Comet may have exploded over planet, causing fires, die-offs, researchers say A meteorite colliding with the Earth 65 million years ago is considered to be the most likely reason dinosaurs vanished from the planet. Now a team of scientists says it has found new evidence that an object from space caused a similar extinction event only 13,000 years ago. In an article to be published Friday in the journal Science, researchers present what one author calls the "smoking bullet"—proof that an exploding comet triggered the sudden, thousand-year freeze that killed off mammoths, saber-toothed tigers and other large mammals that used...