das miller urey experiment

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Introduction

Original protocol and results

Additional trials and discoveries, significance.

Miller-Urey experiment

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National Center for Science Education - The Miller-Urey Experiment
National Center for Biotechnology Information - PubMed Central - Conducting Miller-Urey Experiments
Nature - The role of borosilicate glass in Miller–Urey experiment
Table Of Contents

Miller-Urey experiment , experimental simulation conducted in 1953 that attempted to replicate the conditions of Earth ’s early atmosphere and oceans to test whether organic molecules could be created abiogenically, that is, formed from chemical reactions occurring between inorganic molecules thought to be present at the time. The experiment—the results of which were published in the journal Science as “A Production of Amino Acids Under Possible Primitive Earth Conditions”—documented the production of amino acids and other organic molecules, thereby demonstrating that chemical evolution (that is, the formation of complex chemicals from simple ones) is possible. The Miller-Urey experiment is used as evidence to support hypotheses about the origins of life .

The Miller-Urey experiment was conducted by American chemist Stanley Miller under the supervision of American scientist Harold C. Urey at the University of Chicago . The experiment was designed to test ideas introduced independently in the 1920s by Russian biochemist Aleksandr Oparin and British physiologist J.B.S. Haldane , both of whom suggested that organic molecules, such as amino acids and sugars , could be formed from abiogenic materials when acted on by an external energy source within the context of a reducing atmosphere, that is, one with low levels of free oxygen ( see also oxidation-reduction reaction ). At the time, it was thought that the atmosphere of early Earth between 4 billion and 3.5 billion years ago was primarily composed of ammonia and water vapour. Oparin and Haldane noted that from this “primordial soup” of materials the first organic molecules arose, which became the precursors to molecules of ever-increasing complexity that resulted in the development of living cells ( see also abiogenesis ).

To test Oparin and Haldane’s ideas, Miller and Urey designed a closed experiment in a laboratory . They constructed an enclosed glass apparatus with two large boiling flasks connected to each other with glass tubing, in which water could pool, gases could mix, and matter could change phases between liquid and gas. A large lower chamber was filled with water (a boiling flask that stood in for the oceans), and the water was boiled to produce water vapour, which ascended into the large upper chamber (a boiling flask that simulated Earth’s early atmosphere). Additional tubing allowed material to descend from the upper chamber through a condenser, where water vapour would condense into liquid and fall into a collection trap from which samples could be taken. This trap was set slightly below the lower chamber, but it was also connected to the lower chamber above the water line. The researchers removed the air from the apparatus, replacing it throughout with ammonia, hydrogen , and methane gases, and they let the various materials cycle through liquid and gas phases.

In an early run of the experiment, Miller discovered that the energy produced from boiling water was not enough to drive the chemical reactions necessary to approximate the conditions of early Earth, so in a second version of the experiment (the one whose results were published in 1953) he added electrodes to the upper chamber. After the water was boiled, the mix of gases circulated through the system past electrodes that discharged sparks (which simulated lightning ), and a condenser converted some of the gas to liquid so that it could return to the lower chamber. This process ran continuously for one week. After this period, the contents of the apparatus had visibly changed colour. A red- and yellow-coloured solution had started to collect in the trap after running the experiment for a few days and became a broth of red and brown by the experiment’s end.

To determine the identity of the molecules that resulted from their procedure, Miller and Urey terminated the reaction, added chemicals that prevented the growth of microbes (which could be introduced to the closed system when samples were collected from the broth), extracted samples of the solution, and analyzed them using paper chromatography . They discovered several types of simple organic molecules in the samples, including amino acids, some of which were relevant as the building blocks of the proteins that are present in all living organisms. Miller was able to identify the amino acids glycine , alpha-alanine (α-alanine), and beta-alanine (β-alanine) confidently; however, he was less certain about the presence of aspartic acid and α-amino- n -butyric acid, whose signs in the analysis were weak.

Miller modified the original experiment several times, and each modification captured possible variations in Earth conditions that might influence the system’s products. Some of Miller’s subsequent experiments used different energy sources, such as an electrical source that produced a silent discharge instead of a spark, and improved gas circulation through the addition of glass tubing. Other researchers also repeated the experiment during the 1950s using different energy sources, such as ultraviolet light , and used different atmospheric gases (such as carbon dioxide , hydrogen sulfide , and nitrogen ) in various combinations, which also resulted in a mix of organic chemicals but only a handful of amino acids.

Miller and others would repeat the experiment several times in subsequent decades. He reran the experiment in the early 1970s using better analytical equipment, which revealed the presence of 33 different amino acids, including more than half of the 20 or so that appear in proteins present in living things. Researchers later criticized Miller for using what they considered to be the wrong gases in the experiment; carbon dioxide and nitrogen, not ammonia and methane, were shown later to be the primary gases in Earth’s early atmosphere, with ammonia and methane occurring only in minor amounts. Miller’s 1983 trial replaced methane and ammonia with carbon dioxide and nitrogen; however, fewer amino acids were produced than in the original published experiment. This result was attributed later to a buildup of nitrites in the system, which made the mixture more acidic and caused the amino acids to break down before they could be identified.

American chemist Jeffrey Bada of the Scripps Institution of Oceanography reran the experiment in 2007. In addition to simulating an atmosphere filled with carbon dioxide and nitrogen, he added iron and carbonates to the system (two materials that would have been present in large amounts on ancient Earth)—which neutralized both the nitrites and the acids in the system, thereby allowing the amino acids to persist. A group of Spanish and Italian researchers suggested in 2021 that materials in the glass apparatus itself may have also catalyzed the chemical reactions taking place within it; the various chemicals in the experiment were shown to have reacted with the interior surface of the glass to release silicates (which, in turn, reacted with other chemicals) while also leaving behind small imperfections and cracks on the interior surface that may have served as chambers for other chemical reactions.

Starting in the early 2000s, researchers examined archived vials containing samples of material collected from Miller’s experiments during the 1950s. Aided by modern analytical equipment, they discovered far more than the five amino acids Miller reported in his papers; Miller’s experiments conducted in 1953 and 1958 were each shown to have yielded more than 20 amino acids.

The experiment showed that amino acids, which are important components of proteins (which are critical to life on Earth), could have arisen from inorganic compounds during Earth’s prebiotic phase. It also demonstrated that the speculation that life could have originated through chemical reactions among nonliving materials is possible and that this hypothesis could be tested scientifically. The Miller-Urey experiment sparked research on how simple organic molecules might polymerize into more complex molecules, a process that may have produced the first living cells. Scientists have also considered the possibility that meteors brought the first organic molecules, formed in space, to Earth, and they continue to modify the Miller-Urey protocol to test new ideas about chemical reactions in primitive Earth conditions.

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Miller-Urey Experiment

The Miller-Urey Experiment was a landmark experiment to investigate the chemical conditions that might have led to the origin of life on Earth. The scientist Stanley Miller, under the supervision of the Nobel laureate scientist Harold Urey conducted it in 1952 at the University of Chicago. They tried to recreate the conditions that could have existed in the first billion years of the Earth’s existence (also known as the Early Earth) to check the said chemical transformations.

Miller-Urey Experiment And The Primordial Soup Theory

The experiment tested the primordial or primeval soup theory developed independently by the Soviet biologist A.I. Oparin and English scientist J.B.S. Haldane in 1924 and 1929 respectively. The theory propounds the idea that the complex chemical components of life on Earth originated from simple molecules occurring naturally in the reducing atmosphere of the Early Earth, sans oxygen. Lightning and rain energized the said atmosphere to create simple organic compounds that formed an organic “soup”. The so-called soup underwent further changes giving rise to more complex organic polymers and finally life.

The Miller-Urey Experiment In Support Of Abiogenesis

From what was explained in the previous paragraph, it can undoubtedly be considered as a classic experiment to demonstrate abiogenesis. For those who are not conversant with the term, abiogenesis is the process responsible for the development of living beings from non-living or abiotic matter. It is thought to have taken place on the Earth about 3.8 to 4 billion years ago.

Miller-Urey Experiment Apparatus and Procedure

The groundbreaking experiment used a sterile glass flask of 5 liters attached with a pair of electrodes, to hold water (H 2 O), methane (CH 4 ), ammonia (NH 3 ) and hydrogen (H 2 ), the major components of primitive Earth. This was connected to another glass flask of 500 ml capacity half filled with water. On heating it, the water vaporized to fill the larger container with water vapor. The electrodes induced continuous electrical sparks in the gas mixture to simulate lightning. When the gas was cooled, the condensed water made its way into a U-shaped trap at the base of the apparatus.

After electrical sparking had continued for a day, the solution in the trap turned pink in color. At the end of a week, the boiling flask was removed, and mercuric chloride added to prevent microbial contamination. After stopping the chemical reaction, the scientist duo examined the cooled water collected to find that 10-15% of the carbon present in the system was in the form of organic compounds. 2% of carbon went into the formation of various amino acids, including 13 of the 22 amino acids essential to make proteins in living cells, glycine being the most abundant.

Though the result was the production of only simple organic molecules and not a complete living biochemical system, still the simple prebiotic experiment could, to a considerable extent, prove the primordial soup hypothesis.

Miller-Urey Experiment Animation

Chemistry of the miller and urey experiment.

The components of the mixture can react among themselves to produce formaldehyde (CH 2 O), hydrogen cyanide (HCN) and other intermediate compounds.

CO 2 → CO + [O] (atomic oxygen)

CH 4 + 2[O] → CH 2 O + H 2 O

CO + NH 3 → HCN + H 2 O

CH 4 + NH 3 → HCN + 3H 2

The ammonia, formaldehyde and HCN so produced react by a process known as Strecker synthesis to form biomolecules including amino acids.

CH 2 O + HCN + NH 3 → NH 2 -CH 2 -CN + H 2 O

NH 2 -CH 2 -CN + 2H 2 O → NH 3 + NH 2 -CH 2 -COOH (glycine)

In addition to the above, formaldehyde and water can react by Butlerov’s reaction to produce a variety of sugars like ribose, etc.

Though later studies have indicated that the reducing atmosphere as replicated by Miller and Urey could not have prevailed on primitive Earth, still, the experiment remains to be a milestone in synthesizing the building blocks of life under abiotic conditions and not from living beings themselves.

https://www.bbc.co.uk/bitesize/guides/z2gjtv4/revision/1

https://www.juliantrubin.com/bigten/miller_urey_experiment.html

Article was last reviewed on Thursday, February 2, 2023

One response to “Miller-Urey Experiment”

This experiment is currently seen as not sufficient to support abiogenesis. See Stephen C. Meyer, James Tour.

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Conducting Miller-Urey Experiments

Eric t. parker.

