If only. The now well-documented Younger Dryas event - whatever it was - was thousands of years later, and has plenty of iridium- and platinum-based proxies (an

If only. The now well-documented Younger Dryas event - whatever it was - was thousands of years later, and has plenty of iridium- and platinum-based proxies (and a whole lot more) worldwide ... with equally sophisticated dating techiques. Space has -many- nasties it has thrown at the Earth. When I was kid and saw the Moon through a telescope, I wondered how the Earth could have escaped that shellacking. It couldn't. (There -was- no 'Earth Impact Database' at the time.)