A classic experiment exploring the origin of life has, more than a half-century later, yielded new results.
In 1953, Stanley L. Miller, then a graduate student of Harold C. Urey at the University of Chicago, put ammonia, methane and hydrogen — the gases believed to be in early Earth’s atmosphere — along with water in a sealed flask and applied electrical sparks to simulate the effects of lightning. A week later, amino acids, the building blocks of proteins, were generated out of the simple molecules.
Enshrined in high school textbooks, the Miller-Urey experiment raised expectations that scientists could unravel the origins of life with simple chemistry experiments.
The excitement has long since subsided. The amino acids never grew into the more complex proteins. Scientists now think the composition of air on early Earth was much different from what Dr. Miller used, leading some to question whether the Miller-Urey experiment had any relevance to the still unsolved problem of the origin of life.
After Dr. Miller’s death in May last year, Dr. Jeffrey L. Bada of the Scripps Institution of Oceanography in San Diego, who had been one of Dr. Miller’s graduate students, discovered cardboard boxes containing hundreds of vials of dried residues collected from the experiments conducted in 1953 and 1954.
Consulting Dr. Miller’s notebooks, Dr. Bada discovered that Dr. Miller had constructed two variations of the original apparatus. One simply used a different spark generator. The second injected steam onto the sparks.
That caught Dr. Bada’s attention, because the addition of steam seemed to replicate what might have existed in lagoons and tidal pools around volcanoes.
This spring, Adam P. Johnson, a graduate student at Indiana University who was visiting Dr. Bada’s laboratory on an internship, jumped on the opportunity to work on the vials produced by an experiment he had read about in high school textbooks, although the historic material did not look remarkable. “There were just a brown residue at the bottom of a old vial,” Mr. Johnson said.
In his 1953 paper, Dr. Miller reported that he had detected five amino acids produced by the original apparatus. Mr. Johnson’s work, using modern techniques, revealed small amounts of nine additional amino acids in those samples. In the residues from the apparatus with the steam injector, the scientists detected 22 amino acids including 10 that had never been identified before from the Miller-Urey experiment. … – nyt
… Jeffrey Bada of the Scripps Institution of Oceanography in California and colleagues re-analysed the original 50-year-old samples left by Stanley Miller of the University of Chicago, in 1953 and 1954. His was the first experiment ever to produce amino acids, the building blocks of proteins, from inorganic molecules and a spark of electricity.
Bada’s team discovered more organic molecules than Miller had been able to detect, and also showed that a secondary experiment – one that Miller carried out but never published – offers the best clue to how life on Earth began some 4 billion years ago. …
One criticism of Miller’s experiment is that he got the atmosphere of early Earth slightly wrong. The new discoveries could give it a second life. The conditions in Miller’s flasks may not replicate the ones covering the entire surface of Earth, but they could have been found in small regions around the planet. According to Bada, Miller’s gases could have been spat out by the many volcanoes that dotted the planet at the time.
All that would then be needed is electricity – and many large volcanic eruptions are accompanied by spectacular lightning. This was the case, for instance, when the Chaitén volcano in Chile erupted for the first time in 9000 years in May 2008 (see image, right).
“Instead of Darwin’s warm little pond being the entire ocean, the warm little pond could have consisted of volcanic island tide pools and lagoons,” says Bada.
Why would the bit of extra steam in the volcanic apparatus make such a great difference? One possible explanation is that the steam pushes newly formed amino acids away from the sparks before they are able to react further and form other compounds.
“This is an exciting result leading toward greater understanding of how life might have arisen on Earth,” says Carl Pilcher, director of the NASA Astrobiology Institute.
The findings could also give clues to life on other planets- ns