Astrobiology Collection: Miller-Urey Apparatus
Posted 2/28/2011 12:02 AM by David Grinspoon |
CommentsObject #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.
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