Earth Breathed This Before Oxygen: Incredible New Discovery

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Billions of years ago, way long before oxygen was available, the infamous poison arsenic is said to be the compound that Earth breathed. 

Scientists realized research in Chile’s Atacama Desert, an area known as Laguna La Brava. They studied a purple ribbon of photosynthetic microbes existing in a hypersaline lake that’s free of oxygen permanently.

According to the research, that system is the only one on Earth where scientists could find a microbial mat that worked just fine in the absence of oxygen. Here is what you need to know.

What Was There Before Oxygen?

Microbial mats that fossilize into stromatolites have been present in rich amounts on Earth for approximately 3.5 billion years. Yet, for the first billion years of their presence, there was no oxygen for photosynthesis. 

How life forms existed and survived in those extreme conditions is still unknown. However, analyzing the stromatolites and extremophiles present today, scientists succeeded in finding a lot of essential information. 

Iron, hydrogen, and sulfur were always believed to be the perfect replacements for oxygen. Still, once with the finding of “arsenothrophy” in California’s hypersaline Mono Lake and Searles Lake, arsenic became possible. 

New Discovery Emerges

Last year, scientists found a rich life form in the Pacific Ocean that also breathes arsenic. The La Brava life forms resemble a purple sulfur bacterium dubbed Ectothiohodospira sp., which was recently discovered in an arsenic-abundant lake in Nevada. The bacterium also appears to photosynthesize by oxidizing the compound arsenite into a different form called arsenate. 

If the scientists are right and the La Brava microbes are “breathing” arsenic, these life forms would be the first to do this in a completely and permanently oxygen-free microbial mat. It would also be similar to Precambrian environments. 

“In looking for evidence of life on Mars, [scientists] will be looking at iron, and probably they should be looking at arsenic also,” said Pieter Visscher, a geoscientist from the University of Connecticut. 

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