Earth's biggest mass dinosaurs 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.
The impact occurred when all the Earth's land was joined together into a supercontinent called Pangea. Researchers have no idea where on the planet's surface the space object came down, but they have identified traces of it.
The impact of a body of this size releases an amount of energy that is about one million times the largest earthquake recorded during the last century.
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.
Source from Great Site:http://news.bbc.co.uk/2/hi/science/nature/1184556.stm
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