What’s Earth Like Without O2?

Ah yes, good old oxygen or O2 is the very essence of life itself. But did you know Earth at one point wasn’t abundant in this naturally occurring, life-giving compound?

Indeed, billions of years ago (long before oxygen was readily available) the air was filled with poisonous arsenic which could have been the spark which ignited the birth of the first lifeforms on the planet.

Numerous studies have been made to find out more about this near-mysterious substance which could have been the catalyst to all life on Earth.

What Life On Earth Breathed Before Oxygen

In Laguna La Brava found in Chile’s Atacama Desert, scientists have been steadily investigating a purple ribbon of photosynthetic microbes living in a hypersaline lake that doesn’t have any oxygen whatsoever.

These microbial mats, which fossilize into stromatolites, were found to be abundant on Earth for more than 3 billion years. Yet, for the first billion or so years of their existence, there was no oxygen in the atmosphere for photosynthesis to occur.

How exactly these life forms managed to survive in an environment without oxygen is still a mystery thus far. But through examining modern, living stromatolites and extremophiles, scientists believe they’ve come up with a handful of hypotheses.

And one of the prevailing theories lies with “arsenotrophy”.

While other elements such as iron, sulphur, and hydrogen have long thought to be a possible replacement for oxygen, the discovery of “arsenotrophy” has led to poison arsenic becoming a known contender.

Since then, stromatolites from the Tumbiana Formation in Western Australia have revealed telling signs of consuming arsenic and light as a valid mode of photosynthesis in the days where oxygen was scarce. The same couldn’t be said about iron nor sulphur.

Also, researchers also found a colony of life form in the Pacific Ocean which also “breathes” arsenic just last year.

If the Laguna La Brava microbes do indeed breathe arsenic, it could hold the key to our understanding of some of the earliest life forms on the planet. And if this scenario IS indeed true, then we might need to expand our search for life forms elsewhere.

Life on Mars definitely comes to mind in this case.

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