Two new studies have added new evidence to the theory that a major airburst from a meteor or comet occurred over North America, ushering in a 1,400-year cooling period called the Younger Dryas that occurred between the Pleistocene and the Holocene eras. The Younger Dryas saw the extinction of most of the large land mammals across North America, and also the end of the Clovis People, a Paleo-Indian culture. A charred layer of soil, found at roughly 50 Clovis sites across the continent, suggest a massive wildfire that raged continent-wide, possibly caused by such a massive meteor strike.

The first study, published in early March in the Scientific Reports publication of Nature, found an increased amount of platinum in soil layers corresponding to the Younger Dryas period at 11 different archeological sites across the US.

"Platinum is very rare in the Earth’s crust, but it is common in asteroids and comets," explains lead study author, Christopher Moore. Chemical markers such as this are used by researchers to differentiate between materials that formed on Earth and ones from extraterrestrial sources.

"The presence of elevated platinum in archaeological sites is a confirmation of data previously reported for the Younger-Dryas onset several years ago in a Greenland ice-core. The authors for that study concluded that the most likely source of such platinum enrichment was from the impact of an extraterrestrial object."

The second study involved an analysis of the Carolina bays, elliptical depressions found along the Atlantic coast. The study found that the peculiar depressions, numbering approximately 500,000, form "oblique conical craters formed on ground liquefied by the seismic shock waves of secondary impacts of glacier ice boulders ejected by an extraterrestrial impact on the Laurentide Ice Sheet".

The analysis found that regardless of the size of the individual depression, each of them is a nearly uniform ellipse, with an average width-to-length ratio of 0.58, a ratio that would indicate that if these are formed from impacts, would meant that the projectiles struck at a 35º angle. The orientation of the bays, along with the orientation of the similarly-formed Nebraska Rainwater Basins, all align to a common point above the Great Lakes.

An impact either on or above the Laurentide Ice Sheet in that area would have vaporized a massive portion of the glacier that existed there at that time, launching water high into the atmosphere where it would form clouds of ice crystals that would block out the sun. This would result in the cooling period known to have happened during the Younger Dryas, and would lead to the extinction of many species, a dramatic rise in ocean levels, and numerous legends of that ancient catastrophe that survive to this day.