The Dinosaurs Were Even Unluckier Than We Thought: Their Killer Asteroid Was an Extreme Rarity

Nickel isotopes preserved in the global clay layer left by the Chicxulub impact point to a rare CO carbonaceous chondrite as the object that struck Earth 66 million years ago. The finding narrows the asteroid’s identity and suggests atmospheric dust, rather than sulfur carried by the asteroid itself, played the larger role in the mass extinction.