Bacteria could have plunged the planet into a deep freeze and caused oxygen to dominate the atmosphere, say researchers in America.

The report, from graduate students at the California Institute of Technology, claims that 2.3 billion years ago, blue-green algae gained the ability to break down water which released a flood of oxygen into the atmosphere.

They say the oxygen reacted with the atmospheric methane which insulated Earth at the time, and broke it down, the reaction creating carbon dioxide.

In a process lasting several million years, temperatures plunged to minus 50 degrees Celsius and ice at the equator grew to one mile thick.

Life-forms only recovered after micro-organisms evolved the ability to consume oxygen and turn it into carbon dioxide.

Professor Kirschvink oversaw the project. He said: β€œIt was a close call to a planetary destruction. If Earth had been a bit further from the sun, the temperature at the poles could have dropped enough to freeze the carbon dioxide into dry ice, robbing us of this greenhouse escape from Snowball Earth.”

And he said another Snowball could happen if man messes up the environment badly enough.