Breathe in, breathe out and thank your lucky… rocks?

The Earth’s atmosphere is relatively rich in oxygen but the prevailing wisdom that much of it came from plants and bacteria, might not be entirely correct.

The advent of photosynthesis — the production of energy and oxygen from carbon dioxide and light — by cyanobacteria had a big influence on the evolution of life and multi-cellular organisms in particular.

However, a new study in Nature Communications suggests that hydrogen peroxide (an easy source of oxygen to microbes) was produced in substantial quantities much earlier in the Earth’s history, raising interesting questions about the early evolution of life (and perhaps the origins of life, more generally).

Earth’s surface is not static and in particularly active tectonic regions, stresses build in the crust which are released through earthquakes and faulting activity. This produces defects or imperfections in the rocks below the surface which are then exposed to water filtering down from above.

Lead author Jordan Stone, who conducted this research as part of his MRes in Environmental Geoscience at Newcastle University, UK, sets up one of the experiments. Jon Telling/Jordan Stone/Newcastle University

Jordan Stone, a master’s student at Newcastle University, simulated early rock defect conditions in the Earth’s oceanic and continental crust by crushing granite, basalt and peridotite, and then he exposed them to water in an oxygen-free environment. At temperatures close to the boiling point of water, Stone found that a substantial amount of hydrogen peroxide was produced from the crushed rocks.

The high temperature range is a key discovery, says Stone. “While previous research has suggested small amounts of hydrogen peroxide and other oxidants can be formed by stressing or crushing rocks in the absence of oxygen, this is the first study to show the vital importance of hot temperatures in maximising hydrogen peroxide generation.”

Heat-loving microbes, or hyperthermophiles, are incredibly resilient, growing best in temperatures above 80°C and surviving in temperatures beyond the boiling point of water (100°C). What’s more, they have ancient origins, lying near the root of the Universal Tree of Life and predating the emergence of photosynthesis.

A timeline of the history of life and oxygen showing advent of photosynthesis
A timeline of the history of life and oxygen. Jon Telling/Jordan Stone/Newcastle University.

This is interesting to note as these oxygen-loving hyperthermophiles thrive in temperatures across the range of optimal hydrogen peroxide production and Stone’s research suggests that oxygen may have played a far more important role in the evolution of life before photosynthesis came along.

Read more: Study dates origin of plant photosynthesis to 2.1 billion years ago

As Newcastle University Senior lecturer and Principal Investigator, Dr Jon Telling notes, “All these mechanochemical reactions need to generate hydrogen peroxide, and therefore oxygen, is water, crushed rocks, and high temperatures, which were all present on the early Earth before the evolution of photosynthesis and which could have influenced the chemistry and microbiology in hot, seismically active regions where life may have first evolved.”

Next time you take a big breath in, give a little thanks to the life-giving bedrock under your feet.

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