The origins of oxygen in Earth's atmosphere derive from life. Ancient microbes first produced oxygen through photosynthesis.
Initially, scientists believed that the origin of oxygen on Earth began with photosynthetic microbes called cyanobacteria.
--> However, a new work-place showed that photosynthesis originated a billion years earlier than previously thought which means oxygen was ready for living organisms close to the start of living on earth.
--> Researchers studied the molecular machines responsible for photosynthesis and found that photosynthesis may have occurred more than 3.4 billion years ago.
This is so long before oxygen or cyanobacteria were thought to have had existence on Earth. This means there must have been persons who had the position before, such as of old bacteria that have become to do photosynthesis and produce oxygen. Even though very small microbes were producing the gas as a side-effect of photosynthesis.
--> Earth's early atmosphere and oceans were devoid of free oxygen. Free oxygen does not combine with other elements such as carbon or nitrogen. Much of the oxygen produced reacted with iron, sulfur and other chemicals in the oceans, and in the rocks on Earth's surface.
--> As a result, oxygen entered into the seafloor sediments and eventually into Earth's interior.
About 2.4 billion years ago oxygen in the air suddenly increased by about 10,000 times in just 200 million years. This stage in time is experienced as the Great oxidation event which changed chemical reactions on the top of the Earth completely.
At the same time when free oxygen started to get together in the seas, changes occurred in the thing in place of natural one of Earth's hardcover.
--> Before oxygenation, rocks on earth contained a mineral called Olivine. Research shows that when olivine comes into contact with water it initiates chemical reactions that consume oxygen and lock it up.
However, as the frequently hardcover became a thing in place of natural one more like today. olivine almost gone from view from earth's hard cover, without that mined substance to have a reaction with water and waste oxygen the gas was finally let to get together.
--> Oceans eventually became saturated and oxygen crossed into the atmosphere.
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