An experiment carried out more than 50 years ago has revealed that volcanoes may have played a crucial role in the formation of the first organic building blocks of life, which led to the first replicating lifeforms on earth about 4.5 billion years ago.
Laboratory samples left over from a 1958 experiment in an American university have revealed, with the help of modern analytical techniques, that scientists had unwittingly discovered that gases given off by volcanoes can be used to make the vital sulphur-containing amino acids of proteins. The discovery is further vindication of the pioneering experiments of Stanley Miller, who as a young graduate student demonstrated that a "primordial soup" of water and a few simple gases such as ammonia and hydrogen can, with the help of electricity discharges to simulate lightning, produce the more complex organic molecules of life.
Dr Miller, who died in 2007, conducted many of his experiments at the University of California, San Diego, and received worldwide recognition for his earliest work in 1953.
But there was one set of experiments carried out five years later with the volcanic gas, hydrogen sulphide, that he seemed to have put to one side without fully realising what he had found. Jeffrey Bada, a former student of Dr Miller's who is now a Professor of Marine Chemistry at Scripps Institution of Oceanography in San Diego, discovered the residue samples from the original 1958 experiment and analysed the contents using highly sensitive chemical techniques that were not available 50 years ago. The study, published in the journal Proceedings of the National Academy of Sciences, revealed that Dr Miller was the first scientist to synthesise important sulphur-containing amino acids in this simulation of the environment of early earth. In total, Professor Bada's team found 23 amino acids and four similar compounds known as amines in Dr Miller's discarded samples, including seven substances containing sulphur.
"This experiment marks the first synthesis of sulphur amino acids from spark-discharge experiments designed to imitate primordial environments. The relative yield of some amino acids... are the highest ever found in a spark-discharge experiment," the scientists write. Professor Bada said that Dr Miller's team was only able to use a relatively primitive technique called paper chromatography to detect the presence of organic molecules.
The creation of sulphur-containing amino acids using similar techniques was eventually confirmed in the 1970s, including in Dr Miller's lab. "Unbeknownst to him, he'd already done it in 1958," Professor Bada said.