The Impact Signal: Platinum at the Younger Dryas Boundary

When researchers sought to confirm a cosmic impact at the Cretaceous-Paleogene boundary 66 million years ago, the smoking gun was iridium - a metal rare in Earth's crust but abundant in extraterrestrial material. The anomalous iridium spike in that boundary layer became the foundation of the asteroid impact hypothesis that ended the age of the dinosaurs. The Younger Dryas impact hypothesis now has its own equivalent. On the encouragement of a scientist at Columbia's Lamont-Doherty Earth Observatory, a Harvard researcher named Misha Patel tested the Greenland ice core at the depth corresponding to the Younger Dryas boundary. What came back was a clear platinum anomaly - a spike in platinum concentration sitting precisely at the layer marking the climate crash of 12,800 years ago. Malcolm LeCompte describes this as the most substantial evidence the Comet Research Group currently holds for an impact event at the Younger Dryas boundary. The same platinum signal has since been found at the Bowser Road mastodon site in New York and at multiple other Younger Dryas sites across the northern hemisphere. Platinum, like iridium, is rare in Earth's surface geology but common in asteroidal and cometary material. Its presence, concentrated in a single dateable layer at sites spread across continents, is difficult to explain through any process other than a large-scale cosmic event. LeCompte is careful not to overstate what the evidence proves - but on the question of whether something extraordinary happened at the Younger Dryas boundary, the platinum says yes.