Were the dinosaurs fried by ultraviolet light?
BY NEIL ENGLISH
Posted: May 3, 2000
Many scenarios have been suggested, including a kind of nuclear winter in which enormous quantities of dust were ejected into the stratosphere, circling the globe and blotting out sunlight for weeks or months. But not everyone agrees that such a successful biological lineage as the dinosaurs could have been obliterated in this way.
Now, two American scientists - Charles Cockell of NASA's Ames Research Centre In California, and Andrew Blaustein of Oregon State University, have worked out the events that occasioned themselves immediately after the KT impact.
In a recent paper communicated in Ecology Letters, they explain that the levels of nitrogen and sulphur oxides produced during the impact event would have all but destroyed the ozone layer, thereby doubling the levels of lethal UV radiation incident on the earth's surface. This deluge of ionising radiation would have put additional stresses on the biosphere already stretched to the extreme by the impact.
What is even more remarkable though, is that significant sulphate deposits are only found over 1 percent of the earth's surface, rendering the KT extinction event particularly lethal for the dinosaurs, but not for our kind - the small, furry, milk-suckling mammals.
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