1 School of Chemistry and Biochemistry, Georgia Institute of Technology

James H. Cleaves

2 Earth-Life Science Institute, Tokyo Institute of Technology

3 Institute for Advanced Study

Aaron S. Burton

4 Astromaterials Research and Exploration Science Directorate, NASA Johnson Space Center

Daniel P. Glavin

5 Goddard Center for Astrobiology, NASA Goddard Space Flight Center

Jason P. Dworkin

Manshui zhou, jeffrey l. bada.

6 Geosciences Research Division, Scripps Institution of Oceanography, University of California at San Diego

Facundo M. Fernández

In 1953, Stanley Miller reported the production of biomolecules from simple gaseous starting materials, using an apparatus constructed to simulate the primordial Earth's atmosphere-ocean system. Miller introduced 200 ml of water, 100 mmHg of H 2 , 200 mmHg of CH 4 , and 200 mmHg of NH 3 into the apparatus, then subjected this mixture, under reflux, to an electric discharge for a week, while the water was simultaneously heated. The purpose of this manuscript is to provide the reader with a general experimental protocol that can be used to conduct a Miller-Urey type spark discharge experiment, using a simplified 3 L reaction flask. Since the experiment involves exposing inflammable gases to a high voltage electric discharge, it is worth highlighting important steps that reduce the risk of explosion. The general procedures described in this work can be extrapolated to design and conduct a wide variety of electric discharge experiments simulating primitive planetary environments.

Introduction

The nature of the origins of life on Earth remains one of the most inscrutable scientific questions. In the 1920s Russian biologist Alexander Oparin and British evolutionary biologist and geneticist John Haldane proposed the concept of a "primordial soup" 1,2 , describing the primitive terrestrial oceans containing organic compounds that may have facilitated chemical evolution. However, it wasn't until the 1950s when chemists began to conduct deliberate laboratory studies aimed at understanding how organic molecules could have been synthesized from simple starting materials on the early Earth. One of the first reports to this end was the synthesis of formic acid from the irradiation of aqueous CO 2 solutions in 1951 3 .

In 1952, Stanley Miller, then a graduate student at the University of Chicago, approached Harold Urey about doing an experiment to evaluate the possibility that organic compounds important for the origin of life may have been formed abiologically on the early Earth. The experiment was conducted using a custom-built glass apparatus ( Figure 1A ) designed to simulate the primitive Earth. Miller's experiment mimicked lightning by the action of an electric discharge on a mixture of gases representing the early atmosphere, in the presence of a liquid water reservoir, representing the early oceans. The apparatus also simulated evaporation and precipitation through the use of a heating mantle and a condenser, respectively. Specific details about the apparatus Miller used can be found elsewhere 4 . After a week of sparking, the contents in the flask were visibly transformed. The water turned a turbid, reddish color 5 and yellow-brown material accumulated on the electrodes 4 . This groundbreaking work is considered to be the first deliberate, efficient synthesis of biomolecules under simulated primitive Earth conditions.

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Figure 1. Comparison between the two types of apparatuses discussed in this paper. The classic apparatus used for the original Miller-Urey experiment ( A ) and the simplified apparatus used in the protocol outlined here ( B ). Click here to view larger image .

After the 1953 publication of results from Miller's classic experiment, numerous variations of the spark discharge experiment, for example using other gas mixtures, were performed to explore the plausibility of producing organic compounds important for life under a variety of possible early Earth conditions. For example, a CH 4 /H 2 O/NH 3 /H 2 S gas mixture was tested for its ability to produce the coded sulfur-containing α-amino acids, although these were not detected 6 . Gas chromatography-mass spectrometry (GC-MS) analysis of a CH 4 /NH 3 mixture subjected to an electric discharge showed the synthesis of α-aminonitriles, which are amino acid precursors 7 . In 1972, using a simpler apparatus, first introduced by Oró 8 ( Figure 1B ), Miller and colleagues demonstrated the synthesis of all of the coded α-amino acids 9 and nonprotein amino acids 10 that had been identified in the Murchison meteorite to date, by subjecting CH 4 , N 2 , and small amounts of NH 3 to an electric discharge. Later, using this same simplified experimental design, gas mixtures containing H 2 O, N 2 , and CH 4 , CO 2 , or CO were sparked to study the yield of hydrogen cyanide, formaldehyde, and amino acids as a function of the oxidation state of atmospheric carbon species 11 .

In addition to the exploration of alternative experimental designs over the years, significant analytical advances have occurred since Miller's classic experiment, which recently aided more probing investigations of electric discharge experimental samples archived by Miller, than would have been facilitated by the techniques Miller had access to in the 1950s. Miller's volcanic experiment 12 , first reported in 1955 4 , and a 1958 H 2 S-containing experiment 13 were shown to have formed a wider variety, and greater abundances, of numerous amino acids and amines than the classic experiment, including many of which that had not been previously identified in spark discharge experiments.

The experiment described in this paper can be conducted using a variety of gas mixtures. Typically, at the very least, such experiments will contain a C-bearing gas, an N-bearing gas, and water. With some planning, almost any mixture of gases can be explored, however, it is important to consider some chemical aspects of the system. For example, the pH of the aqueous phase can have a significant impact on the chemistry that occurs there 14 .

The method described here has been tailored to instruct researchers how to conduct spark discharge experiments that resemble the Miller-Urey experiment using a simplified 3 L reaction vessel, as described in Miller's 1972 publications 9,10 . Since this experiment involves a high voltage electric arc acting on inflammable gases, it is crucial to remove O 2 from the reaction flask to eliminate the risk of explosion, which can occur upon combustion of reduced carbon-bearing gases such as methane or carbon monoxide, or reaction of H 2 with oxygen.

There are additional details that should be kept in mind when preparing to conduct the experiment discussed here. First, whenever working with glass vacuum lines and pressurized gases, there exists the inherent danger of both implosion and over-pressuring. Therefore, safety glasses must be worn at all times. Second, the experiment is typically conducted at less than atmospheric pressure. This minimizes the risk of over-pressuring the manifold and reaction flask. Glassware may be rated at or above atmospheric pressure, however, pressures above 1 atm are not recommended. Pressures may increase in these experiments as water-insoluble H 2 is liberated from reduced gases (such as CH 4 and NH 3 ). Over-pressuring can lead to seal leakage, which can allow atmospheric O 2 to enter the reaction flask, making it possible to induce combustion, resulting in an explosion. Third, it should be borne in mind that modification of this protocol to conduct variations of the experiment requires careful planning to ensure unsafe conditions are not created. Fourth, it is highly recommended that the prospective experimenter read through the entire protocol carefully several times prior to attempting this experiment to be sure he or she is familiar with potential pitfalls and that all necessary hardware is available and in place. Lastly, conducting experiments involving combustible gases require compliance with the experimenter's host institution's Environmental Health and Safety departmental guidelines. Please observe these recommendations before proceeding with any experiments. All steps detailed in the protocol here are in compliance with the authors' host institutional Environmental Health and Safety guidelines.

1. Setting Up a Manifold/Vacuum System

Use ground glass joints and glass plugs with valves on the manifold. Ensure that all O-rings on the plugs are capable of making the necessary seals. If using glass joints, a sufficient amount of vacuum grease can be applied to help make a seal, if necessary. Silicon vacuum grease can be used to avoid potential organic contamination.
Use glass stopcocks on the manifold. Apply the minimum amount of vacuum grease necessary to make a seal.
Measure the manifold volume. This volume will be used for calculations related to final gas pressures in the 3 L reaction flask and should be known as precisely as possible.
Unless the manifold has enough connections to accommodate all gas cylinders simultaneously, connect one cylinder at a time to the manifold. Include in this connection, a tap allowing the manifold to be isolated from the ambient atmosphere.
Use suitable, clean, inert, and chemical and leak resistant tubing and ultratorr vacuum fittings to connect the gas cylinders to the manifold. Ultratorr fittings, where used, are to be finger-tightened.
To ensure rapid attainment of vacuum and to protect the pump, insert a trap between the manifold and the vacuum pump. A liquid nitrogen finger-trap is recommended as it will prevent volatiles such as NH 3 , CO 2 , and H 2 O from entering the pump. Care should be taken, as trapped volatiles, upon warming, may overpressure the manifold and result in glass rupture.
Connect to the manifold, a manometer or other vacuum gauge capable of 1 mmHg resolution or better. While various devices can be used, a mercury manometer, or MacLeod gauge, is preferable as mercury is fairly nonreactive.
Measure and record the ambient temperature using a suitable thermometer.

2. Preparation of Reaction Flask

Clean the tungsten electrodes by gently washing with clean laboratory wipes and methanol, and drying in air.
Introduce a precleaned and sterilized magnetic stir bar, which will ensure rapid dissolution of soluble gases and mixing of reactants during the experiment.
Attach the tungsten electrodes to the 3 L reaction flask using a minimal amount of vacuum grease, with tips separated by approximately 1 cm inside the flask. Fasten with clips.
Insert an adapter with a built-in stopcock into the neck of the 3 L reaction flask and secure with a clip.
Lightly grease all connections to ensure a good vacuum seal.
Open all valves and stopcocks on the manifold, except Valve 6 and Stopcock 1 ( Figure 4 ), and turn on the vacuum pump to evacuate the manifold. Once a stable vacuum reading of <1 mmHg has been attained, close Valve 1 and allow the manifold to sit for ~15 min to check for vacuum leaks. If none are detected, proceed to step 2.8. Otherwise troubleshoot the various connections until the leaks can be identified and fixed.
Apply magnetic stirring to the reaction vessel. Open Valve 1 and Stopcock 1 ( Figure 4 ) to evacuate the headspace of the 3 L reaction flask until the pressure has reached <1 mmHg.
Close Valve 1 ( Figure 4 ) and monitor the pressure inside the 3 L reaction flask. The measured pressure should increase to the vapor pressure of water. To ensure that no leaks exist, wait ~5 min at this stage. If the pressure (as read on the manometer) increases while Valve 1 is closed during this step, check for leaks in Stopcock 1 and the various reaction flask connections. If no leak is found, proceed to the next step.

3. Introduction of Gaseous NH 3

Calculate the necessary pressure of gaseous NH 3 to introduce into the manifold such that 200 mmHg of NH 3 will be introduced into the reaction flask. Details on how to do this are provided in the Discussion section.
Close Valves 1 and 6, and Stopcock 1 ( Figure 4 ) before introducing any gas into the manifold. Leave the other valves and stopcock open.
Introduce NH 3 into the manifold until a small pressure (approximately 10 mmHg) is reached and then evacuate the manifold to a pressure of <1 mmHg by opening Valve 1 ( Figure 4 ). Repeat 3x.
Introduce NH 3 into the manifold to reach the pressure determined in step 3.1.
Open Stopcock 1 ( Figure 4 ) to introduce 200 mmHg of NH 3 into the 3 L reaction flask. The NH 3 will dissolve in the water in the reaction flask and the pressure will fall slowly.
Once the pressure stops dropping, close Stopcock 1 ( Figure 4 ) and record the pressure read by the manometer. This value represents the pressure inside the flask and will be used to calculate the pressures for other gases that will be introduced into the manifold later.
Open Valve 1 ( Figure 4 ) to evacuate the manifold to a pressure of <1 mmHg.
Close Valve 2 ( Figure 4 ) and disconnect the NH 3 gas cylinder from the manifold.

