The fact that about three fourth of Earth is covered with water in the form of oceans, seas, rivers, lakes etc. is known by all of us.
But, how these water bodies were formed and what is the source of this much amount of water on Earth is the major topic of controversies and debate for the scientists.
The oceans are significant domains of the Earth because the first life was originated in the oceans and it protected the first organic molecules and organisms from the meteoritic bombardment and UV radiations.
Various theories have been proposed about the particular topic but, none of those is universally accepted till now.
The major theories can be studied as follows:
1. Cometary Theory
The present volume of the water of the oceans is 1.4×10²¹ kg. The theory stated that during the earlier days of the formation of Earth, it was hit by several comets. These comets were full of water and about 2.2- 8.5×10²¹ kg of water was supplied to the Earth. But, it was not possible that the comets actually hit the planet during its formation period so, this theory is not accepted.
2. Terrestrial Water Inventory
This states that the source of water and other volatile substances (including water and carbon dioxide) is the interior of Earth. During the time when the planet was formed, the substances were degassed outside.
This states that the major source of volatiles is the volcanic eruption which released a large amount of water and carbon dioxide into atmosphere.
About 90% of the total water on Earth’s surface was brought to the Earth through asteroids which entered inside. This is proved by the fact that deuterium to hydrogen ratio of oceanic water is close to that of asteroids. But, the ratio was found to be slightly different in deeper regions of Earth indicating that there are other sources of water also, besides the asteroids.
5. Solar nebula
It is the clouds of gas and dust left after the formation of sun. Scientist Jun Wu suggests that one or two water molecules out of the 100 water molecules on Earth were formed from solar nebula.
When the Earth was formed, its upper surface comprised of a large amount of magma. The atmosphere was initially composed of the hydrogen and noble gases brought by the solar nebula.
Hope you found the post knowledgeable.
Have a Great Day Ahead.