An illustration of the asteroid impact over Tunguska, Siberia, on June 30, 1908 — the date on which Asteroid Day is marked. | Detlev van Ravenswaay/Picture Press/Getty Images

The Search for the Next Large Asteroid That Might Slam Into Earth

On June 30 — International Asteroid Day — skywatchers are raising awareness about "humanity's greatest challenge": the lack of defense measures against a large collision with Earth.

Published On 06/28/2017
11:27 AM EDT