4. Introduction of CH 4

Calculate the necessary pressure of CH 4 to be introduced into the manifold such that 200 mmHg of CH 4 will be introduced into the 3 L reaction flask. Example calculations are shown in the Discussion section.
Connect the CH 4 gas cylinder to the manifold.
Open all valves and stopcocks, except Valve 6 and Stopcock 1 ( Figure 4 ), and evacuate the manifold to a pressure of <1 mmHg.
Close Valve 1 once the manifold has been evacuated ( Figure 4 ).
Introduce CH 4 into the manifold until a small pressure (approximately 10 mmHg) is obtained. This purges the line of any contaminant gases from preceding steps. Open Valve 1 ( Figure 4 ) to evacuate the manifold to <1 mmHg. Repeat 2x more.
Introduce CH 4 into the manifold until the pressure calculated in step 4.1, is reached.
Open Stopcock 1 ( Figure 4 ) to introduce 200 mmHg of CH 4 into the 3 L reaction flask.
Close Stopcock 1 once the intended pressure of CH 4 has been introduced into the 3 L reaction flask ( Figure 4 ) and record the pressure measured by the manometer.
Open Valve 1 (Figure 4 ) to evacuate the manifold to <1 mmHg.
Close Valve 2 ( Figure 4 ) and disconnect the CH 4 cylinder from the manifold.

5. Introduction of Further Gases ( e.g. N 2 )

At this point, it is not necessary to introduce additional gases. However, if desired, it is recommended to add 100 mmHg of N 2 . In this case, calculate the necessary pressure of N 2 to be introduced into the manifold such that 100 mmHg of N 2 will be introduced into the 3 L reaction flask. Example calculations are shown in the Discussion section.
Connect the N 2 gas cylinder to the manifold.
Introduce N 2 into the manifold until a small pressure (approximately 10 mmHg) is obtained. Open Valve 1 ( Figure 4 ) to evacuate the manifold to <1 mmHg. Repeat 2x more.
Introduce N 2 into the manifold until the pressure calculated in step 5.1 is reached.
Open Stopcock 1 ( Figure 4 ) to introduce 100 mmHg of N 2 into the reaction flask.
Close Stopcock 1 once the intended pressure of N 2 has been introduced into the reaction flask, ( Figure 4 ) and record the pressure using the manometer.
Open Valve 1 ( Figure 4 ) to evacuate the manifold to <1 mmHg.
Close Valve 2 ( Figure 4 ) and disconnect the N 2 cylinder from the manifold.

6. Beginning the Experiment

Detach the reaction flask from the manifold by closing Stopcock 1 and Valve 1 ( Figure 4 ) once all gases have been introduced into the reaction flask, so that ambient air may enter the manifold and bring the manifold up to ambient pressure.
After carefully disconnecting the reaction flask from the manifold, set the flask somewhere it will not be disturbed ( e.g. inside an empty fume hood).
Disconnect the vacuum pump and carefully remove the cold trap and allow venting inside a fully operational fume hood.
Secure the Tesla coil connected to the high frequency spark generator.
Connect the opposite tungsten electrode to an electrical ground to enable the efficient passage of electrical current across the gap between the two electrodes.
Set the output voltage of the spark generator to approximately 30,000 V, as detailed by documents available from the manufacturer.
Prior to initiating the spark, close the fume hood sash, to serve as a safety shield between the apparatus and the experimenter. Turn the Tesla coil on to start the experiment, and allow sparking to continue for 2 weeks (or other desired period) in 1 hr on/off cycles.

7. End of Experiment

Stop the experiment by turning off the Tesla coil.
Open Stopcock 1 ( Figure 4 ) to slowly introduce ambient air into the reaction flask and facilitate the removal of the adapter and the tungsten electrodes so samples can be collected. If desired, a vacuum can be used to evacuate the reaction flask of noxious reaction gases.

8. Collecting Liquid Sample

Transfer the sample to a sterile plastic or glass receptacle. Plastic receptacles are less prone to cracking or breaking upon freezing, compared to glass receptacles.
Seal sample containers and store in a freezer capable of reaching temperatures of -20 °C or lower, as insoluble products may prevent the sample solution from freezing at 0 °C.

9. Cleaning the Apparatus

Use clean laboratory wipes to carefully remove vacuum grease from the neck of the apparatus, the adapter and stopcock, and the glass surrounding the tungsten electrodes.
Thoroughly clean the same surfaces described in step 9.1 with toluene to fully remove organic vacuum grease from the glassware. If using silicon grease, the high vacuum grease may remain on the glassware after pyrolysis, creating future problems, as detailed in the Discussion section.
Thoroughly clean the reaction flask with a brush and the following solvents in order: ultrapure water (18.2 MΩ cm, <5 ppb TOC), ultrapure water (18.2 MΩ cm, <5 ppb TOC) with 5% cleaning detergent, methanol, toluene, methanol, ultrapure water (18.2 MΩ cm, <5 ppb TOC) with 5% cleaning detergent, and finally ultrapure water (18.2 MΩ cm, <5 ppb TOC).
Cover all open orifices of the reaction flask with aluminum foil and wrap the adapter and its components in aluminum foil.
Once all the glassware has been wrapped in aluminum foil, pyrolyze for at least 3 hr in air at 500 °C.
Gently clean electrodes with methanol and let air dry.

10. Sample Analysis

Note: When preparing samples for analysis, the use of an acid hydrolysis protocol such as has been described in detail elsewhere 15 , is useful for obtaining more amino acids. Hydrolysis of a portion of the recovered sample provides the opportunity to analyze both free amino acids as well as their acid-labile precursors that are synthesized under abiotic conditions.

For amino acid analysis, use a suitable technique (such as liquid chromatography and mass spectrometry-based methods, or other appropriate approaches). Such analytical techniques include high performance liquid chromatography with fluorescence detection (HPLC-FD) 14 , and ultrahigh performance liquid chromatography with fluorescence detection in parallel with time-of-flight positive electrospray ionization mass spectrometry (UHPLC-FD/ToF-MS) 12,13 . This manuscript describes analysis using mass spectrometric analyses via a triple quadrupole mass spectrometer (QqQ-MS) in conjunction with HPLC-FD.

Representative Results

The products synthesized in electric discharge experiments can be quite complex, and there are numerous analytical approaches that can be used to study them. Some of the more commonly used techniques in the literature for analyzing amino acids are discussed here. Chromatographic and mass spectrometric methods are highly informative techniques for analyzing the complex chemical mixtures produced by Miller-Urey type spark discharge experiments. Amino acid analyses can be conducted using o -phthaldialdehyde/N-acetyl-L-cysteine (OPA/NAC) 16 , a chiral reagent pair that tags primary amino groups, yielding fluorescent diastereomer derivatives that can be separated on an achiral stationary phase. Figure 2 shows a chromatogram of an OPA/NAC-derivatized amino acid standard obtained by HPLC coupled to fluorescence detection and QqQ-MS. The amino acids contained in the standard include those typically produced in Miller-Urey type spark discharge experiments. The identities of these amino acids are listed in Table 1 . Representative fluorescence traces of a typical sample and analytical blank are shown in Figure 3 , demonstrating the molecular complexity of Miller-Urey type electric discharge samples. The sample chromatogram in Figure 3 was produced from a spark discharge experiment using the following starting conditions: 300 mmHg of CH 4 , 250 mmHg of NH 3 , and 250 ml of water.

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Figure 2. The 3-21 min region of the HPLC-FD/QqQ-MS chromatograms produced from the analysis of an OPA/NAC-derivatized amino acid standard . Amino acid peak identities are listed in Table 1 . The fluorescence trace is shown at the bottom and the corresponding extracted mass chromatograms are shown above. The electrospray ionization (ESI) QqQ-MS was operated in positive mode and monitored a mass range of 50-500 m/z. The ESI settings were: desolvation gas (N 2 ) temperature: 350 °C, 650 L/hr; capillary voltage: 3.8 kV; cone voltage: 30 V. The unlabeled peaks in the 367 extracted ion chromatogram are the 13 C 2 peaks from the 365 extracted ion chromatogram, as a result of the approximately 1% natural abundance of 13 C. Click here to view larger image .

Peak	Amino Acid
1	D-aspartic acid
2	L-aspartic acid
3	L-glutamic acid
4	D-glutamic acid
5	D-serine
6	L-serine
7	Glycine
8	b-Alanine
9	D-alanine
10	g-amino-n-butyric acid (g-ABA)
11	L-alanine
12	D-b-amino-n-butyric acid (D-b-ABA)
13	a-aminoisobutyric acid (a-AIB)
14	L-b-amino-n-butyric acid (L-b-ABA)
15	D/L-a-amino-n-butyric acid (D/L-a-ABA)
16	D-isovaline
17	L-isovaline
18	L-valine
19	e-amino-n-caproic acid (EACA)
20	D-valine
21	D-isoleucine
22	L-isoleucine
23	D/L-leucine

Table 1. Peak identities for amino acids detected in the standard and that are typically produced in Miller-Urey type spark discharge experiments.

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Figure 3. The 3-21 min region of the HPLC-FD chromatograms representative of Miller-Urey type spark discharge experiments. Peaks were identified and quantitated by retention time and mass analysis of target compounds compared to a standard and analytical blank. All target analytes with coeluting fluorescence retention times can be separated and quantitated using mass spectrometry, except for α-AIB and L-β-ABA (peaks 13 and 14), and D/L-norleucine, which coelutes with D/L-leucine (peak 23), under the chromatographic conditions used. D/L-norleucine was added as an internal standard to samples and analytical blanks during sample preparation. Amino acid separation was achieved using a 4.6 mm x 250 mm, 5 μm particle size Phenyl-Hexyl HPLC column. The mobile phase was composed of: A) ultrapure water (18.2 MΩ cm, <5 ppb TOC), B) methanol, and C) 50 mM ammonium formate with 8% methanol, at pH 8. The gradient used was: 0-5 min, 100% C; 5-15 min, 0-83% A, 0-12% B, 100-5% C; 15-22 min, 83-75% A, 12-20% B, 5% C; 22-35 min, 75-35% A, 20-60% B, 5% C; 35-37 min, 35-0% A, 60-100% B, 5-0% C; 37-45 min, 100% B; 45-46 min, 100-0% B, 0-100% C 46-55 min, 100% C. The flow rate was 1 ml/min. Click here to view larger image .

