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The Miller Urey Experiment

In the 1950's, biochemists Stanley Miller and Harold Urey, conducted an experiment which demonstrated that several organic compounds, including amino acids, could be formed spontaneously by simulating the conditions of Earth's early atmosphere.

They designed an apparatus which held a mix of gases similar to those found in Earth's early atmosphere over a pool of water, representing the primeval sea. Electrodes delivered an electric current, simulating lightning, into the gas-filled chamber. After allowing the experiment to run for one week, they analyzed the contents of the liquid pool. They found that several organic amino acids had formed spontaneously from inorganic raw materials including water, ammonia, and methane. The equation for the combination of elements is shown below.


Their experiment (with different reactions) still holds if the Earth's initial atmosphere was not reducing but contained significant amounts of CO2. These molecules collected together in the pool of water to form coacervates.

Their experiments, along with considerable geological, biological, and chemical evidence, lends support to the theory that the first life forms arose spontaneously through chemical evolution. However, there are still many skeptics of this theory who remain unconvinced. British astrophysicist, Fred Hoyle, compares the likelihood of life appearing on Earth by chemical evolution "as equivalent to the possibility that a tornado sweeping through a junkyard might assemble a Boeing 747 from the materials therein".

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA