Object #1: The Miller-Urey Apparatus

The Miller-Urey Apparatus on display in the Prehistoric Journey exhibit at the Denver Museum of Nature & Science.

In 1952, Stanley Miller, a graduate student at the University of Chicago, had an idea for an experiment.  He had studied the ideas about the origin of life developed by Alexander Oparin and J.B.S. Haldane, who earlier in the 20th century had suggested that the essential organic molecules needed to make living cells from nonliving matter, would have assembled easily and spontaneously in the watery pools dotting the young Earth.  Early Earth, they thought, was awash in methane (CH4), ammonia(NH3) and water (H2O).  A spark of lightning or even shining ultraviolet light from the sun might reassemble these atoms of carbon, nitrogen, oxygen and hydrogen into amino acids (like NH2CH2COOH).

Were the original building blocks of life simply self-assembled from some of the most common compounds in the universe?

"Lets try it!", thought Miller. Lets simulate the atmosphere of the primitive Earth, zap it with some electrical sparks to simulate lightening, and see if anything happens. Yet when he first suggested the experiment, his graduate advisor, Harold Urey, was skeptical.  He thought it wouldn't work - it couldn't be that easy.  But Miller was insistent, and Urey was no fool.

Far from it.  Harold Urey is one of the fathers of modern planetary science (along with Gerard Kuiper and Eugene Shoemaker).  He was the first person to apply sophisticated chemistry to models of the formation of the Solar System and the Earth, founding a field known as "cosmochemistry", and contributing insights that are still very important to our understanding of planetary origins and evolution.  Oh and he won a Nobel Prize for discovering deuterium (heavy hydrogen).

(Incidentally, Urey is also my academic grandfather - that is, the PhD advisor of my PhD advisor John Lewis.  Lewis liked to joke hat he -Urey's final grad student- drove old Harold over the edge.  But he had a large file drawer of their correspondence about all matters cosmochemical, out of which he'd occasionally pull out a letter (see glossary - an archaic form of communication actually written or typed on paper.) from Urey relevant to a scientific discussion we were having.) But I digress...

Urey recognized that Miller's idea, which he thought was a long shot, was worth a try, because the implications of success would be huge.  So Stanley set about assembling a loop of flasks and glass tubes, into which he added water, ammonia and methane.  The water was heated to get it to evaporate, then as it circulated through the tubes it was zapped with simulated lightening and cooled to condense back into the original flask, where it would evaporate and continuously cycle through, simulating the cycle of evaporation, rainfall and lightening (in the presence of NH3 and CH4) on the primitive Earth.

After about one week, the water had turned into an ugly brown mixture.  When they opened it up and analyzed this sludge... voila!  It was full of amino acids, not to mention sugars and other compounds important for life.

This result, and those that followed, proved that the chemical building blocks of life are made easily from common materials available all over the universe.  Our ideas about the early Earth have changed in the intervening decades, and we are still chasing the exact sequence of steps from non-life to life.  But today the Miller-Urey experiment is seen as a bold and crucial step in our still evolving understanding of the origin of life.

You can see the original apparatus on display here at the Museum in the Prehistoric Journey exhibit.