Numerous steps in the protocol described here are critical for conducting Miller-Urey type experiments safely and correctly. First, all glassware and sample handling tools that will come in contact with the reaction flask or sample need to be sterilized. Sterilization is achieved by thoroughly rinsing the items in question with ultrapure water (18.2 MΩ cm, <5 ppb TOC) and then wrapping them in aluminum foil, prior to pyrolyzing at 500 °C in air for at least 3 hr. Once the equipment has been pyrolyzed and while preparing samples for analysis, care must be taken to avoid organic contamination. The risk of contamination can be minimized by wearing nitrile gloves, a laboratory coat, and protective eyewear. Be sure to work with samples away from one's body as common sources of contamination include finger prints, skin, hair, and exhaled breath. Avoid contact with wet gloves and do not use any latex or Nylon materials. Second, thorough degassing of the reaction flask prior to gas addition into the reaction flask is critical. The presence of even small amounts of molecular oxygen in the reaction flask poses an explosion risk when the spark is discharged into inflammable gases such as CH 4 . While degassing the flask, the water inside the flask will boil, which will prevent a stable reading. At this stage there are two options: 1) degas the flask via freeze-thaw cycles (typically 3 are used), or 2) simply degas the liquid solution. In the latter case, some water will be lost, however, the amount will be relatively minor compared to the remaining volume. Third, a well-equipped and efficient setup must be carefully constructed to establish a consistent spark across the electrodes throughout the entirety of the experiment. BD-50E Tesla coils are not designed for prolonged operation, as they are intended for vacuum leak detection. Intermittent cooling of the Tesla coil is thus recommended for extended operational lifetime. There are multiple ways of achieving this. One simple way is to attach a timer in-line between the spark tester and its power supply and program the timer such that it alternates in 1 hour on/off cycles. Cooling the Tesla coil with a commercial fan may also be necessary to prolong the life of the Tesla coil. The Tesla coil tip should be touching or almost touching one of the tungsten electrodes; a distance between the two of approximately 1 mm or less. Additionally, an intense discharge can be achieved using a length of conductive metal wire with a loop in one end draped lightly over the electrode opposite the one touching the Tesla coil to avoid breaking the seal to the contents. It is also recommended to have a second spark generator available in case the primary spark generator fails due to extended use.

There are many additional notes worth keeping in mind when carrying out various steps in the protocol outlined here. When preparing the manifold system for an experiment and using a mercury manometer, it is generally conceded that a precision of 1 mmHg is the best achievable, due to the resolution of the human eye. Some gases may present conductivity problems with resistance-based gauges. Mercury manometers present potential spill hazards, which should be prepared for in advance.

While assembling the 3 L reaction flask, the use of silicon vacuum grease can mitigate potential organic contamination, but care should be taken to remove this thoroughly between runs. Failure to do so will result in the accumulation of silica deposits during high-temperature pyrolysis, which can interfere with vacuum seals. Additionally, the tungsten electrodes are commercially available as 2% thoriated tungsten and should be annealed into half-round ground glass fittings . Do not pyrolyze the glass-fitted tungsten electrodes in an oven. The coefficients of thermal expansion of tungsten and glass are different and heating above 100 °C may weaken the seal around the glass annealed electrodes and introduce leaks to the system. Also, ultrapure water can be introduced into the 3 L reaction flask by pouring, using care to avoid contact with any grease on the port used, or by pipetting, using a prepyrolyzed glass pipette. The aqueous phase in the reaction flask can be buffered, if desired. For example, Miller and colleagues 9 buffered the solution to pH ~8.7 with an NH 3 /NH 4 Cl buffer. To do this the aqueous phase is made 0.05 M in NH 4 Cl prior to introducing it into the reaction flask. NH 4 Cl of 99.5% purity, or greater, should be used. The remainder of the NH 3 is then added to the reaction flask as a gas.

In preparation for gas introduction into the 3 L reaction flask, the flask can be secured onto the manifold by placing the flask on a cork ring, set atop a lab jack and gently raising the flask assembly until a snug connection is achieved. When checking for leaks, it is worth noting that likely sources of leaks include poor seals at the junctions of the half-round ground glass joints, which attach the tungsten electrodes to the reaction flask, and the stopcock of the adapter attached to the neck of the 3 L reaction flask. If leaks from these sources are detected, carefully remove the 3 L reaction flask from the manifold, wipe these areas with clean laboratory tissue, reapply a fresh coating of vacuum grease and reattach the flask to the manifold to search for leaks. If no leaks are found, proceed to introduce gases into the reaction flask.

While introducing gases into the apparatus, gas cylinders should be securely fastened to a support. Care should be taken to introduce gases slowly. Valves on gas cylinders should be opened slowly and carefully while monitoring the manometer to avoid over-pressuring the glassware and attached fittings. It is important to note that while adding NH 3 into the reaction flask, because NH 3 is appreciably soluble in water below the pK a of NH 4 + (~9.2), essentially all of the NH 3 gas introduced into the manifold will dissolve in the aqueous phase, rendering the final pressure in the flask and manifold as the vapor pressure of water at the ambient temperature. Once this pressure is attained, one may assume the transfer is complete. The following are examples of the calculations that must be executed in order to precisely introduce gases into the reaction flask at their desired pressures:

Introduction of Gaseous NH 3

Due to the solubility of NH 3 , essentially all of it will transfer from the manifold to the reaction flask and dissolve in the aqueous phase as long as the NH 3 in the manifold is at a higher pressure than the vapor pressure of water in the reaction flask. Therefore, the ambient temperature should be noted and the vapor pressure of water at that temperature should be referenced prior to introducing NH 3 into the manifold. The target pressure of NH 3 to be introduced into the reaction flask should be equal to the target pressure of NH 3 in the 3 L reaction flask, plus the vapor pressure of water in the reaction flask, at the recorded ambient temperature. For example, at 25 °C, the vapor pressure of water is approximately 24 mmHg. Thus, in order to introduce 200 mmHg of NH 3 into the reaction flask, load roughly 225 mmHg of NH 3 into the manifold prior to transferring NH 3 from the manifold and into the reaction flask. This will result in approximately 200 mmHg of NH 3 being introduced into the reaction flask.

Introduction of CH 4

After NH 3 addition and its dissolution in the aqueous phase, the pressure in the headspace of the reaction flask will be equal to the vapor pressure of water at 25 °C, approximately 24 mmHg. This value will be used, in conjunction with the example manifold shown in Figure 4 , to carry out a calculation for how much CH 4 to introduce into the manifold such that 200 mmHg of CH 4 will be introduced into the reaction flask:

P 1 = total pressure desired throughout the entire system, including the reaction flask V 1 = total volume of the entire system, including the reaction flask

P 2 = pressure of CH 4 needed to fill manifold volume prior to introduction into reaction flask V 2 = volume of manifold used for gas introduction

P 3 = pressure already in the headspace of the reaction flask V 3 = volume of the reaction flask

P 1 = 200 mmHg of CH 4 + 24 mmHg of H 2 O = 224 mmHg V 1 = 3,000 ml + 100 ml + 300 ml + 40 ml + 20 ml + 3,000 ml + 40 ml + 500 ml = 7,000 ml

P 2 = pressure of CH 4 being calculated V 2 = 100 ml + 300 ml + 40 + 20 + 3,000 ml+ 40 ml + 500 ml = 4,000 ml

P 3 = 24 mmHg of H 2 O V 3 = 3,000 ml

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Introduction of N 2

After introduction of CH 4 , the headspace of the reaction flask is occupied by 200 mmHg of CH 4 and 24 mmHg of H 2 O for a total of 224 mmHg. This value will be used, along with the dimensions of the example manifold shown in Figure 4 , to calculate the N 2 pressure that needs to be introduced into the manifold such that 100 mmHg of N 2 will be introduced into the reaction flask:

P 2 = pressure of N 2 needed to fill manifold volume prior to introduction into reaction flask V 2 = volume of manifold used for gas introduction

P 1 = 24 mmHg of H 2 O + 200 mmHg of CH 4 + 100 mmHg of N 2 = 324 mmHg V 1 = 3,000 ml + 100 ml > + 300 ml + 40 ml + 20 ml + 3,000 ml + 40 ml + 500 ml = 7,000 ml

P 2 = pressure of N 2 being calculated V 2 = 100 ml + 300 ml + 40 ml + 20 ml + 3,000 ml + 40 ml + 500 ml = 4,000 ml

P 3 = 200 mmHg of CH 4 + 24 mmHg of H 2 O = 224 mmHg V 3 = 3,000 ml

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Figure 4. Manifold/vacuum system used to introduce gases into the 3 L reaction flask. Valves controlling gas flow are labeled as V 1 - V 8 , while stopcocks controlling gas flow are labeled as S 1 and S 2 . It is worth noting that while Valves 1, 2, and 6, and Stopcock 1 are referred to explicitly in the protocol, the other valves and stopcock in the manifold shown here are useful for adding or removing volume ( i.e. holding flasks) to or from the manifold. For example, when introducing gases into the manifold at relatively high pressures (approximately 500 mmHg or greater), it is advised that the experimenter makes use of all purge flasks attached to the manifold to increase the accessible volume of the manifold and help minimize the risk of over-pressuring the manifold.

After initiating the experiment, the system must be checked on regularly to ensure the experiment is running properly. Things to check include: 1) the spark generator is producing a spark, and 2) the spark is being generated across the tungsten electrodes in a continuous manner. If the above conditions are not met, disconnect the Tesla coil from its power supply and replace it with the backup Tesla coil. Meanwhile, repairs to the malfunctioning Tesla coil can be made. Often times, the contact plates inside the spark generator housing can become corroded from extended use and should be polished, or replaced.

Upon completion of the experiment, the gases in the head-space may be irritating to the respiratory system. Harmful gases, such as hydrogen cyanide 4 can be produced by the experiment. If the experimenter is not collecting gas samples for analysis, it may be helpful to connect the apparatus to a water aspirator to evacuate volatiles for approximately one hour after completion of the experiment, while the apparatus remains in the fume hood, prior to collecting liquid samples. For safety reasons, it is advised that the apparatus is vented in a fully-operational fume hood. Sample collection should be performed in an operational fume hood and sample handling in a positive-pressure HEPA filtered flow bench is recommended.

Among the numerous types of products formed by spark discharge experiments, amino acids are of significance. Amino acids are synthesized readily via the Strecker synthesis 17 . The Strecker synthesis of amino acids involves the reaction of aldehydes or ketones and HCN generated by the action of electric discharge on the gases introduced into the reaction apparatus, which upon dissolving in the aqueous phase, may react with ammonia to form α-aminonitriles that undergo hydrolysis to yield amino acids. This is, of course, but one mechanism of synthesis, and others may also be operative, such as direct amination of precursors including acrylonitrile to give β-alanine precursors, or direct hydrolysis of higher molecular weight tholin-like material to give amino acids directly, by-passing the Strecker mechanism.

