Scientists predict a significant change in Earth’s atmosphere that could revert to a state resembling the period before the Great Oxidation Event (GOE) roughly 2.4 billion years ago. The GOE marked a substantial increase in atmospheric oxygen, leading to a transformed environment conducive to the emergence of aerobic life forms, including humans.
However, a 2021 study suggests this oxygen-rich phase might not be permanent in Earth’s history. Within the next billion years, a rapid deoxygenation event could occur, resulting in an atmosphere dominated by methane, similar to ancient Earth during the Archaean period.
This change would signal the end of oxygen-dependent life, including human civilization, unless technology enables us to leave the planet. Researchers used complex Earth biosphere models, considering the Sun’s increasing luminosity and subsequent decline in carbon dioxide due to intensified heat breaking down the gas. Lower CO2 levels would diminish oxygen production from photosynthetic organisms like plants.
Previous theories suggested that escalating solar radiation would evaporate Earth’s oceans in about 2 billion years. However, this new model, based on nearly 400,000 simulations, indicates that oxygen depletion would precede water loss, proving more immediately fatal to life as we know it.
Chris Reinhard, an Earth scientist at the Georgia Institute of Technology, emphasized the severity of the predicted oxygen decline, estimated to be a million times less than current levels. This reduction would render the planet uninhabitable for aerobic organisms, leading to the end of most life forms thriving on Earth today.
The study has implications for the search for extraterrestrial life, suggesting that oxygen might not be the sole indicator of life. It advises considering alternative biosignatures while exploring habitable exoplanets.
The post-deoxygenation atmosphere would feature elevated methane levels, low CO2, and no protective ozone layer. In this scenario, anaerobic life forms would prevail, continuing the cycle of life after oxygen-dependent species vanish.
This research suggests that Earth’s oxygen-rich era might last only 20-30 percent of the planet’s total lifespan. As humanity faces climate change and environmental issues, this glimpse into the distant future reminds us of our planet’s changing nature and the transient conditions supporting life.