New results from rock tracing procedures conducted by researchers at the University College London found that it took 100 million years for oxygen levels in the ocean's and atmosphere of the Earth to reach a level that allowed animal life to expand approximately 600 million years ago.
Prior to the findings, scientists were unsure of how fast the Earth's oceans and atmosphere became oxygenated and whether the explosion of animal life occurred before or after this rise.
"We want to find out how the evolution of life links to the evolution of our climate," Philip Pogge von Strandmann, lead researcher of the study, said in a press release. "The question on how strongly life has actively modified Earth's climate, and why the Earth has been habitable for so long is extremely important for understanding both the climate system, and why life is on Earth in the first place."
The researchers examined rocks across the U.S., Canada and China that were laid down under the sea and pieced together a picture of how oxygen levels of the Earth's oceans and atmosphere rose. They measured selenium isotopes in the rocks to determine that it took approximately 100 million years for the oxygen in the atmosphere to increase from less than one percent to over 10 percent of the current levels seen today.
"We took a new approach by using selenium isotope tracers to analyze marine shales which gave us more information about the gradual changes in oxygen levels than is possible using the more conventional techniques used previously," von Strandmann said. "We were surprised to see how long it took Earth to produce oxygen and our findings dispel theories that it was a quick process caused by a change in animal behavior."
The insights into Earth's early oxygen increase are just the first steps towards a better understanding of why the process took so long and a better grasp on the possibility of animal-like life existing on other Earth-like planets in the solar system.
The findings were published in the Dec. 18 issue of Nature Communications.