Amino acid contamination of the samples produced by Miller-Urey experiments can occur if the precautions mentioned earlier are not followed explicitly. During sample analysis, it is important to search for signs of terrestrial contamination that may have originated from sample handling or sample storage. The use of OPA/NAC 16 in conjunction with LC-FD techniques allows for the chromatographic separation of D- and L-enantiomers of amino acids with chiral centers and their respective, individual quantitation. Chiral amino acids synthesized by the experiment should be racemic. Acceptable experimental error during the synthesis of amino acids with chiral centers is generally considered to be approximately 10%. Therefore chiral amino acid D/L ratios suggestive of enrichment in one enantiomer by more than 10% is a good metric by which to determine if the sample has been contaminated.

The methods presented here are intended to instruct how to conduct a Miller-Urey type spark discharge experiment; however, there are limitations to the technique described here that should be noted. First, heating the single 3 L reaction flask ( Figure 1B ), will result in condensation of water vapor onto the tips of the electrodes, dampening the spark, and reducing the generation of radical species that drive much of the chemistry taking place within the experiment. Furthermore, the use of a heating mantle to heat the apparatus is not necessary to synthesize organic compounds, such as amino acids. This differs from Miller's original experiment where he used a more complex, custom-built, dual flask apparatus ( Figure 1A ) 5 and heated the small flask at the bottom of the apparatus, which had water in it ( Figure 1A ). Heating the apparatus helped with circulation of the starting materials and aimed to mimic evaporation in an early Earth system. Second, the protocol detailed here recommends a 1 hr on/off cycle when using the Tesla coil, which effectively doubles the amount of time an experiment takes to complete, compared to the experiments conducted by Miller, as he continuously discharged electricity into the system 4 . Third, as spark generators are not intended for long-term use, they are prone to malfunction during prolonged use and must be regularly maintained and sometimes replaced by a back-up unit, if the primary spark generator fails during the course of an experiment. Last, the protocol described here involves the use of glass stopcocks, which require high vacuum grease to make appropriate seals. If desired, polytetrafluoroethylene (PTFE) stopcocks can be used to avoid vacuum grease. However, if examining these stopcocks for potential leaks with a spark leak detector, be cautious to not overexpose the PTFE to the spark as this can compromise the integrity of the PTFE and lead to poor seals being made by these stopcocks.

The significance of the method reported here with respect to existing techniques, lies within its simplicity. It uses a commercially available 3 L flask, which is also considerably less fragile and easier to clean between experiments than the original design used by Miller 5 . Because the apparatus is less cumbersome, it is small enough to carry out an experiment inside a fume hood.

Once the technique outlined here has been mastered, it can be modified in a variety of ways to simulate numerous types of primitive terrestrial environments. For example, more oxidized gas mixtures can be used 14,18,19 . Furthermore, using modifications of the apparatus, the energy source can be changed, for example, by using a silent discharge 4 , ultraviolet light 20 , simulating volcanic systems 4,12,21 , imitating radioactivity from Earth's crust 22 , and mimicking energy produced by shockwaves from meteoritic impacts 23 , and also cosmic radiation 18,19 .

The classic Miller-Urey experiment demonstrated that amino acids, important building blocks of biological proteins, can be synthesized using simple starting materials under simulated prebiotic terrestrial conditions. The excitation of gaseous molecules by electric discharge leads to the production of organic compounds, including amino acids, under such conditions. While amino acids are important for contemporary biology, the Miller-Urey experiment only provides one possible mechanism for their abiotic synthesis, and does not explain the origin of life, as the processes that give rise to living organisms were likely more complex than the formation of simple organic molecules.

Disclosures

The authors declare no competing financial interests.

Acknowledgments

This work was jointly supported by the NSF and NASA Astrobiology Program, under the NSF Center for Chemical Evolution, CHE-1004570, and the Goddard Center for Astrobiology. E.T.P. would like to acknowledge additional funding provided by the NASA Planetary Biology Internship Program. The authors also want to thank Dr. Asiri Galhena for invaluable help in setting up the initial laboratory facilities.

Oparin AI. The Origin of Life. Izd. Moskovshii Rabochii; 1924. [ Google Scholar ]
Haldane JB. The origin of life. Rationalist Annu. 1929; 148 :3–10. [ Google Scholar ]
Garrison WM, Morrison DC, Hamilton JG, Benson AA, Calvin M. Reduction of Carbon Dioxide in Aqueous Solutions by Ionizing Radiation. Science. 1951; 114 :416–418. [ PubMed ] [ Google Scholar ]
Miller SL. Production of Some Organic Compounds under Possible Primitive Earth Conditions. J. Am. Chem. Soc. 1955; 77 :2351–2361. [ Google Scholar ]
Miller SL. A Production of Amino Acids Under Possible Primitive Earth Conditions. Science. 1953; 117 :528–529. [ PubMed ] [ Google Scholar ]
Heyns HK, Walter W, Meyer E. Model experiments on the formation of organic compounds in the atmosphere of simple gases by electrical discharges (Translated from German) Die Naturwissenschaften. 1957; 44 :385–389. [ Google Scholar ]
Ponnamperuma C, Woeller F. α-Aminonitriles formed by an electric discharge through a mixture of anhydrous methane and ammonia. Biosystems. 1967; 1 :156–158. [ PubMed ] [ Google Scholar ]
Oró J. Synthesis of Organic Compounds by Electric Discharges. Nature. 1963; 197 :862–867. [ Google Scholar ]
Ring D, Wolman Y, Friedmann N, Miller SL. Prebiotic Synthesis of Hydrophobic and Protein Amino Acids. Proc. Natl. Acad. Sci. U.S.A. 1972; 69 :765–768. [ PMC free article ] [ PubMed ] [ Google Scholar ]
Wolman Y, Haverland WJ, Miller SL. Nonprotein Amino Acids from Spark Discharges and Their Comparison with the Murchison Meteorite Amino Acids. Proc. Natl. Acad. Sci. U.S.A. 1972; 69 :809–811. [ PMC free article ] [ PubMed ] [ Google Scholar ]
Roscoe S, Miller SL. Energy Yields for Hydrogen Cyanide and Formaldehyde Syntheses: The HCN and Amino Acid Concentrations in the Primitive Ocean. Orig. Life. 1987; 17 :261–273. [ PubMed ] [ Google Scholar ]
Johnson AP, et al. The Miller Volcanic Spark Discharge Experiment. Science. 2008; 322 [ PubMed ] [ Google Scholar ]
Parker ET, et al. Primordial synthesis of amines and amino acids in a 1958 Miller H2S-rich spark discharge experiment. Proc. Natl. Acad. Sci. U.S.A. 2011; 108 :5526–5531. [ PMC free article ] [ PubMed ] [ Google Scholar ]
Cleaves HJ, Chalmers JH, Lazcano A, Miller SL, Bada JL. A reassessment of prebiotic organic synthesis in neutral planetary atmospheres. Orig. Life Evol. Biosph. 2008; 38 :105–115. [ PubMed ] [ Google Scholar ]
Glavin DP, et al. Amino acid analyses of Antarctic CM2 meteorites using liquid chromatography-time of flight-mass spectrometry. Meteorit. Planet. Sci. 2006; 41 :889–902. [ Google Scholar ]
Zhao M, Bada JL. Determination of α-dialkylamino acids and their enantiomers in geologic samples by high-performance liquid chromatography after a derivatization with a chiral adduct of o-phthaldialdehyde. J. Chromatogr. A. 1995; 690 :55–63. [ PubMed ] [ Google Scholar ]
Strecker A. About the artificial formation of lactic acid and a new Glycocoll the homologous body Justus Liebigs Annalen der Chemie. 1850; 75 :27–45. [ Google Scholar ]
Miyakawa S, Yamanashi H, Kobayashi K, Cleaves HJ, Miller SL. Prebiotic synthesis from CO atmospheres: implications for the origins of life. Proc. Natl. Acad. Sci. U.S.A. 2002; 99 :14628–14631. [ PMC free article ] [ PubMed ] [ Google Scholar ]
Kobayashi K, Kaneko T, Saito T, Oshima T. Amino Acid Formation in Gas Mixtures by Particle Irradiation. Orig. Life Evol. Biosph. 1998; 28 :155–165. [ PubMed ] [ Google Scholar ]
Sagan C, Khare BN. Long-Wavelength Ultraviolet Photoproduction of Amino Acids on the Primitive Earth. Science. 1971; 173 :417–420. [ PubMed ] [ Google Scholar ]
Harada K, Fox SW. Thermal Synthesis of Natural Amino-Acids from a Postulated Primitive Terrestrial Atmosphere. Nature. 1964; 201 :335–336. [ PubMed ] [ Google Scholar ]
Ponnamperuma C, Lemmon RM, Mariner R, Calvin M. Formation of Adenine by Electron Irradiation of Methane Ammonia, and Water. Proc. Natl. Acad. Sci. USA. 1963; 49 :737–740. [ PMC free article ] [ PubMed ] [ Google Scholar ]
Bar-Nun A, Bar-Nun N, Bauer SH, Sagan C. Shock Synthesis of Amino Acids in Simulated Primitive Environments. Science. 1970; 168 :470–473. [ PubMed ] [ Google Scholar ]

March 28, 2007

Primordial Soup's On: Scientists Repeat Evolution's Most Famous Experiment

Their results could change the way we imagine life arose on early Earth

By Douglas Fox

A Frankensteinesque contraption of glass bulbs and crackling electrodes has produced yet another revelation about the origin of life.

The results suggest that Earth's early atmosphere could have produced chemicals necessary for life—contradicting the view that life's building blocks had to come from comets and meteors. "Maybe we're over-optimistic, but I think this is a paradigm shift," says chemist Jeffrey Bada, whose team performed the experiment at the Scripps Institution of Oceanography in La Jolla, Calif.

Bada was revisiting the famous experiment first done by his mentor, chemist Stanley Miller, at the University of Chicago in 1953. Miller, along with his colleague Harold Urey, used a sparking device to mimic a lightning storm on early Earth. Their experiment produced a brown broth rich in amino acids, the building blocks of proteins. The disclosure made the pages of national magazines and showed that theories about the origin of life could actually be tested in the laboratory.

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But the Miller-Urey results were later questioned: It turns out that the gases he used (a reactive mixture of methane and ammonia) did not exist in large amounts on early Earth. Scientists now believe the primeval atmosphere contained an inert mix of carbon dioxide and nitrogen—a change that made a world of difference.

When Miller repeated the experiment using the correct combo in 1983, the brown broth failed to materialize. Instead, the mix created a colorless brew, containing few amino acids. It seemed to refute a long-cherished icon of evolution—and creationists quickly seized on it as supposed evidence of evolution's wobbly foundations.

