Dinos bite the dust.

Approximately 65 million years ago, dinosaurs and most other species suddenly became extinct. Some scientists have theorized that a single, large asteroid may have hit the Yucatan Peninsula in present-day Mexico, sparking the die-off. Another theory blames multiple asteroid impacts for the mass extinction. Which is correct? New evidence suggests it was indeed one hit that did in the dinos.

Ken MacLeod, a geologist at the University of Missouri, was part of a drilling expedition in the Atlantic Ocean that collected the evidence. Roughly 4,500 kilometers (2,800 miles) from the Yucatan Peninsula, the team collected sediment samples from deep beneath the seafloor. If evidence of many asteroid impacts existed, it would be scattered throughout multiple sediment layers. Instead scientists found only one layer loaded with elements common in space rocks. The conclusion: a single impact.

How could one asteroid cause such widespread destruction? Upon slamming into Earth, the massive space rock could have sent dirt flying into the atmosphere. This would have blocked sunlight and killed off the food source of many dinosaurs--plants. "It sometimes seems harder to explain how anything survived [the impact] rather than how so much died," says MacLeod.

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