User blog comment:JMAC308/Mark of athena/@comment-4551739-20111104035919/@comment-4531192-20111106190454

Yes but at the time life on earth was primitive. The species had no ways of preparing let alone knowing that such event would take place. So their mass destruction was obvious. Now back to asteroids :D. I quote "Near-Earth Asteroids orbit the sun in the vicinity of the rocky terrestrial planets and pose the greatest threat to Earth. [Astrologists] assume that the total mass of all the asteroids combined is less than that of the Moon." So they aren't that big are they. Of course big asteroids (like Ceres) have had particles of themselves hit or gone close the earth surface. Those events however are extremely rare and do not take place "often".