[X] My Assistant

[Guest_BruceMoomaw_*]

...in Antarctica. This was the biggest mass extinction event in the history of multicellular life -- it wiped out something like 95% of all existing marine species as opposed to only about 50% for the impact that ended the dinosaurs -- and it has been one of the biggest remaining geological mystery stories. An even bigger giant impact has always been a serious suspect -- but because no crater could be found, other suspects have also been high on the list, ranging from the titanic flood volcanic outburst of the "Siberian Traps" region to a huge buildup of CO2 in the deep sea that was then suddenly released due to geological events (a planet-wide version of the Lake Nyos CO2 eruption that smothered hundreds of people in a matter of seconds in Cameroon). Indeed, there has been a recent comprehensive book on the mystery which ended by concluding that the mystery is still utterly unsolved.

Well, we seem finally to have found a crater that is both gigantic enough, and of just the right age, to be the culprit -- in the only place on Earth it could have hidden for so long: beneath the Antarctic ice layer.

http://www.space.com/scienceastronomy/060601_big_crater.html

It isn't quite settled yet, but this looks like an impact crater fully 500 km wide -- more than twice as wide as Chiczulub -- and thus quite big enough to have done the job, if it really IS an impact crater.