Which experiment simulated early Earth conditions to produce amino acids?

The Miller–Urey experiment simulated early Earth conditions and produced amino acids from inorganic starting materials.

Stanley Miller carried out the landmark experiment in 1952 under the supervision of chemist Harold Urey at the University of Chicago; the results were published in 1953. Their apparatus circulated water and a mixture of gases through a heated flask, then exposed the gases to electric sparks representing lightning.

The original gas mixture included methane, ammonia, hydrogen, and water vapor. After several days, the liquid became brownish and contained organic compounds, including amino acids such as glycine and alanine. The result showed that some chemical building blocks of life could form without living organisms.

The experiment did not create life, and scientists now question whether Earth’s entire early atmosphere matched the strongly reducing mixture used in the classic setup. Later experiments using different gases, volcanic conditions, or impact-generated atmospheres have also produced organic compounds. The names of Alexander Oparin and J. B. S. Haldane are associated with the hypothesis that inspired the experiment, not with the experiment itself.