A study suggests that, just as the Earth’s atmosphere was extremely low in oxygen 2.4 billion years ago, it will drop dramatically to previous levels in another billion years. Understanding Earth’s evolutionary history will help scientists explore exoplanets and expand their knowledge of whether they are, or were, habitable.
Researchers believe that since the Earth has undergone such amazing changes, exoplanets are likely to undergo a similar evolutionary history. So when scientists see exoplanets that are not currently habitable, they cannot rule out that Life once flourished on them.
The study, a collaboration between Toho University (Japan) and the Georgia Institute of Technology (USA), models the Earth’s climate, biology and geographic systems to make such predictions about the future of the planet’s environment, according to New Scientist magazine. This is what is predicted.
The Earth’s atmosphere now contains 21 percent oxygen, which is an ideal environment for the planet’s biosphere, including humans. However, scientists found that about 2.4 billion years ago, the oxygen content of the Earth’s atmosphere was once quite low and unsuitable for human survival. This study argues that in the future, the oxygen content of the Earth’s atmosphere will again be reduced to that level, as low as less than 1 percent.
“We found that the oxygen-rich condition is not a permanent feature of the Earth’s atmosphere.” Kazumi Ozaki of Toho University, one of the lead researchers, said.
They believe the main reason for the change is that as the sun ages, higher temperatures emit more energy. This causes more carbon dioxide in the Earth’s atmosphere to break down as it absorbs heat, leaving too little carbon dioxide to support photosynthesis, leading to the death of a large number of organisms that need photosynthesis, and then a dramatic decrease in the amount of oxygen in the atmosphere.
Co-investigator Chris Reinhard of the Georgia Institute of Technology said, “The extent of the plunge in oxygen would then be so extreme that only one millionth of the current atmospheric oxygen content would remain.”
The study also predicts that the amount of methane gas in the atmosphere will increase dramatically at that point, reaching 10,000 times current levels. The researchers estimate that it will only take 10,000 years for Earth’s atmosphere to complete from the Time it begins to experience this change until oxygen levels drop to their lowest levels.
Kazu Ozaki said, “The Earth’s biosphere will not be able to adapt to such a drastic environmental change.” They estimate that by then only microorganisms will survive on Earth.
The study was published March 1 in the journal Nature Geoscience.