Interesting.
Events such as the Tunguska Event in Siberia in the early 1900s apparently occur once every 100 years as a statistical average, I think I read that in "Universe by Freedman and Kauffman" but I'm not sure.
Quite astonishing the Tunguska event, it released an amount of energy equivalent to several Hiroshima bombs - it really does outline the significance of the velocity squared term in the classical mechanics kinetic energy equation; the future of weapons of mass destruction lies not in nuclear weapons, but in extremely high velocity weapons which need not have a huge mass.
Also, just to mention, events the size of the Chicxulub event of roughly 65 million years ago happen, on average, every 100 million years - so, statistically, we are alright for the next 35 million; but, in all likelihood, humanity will be long gone by that point anyway.