An ancient source of oxygen has been discovered deep in the Earth's crust, by scientists from Newcastle University. The researchers were able to unravel a mechanism through which hydrogen peroxide could be generated from rocks during geological faults, by conducting laboratory experiments and replicating conditions seen beneath the Earth's surface. This extra source of oxygen, according to researchers may have influenced the early evolution of life on Earth when photosynthesis wasn't there. Hydrogen peroxide can be harmful to living beings in high concentrations. But it can also serve as an efficient source of oxygen for microbes.
When the Earth's crust moves in tectonically active regions, besides causing earthquakes, it also results in cracks and fractures on the subsurface. This subsurface has some highly reactive rock surfaces that feature defects and imperfections. Water tends to seep down the surface and react with new defects in the fractured rocks.
In the study, Master's student Jordan Stone was able to successfully replicate these conditions in the laboratory. He crushed rocks like granite, basalt, and peridotite that would be present in the early Earth's crust. These crushed rocks were added to water while maintaining controlled and oxygen-free conditions at varying temperatures.
The team observed that a significant amount of hydrogen peroxide could be generated only at temperatures near the boiling point of water. It was also noted the temperature needed for hydrogen peroxide formation overlapped with the growth ranges of hyperthermophiles, some of the most heat-loving microbes on Earth. These also included the evolutionary ancient microbes near the root of the metaphorical Universal Tree of Life that were said to utilise oxygen.
“While previous research has suggested that 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,” said Stone.
He is the lead author of the study published in Nature Communications.
Highlighting the significance of the experiment, senior lecturer and principal investigator Dr Jon Telling said that defects on crushed rock and minerals can behave differently from how one would expect more perfect mineral surfaces to react. He said that the mechanism observed in the rocks needs to generate peroxide and thus oxygen too. This, he added, could have an impact and influence on the chemistry and microbiology in seismically active regions before the evolution of photosynthesis.