Rock record shows signs of oxidation 200 million years earlier than previously thought
The first oxygen-producing life-forms appeared hundreds of millions of years earlier than previously known, new evidence suggests.
Analyzing iron and uranium embedded inside primeval rocks, researchers discovered that shallow seawater contained whiffs of dissolved oxygen around 3.2 billion years ago. The new date places the appearance of Earth’s oxygen around 200 million years earlier than previous studies, the researchers report online August 24 in Earth and Planetary Science Letters.
This early oxygen pins the evolution of oxygen-producing photosynthesis to nearly a billion years before cyanobacteria flooded Earth with oxygen during the Great Oxygenation Event, says Penn State geoscientist James Kasting, who was not involved with the study. “This is further evidence that cyanobacteria came early,” he says, noting that the finding raises more questions.