Life on Earth thrives today thanks to our rich atmosphere filled with oxygen. But this won’t last forever. Scientists believe that one day, Earth will undergo a significant atmospheric change, leading to the extinction of most life, including humans. This drastic transformation marks the end of life as we currently understand it.
Oxygen is a relatively new addition to Earth’s atmosphere. Before the Great Oxidation Event (GOE) around 2.4 billion years ago, the atmosphere was filled with methane, and oxygen was nearly absent. During this time, life was dominated by anaerobic organisms like cyanobacteria. These tiny organisms thrived in an environment that was rich in methane and iron, making the oceans appear green, not blue.
The GOE changed everything. When cyanobacteria began producing oxygen, the atmosphere transformed dramatically. This event set the stage for the development of diverse life forms that rely on oxygen.
Now, researchers suggest that Earth’s atmosphere could revert to its ancient state, becoming low in oxygen once again. This change could happen before Earth loses its vital surface water due to increased solar radiation. As the Sun ages, it will gradually become hotter, breaking down carbon dioxide in the atmosphere. With less carbon dioxide available, oxygen-producing plants will diminish, leading to a decline in breathable air.
As photosynthetic organisms decrease, oxygen levels could drop dramatically. This decline might happen rapidly on a geological scale, leaving many oxygen-dependent organisms with little time to adapt. The result? The extinction of not just animals and plants, but entire ecosystems that rely on oxygen.
Even though most life will disappear, some microbial life is expected to survive. Bacteria and archaea, which do not need oxygen, will likely thrive in this new, oxygen-free world. While the variety of life we know will end, Earth will still host life, just not in the form we recognize today.
Looking forward, if humanity is still around in a billion years, we might need to look for new homes. Ideas include colonizing other planets or creating artificial environments where people can live.
Though the loss of oxygen seems like the end for many species, it’s just another chapter in Earth’s long history of change. The planet will continue to exist, evolving into something entirely different from what we know today.
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