What do theories hypothesize about the conditions of earth's early atmosphere?

I think it is that organic molecules like carbon combined together using the power for lightning to make inorganic molecules, and amino acids, etc. this can be seen in the Miller-Urey experiment

Explanation:

The conditions present on early earth were like: High temperature, reducing atmosphere containing methane, ammonia, etc. and volcanic eruptions.

Explanation:

The gaseous atmosphere which we see today was not present on the early earth. Due to volcanic eruptions, the molten mass was released and moved slowly over the surface of earth. From this molten mass several gases were release into the surroundings such as carbon dioxide, methane, ammonia and  water vapor. The ultra violet radiation from sunlight caused the breakdown of water molecules into hydrogen and oxygen. Hydrogen being lighter escaped into the surroundings and oxygen readily combined with other gases to form again H2O, CO2 and many other gases. So we can say that there was no free oxygen available in the early atmosphere and it was reducing in nature. Oxygen also participated in the formation of ozone i.e O3 molecule under the influence of UV rays. These ozone molecules resulted in the formation of ozone layer which acts as a shield to save present atmosphere from harmful UV rays.