Earth’s oxygen-rich atmosphere faces a finite lifespan of about 1.08 billion years before a sharp decline, according to a detailed modeling study published in Nature Geoscience.
Researchers combining climate, chemistry, and solar evolution data warn that rising solar brightness will disrupt the carbon cycle, ending large-scale photosynthesis and triggering what they term “future deoxygenation.” This projection halves previous estimates of two billion years, revealing that breathable conditions occupy only 20 to 30 percent of Earth’s total habitable period.
The Team and Their Methods
Kazumi Ozaki from Toho University led the effort, partnering with Christopher Reinhard from the Georgia Institute of Technology and NASA-linked planetary scientists. Their integrated model simulates interactions among sunlight, volcanic emissions, rock weathering, and biological processes over billions of years.
The team executed roughly 400,000 supercomputer runs, varying initial conditions to pinpoint reliable trends. These revealed oxygen levels staying above 1 percent of current concentrations for an average of 1.08 billion years, with a 140-million-year uncertainty range.
Solar Brightening’s Role
The Sun’s gradual core contraction boosts its luminosity by about 1 percent every 100 million years. This intensifies rock weathering, which sequesters atmospheric carbon dioxide into minerals, initially cooling the planet but eventually starving photosynthesis—the primary oxygen source.
Plants and algae require sufficient carbon dioxide to produce oxygen; below critical thresholds, they perish, halting replenishment. Remaining oxygen then consumes through oxidation and biological respiration, setting off a cascade.
Carbon Cycle Collapse
Earth’s current carbon cycle maintains balance: photosynthesis fixes carbon dioxide into biomass while releasing oxygen, countered by decay and respiration. Intensified weathering tips this equilibrium, driving carbon dioxide to negligible levels.
Models predict photosynthesis fails globally once carbon dioxide dips too low, causing oxygen to plummet orders of magnitude in geologically brief time. The post-deoxygenation atmosphere features high methane, scant carbon dioxide, and no ozone layer, resembling conditions from 2.4 billion years ago.
Life’s Endgame
Complex aerobic life—animals, plants, humans—relies on 21 percent oxygen for metabolism. The plunge renders it uninhabitable for such organisms, marking the chief driver of a mass extinction.
Anaerobic microbes, including extremophiles, persist in subsurface, deep-ocean, or biofilm refuges. These methane-producers thrive in low-oxygen, high-radiation settings, forming mats akin to ancient Earth. Oceans briefly buffer warming by absorbing heat, but eventual evaporation leads to a moist greenhouse state and water loss to space.
Implications Ahead
This timeline poses no near-term risk yet underscores oxygen-rich phases as transient on habitable worlds. It challenges assumptions of perpetual adaptability, suggesting many exoplanets detectable for oxygen may soon lose it. For Earth, the shift prompts reflection on biosphere fragility, even as the planet lingers in the liquid-water zone, with microbial remnants outlasting multicellular domains.
Sources:
Nature Geoscience, The future lifespan of Earth’s oxygenated atmosphere, 2 March 2021
NASA Astrobiology, The Future of Earth’s Oxygen, 9 March 2021
Toho University, Earth’s oxygen-rich atmosphere will probably last for approximately one billion years, 2 March 2021
EurekAlert!, How much longer will the oxygen-rich atmosphere be sustained on Earth?, 1 March 2021
New Scientist, Most life on Earth will be killed by lack of oxygen in a billion years, 2021
Tech Explorist, The study suggests the end of the Earth will happen due to…, 6 May 2025