that was the food supply of many of larger mammals like the woolly mammoths, causing them to go extinct. Since the Clovis people of North America hunted the mammoths as a major source of their food, they too would have been affected by the impact. Their culture eventually died out.

The scientific team visited more than a dozen archaeological sites in North America, where they found high concentrations of iridium, an element that is rare on Earth, and is almost exclusively associated with extraterrestrial objects such as comets and meteorites.

They also found metallic microspherules in the comet fragments; these microspherules contained nano-diamonds. The comet also carried carbon molecules called fullerenes (buckyballs), with gases trapped inside that indicated an extraterrestrial origin.

The team concluded that the impact of the comet likely destabilized a large portion of the Laurentide ice sheet, causing a high volume of freshwater to flow into the north Atlantic and Arctic Oceans.

"This, in turn, would have caused a major disruption of the ocean's circulation, leading to a cooler atmosphere and the glaciation of the Younger Dryas period," said Kennett. "We found evidence of the impact as far west as the Santa Barbara Channel Islands."

NSF's Paleoclimate Program funded the research.

Atlantis, Lemuria, and Mu are names that float out there, and legends say that they had advanced warning of the impending disaster. If these civilizations had astronomical skills, then they would have seen the comet long before its arrival and would have sent out ships to higher ground to try to carry on the human race. Some went underground and were able to retain much of their ancient knowledge, and some stayed above ground, and eventually lost their heritage. Perhaps the hardships of the resulting global cooling and the extinction of so much of the food chain caused some of the survivors to revert to the 'basics of life' and science became superstition and religion.

Just thinking out loud,
Stephen Hudson

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