But Bada's repeat of the experiment—armed with a new insight—seems likely to turn the tables once again.

Bada discovered that the reactions were producing chemicals called nitrites, which destroy amino acids as quickly as they form. They were also turning the water acidic—which prevents amino acids from forming. Yet primitive Earth would have contained iron and carbonate minerals that neutralized nitrites and acids. So Bada added chemicals to the experiment to duplicate these functions. When he reran it, he still got the same watery liquid as Miller did in 1983, but this time it was chock-full of amino acids. Bada presented his results this week at the American Chemical Society annual meeting in Chicago.

"It's important work," says Christopher McKay, a planetary scientist at NASA Ames Research Center in Moffett Field, Calif. "This is a move toward more realism in terms of what the conditions were on early Earth."

Most researchers believe that the origin of life depended heavily on chemicals delivered to Earth by comets and meteorites. But if the new work holds up, it could tilt that equation, says Christopher Chyba, an astrobiologist at Princeton University. "That would be a terrific result for understanding the origin of life," he says, "and for understanding the prospects for life elsewhere."

But James Ferris, a prebiotic chemist at Rensselaer Polytechnic Institute in Troy, N.Y., doubts that atmospheric electricity could have been the only source of organic molecules. "You get a fair amount of amino acids," he says. "What you don't get are things like building blocks of nucleic acids." Meteors, comets or primordial ponds of hydrogen cyanide would still need to provide those molecules.

Bada's experiment could also have implications for life on Mars, because the Red Planet may have been swaddled in nitrogen and carbon dioxide early in its life. Bada intends to test this extrapolation by doing experiments with lower-pressure mixes of those gases.

Chyba is cautious: "We don't know," he says, "whether Mars really ever had that atmosphere." That's because Mars today has carbon dioxide, but hardly any nitrogen—which is also needed for making amino acids. Some scientists suspect that nitrogen gas existed on Mars, but was blasted away by asteroid impacts billions of years ago.

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Miller Urey Experiment: Hypothesis, Steps, Conclusions, and Limitations

The Miller Urey Experiment played a crucial role in investigating the origin of life on our planet. This comprehensive guide explores the experiment’s hypothesis, step-by-step process, key findings, and limitations, shedding light on its significance in unraveling the mysteries of life’s beginnings.

Oparin-Haldane Hypothesis

The Oparin-Haldane Hypothesis, proposed by Aleksandr Oparin and J.B.S. Haldane, postulates that life didn’t spontaneously emerge on early Earth due to different environmental conditions. It suggests that life gradually evolved from chemical reactions, starting with the combination of atoms into inorganic molecules and the subsequent formation of simple organic compounds. These compounds then assembled into complex organic structures, ultimately leading to the emergence of the first cell.

Steps of the Miller Urey Experiment

The Miller-Urey experiment, conducted in 1953 by Stanley L. Miller and Harold C. Urey, aimed to simulate early Earth’s conditions and test the Oparin-Haldane Hypothesis. Here are the key steps of the experiment:

Simulating Early Earth’s Atmosphere: The researchers recreated early Earth’s atmosphere in a closed system using a mixture of gases believed to be present during that era. They used a mixture of gases, including methane (CH4), ammonia (NH3), water vapor (H2O), and hydrogen (H2).

Introduction of Energy: Sparks or electric discharges were introduced to simulate the energy sources on early Earth, such as lightning strikes.

Circulation and Condensation: The gas mixture and energy were circulated continuously, mimicking Earth’s water cycle and allowing for the formation of various organic compounds.

Collection and Analysis: Samples were collected from the closed system and analyzed using chromatography and spectrometry to identify and characterize the organic compounds formed during the experiment.

Results and Findings: The experiment produced a variety of organic molecules, including amino acids—the building blocks of proteins —supporting the notion that early Earth’s conditions could have facilitated the synthesis of organic compounds essential for life’s origin.

Conclusions of the Miller Urey Experiment

The Miller-Urey experiment yielded significant conclusions, including:

Organic compounds, including amino acids, can be synthesized from inorganic materials under simulated early Earth conditions.
Basic building blocks of life may have emerged spontaneously from non-living matter.
The experiment demonstrated the potential for diverse organic compound formation, including rare amino acids.
External energy sources played a crucial role in facilitating chemical reactions and organic compound synthesis.
The experiment offered insights into the chemical reactions that might have occurred in early Earth’s atmosphere.
The findings supported the concept of abiogenesis, where life can arise from non-living matter through natural processes.
The Miller-Urey experiment laid the foundation for further research in prebiotic chemistry and the study of life’s origins.

Limitations of the Miller Urey Experiment

It’s important to consider the limitations of the Miller-Urey experiment, which include:

The experiment’s simulation of early Earth’s atmosphere may not perfectly represent the actual conditions.
The specific gases used may not accurately reflect the true composition of early Earth’s atmosphere.
The experiment’s short duration and scale may not fully capture the complexity and length of natural processes involved in life’s origin.
While the experiment produced organic compounds, it didn’t address the assembly of complex biomolecules or replicating systems crucial for life’s origin.

Ongoing Debates and Significance

Critics argue that the experiment oversimplifies the interconnected nature of biochemical systems and may not fully represent the processes behind life’s origin. There is an ongoing debate regarding the specific conditions and pathways leading to life’s emergence, with the Miller-Urey experiment presenting one plausible scenario. While it doesn’t address the origin of genetic information or self-replicating systems, subsequent research has refined and expanded upon its findings, leading to revised interpretations. The Miller-Urey experiment remains a significant milestone in our understanding of prebiotic chemistry and contributes to unraveling the complex puzzle of life’s origin.

In conclusion, the Miller-Urey experiment’s hypothesis, steps, conclusions, and limitations provide valuable insights into the origin of life on Earth. It serves as a foundation for further research, stimulating ongoing debates and refining our understanding of life’s emergence from non-living matter.

Learn more:

Amino Acids: Types, Functions, Sources, and Differences between Essential and Non-Essential Amino Acids

Chapter 18: Life On Earth

Chapter 1 how science works.

The Scientific Method
Measurements
Units and the Metric System
Measurement Errors
Mass, Length, and Time
Observations and Uncertainty
Precision and Significant Figures
Errors and Statistics
Scientific Notation
Ways of Representing Data
Mathematics
Testing a Hypothesis
Case Study of Life on Mars
Systems of Knowledge
The Culture of Science
Computer Simulations
Modern Scientific Research
The Scope of Astronomy
Astronomy as a Science
A Scale Model of Space
A Scale Model of Time

Chapter 2 Early Astronomy

The Night Sky
Motions in the Sky
Constellations and Seasons
Cause of the Seasons
The Magnitude System
Angular Size and Linear Size
Phases of the Moon
Dividing Time
Solar and Lunar Calendars
History of Astronomy
Ancient Observatories
Counting and Measurement
Greek Astronomy
Aristotle and Geocentric Cosmology
Aristarchus and Heliocentric Cosmology
The Dark Ages
Arab Astronomy
Indian Astronomy
Chinese Astronomy
Mayan Astronomy

Chapter 3 The Copernican Revolution

Ptolemy and the Geocentric Model
The Renaissance
Copernicus and the Heliocentric Model
Tycho Brahe
Johannes Kepler
Elliptical Orbits
Kepler's Laws
Galileo Galilei
The Trial of Galileo
Isaac Newton
Newton's Law of Gravity
The Plurality of Worlds
The Birth of Modern Science
Layout of the Solar System
Scale of the Solar System
The Idea of Space Exploration
History of Space Exploration
Moon Landings
International Space Station
Manned versus Robotic Missions
Commercial Space Flight
Future of Space Exploration
Living in Space
Moon, Mars, and Beyond
Societies in Space

Chapter 4 Matter and Energy in the Universe

Matter and Energy
Rutherford and Atomic Structure
Early Greek Physics
Dalton and Atoms
The Periodic Table
Structure of the Atom
Heat and Temperature
Potential and Kinetic Energy
Conservation of Energy
Velocity of Gas Particles
States of Matter
Thermodynamics
Laws of Thermodynamics
Heat Transfer
Thermal Radiation
Radiation from Planets and Stars
Internal Heat in Planets and Stars
Periodic Processes
Random Processes

Chapter 5 The Earth-Moon System

Earth and Moon
Early Estimates of Earth's Age
How the Earth Cooled
Ages Using Radioactivity
Radioactive Half-Life
Ages of the Earth and Moon
Geological Activity
Internal Structure of the Earth and Moon
Basic Rock Types
Layers of the Earth and Moon
Origin of Water on Earth
The Evolving Earth
Plate Tectonics
Geological Processes
Impact Craters
The Geological Timescale
Mass Extinctions
Evolution and the Cosmic Environment
Earth's Atmosphere and Oceans
Weather Circulation
Environmental Change on Earth
The Earth-Moon System
Geological History of the Moon
Tidal Forces
Effects of Tidal Forces
Historical Studies of the Moon
Lunar Surface
Ice on the Moon
Origin of the Moon
Humans on the Moon

Chapter 6 The Terrestrial Planets

Studying Other Planets
The Planets
The Terrestrial Planets
Mercury's Orbit
Mercury's Surface
Volcanism on Venus
Venus and the Greenhouse Effect
Tectonics on Venus
Exploring Venus
Mars in Myth and Legend
Early Studies of Mars
Mars Close-Up
Modern Views of Mars
Missions to Mars
Geology of Mars
Water on Mars
Polar Caps of Mars
Climate Change on Mars
Terraforming Mars
Life on Mars
The Moons of Mars
Martian Meteorites
Comparative Planetology
Incidence of Craters
Counting Craters
Counting Statistics
Internal Heat and Geological Activity
Magnetic Fields of the Terrestrial Planets
Mountains and Rifts
Radar Studies of Planetary Surfaces
Laser Ranging and Altimetry
Gravity and Atmospheres
Normal Atmospheric Composition
The Significance of Oxygen

Chapter 7 The Giant Planets and Their Moons

The Gas Giant Planets
Atmospheres of the Gas Giant Planets
Clouds and Weather on Gas Giant Planets
Internal Structure of the Gas Giant Planets
Thermal Radiation from Gas Giant Planets
Life on Gas Giant Planets?
Why Giant Planets are Giant
Ring Systems of the Giant Planets
Structure Within Ring Systems
The Origin of Ring Particles
The Roche Limit
Resonance and Harmonics
Tidal Forces in the Solar System
Moons of Gas Giant Planets
Geology of Large Moons
The Voyager Missions
Jupiter's Galilean Moons
Jupiter's Ganymede
Jupiter's Europa
Jupiter's Callisto
Jupiter's Io
Volcanoes on Io
Cassini Mission to Saturn
Saturn's Titan
Saturn's Enceladus
Discovery of Uranus and Neptune
Uranus' Miranda
Neptune's Triton
The Discovery of Pluto
Pluto as a Dwarf Planet
Dwarf Planets

