Reuters/NASA
Some scientists think the giant asteroid that went on to strike the Earth - and lead to the extinction of the dinosaurs - first broke up in the main asteroid belt between Mars and Jupiter.
An impact by one could mean anything from broken windows to global extinction, which is why scientists are working hard to find and, if necessary, deflect or destroy these rogue space rocks.
Though a big strike has a low likelihood of happening, the consequences would be enormous, according to Nahum Melamed, a project manager with the Aerospace Corporation.
Melamed recently spoke at an event for the American Institute of Aeronautics and Astronautics in Manhattan Beach, California, about what scientists refer to as planetary defense, and Tech Insider was in the audience.
Here's what asteroids have done in the past, and what scientists at NASA and other institutions are doing to mitigate their threat in the future.