Earth's Oxygen Timeline Changed Due to First Direct Measurements

Pockets of gas were trapped in halite, commonly called rock salt, for 813 million years old -- direct measurements of that gas are now challenging the commonly accepted timeline of oxygen in the Earth's atmosphere.

Earth's timeline was revised once again this week. A paper published on Monday in Geology by researchers at West Virginia University (WVU) provided the first evidence based on direct measurements as to the age of Earth's oxygenation.

Studies about atmospheric composition are widely important, affecting everything from evolutionary history to the possibility of life on other planets. The current oxygen level in Earth's atmosphere is 21 percent.

Indirect methods using hard to date sedimentary rocks had previously placed the oxygenation of Earth at approximately 550 million years ago. The team of researchers at WVU measured the amount of oxygen in air pockets that had been trapped by ancient halite to conclude that Earth's atmosphere was composed of 10.9 percent Oxygen 813 million years ago.

"Diversity of life emerges right around this time period," geologist at WVU Kathleen Benison said.

"We used to think that to have diversity of life we needed specific things, including a certain amount of oxygen. (The findings) show that not as much oxygen is required for organisms to develop."

Samples were gathered from Officer Basin in southwest Australia and testing was performed to ensure the gases had remained undisturbed. The research team performed 31 measurements on the gas pockets, referred to as inclusion gases.

Levels of oxygen in the atmosphere are one of the main components necessary for life. Throughout the history of Earth, surface conditions have been changing and life has been evolving accordingly.

Climate change is altering the composition of Earth's atmosphere. Benison stated that past environmental conditions inform about Earth's range of conditions as well as having implications for Mars.