Take a deep breath and taste the moment, because it will not last. A new study estimates that Earth’s oxygen will last for about 1 billion years, a spell disaster for most of the life on the planet. As published in the journal Nature Geosciences, two scientists predict that the Earth’s oxygen-rich atmosphere will return to oxygen-poor, methane-rich composition – similar to the conditions seen on Earth in the early days before the Great Oxidation Event about 2.4 billion years ago.
Kazumi Ozaki and Christopher Reinhard reached this conclusion by modeling a number of systems on Earth, including climate and biological and geological processes, to examine the timing of Earth’s atmospheric conditions. Life on Earth has made possible thanks to our planet’s high oxygen atmosphere, which is a fertile ground for light-loving creatures that serve as the basis for most of life on the planet. New estimates, however, suggest that this oxygen-rich atmosphere – as well as oxygen-dependent life – is unlikely to be a permanent feature of the Earth.
Kazumi Ozaki, study author and Assistant Professor at Toho University in Tokyo, said in a statement, “After great deoxygenation, the atmosphere is characterized by advanced methane, low levels of CO2, and an ozone layer. The Earth system will probably be a world of anaerobic life forms.”
These changes will occur over millions and billions of years of geological timescale, so we should not be confused with the dramatic changes that humans have seen in the Earth’s atmosphere over the past century. One of the major forces contributing to this long-term change in oxygen levels is the gradual illumination of the sun. As the planet heats up, researchers argue that it will eventually reduce the amount of carbon dioxide in the atmosphere, as CO2 absorbs heat and breaks down. Finally, plants and other photosynthetic organisms will not have enough CO2 to produce oxygen, which depletes the atmosphere of this vital gas.
“For many years, the life span of the Earth’s fauna has been discussed on the basis of scientific knowledge about the continuous illumination of the sun and the global carbonate-silicate geochemical cycle,” Ozaki explained. “One of the main reasons for such a theoretical framework is the continuous deterioration of atmospheric CO2 levels and global warming in the geological time cycle. In fact, it is thought that the combination of excess heat for the synthesis of light and CO2 deficiency will result in the extinction of the Earth’s biosphere in the next 2 billion years, “Ozaki added.
“If true, one can only hope that atmospheric and 2 levels will eventually decrease in the distant future. However, it is not yet clear when and how this will happen.” This new hypothesis not only involves life on Earth, but also can guide our understanding of life on other planets. Oxygen and related byproducts are some of the basic biomarkers that scientists use to soften potential residential exoplanets elsewhere in the universe. However, as this new study shows, even the Earth’s habitat may not be permanently rich in oxygen; it suggests that we need to broaden our perspective as we search for life outside the solar system.
