GENERAL GEOLOGY

Detailed explanation-1: -Ancient sediments and rocks record past changes in atmospheric composition due to chemical reactions with Earth’s crust and, in particular, to biochemical processes associated with life. Earth’s original atmosphere was rich in methane, ammonia, water vapour, and the noble gas neon, but it lacked free oxygen.

Detailed explanation-2: -Oxygen is produced by plants by the process of photosynthesis, earlier there were no plants and vegetation, which’s why no oxygen in the early atmosphere.

Detailed explanation-3: -They concluded that Earth’s early atmosphere contained CH4, H2, H2O, N2, and NH3, similar to the gas mixtures used in the Miller–Urey synthesis of organic compounds.

Detailed explanation-4: -The early Earth had no atmosphere or free water. The planet was far too hot for gases and water to collect. The gases came from volcanic eruptions and from comets. Nitrogen, carbon dioxide, hydrogen, and water vapor, or water in gas form, were in the first atmosphere.

Detailed explanation-5: -Before photosynthesis evolved, Earth’s atmosphere had no free oxygen (O2). Small quantities of oxygen were released by geological and biological processes, but did not build up in the atmosphere due to reactions with reducing minerals.