I want to know what theories exist about life formation on earth?

Answer 1

There is no real model yet for the origin of life. However a number of discoveries have been made concerning the origin of molecular and cellular components that are necessary for life on earth:

1. Conditions that existed 4.5x10^9 years ago result in the creation of certain basic small molecules of life, such as amino acids. This was demonstrated in the Urey-Miller experiment in the 50s.

2. Fat molecules can organise spontaneously into layers which form the basis of cell membranes.

3. Amino acids polymerize spontaneously into random RNA molecules.

4. The resulting molecule soup will compete for resources, by which I mean smaller molecules, to be able to grow further. Therefore there will be selection pressures for efficiency and diversity which will favour those macromolecules that can reproduces themselves or part of themselves most quickly and efficiently.

5. Thus evolution begins: once certain molecules are formed in the soup that can reproduce itself partly, they will soon dominate in the mix. In the next step the *better* ones among those will be selected and so on.

To summarize:
When: between 4.5 and 2.5 billion years ago
Where: in water ponds at the surface of the earth
Why: any mixture of organic molecules will change into a mix of more complex molecules by polymerization
How: Selective pressure will favour those molecules that react faster and more efficient.

Answer 2

Researchers recently mimicked Titan's atmosphere by exposing methane gas to an ultraviolet lamp, then added carbon dioxide gas. A condition that was probably present on early Earth as an organic haze. Organic haze can form over a wide range of methane and carbon dioxide concentrations meaning that hazy conditions could have been present for many millions or even a billion years on Earth while life was evolving."

According to the study, a similar haze hanging over Earth early in its history could have supplied more than 100 million tons of organic material to the planet's surface each year.
In addition to serving as a source of organic material, a haze layer over Earth could have shielded living organisms from harmful UV rays and helped to regulate Earth's early climate

Answer 3

That would be in the realm of Biology, or perhaps Biochemistry. In Geology, we find and report fossils, we do not try to invent theories outside the realm of Geology.