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The American Association for the Advancement of Science: Meteorites 'led to life on earth'

LIFE on Earth began when giant meteorites from outer space crashed into a frozen planet, melting the oceans enough for the first life forms to emerge, scientists say.

A new view of the early history of the Earth suggests there was no carbon dioxide and so no greenhouse effect to warm the planet, resulting in the oceans being frozen to a depth of 300 metres.

Experts on the origin of life suggest that such an inhospitable environment, far from being a barrier to the formation of life, could have spawned the very organic ingredients necessary to generate the first organisms.

Jeffrey Bada, professor of marine chemistry at the Scripps Institution of Oceanography in San Diego, California, said there is no reason to believe that there was a greenhouse effect on the early Earth with carbon dioxide acting as a heat-trapping blanket that prevented the oceans from freezing. A carbon dioxide atmosphere would have been anathema to the prospect of primitive life forms evolving, he said.

'The dogma is that you have to have high carbon dioxide in the atmosphere to keep the Earth from freezing. What bothered me about this was that a carbon dioxide- rich atmosphere is the kiss of death for organic chemistry.'

A study he has just completed suggests that life on early Earth could still have thrived in a frozen world.