c. Formation of Simple Organic Molecules

As Earth's temperature fell further, the atmosphere's steam condensed into liquid water, triggering heavy and prolonged rainfall that gradually cooled the planet's surface. This rainwater collected on land to form the first rivers, streams, lakes, seas and oceans. Because the atmosphere at this stage still had no ozone layer, high-energy ultraviolet radiation from the sun struck the Earth's surface directly and unfiltered. Working together with this UV radiation, lightning discharges and volcanic activity supplied the energy needed to drive the early molecules of hydrocarbons, ammonia, methane and water through reactions such as condensation, polymerisation, oxidation and reduction. These reactions built the first simple organic molecules — monosaccharides, amino acids, purines, pyrimidines, fatty acids and glycerol — which then accumulated at the bottom of the newly formed water bodies. Haldane memorably described this accumulation as a 'hot dilute …