A sample of ancient oxygen, teased out of a 1.4 billion-year-old evaporative lake deposit in Ontario, provides fresh evidence of what the Earth鈥檚 atmosphere and biosphere were like during the...
An analysis of sulfide ore deposits from one of the world鈥檚 richest base-metal mines confirms that oxygen levels were extremely low on Earth 2.7 billion years ago, but also shows that microbes were...
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