Replies

Thanks LucyT for the ping, and george76 for the topic. Of course, the volcanism "explanation" will always be found wanting because it doesn't leave the proxy data found at the paleontological boundaries, but that's the gradualist ninnies for ya.

Asteroid 'destroyed life 250m years ago'
by Dr David Whitehouse
Friday, February 23, 2001
Earth's biggest mass extinction 251 million years ago was triggered by a collision with a comet or asteroid, US scientists say. They have reached this conclusion by looking at atoms from a star trapped inside molecular cages of carbon...

In rock layers laid down at the time, there is a much higher concentration of complex carbon molecules called fullerenes that have different types, or isotopes, of helium and argon trapped inside them. These molecules could only have been delivered from space, the researchers say...

The researchers believe these particular fullerenes are extraterrestrial because the gases trapped inside have an unusual ratio of isotopes that indicate they were made in the atmosphere of a star that exploded before our Sun was born...

The telltale fullerenes were extracted from sites in Japan, China and Hungary, where the sedimentary layer at the boundary between the Permian and Triassic periods had been exposed...

The research was made difficult because there are few 251-million-year-old rocks left on Earth. Most rocks of that age have been recycled through the planet's tectonic processes...

Researchers estimate the comet or asteroid was six to 12 km (3.7 - 7.4 miles) across, or about the size of the asteroid believed responsible for the extinction of the dinosaurs 67 million years ago...

The mass extinction of 251 million years ago was the greatest on record.



· join · view topics · view or post blog · bookmark · post new topic ·