Huge asteroids have hit the Earth before and it's probably a statistical certainty they will again. Look what happened to poor Jupiter. Last I read the Gulf of Mexico is the result of an enormous asteroid impact that wiped out almost all life on the planet. The asteroid is out there right now heading for us at incredible velocity. We know it's going to get here, we just don't know when. The only important question is "WILL WE BE READY?".