Today, life thrives on our oxygen-rich planet, but Earth hasn’t always been like this, and scientists predict that the atmosphere will return to one rich in methane in the future.
And that probably won’t happen for another billion years or so. But when change does come, it will happen fairly quickly, according to a study published in 2021.
This transformation will return the planet to the state it was in before what happened about 2.4 billion years ago, known as the Great Oxidation Event (GOE).
What’s more, the researchers behind the study say that atmospheric oxygen is unlikely to be a consistent feature of habitable worlds in general, which affects our efforts to detect signs of life in the universe.
“The model predicts that the removal of oxygen from the atmosphere, dropping sharply to levels reminiscent of ancient Earth, is likely to occur before the onset of wet greenhouse conditions in the Earth’s climate system and before significant loss of surface water from the Earth. “, the researchers explained.
And at that point it will be the end of the road for humans and most other oxygen dependent life forms, so let’s hope we figure out how to get off the planet at some point within the next billion years.
To reach their conclusions, the researchers created detailed models of the Earth’s biosphere, taking into account changes in the brightness of the sun and the corresponding decrease in carbon dioxide levels as the gas decays due to rising heat levels. Low carbon dioxide means fewer photosynthetic organisms like plants, which results in less oxygen.
Scientists previously predicted that an increase in solar radiation would wipe out ocean water from our planet’s surface within about 2 billion years, but the model presented here, based on an average of less than 400,000 simulations, says the decrease in oxygen would kill life first.
“The reduction in oxygen is quite strong,” geologist Chris Reinhard of the Georgia Institute of Technology told New Scientist. “We’re talking about a million times less oxygen than it is today.”
What makes the study especially relevant today is the search for habitable planets outside the solar system.
It is likely, the researchers say, that we will need to look for biosignatures other than oxygen to have the best chance of detecting life. Their study is part of NASA’s NExSS (Nexus for Exoplanet System Science, which investigates the habitability of planets other than our own.
According to calculations by Reinhard and environmentalist Kazumi Ozaki of the University of Toho in Japan, the Earth’s oxygen-rich history could only end 20 to 30 percent of the life of the planet as a whole.
“The atmosphere after significant deoxygenation is characterized by high methane content, low levels of carbon dioxide and the absence of an ozone layer. The Earth system is likely to be a world of anaerobic life forms,” Ozaki said.
The study is published in the journal Nature Geoscience.
Source: Science Alert