Later today, an asteroid designated 2012 DA14 will pass just 17,200 miles over Earth’s surface. Although this 150-foot space rock will slip harmlessly by, researchers estimate there are nearly 500,000 near-Earth asteroids. So far, they’ve tracked the orbit of 9,600.
How do researchers track asteroids, anyway? And how often have asteroids collided with Earth? (Hint: far more than the number of impact craters on our planet would suggest.)
The video below explains more about the odds and potential hazards of asteroid impacts, and about the process of tracking the orbits of near-Earth asteroids.