What 50-year-old experiment reveals about life

Modern tests on 1953 vial samples confirm volcanoes may have played role

An old experiment, rediscovered after more than 50 years, may demonstrate how volcanoes – and possibly chemical reactions far from primitive Earth in outer space – played a role in creating the first amino acids, the building blocks of life.

In 1953, chemists Harold Urey and Stanley Miller performed a landmark experiment intended to mimic the primordial conditions that created the first amino acids, by exposing a mix of gases to a lightning-like electrical discharge. Five years later, in 1958, Miller performed another variation on this experiment. This time he added hydrogen sulfide, a gas spewed out by volcanoes, to the mix.

But for some reason, Miller never analyzed the products of the hydrogen sulfide reaction. About half a century later, a former student of Miller's, Jeffrey Bada, a marine chemist at the Scripps Institution of Oceanography in California, discovered the old samples in a dusty cardboard box in Miller's laboratory, which Bada had inherited. (Miller passed away in 2007.)

Old experiment, new analysis 

Using modern analytical techniques, Bada and his team, which included Eric Parker, then at Scripps, analyzed the products of the reaction, which were housed in small vials. They found an abundance of promising molecules: 23 amino acids and four amines, another type of organic molecule. The addition of hydrogen sulfide had also led to the creation of sulfur-containing amino acids, which are important to the chemistry of life. (One of these, methionine, initiates the synthesis of proteins.)

The results of the experiment – which exposed a mix of volcanic gases, including hydrogen sulfide, methane, ammonia and carbon dioxide gas to an electrical discharge – tell us that volcanic eruptions coinciding with lightning may have played a role in synthesizing large quantities and a variety of biologically crucial molecules on the primitive Earth, Parker, now a graduate student at Georgia Institute of Technology, told LiveScience.

"The gas mixture Miller used in this experiment was likely not ubiquitous throughout early Earth's atmosphere on a global scale, but it may have been common on a more local scale where there was heavy volcanic activity," Parker said.

Parallel to the Urey-Miller experiment 

By comparison, the famous Urey-Miller experiment in 1953 exposed hydrogen, steam, methane and ammonia to an electrical discharge. The initial results included far fewer organic molecules – only five amino acids. However, Bada and his team reanalyzed these old samples along with previously unpublished results with modern techniques, revealing a much greater variety of biologically important products. 

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