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Primordial Soup: Interview with Stanley Miller
An anonymous reader writes "Stanley Miller's classic 'primordial soup' experiments showed that 13 of the 21 amino acids necessary for life could be made in a glass flask. For its fifty-year commemoration, Miller is interviewed today and reflects on what Carl Sagan
called 'the single most significant step in convincing many scientists that life is likely to be abundant in the cosmos.'"
Primordial Recipe: Spark and Stir
Date Wednesday, May 14 @ 00:48:06
Topic Extrasolar Life
No single experiment, according to Carl Sagan, has done more to convince scientists that life is 'likely abundant in the cosmos' than the work fifty years ago by then graduate student, Stanley Miller. This week celebrates his milestone publication, and Astrobiology Magazine interviewed him about his work and reflections today.
Primordial Recipe: Spark and Stir
by Astrobiology Magazine staffwriter
Fifty years ago on May 15, 1953, a University of Chicago graduate student, Stanley Miller, published a landmark two-page paper in Science magazine. He considered if amino acids could be made from what was known about the early Earth's atmosphere. Could the building blocks of life be cooked up?
"... some warm little pond, with all sorts of ammonia and phosphoric salts, light, heat, electricity etc...", Charles Darwin, on the origins of life in tidal pools
Credit:Smithsonian
Miller began his paper:
"The idea that the organic compounds that serve as the basis of life were formed when the earth had an atmosphere of methane, ammonia, water and hydrogen instead of carbon dioxide, nitrogen, oxygen and water was suggested by Oparin and has been given emphasis by Urey and Bernal. In order to test this hypothesis..."
When Miller first presented his experimental findings to a large seminar, it is reported that at one point, Enrico Fermi politely asked if it was known whether this kind of process could have actually taken place on the primitive Earth. Harold Urey, Stanley's research advisor, immediately replied, saying 'If God did not do it this way, then he missed a good bet'. The seminar ended amid the laughter and, as the attendees filed out, some congratulated Stanley on his results.
Although Miller had submitted his paper in mid-December 1952, one reviewer did not believe the results and delayed its publication until May 15th. Later Carl Sagan would do many experiments varying the chemical percentages, but described the Miller-Urey experiments as "the single most significant step in convincing many scientists that life is likely to be abundant in the cosmos."
Early Earth: Flash in a Flask
Even today, only a few definitive things are known about what the Earth might have been like four billion years ago. It is thought that the early sun radiated only 70 percent of its modern power. No free oxygen could be found in Earth's atmosphere. The rocky wasteland lacked life. Absent were viruses, bacteria, plants and animals. Even the temperature itself is uncertain, since three schools of thought today maintain that the Earth could have been alternatively frozen, temperate or steamy.
Charles Darwin imagined life springing from a temperate world, with small ponds or runoff channels. Compared to diluted chemistry in a vast ocean, repeated evaporation and refilling have possible advantages, to find just the right concentrations somewhere so that biochemistry could begin. Glaciers, volcanoes, geysers and cometary debris potentially resupplied this primordial pond with both energy and more complex organic compounds. That is a scenario requiring relatively temperate starting conditions, and more extreme possibilities are also in the mix.
If the early Earth was a cauldron of volcanic activity, then seepage of acidic gases and heating might have circulated vital compounds to the surface. These vents may have been underwater, and precursors to biochemistry like acetic acid may have become reactive in combination with carbon monoxide. Alternatively, if the early Earth lacked any greenhouse of blanketing carbon dioxide, life could still have begun in a ball of ice. When combined with water, even a thin atmosphere of organics (formaldehyde, cyanide and ammonia) can create some building blocks of life (such as the amino acid, glycine). Thawing this 'snowball Earth' could then be triggered by a chance collision with large comets or meteors.
Terrestrial options for ea
from October 1996: Exobiology interview
On a related note: exobiology vs astrobiology? which do people prefer? (The definitions are in the links)
Suicide Booth: You are now dead! Thank you for using Stop and Drop, America's favorite since 2008.
Racemic mixtures are not decompsed anything. They are mixtures of "mirror-image" molecules. A completely racemized mixture is one with equal numbers of "left" and "right" members. Presence of both will not prevent you from using one or the other.
Look at you set of hands, one is racemic "left" and the other is racemic "right". You have a completely racemized mixture of hands. This does not deny you use of your left hand.
If amino acid procduction is industrial, usually you get (depending on the process) a mixture of the two racimic (D and L) formations that an amino acid can take. They are mirror images of each other.
Why is this important, well on planet Earth, almost all amino acids involed in life are of type L. (Metorites and non-living processes contribute the majority, if not all, of the D racemes discovered today)
Why only L-amino acids? Today we do not "know" with 100% certainty, but the theory is a living system, for whatever reason, started producing L-amino acids, which unbalanced the ratio. Other living systems (or perhaps the same one) which harvestd these L-amino acids survived and thrived in this L-amino acid rich environment while those that required D-amino acids may have never existed or may have died out due to competition.
Replies to several different posts (sorry for the lack of attribution): /Ah, but does he mention that his amino acids... /broke down as fast as they were made (in a /carefully customised device, not in the wild), /and were completely racemised at formation? Or /that no evidence of a reducing atmosphere exists?
/Also Miller had to create a "trap" to collect the /amino acids being formed to protect them from /breaking down again. What would the comparable /"natural" trap be?
/As a student of Biological Anthropology, I have /had the oppertunity to take a history of /biological anthropology in which Miller was /mentioned. Interesting guy, but the theory is not /supported any more except by the few staunchest /researchers. In other words, this is pop science. /It survives in text books (like many other /evolutionary inaccuracies that nobody seems to be /willing to update). In truth, the experiment did /not conclude much. In short, the amino acid /theory in reality did not produce very much at /all
Amino acids tend not to break down much. They are exceedingly stable once made. Those that happened to wander back into the electric current might have suffered, but the majority would have stayed safely in solution. The chemical reaction was proceeding in the gas phase; the products were sequestered in the water.
The products are racemic amino acids. Several plausible hypotheses have been put as to how it happened that the L amino acids became predominate: circular dichroism in natural radiation, preferential decompostion of D 14C labeled amino acids, etc.
We don't know all that much about the exact composition of the atmosphere at every time in the earth's history, but the fact that high-energy processes can give amino acids from simple precursors trumps all nit-picking.
The natural trap would be water. High energy events are always happening in the atmosphere (lightning, UV rays, cosmic rays). Lighting blasts convert nitrogen to nitrates. Roughly 10% of the nitrate in soil comes from nitrogen transformed by lightning, and the nitrates are trapped by water. The point to take home from the Miller experiment is that the small, high-energy intermediates formed by these processes can combine to form biologially complex building blocks.
This is just wrong. The conclusion drawn from the results of the experiment was revolutionary. It is of at least on the scale of Wohler's synthesis of urea, a biochemical, from "dead" cyanogen and ammonia.
If Slashdot were chemistry it would look like this:Cadaverine