THE world’s largest mass extinction at the end of the Permian period 251 million years ago was probably not caused by a massive asteroid impact, despite recent claims that it was.
The case for an impact seemed to be strengthened earlier this year when researchers claimed to have found evidence of meteorite impacts dating back to the end of the Permian near an undersea mound off the coast of Australia. Earlier, other researchers had found rock layers from that era laced with iridium, a telltale sign of asteroids.
But when Christian Koeberl of the University of Vienna in Austria and…
