Doubts on Dinosaurs

Abstract

This article focuses on research into the Chicxulub crater, which is widely believed to be the impact crater of the asteroid that wiped out the dinosaurs. According to conventional paleontological wisdom, an asteroid or comet 10 to 14 kilometers wide crashed into the present-day Yucatan Peninsula 65 million years ago and wiped out the dinosaurs. Most scientists currently consider the Chicxulub impact crater, perhaps about 145 kilometers wide, to be the smoking gun of this Cretaceous-Tertiary (KT) extinction. Not so fast, says Princeton University micropaleontologist Gerta Keller. The collision that created the Chicxulub crater, she argues, happened before the KT extinction--300,000 years too soon, to be more precise. She has several lines of evidence: one in particular relates to the layer of iridium, an extremely rare element known to be abundant in many meteorites, that exists at the KT boundary at sites around the world. Keller discovered that the original Chicxulub microtektite layers lie up to 14 meters below the KT iridium layer at the northeastern Mexico site.