Analyses of the gases dissolved in water trapped in ancient minerals suggest that methane-generating microbes have been around almost 3.5 billion years, more than 700 million years longer than previous geologic evidence had indicated. Because methane prevents the loss of heat from Earth, the gas generated by those microbes could explain how the planet kept warm during the Archaean era even though the sun then produced less than three-fourths the radiation that it does today.
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