ORIGIN OF OXYGEN IN EARTH’S ATMOSPHERE
By Suhail Jalbout
Most scientists agree that there was no free oxygen in the atmosphere of early Earth. However, some scientists claim that the original atmosphere of the Earth was composed from methane, ammonia, hydrogen, and water because this mixture of molecules is present in interstellar space. Other scientists believe that as Earth began to develop a solid crust about 4 billion years ago, gases from volcanic eruptions formed an atmosphere with a composition similar to the present emanations from volcanoes. If we assume that both theories are correct, then the early atmosphere of the Earth consisted of: water (H2O), carbon dioxide (CO2), methane (CH4), ammonia (NH3), hydrogen (H2), nitrogen (N2), and other small amounts of miscellaneous gases.
It seems that free oxygen was produced on the Earth around 2.5 billion years ago. It was generated by photosynthesizing organisms known as cyanobacteria or blue-green algae. These tiny organisms conduct photosynthesis by using ordinary sunlight, water, and carbon dioxide to produce carbohydrates and oxygen. Since these organisms lived in oceans, the produced oxygen molecules bubbled up from the oceans into the atmosphere. The presence of oxygen changed the composition of the early atmosphere into the present oxidizing atmosphere which consists of: nitrogen (N2 -78%), oxygen (O2– 21%), and other gases such as water and carbon dioxide.
The first living forms on Earth appeared around 3.5 billion years ago. Since free oxygen was generated about 2.5 billion years ago, this means living organisms on the Earth were exposed to ultraviolet light for 1 billion years. Ozone did not exist during this period to form a protective shield. Consequently, it is very difficult to explain how primitive life developed and evolved into complex organisms in the presence of UV.
I believe oxygen was produced on the Earth about 3.5 billion years ago. Sometimes around this date, Earth experienced the following important changes:
In my hypothesis “Origin of Water on Earth” I have reached a conclusion that oceans were created on the Earth from the collapsed water-ice ring that was in its orbit. Water in huge amounts flooded the Earth and created oceans during a short period of time.[1]
- Oceans were formed on the surface
- Single-cell organisms appeared for the first time
- Ozone layer was formed in the upper atmosphere
In my hypothesis “Origin of Life on Earth (Parts I and 2)” I have concluded that the creation of single-cell organisms during the formation of stars is 157 million times more probable than their creation on Earth- like planets, a pessimistic estimate.[2] Consequently, the water-ice ring that was orbiting the Earth must have harbored single-cell organisms in a frozen state. When the ring collapsed, it created oceans and populated the Earth with life about 3.5 billion years ago.
When the ring entered the early atmosphere of the Earth, a large percentage of its water-ice evaporated due to friction. Since the ring contained about 1.33x10^18 tons of water, the atmosphere became completely saturated with water vapor extending from the surface of the Earth to very high levels in the atmosphere. Water molecules and dust particles from volcanic eruptions formed enormous electrically charged clouds around the Earth. As a result, lightening with immense intensity dominated the skies all over the world. These new conditions paved the way for the production of oxygen by the following two methods:
PHOTOCHEMICAL DISSOCIATION
Water molecules, at the upper levels of the atmosphere, were broken up by ultraviolet light into hydrogen and oxygen atoms. Two oxygen atoms combined to form an oxygen molecule and a third oxygen atom combined with an oxygen molecule to form ozone. This means an ozone layer was formed in the upper levels of the atmosphere shielding the ultraviolet light and reducing its harmful effects.
ELECTROLYTIC OXYGEN AND OZONE GENERATION
The formed highly charged clouds and the surface of the Earth acted as a gigantic electrolytic oxygen and ozone generator. The discharge of electrons, during lightening, between the charged clouds and Earth’s surface dissociated water molecules and produced hydrogen, oxygen, and ozone. It is to be noted that ozone is created in nature by lightening and can be smelled after a storm. The newly formed ozone ascended to the upper levels of the atmosphere and joined in the formation of the ozone shield. While the newly formed free oxygen combined with the gases of the early atmosphere to form an intermediate atmosphere about 3.5 billion years ago. For example:
The newly formed intermediate atmosphere consisted mainly of: nitrogen, carbon dioxide, hydrogen, and water with very small amount of oxygen. Most of the oxygen that was generated formed the ozone layer and combined with the gases of the early atmosphere.
- Oxygen combined with methane to produce carbon dioxide and water: (CH4 + 2O2 = CO2 + 2H2O)
- Oxygen combined with ammonia to produce nitrogen and water: (4NH3 + 3O2 = 2N2 + 6H2O)
- Hydrogen combined with oxygen to form water: (2H2 + O2 = 2H2O)
In conclusion, the intermediate atmosphere and the ozone shield provided favorable conditions for simple primitive life forms to grow and develop into very complex organisms. Some of these complex organisms produced free oxygen which increased the amount of oxygen in the atmosphere to 21% forming our present atmosphere.
END NOTES
[1] www.thescienceforum.com/.../22663-origin-water-earth.html
[1] 2012 Forum • ORIGIN OF WATER ON EARTH
[2] www.thescienceforum.com/.../23461-origin-life-earth-4.html
[2] 2012 Forum • ORIGIN OF WATER ON EARTH
[2] 2012 Forum • ORIGIN OF LIFE ON EARTH (PART 2)
[2] ORIGIN OF LIFE ON EARTH