Scientists have taken a huge step in answering one of the fundamental questions about life on earth – what came first: oxygen or life?
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.