Chapter 8 Interplanetary Bodies

Interplanetary Bodies
Early Observations of Comets
Structure of the Comet Nucleus
Comet Chemistry
Oort Cloud and Kuiper Belt
Kuiper Belt
Comet Orbits
Life Story of Comets
The Largest Kuiper Belt Objects
Meteors and Meteor Showers
Gravitational Perturbations
Surveys for Earth Crossing Asteroids
Asteroid Shapes
Composition of Asteroids
Introduction to Meteorites
Origin of Meteorites
Types of Meteorites
The Tunguska Event
The Threat from Space
Probability and Impacts
Impact on Jupiter
Interplanetary Opportunity

Chapter 9 Planet Formation and Exoplanets

Formation of the Solar System
Early History of the Solar System
Conservation of Angular Momentum
Angular Momentum in a Collapsing Cloud
Helmholtz Contraction
Safronov and Planet Formation
Collapse of the Solar Nebula
Why the Solar System Collapsed
From Planetesimals to Planets
Accretion and Solar System Bodies
Differentiation
Planetary Magnetic Fields
The Origin of Satellites
Solar System Debris and Formation
Gradual Evolution and a Few Catastrophies
Chaos and Determinism
Extrasolar Planets
Discoveries of Exoplanets
Doppler Detection of Exoplanets
Transit Detection of Exoplanets
The Kepler Mission
Direct Detection of Exoplanets
Properties of Exoplanets
Implications of Exoplanet Surveys
Future Detection of Exoplanets

Chapter 10 Detecting Radiation from Space

Observing the Universe
Radiation and the Universe
The Nature of Light
The Electromagnetic Spectrum
Properties of Waves
Waves and Particles
How Radiation Travels
Properties of Electromagnetic Radiation
The Doppler Effect
Invisible Radiation
Thermal Spectra
The Quantum Theory
The Uncertainty Principle
Spectral Lines
Emission Lines and Bands
Absorption and Emission Spectra
Kirchoff's Laws
Astronomical Detection of Radiation
The Telescope
Optical Telescopes
Optical Detectors
Adaptive Optics
Image Processing
Digital Information
Radio Telescopes
Telescopes in Space
Hubble Space Telescope
Interferometry
Collecting Area and Resolution
Frontier Observatories

Chapter 14 The Milky Way

The Distribution of Stars in Space
Stellar Companions
Binary Star Systems
Binary and Multiple Stars
Mass Transfer in Binaries
Binaries and Stellar Mass
Nova and Supernova
Exotic Binary Systems
Gamma Ray Bursts
How Multiple Stars Form
Environments of Stars
The Interstellar Medium
Effects of Interstellar Material on Starlight
Structure of the Interstellar Medium
Dust Extinction and Reddening
Groups of Stars
Open Star Clusters
Globular Star Clusters
Distances to Groups of Stars
Ages of Groups of Stars
Layout of the Milky Way
William Herschel
Isotropy and Anisotropy
Mapping the Milky Way

Chapter 15 Galaxies

The Milky Way Galaxy
Mapping the Galaxy Disk
Spiral Structure in Galaxies
Mass of the Milky Way
Dark Matter in the Milky Way
Galaxy Mass
The Galactic Center
Black Hole in the Galactic Center
Stellar Populations
Formation of the Milky Way
The Shapley-Curtis Debate
Edwin Hubble
Distances to Galaxies
Classifying Galaxies
Spiral Galaxies
Elliptical Galaxies
Lenticular Galaxies
Dwarf and Irregular Galaxies
Overview of Galaxy Structures
The Local Group
Light Travel Time
Galaxy Size and Luminosity
Mass to Light Ratios
Dark Matter in Galaxies
Gravity of Many Bodies
Galaxy Evolution
Galaxy Interactions
Galaxy Formation

Chapter 16 The Expanding Universe

Galaxy Redshifts
The Expanding Universe
Cosmological Redshifts
The Hubble Relation
Relating Redshift and Distance
Galaxy Distance Indicators
Size and Age of the Universe
The Hubble Constant
Large Scale Structure
Galaxy Clustering
Clusters of Galaxies
Overview of Large Scale Structure
Dark Matter on the Largest Scales
The Most Distant Galaxies
Black Holes in Nearby Galaxies
Active Galaxies
Radio Galaxies
The Discovery of Quasars
Types of Gravitational Lensing
Properties of Quasars
The Quasar Power Source
Quasars as Probes of the Universe
Star Formation History of the Universe
Expansion History of the Universe

Chapter 17 Cosmology

Early Cosmologies
Relativity and Cosmology
The Big Bang Model
The Cosmological Principle
Universal Expansion
Cosmic Nucleosynthesis
Cosmic Microwave Background Radiation
Discovery of the Microwave Background Radiation
Measuring Space Curvature
Cosmic Evolution
Evolution of Structure
Mean Cosmic Density
Critical Density
Dark Matter and Dark Energy
Age of the Universe
Precision Cosmology
The Future of the Contents of the Universe
Fate of the Universe
Alternatives to the Big Bang Model
Particles and Radiation
The Very Early Universe
Mass and Energy in the Early Universe
Matter and Antimatter
The Forces of Nature
Fine-Tuning in Cosmology
The Anthropic Principle in Cosmology
String Theory and Cosmology
The Multiverse
The Limits of Knowledge

Chapter 18 Life On Earth

Nature of Life
Chemistry of Life
Molecules of Life
The Origin of Life on Earth
Origin of Complex Molecules

Miller-Urey Experiment

Pre-RNA World
From Molecules to Cells
Extremophiles
Thermophiles
Psychrophiles
Acidophiles
Alkaliphiles
Radiation Resistant Biology
Importance of Water for Life
Hydrothermal Systems
Silicon Versus Carbon
DNA and Heredity
Life as Digital Information
Synthetic Biology
Life in a Computer
Natural Selection
Tree Of Life
Evolution and Intelligence
Culture and Technology
The Gaia Hypothesis
Life and the Cosmic Environment

Chapter 19 Life in the Universe

Life in the Universe
Astrobiology
Life Beyond Earth
Sites for Life
Complex Molecules in Space
Life in the Solar System
Lowell and Canals on Mars
Implications of Life on Mars
Extreme Environments in the Solar System
Rare Earth Hypothesis
Are We Alone?
Unidentified Flying Objects or UFOs
The Search for Extraterrestrial Intelligence
The Drake Equation
The History of SETI
Recent SETI Projects
Recognizing a Message
The Best Way to Communicate
The Fermi Question
The Anthropic Principle
Where Are They?

Hardly a conversation can be had about the origin of life on Earth without mention of the Miller-Urey experiment. Very little is known about the conditions on Earth during the time that life would have been forming. Harold Urey and his then-graduate student Stanley Miller were amongst the first scientists to postulate about early conditions. They conducted an experiment that has been repeated in its original and altered form for over five decades. Their work has become seminal for those studying the chemistry of the origin of life on Earth.

Although scientists continue to collect new data that sheds light on the subject, there is still quite a bit of debate over the composition of early Earth's atmosphere . What does the atmosphere have to do with the origin of life, you might ask? Well, the chemical composition of the atmosphere strongly influences the types of chemical reactions occurring at the surface of the planet and consequently impacts the conditions under which life would have originated. Based on work published in The Origin of Life by the Russian scientist Alexander Oparin in 1938, Miller suggested that life was forming during a time when Earth's atmosphere consisted of methane, ammonia, water, and hydrogen. This chemical makeup is quite different from our modern atmosphere of nitrogen, oxygen, and other gases. Miller introduced these molecules into a sealed flask, applied an electric discharge, and allowed the system to cycle for a week. What he discovered has impacted origins research for over fifty years.

The original apparatus used by Miller and Urey was quite simple compared to today's standards. It essentially consisted of two glass flasks connected by glass tubing. One flask served as the boiling flask, where gases and other molecules could accumulate in a water phase. The other flask (located above the boiling flask) served as a place where gases could accumulate and mix together. An electrical discharge, meant to simulate lightning to produce free radicals, was provided by using an induction coil.

The experimental procedure was also straightforward. Water was first added to the boiling flask. Then the apparatus was evacuated completely of air. Once the air had been removed, hydrogen gas (H 2 ), methane (CH 4 ), and ammonia (NH 3 ) were pumped into the apparatus. Finally, the water in the flask was boiled and the electrical discharge was started. The entire system was allowed to run continuously for a week.

Like any good scientist, Miller took copious notes of what happened inside the apparatus during the weeklong experiment. After the first day, the water in the flask turned distinctly pink. As the week progressed, the solution inside became redder and redder and also a bit cloudy. Once the experiment was complete, Miller and Urey determined that the cloudiness, or turbidity, of the solution was due to silica from the glass. The reddish color, however, resulted from organic compounds that "stuck" to the silica. Although difficult to see at first, Miller also noted yellow organic molecules.

At the end of the week, Miller collected the contents of the apparatus and tested the contents for amino acids using chromatography. Initial tests confirmed the presence of glycine, alpha-alanine, and beta-alanine and suggested that aspartic acid and alpha-amino-n-butyric acid had also been produced. This list of amino acids falls miles short of the 20 amino acids commonly used by life on Earth. However, Miller and Urey both suspected that other amino acids were also present, but in such small amounts that their detection was difficult to impossible.

The intent of Miller was not to try and produce amino acids. Rather, his intent was to explore the early conditions on Earth and what the naturally occurring results would be. What he discovered was that, although the conditions he proposed are not optimum, organic molecule synthesis could have been a natural consequence in Earth's history. More importantly, Miller and Urey went on to explore amino acid synthesis by developing a more efficient apparatus and altering the initial atmospheric conditions in the simulated environment.

Scientists studying the atmosphere of early Earth now believe that the primary atmospheric constituents were different from those first proposed by Oparin and later tested by Urey. James Kasting at Pennsylvania State University has suggested that the atmosphere on Earth just after the succession of heavy bombardment would have been dominated by carbon dioxide and nitrogen and contained small amounts of carbon monoxide, hydrogen gas, and reduced sulfur gases. Now instead of a simple set of glass flasks connected by tubes and sealed, scientists use complex computer models and mathematical equations to simulate the conditions of early Earth. Unless we develop a time machine, we will never know exactly what the planet was like. But through good observations and critical analysis by all scientists in the field, we will definitely arrive at feasible theories about the beginnings of Earth. The Miller-Urey experiment traveled only the first tentative steps along the road from simple molecules to a cell. But it showed that some of life's core ingredients can form quickly and naturally and that concentrating chemicals and adding energy can lead to a progression from simplicity to complexity.

