Oxygen is a highly reactive element responsible for the thriving and diverse life on earth essential for not only human life but the life of all living organisms on earth. Our oxygen-rich planet was not always so – according to scientists, the Earth formed approximately 4.6 billion years ago and was once home to a toxic atmosphere, presumably made up of gasses such as methane, ammonia and carbon dioxide.
Scientists believe that around 2.7 – 2.8 billion years ago Oxygen was first released into the atmosphere and early photosynthetic microorganisms were able to convert carbon dioxide into oxygen. After sometime, oxygen became a significant component of Earth’s atmosphere, paving the way for life. Today Earth’s atmosphere is made up of around 21 percent of oxygen and 78 percent Nitrogen. New research posits that Earth’s atmosphere will remain high in oxygen levels for the next billion years before returning to levels similar to those before the Oxidation of planet Earth, approximately 2.4 billion years ago.
Researchers from Toho University and NASA Nexus for Exoplanet System Science have now predicted scientific via stimulation that the Earth will lose its oxygen-based atmosphere in 1 billion years. The research was recently published in Nature Geoscience under the paper title: ‘The future lifespan of Earth’s oxygenated atmosphere’. Stating in their abstract that: ‘Earth’s modern atmosphere is highly oxygenated and is a remotely detectable signal of its surface biosphere. However, the lifespan of oxygen-based biosignatures in Earth’s atmosphere remains uncertain, particularly for the distant future. Here we use a combined biogeochemistry and climate model to examine the likely timescale of oxygen-rich atmospheric conditions on Earth.’
Scientists have long agreed that life on Earth would eventually come to an end and theories largely rested on the ageing sun, which will grow steadily hotter. With this increased heat, earths oceans will begin to evaporate and the atmosphere will change, depleting the ozone layer. At some point, the sun will die, destroying itself and its closer planets, including Earth.
By modelling Earth’s climatic, biological and geological systems, Kazumi Ozaki at Toho University in Funabashi, Japan, and Chris Reinhard at the Georgia Institute of Technology in Atlanta, predicted how these changes would occur and when. As the sun ages and becomes hotter, it will lead to a decrease in the amount of carbon dioxide in the atmosphere. This is due to the fact that CO2 absorbs heat and then breaks down. Due to the lower levels of CO2, organisms such as plants which require photosynthesis to survive will slowly dwindle. As photosynthesis is a primary producer of oxygen, O2 levels will drop rapidly. The drop, is estimated by Reinhard and Ozaki as approximately a million times less than there is in the atmosphere today. Further, this will coincide with an increase in methane levels as high as 10,000 times the amount in the atmosphere today.
Ozaki explained in a statement: “For many years, the lifespan of Earth’s biosphere has been discussed based on scientific knowledge about the steadily brightening of the sun and global carbonate-silicate geochemical cycle… One of the corollaries of such a theoretical framework is a continuous decline in atmospheric CO2 levels and global warming on geological timescales. Indeed, it is generally thought that Earth’s biosphere will come to an end in the next 2 billion years due to the combination of overheating and CO2 scarcity for photosynthesis, if true, one can expect that atmospheric O2 levels will also eventually decreases in the distant future. However, it remains unclear exactly when and how this will occur.”
After these changes occur, life on earth will be microbial, terrestrial and aquatic life unable to survive in the new conditions. Reinhard stated: “A world where many of the anaerobic and primitive bacteria are currently hiding in the shadows will, again, take over.”
The research was conducted as part of a NASA project looking at planet habitability, and has implications into life on other planets. New Scientist reported that ‘Oxygen-containing biosignatures are typically used to identify habitable planets.’ But this research now shows that oxygen presence could be variable and subject to change. Kevin Ortiz Ceballos at the University of Puerto Rico said to New Scientist that not detecting oxygen no longer means that the planet is uninhabitable, stating: “It suggests that even for planets around other stars that are very similar to Earth, large amounts of oxygen may not be detected in their atmosphere, even if they can support, or have supported, complex life.”
These predicted changes are the natural evolution of earth, taking place over the next billion years and are separate to the human-driven climate change problems we are facing and still need to tackle today.