The discovery of 'nanodiamonds' - a thin layer of miniature gemstones - in North American soil apparently authenticates the theory that nearly 13,000 years back, a comet struck the continent, and set off an ice age, which resulted in the extinction of some mammal species and the annihilation of the earliest human colonies of the continent.

According to Douglas J. Kennett, a University of Oregon archaeologist and the leading proponent of the comet theory, the extremely small nanodiamonds can only be formed under extreme temperatures and pressure of a massive explosion, similar to a meteor or comet impact. Kennett said: "There's no other way we can interpret the presence of these diamonds other than an extraterrestrial impact."

While reporting his research team's discovery of the nanodiamonds in the journal Science, Kennett accepted that due to the limiting format of the rapid publication, the amount of data the team could include has been restricted.

Nonetheless, Kennett said that three separate laboratories have now confirmed the existence of nanodiamonds, and added: "There are going to be a lot of follow-up papers that will clearly demonstrate that these are diamonds."

Though the critics agree that the impact of a comet would be the most possible cause of nanodiamonds, they argue that it is not evidence enough in support of the resultant catastrophe. Some of them are even not convinced that the nanodiamonds have actually been found.

Peter Buseck, spectroscopist at Arizona State University, said that such a potentially significant discovery needs to be "well-supported."