Its common knowledge oxygen plays an important role in the physiological processes of most living organisms. At present, oxygen is found in abundance in the earth’s atmosphere. However, a recent study reported that oxygen levels would plummet akin to a time before the Great Oxidation Event (GOE) approximately 2.4-2.0 billion years ago. Although not known with certainty, studies suggest that the early atmosphere was dominated by dinitrogen (N2) and carbon dioxide (CO2). In addition, cyanobacteria have been thought to start the GOE by producing oxygen via photosynthesis.
This research titled “The future life span of Earth’s oxygenated atmosphere” conducted by a team of scientists (Kazumi Ozaki, and Christopher T. Reinhard) used a model that combines both biogeochemistry and climate data to get a better grasp on the future state of oxygen. The study shows that the earth’s oxygen could be reduced to less than 10% of today’s concentration in approximately a billion years.
As per the study, the mean future lifespan of Earth’s atmosphere, with oxygen levels more than 1% of the present atmospheric level, is 1.08 ± 0.14 billion years.
As the sun ages, its temperature increases due to reactions at its core, while it currently helps support life on earth, it will eventually be the driving force for the reduction of oxygen. As warmer temperatures persist the carbon dioxide in the atmosphere will react by breaking down. This breakdown will in turn lead to plants –which need carbon dioxide to live to start perishing thus removing the source of oxygen from the earth. The scientists however have noted that it is unclear when and how this process will occur. Furthermore, as oxygen levels drop, the level of methane (CH4) will sharply increase. A critical distinction between the future state and the state of the atmosphere before the GOE is the prediction of much lower levels of carbon dioxide, this, in turn, will lead to greatly elevated methane to carbon dioxide ratios. This elevation is predicted to result in the formation of ‘organic haze’ with potentially great impacts on climate, atmospheric chemistry, and remote life detection.
The research also suggests that using oxygen and ozone as a biosignature would now not be sufficient for the search of life on other earth-like planets as the results imply that the atmospheric oxygen state is not a permanent feature and that in the entirety of earth’s history only portions of its life would be characterized by an oxygen-rich state. Hence, arises a need for further research on applicable biosignatures especially in weakly-oxygenated planets.
Bottom line: A billion years from now, oxygen levels would drastically decrease due to the absence of plant life that depends on carbon dioxide which underwent breakdown attributed to rising temperatures of the sun.