Earth was not always an oxygen-rich world. Researchers believe that the atmosphere will return to a methane-rich, low-oxygen state in the future.
This is unlikely to happen in any of our lifetimes. In fact, this is not possible for at least a billion years or so. But according to research published in Nature Geoscience earlier this year, when this happens, the change will happen faster. This change will return Earth to the same state it existed before the 2.4 billion year old Great Oxidation Event (GOE).
The increased solar radiation will eliminate the aquatic atmosphere from our planet’s surface in about 2 billion years. The researchers used a comprehensive model of Earth’s biosphere to derive their discoveries, taking into account fluctuations in the Sun’s brightness. Less carbon dioxide causes fewer photosynthetic organisms such as plants, which means fewer oxygen-producing species.
Furthermore, the scientists behind the current study say that atmospheric oxygen in general is expected to be a persistent feature of Earth-like planets. These are the results of human efforts to find evidence of further life in the universe.
Researchers believe that we may need to look for biosignatures other than oxygen to be most likely to find life. Their research is part of NASA’s NEXSS (Nexus for Exoplanet System Science) initiative, which looks at the habitability of planets other than Earth. According to their estimates, Earth may only survive 20-30% of the planet’s total lifespan, with microbial life continuing long after humans and other large species have disappeared.