Interpretation of the Miller-Urey Experiment
The molecules produced form this experiment were relatively simple organic molecules, far from a complete living biochemical system, but the experiment established that natural processes could produce the building blocks of life without requiring life to synthesize them in the first place. With time these substances probably increased and interacted with each other to form more complex molecules. Eventually one substance essential to life as we know it appeared. This substance was called deoxyribonucleic acid or DNA.
This experiment inspired many experiments in a similar vein. In 1961, Joan Oro found that amino acids could be made from hydrogen cyanide (HCN) and ammonia in a water solution. He also found that his experiment produced a large amount of the nucleotide base adenine. Experiments conducted later showed that the other RNA and DNA bases could be obtained through simulated prebiotic chemistry with a reducing atmosphere.
Conditions similar to those of the Miller-Urey experiments are present in other regions of the solar system, often substituting ultraviolet light for lightning as the driving force for chemical reactions. On September 28, 1969, a meteorite that fell over Murchison, Victoria, Australia was found to contain over 90 different amino acids, nineteen of which are found in Earth life. Comets and other icy outer-solar-system bodies are thought to contain large amounts of complex carbon compounds (such as tholins) formed by these processes, in some cases so much so that the surfaces of these bodies are turned dark red or as black as asphalt. The early Earth was bombarded heavily by comets, possibly providing a large supply of complex organic molecules along with the water and other volatiles they contributed. (This could also imply an origin of life outside of Earth, which then migrated here. See:Panspermia)