Researchers have made the discovery that oxygen in the atmosphere reached much higher levels, much sooner by studying the composition of rock salt in ancient rocks dating back 815 million years, over 100 million years before the earliest evidence of life on earth.
The salt was crushed in a vacuum, and each piece would release between five and 12 puffs of gas. By crushing the rock salt carefully, they were able to analyze the chemical makeup of the air pockets in the salt. The oxygen that was released could then be measured, and it was discovered to have an oxygen composition of 10.9% – over five times the amount that was predicted.
Through this technique, they were able to show that oxygen made up 10.9% of the earth’s atmosphere 815 million years ago.
This finding is revolutionary in the field, as previous estimates suggested that oxygen levels only reached 10% between 600-700 million years ago. With the earliest fossil evidence of life coming around 650 million years ago, it alters our collective understanding of how life evolved. The new evidence suggests that life could only evolve when the oxygen level reached 10%. Scientists had previously believed that a 10% oxygen level served to accelerate the evolutionary process rather than mark the start of life on earth.
All previous research in the field had been done by examining examples of chemical reactions that could only take place with oxygen present. This technique led to a series of differing results and made it tough to pinpoint the exact oxygen levels and was only able to show the significant rise in oxygen levels between 600-700 million years ago. The new technique goes right to the source by examining air that has been trapped for nearly a billion years!
The co-author of the paper published in this month’s Geology journal, Nigel Blamey, admitted that the results were both surprising and extraordinary. ‘We came out of left field’ Blamey said, ‘I think some people are going to embrace it, and other people are going to be very skeptical. But the data is what the data is.’
Those who are skeptical of the results argue that the rock salt they tested is likely to have been contaminated after hundreds of millions of years on a planet with high oxygen levels. Timothy Lyons, a senior geologist at the University of California, said that ‘There is nothing about the shifts you see in life or climate that demands an oxygen jump that high. That could be a worry.’
Despite the skepticism and questioning, the research reopens a significant debate about the beginning of life on earth and the potential of life on other planets in the universe. The evidence presented in the study doesn’t answer every question.
If the findings are correct there is at least a 150 million year gap between the 10% oxygen level that scientist believe is required to accelerate evolution and the first living organisms on earth. Additionally, scientists will then need to reevaluate what triggered bacteria and other single celled organisms to evolve into the complexity of life that we can now marvel at today.
The study and the findings only illustrate further the beautiful and complicated history of life on this unique planet. We may not have all of the answers but there is still so much to discover.