If a massive asteroid collides with earth, it could end life on our planet as we know it; new discoveries and cutting-edge tech reveal just how close we are to apocalypse and what it would take for the world's leading space agencies to stop it.

The discovery of extraterrestrial life might face an impossible challenge: the physics of the universe itself; but using cutting-edge tech, experts might be on the verge of a groundbreaking find -- and the evidence could already be in hand.