Life originated in anoxia, but many organisms came to depend upon oxygen for survival, independently evolving diverse respiratory systems to acquire oxygen from the environment. A new study by Newcastle University has uncovered a source of oxygen that may have influenced the evolution of life before the advent of photosynthesis.
Scientists discovered a mechanism that allows rocks to produce hydrogen peroxide while moving along geological faults.
Hydrogen peroxide can be toxic to life at large doses, yet it can also be a beneficial source of oxygen for bacteria. Before the development of photosynthesis, this additional supply of oxygen may have influenced the early evolution, and possibly even the origin, of life in hot settings on the early Earth.
In tectonically active areas, the movement of the Earth’s crust causes not just earthquakes but also fractures and cracks in the subsurface that are bordered by highly reactive rock surfaces that have many defects. The flaws on the newly fractured rock can then filter down and react with the water.
Scientists simulated these conditions by crushing granite, basalt, and peridotite. These were then added to water under well-controlled, oxygen-free conditions at varying temperatures.
The investigations showed that significant levels of hydrogen peroxide, and hence, possibly oxygen, were only produced at temperatures near the boiling point of water. Importantly, the temperature at which hydrogen peroxide is formed overlaps the growth ranges of some of the Earth’s most heat-loving bacteria, known as hyperthermophiles, including oxygen-using ancient evolutionary microbes close to the base of the Universal Tree of Life.
Lead author Jordan Stone, who conducted this research as part of his MRes in Environmental Geoscience, said: “While previous research has suggested that small amounts of hydrogen peroxide and other oxidants can be formed by stressing or crushing of rocks in the absence of oxygen, this is the first study to show the vital importance of hot temperatures in maximizing hydrogen peroxide generation.”
Principal Investigator Dr. Jon Telling, Senior Lecturer, added: “This research shows that defects on crushed rock and minerals can behave very differently to how you would expect more ‘perfect’ mineral surfaces to react. All these mechanochemical reactions need to generate hydrogen peroxide. 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.”
The work was supported through grants from the Natural Environmental Research Council (NERC) and the UK Space Agency. A major new follow-up project led by Dr. Jon Telling, funded by NERC, is underway to determine the significance of this mechanism for supporting life in the Earth’s subsurface.