Earth’s Atmosphere Got Its Oxygen in Periodic Bursts Over a 100 Million Year Period

Posted November 20th, 2015 at 5:11 pm (UTC-4)
3 comments

A view of Earth's atmosphere at sunset as seen by the International Space Station Expedition 23 crew in 2010. Colors here roughly denote the various layers of the atmosphere. (NASA)

A view of Earth’s atmosphere at sunset as seen by the International Space Station Expedition 23 crew in 2010. Colors here roughly denote the various layers of the atmosphere. (NASA)

For about the first 2.1 billion years of Earth’s history, its atmosphere didn’t have enough oxygen to support complex life.

Scientists believe that Earth’s first atmosphere,formed after its creation, was probably made up of hydrogen and helium. Then as a result of volcanic eruptions that spewed gases from Earth’s interior, in a process known as “outgassing”, a secondary atmosphere became filled with those such as carbon dioxide, sulfur dioxide, ammonia and water vapor.

Then about 2.3 to 2.5 billion years ago, during the Proterozoic Eon, blue/green algae called cyanobacteria, living in Earth’s shallow oceans, began emitting enough oxygen through photosynthesis to create the permanently oxygenated atmosphere that keeps us alive today.

Researchers from five North American universities have collaborated on a study that found the process in fully oxidizing the atmosphere didn’t happen suddenly, but instead took place in scattered bursts over an approximately 100-million-year period in what has become known as the Great Oxidation Event.

It may look like mere pond scum to you but this is cyanbacteria or blue/green algae which provided, through photosynthesis, enough oxygen to create the permanently oxygenated atmosphere that keeps us alive today. (Lamiot/Creative Commons)

It may look like mere pond scum to you but this is cyanbacteria or blue/green algae which helped provide, through photosynthesis, enough oxygen to create the permanently oxygenated atmosphere that keeps us alive today. (Lamiot/Creative Commons)

“The onset of Earth’s surface oxygenation was likely a complex process characterized by multiple whiffs of oxygen until a tipping point was crossed,” said one of the study’s authors, Brian Kendall from Canada’s University of Waterloo in a university press release. “Until now, we haven’t been able to tell whether oxygen concentrations 2.5 billion years ago were stable or not. These new data provide a much more conclusive answer to that question,” he said.

Prior to these large bursts of oxygen from the cyanobacteria, scientists say most of the oxygen that had been produced by early microbial life was simply chemically captured by materials such as dissolved iron or organic matter before having the chance to escape into the atmosphere.

But O2 began to collect in the atmosphere after these oxygen sinks filled up and couldn’t absorb any more.

The researchers were able to make their findings after discovering certain chemicals in black shale that had been deposited in the seafloor of an ancient ocean in West Australia.

The elements that provided the link to the researcher’s findings are osmium, molybdenum and rhenium. They are produced by a reaction of oxygen with land-based sulfide minerals.  The scientists say that after the chemicals are produced they then make their way into rivers, which flow into oceans and are eventually deposited on the sea floor.

The research collaborators from Canada’s Universities of Alberta and Waterloo along with Arizona State University, University of California Riverside, and Georgia Institute of Technology, all in the U.S., published their findings in the journal Science Advances.

Rick Pantaleo
Rick Pantaleo maintains the Science World blog and writes stories for VOA’s web and radio on a variety of science, technology and health topics. He also occasionally appears on various VOA programs to talk about the latest scientific news. Rick joined VOA in 1992 after a 20 year career in commercial broadcasting.

3 responses to “Earth’s Atmosphere Got Its Oxygen in Periodic Bursts Over a 100 Million Year Period”

  1. Aloha from Honolulu, Hawaii. Thanks for the informative information about how the Earth’s atmosphere developed oxygen over billions of years. Sincerely, Rick Jackson

  2. Jeff says:

    If you can’t make it as a Fiction Writer … become a Scientist !

  3. MJ Darling says:

    If you’re writing about our thin blue line, surely you know geoengineers are destroying it. geoengineeringwatch.org
    Check out NASA Technical Reports Server and type in:

    geoengineering ozone depletion
    role of heterogeneous conversion of N2O5 on sulphate aerosols in global ozone losses
    sulphate aerosols
    human health and geoengineering
    sulphates and human health
    geoengineering ozone depletion
    and much, much more insanity as these psychopaths play with our thin blue line like it’s a giant chemistry set. Fun!!…until, of course, there is no more oxygen, no more life–we can’t breathe, there is no food, …