Oxygen in the air
Although oxygen in the atmosphere now seems to be the fundamental basis of life, its initial appearance was more of a catastrophe for the young Earth. The environmental impact of this oxygen catastrophe was global and had three significant consequences:
- The rising oxygen levels in the oceans likely led to the extinction of a large portion of the organisms that inhabited the Earth at that time. Oxygen was lethal to these organisms and thus responsible for a mass extinction event.
- Atmospheric methane (a potent greenhouse gas) was oxidized to carbon dioxide (a weaker greenhouse gas) and water, which triggered a prolonged and complete ice age on Earth.
- Free oxygen caused dramatic changes in the chemical interactions between the Earth's solid materials, the atmosphere, and the oceans, among other factors. This led to a significant increase in the diversity of minerals found on Earth. It is estimated that more than 2,500 of the approximately 4,500 known minerals were formed as a result.
However, the increased oxygen levels also opened new avenues for the evolution of living organisms. The availability of free oxygen in the atmosphere was a breakthrough in the evolution of energy metabolism, greatly increasing the supply of free energy for living beings.