Figure 3.1 : Cross section of Earth

Now the next question, what will be the pre-requisite of life on earth? There are multiple conditions on earth to support the life on earth. These are as follows:

• Primitive earth with little or no oxygen. The earth original had a reducing environment due to presence of hydrogen and hydrogen compounds with water (such as CH4) and ammonia (NH3). Due to gravitional forces, these gases remains within the atmosphere of primitive earth. The reducing environment of primitive earth will help to synthesize organic compounds from interaction of inorganic substances.

• Inorganic raw material for origin of life: Inorganic material in the earth interact to form organic material required to to produce life.
• Energy source. The energy source on primitive earth came from the following sources:

Solar radiation
Electric discharge
Volcanic eruptions
Heat
Cosmic Rays
Radioactive Decays

• Infinite time: As per estimate it tooks almost 1 billion years from the formation of earth to appearance of life. Such a lon time is needed for chemical reactions to occur without the help of enzyme.