Asteroids are rocks that revolve around the sun and that occasionally collide with the Earth.

The incoming asteroid is large enough to cause a global catastrophe that likely will hit Earth in 100 years, scientists estimate. It’s likely what killed the dinosaurs, and if an asteroid even one-tenth the size of the one that caused their extinction hit Earth today, the results would be devastating. Scientists estimate it could release enough particles to block the sun for months and cause a famine killing hundreds of millions.