At www.physorg.com/print193556580.html … Australian scientists have found a crater at the bottom of the Timor Sea and this has been dated (how?) contemporary with a heavy bombardment event some 35 million years ago. Archaeologist Andrew Glikson said the identification of microstructural and chemical features in drill fragment revealed further evidence of impact saying it was a 50km wide scar. A meteorite, or small asteroid, some 100km wide, is thought to have hit Siberia at the same time, and another one struck what is now Chesapeake Bay in N America. Glikson describes it as an impact cluster across the planet ( see also Australian Journal of Earth Sciences) and proposes a link also with a sharp fall in global temperatures about 1 million years before the Drake Passage, the ocean gap between Antarctica and S America was split open – which isolated the Antarctic continent and allowed an ice sheet to develop. Glikson is of course married to the AGW hypothesis and this is why he is able to join up the dots – but some caution is worth taking before swallowing the ideas he has presented. First of all is the dating of the three events – how do we know they took place at the same time? While an impact might generate accelerated plate movement leading to the separation of Antarctic from S America, why is it supposed to have happened at that particular moment in time? Is he saying the ice sheet on Antarctica only developed as a result of the separation of the continent from S America – and it is entirely due to ocean circulation? Surely there are alternative ideas to all three questions that are equally worth taking on board. If he had said the ice sheet had developed because so much dust and debris from the impacts had become trapped in the atmosphere I might have been persuaded – but he didn’t. Therefore the dating does not match – or something like that.