It may have been unexpected that the Earth’s oxygen richness was unexpectedly easier. In fact, there is much less need for living organisms in the rise of oxygen.
A new study suggests that planets with oxygen-rich atmospheres may be more common than we thought. The author of the study, Lewis Alcott of the University of Leeds, UK, says that oxygen formation can be easy not only for the Earth but also for other planets.
During the first 2 billion years of world history, there was no oxygen in the air. However, this changed with the Great Oxidation Event 2.4 billion years ago, when low oxygen levels first appeared. The emergence of oxygen has been associated with the evolution of photosynthetic bacteria that release oxygen as a waste product. Oxygen levels then rose twice more, 800-540 million years and 450-400 million years ago.
Science had previously attempted to explain oxidation events by associating them with significant evolutionary changes or tectonic activities. For example, the rise of oxygen was explained in connection with the spread of soil plants.
In fact, the key point is that the Earth slowly cools down after its formation, and as it cools, the release of volcanic gas, such as sulfur dioxide, which reacts with oxygen and removes it from the air. When the team modeled how this change affects the oxygen cycle around the planet, they observed three sharp increases corresponding to the oxidation events known to date.
The first event of the Great Oxidation took place because the oxygen produced by the bacteria suppressed the volcanic gases in the air. Oxygen levels then remained constant for millions of years as excess oxygen reacted with minerals on land. Then the second rise occurred because the extra oxygen changed the structure of phosphorus-containing substances and increased the likelihood of descent into marine sediments.
Phosphorus is a vital nutrient, and this change allowed more oxygen to pass through the air and surface layers of the sea. Thus, more organisms survived. The same shift led to a third sharp rise in oxygen when it reached the deep oceans.
Researchers say the same processes can be experienced on any planet with oceans and continents, where photosynthesis can develop oxygen. So life can occur on other planets.