Evidence for an Extraterrestrial Impact 12,900 Years Ago

Richard Firestone, Allen West, James Kennett, and twenty-two co-authors' October 2007 Proceedings of the National Academy of Sciences paper — the principal peer-reviewed scientific publication of the Younger Dryas Impact Hypothesis. The paper reports geochemical and stratigraphic evidence (a layer of nanodiamonds, magnetic spherules, and platinum-group anomalies at the Younger Dryas boundary) consistent with a substantial extraterrestrial impact event at approximately 12,900 years before present. The hypothesis remains contested in mainstream science; this paper is the foundational scientific source.