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From Old Vials, New Hints on Origin of Life

By Kenneth Chang

Oct. 16, 2008

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.

“It just opens our eyes,” Dr. Bada said. “It’s still revealing new things. What else is there that we haven’t found out from this experiment?”

The findings by Mr. Johnson, Dr. Bada and other collaborators appears in Friday’s issue of the journal Science.

Although scientists no longer think that the early atmosphere resembled the gases Dr. Miller used, the gases released by volcanic eruptions do have similar properties. The scientists hypothesize that the sparks split apart water molecules in the steam, enabling a wider range of chemical reactions to take place.

In recent years, as the Miller-Urey experiment subsided in importance, scientists suggested places like the ocean bottom as more likely locations for the origin of life. The discovery of amino acids in meteorites suggested that the building blocks of life came from space, eliminating the need for finding chemical processes that could produce them on Earth.

But, Dr. Bada said, the amount of amino acids that could have rained from the skies is still unclear, and the tidal pools would have been a place where the amino acids could have accumulated in concentrations, enabling more complex reactions to occur.

“My take on this is you want to consider everything,” Dr. Bada said. “If you can have a homegrown synthesis, perhaps by this mechanism we’ve described here, complemented by stuff falling from space, well, you’ve got a really rich inventory of compounds to work with and set the stage for the origin of life.”

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Miller-Urey Revisited

Members of NAI ’s Carnegie Institution of Washington, Indiana University, and NASA Goddard Space Flight Center Teams and their colleagues have revisited the Miller-Urey experiments, and found some surprising results.

A classic experiment proving amino acids are created when inorganic molecules are exposed to electricity isn’t the whole story, it turns out. The 1953 Miller-Urey Synthesis had two sibling studies, neither of which was published. Vials containing the products from those experiments were recently recovered and reanalyzed using modern technology. The results are reported in this week’s Science .

One of the unpublished experiments by American chemist Stanley Miller (under his University of Chicago mentor, Nobelist Harold Urey) actually produced a wider variety of organic molecules than the experiment that made Miller famous. The difference between the two experiments is small — the unpublished experiment used a tapering glass “aspirator” that simply increased air flow through a hollow, air-tight glass device. Increased air flow creates a more dynamic reaction vessel, or “vapor-rich volcanic” conditions, according to the present report’s authors.

“The apparatus Stanley Miller paid the least attention to gave the most exciting results,” said Adam Johnson, lead author of the Science report. “We suspect part of the reason for this was that he did not have the analytical tools we have today, so he would have missed a lot.”

Johnson is a doctoral student in IU Bloomington’s Biochemistry Program. His advisor is biogeochemist Lisa Pratt, professor of geological sciences and the director of NASA ’s Indiana-Princeton-Tennessee Astrobiology team.

In his May 15, 1953, article in Science, “A Production of Amino Acids Under Possible Primitive Earth Conditions,” Miller identified just five amino acids: aspartic acid, glycine, alpha-amino-butyric acid, and two versions of alanine. Aspartic acid, glycine and alanine are common constituents of natural proteins. Miller relied on a blotting technique to identify the organic molecules he’d created — primitive laboratory conditions by today’s standards. In a 1955 Journal of the American Chemical Society paper, Miller identified other compounds, such as carboxylic and hydroxy acids. But he would not have been able to identify anything present at very low levels.

Johnson, Scripps Institution of Oceanography marine chemist Jeffrey Bada (the present Science paper’s principal investigator), National Autonomous University of Mexico biologist Antonio Lazcano, Carnegie Institution of Washington chemist James Cleaves, and NASA Goddard Space Flight Center astrobiologists Jason Dworkin and Daniel Glavin examined vials left over from Miller’s experiments of the early 1950s. Vials associated with the original, published experiment contained far more organic molecules than Stanley Miller realized — 14 amino acids and five amines. The 11 vials scientists recovered from the unpublished aspirator experiment, however, produced 22 amino acids and the same five amines at yields comparable to the original experiment.

“We believed there was more to be learned from Miller’s original experiment,” Bada said. “We found that in comparison to his design everyone is familiar with from textbooks, the volcanic apparatus produces a wider variety of compounds.”

Johnson added, “Many of these other amino acids have hydroxyl groups attached to them, meaning they’d be more reactive and more likely to create totally new molecules, given enough time.”

The results of the revisited experiment delight but also perplex.

What is driving the second experiment’s molecular diversity? And why didn’t Miller publish the results of the second experiment?

A possible answer to the first question may be the increased flow rate itself, Johnson explained. “Removing newly formed molecules from the spark by increasing flow rate seems crucial,” he said. “It’s possible the jet of steam pushes newly synthesized molecules out of the spark discharge before additional reactions turn them into something less interesting. Another thought is that simply having more water present in the reaction allows a wider variety of reactions to occur.”

An answer to the second question is relegated to speculation — Miller, still a hero to many scientists, succumbed to a weak heart in 2007. Johnson says he and Bada suspect Miller wasn’t impressed with the experiment two’s results, instead opting to report the results of a simpler experiment to the editors at Science.

Miller’s third, also unpublished, experiment used an apparatus that had an aspirator but used a “silent” discharge. This third device appears to have produced a lower diversity of organic molecules.

Research on early planetary geochemistry and the origins of life isn’t limited to Earth studies. As humans explore the Solar System, investigations of past or present extra-terrestrial life are inevitable. Recent speculations have centered on Mars, whose polar areas are now known to possess water ice, but other candidates include Jupiter’s moon Europa and Saturn’s moon Enceladus, both of which are covered in water ice. The NASA Astrobiology Institute, which supports these investigations, has taken a keen interest in the revisiting of the Miller-Urey Synthesis.

“This research is both a link to the experimental foundations of astrobiology as well as an exciting result leading toward greater understanding of how life might have arisen on Earth,” said Carl Pilcher, director of the NASA Astrobiology Institute, headquartered at NASA Ames Research Center in Mountain View, Calif.

Henderson Cleaves (Carnegie Institution for Science) also contributed to the report. It was funded with grants from the NASA Astrobiology Institute, the Marine Biological Laboratory in Woods Hole, Mass., and Mexico’s El Consejo Nacional de Ciencia y Tecnologia.

Scripps Institution of Oceanography is a research center of the University of California at San Diego.

The NASA Astrobiology Institute ( NAI ), founded in 1998, is a partnership among NASA , 16 U.S. teams and five international consortia. NAI ’s goal is to promote, conduct and lead interdisciplinary astrobiology research and to train a new generation of astrobiology researchers. For more information, see http://astrobiology.nasa.gov/nai.

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The Miller-Urey Experiment – Chemical Evolution

The Miller-Urey experiment was a simulation of conditions on the early Earth testing the idea that life, or more specifically organic molecules, could have formed by nothing more than simple chemical reactions. Miller’s success validated the theoretical ideas of A.I. Oparin and is considered to be the classic experiment investigating the concept of abiogenesis.

According to the new law on the legalization of gambling, which was signed by President Zelenskiy in August last year, casinos, slot machine halls, online casinos and betting shops can now legally operate in Ukraine.

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Scientific Article:

Scientists finish a 53-year-old classic experiment on the origins of life

In 1958, a young scientist called Stanley Miller electrified a mixture of simple gases, designed to mimic the atmosphere of our primordial lifeless planet. It was a sequel to one of the most evocative experiments in history, one that Miller himself had carried five years earlier. But for some reason, he never finished his follow-up. He dutifully collected his samples and stored them in vials but, whether for ill health or dissatisfaction, he never analysed them.

The vials languished in obscurity, sitting unopened in a cardboard box in Miller’s office. But possessed by the meticulousness of a scientist, he never threw them away. In 1999, the vials changed owners. Miller had suffered a stroke and bequeathed his old equipment, archives and notebooks to Jeffrey Bada , one of his former students. Bada only twigged to the historical treasures that he had inherited in 2007. “Inside, were all these tiny glass vials carefully labeled, with page numbers referring Stanley’s laboratory notes. I was dumbstruck. We were looking at history,” he said in a New York Times interview .

By then, Miller was completely incapacitated. He died of heart failure shortly after, but his legacy continues. Bada’s own student Eric Parker has finally analysed Miller’s samples using modern technology and published the results, completing an experiment that began 53 years earlier.

Miller conducted his original 1953 experiment as a graduate student, working with his mentor Harold Urey. It was one of the first to tackle the seemingly insurmountable question of how life began. In their laboratory, the pair tried to recreate the conditions on early lifeless Earth, with an atmosphere full of simple gases and laced with lightning storms. They filled a flask with water, methane, ammonia and hydrogen and sent sparks of electricity through them.

The result, both literally and figuratively, was lightning in a bottle. When Miller looked at the samples from the flask, he found five different amino acids – the building blocks of proteins and essential components of life.

The relevance of these results to the origins of life is debatable, but there’s no denying their influence. They kicked off an entire field of research, graced the cover of Time magazine and made a celebrity of Miller. Nick Lane beautifully describes the reaction to the experiment in his book, Life Ascending : “Miller electrified a simple mixture of gases, and the basic building blocks of life all congealed out of the mix. It was as if they were waiting to be bidden into existence. Suddenly the origin of life looked easy.”

Over the next decade, Miller repeated his original experiment with several twists. He injected hot steam into the electrified chamber to simulate an erupting volcano, another mainstay of our primordial planet. The samples from this experiment were among the unexamined vials that Bada inherited. In 2008, Bada’s student Adam Johnson showed that the vials contained a wider range of amino acids than Miller had originally reported in 1953.

Miller also tweaked the gases in his electrified flasks. He tried the experiment again with two newcomers – hydrogen sulphide and carbon dioxide – joining ammonia and methane. It would be all too easy to repeat the same experiment now. But Parker and Bada wanted to look at the original samples that Miller had himself collected, if only for their “considerable historical interest”.

Using modern techniques, around a billion times more sensitive than those Miller would have used, Parker identified 23 different amino acids in the vials, far more than the five that Miller had originally described. Seven of these contained sulphur, which is either a first for science or old news, depending on how you look at it. Other scientists have since produced sulphurous amino acids in similar experiments, including Carl Sagan . But unbeknownst to all of them, Miller had beaten them to it by several years. He had even scooped himself – it took him till 1972 to publish results where he produced sulphur amino acids!

The amino acids in Miller’s vials all come in an equal mix of two forms, each the mirror image of the other. You only see that in laboratory reactions – in nature, amino acids come almost entirely in one version. As such, Parker, like Miller before him, was sure that the amino acids hadn’t come from a contaminating source, like a stray bacterium that had crept into the vials.

Imagine then, a young and violent planet, wracked with exploding volcanoes, noxious gases and lightning strikes. These ingredients combined to brew a “primordial soup”, fashioning the precursors of life in pools of water. On top of that, meteorites raining down from space could have added to the accumulating molecules. After all, Parker found that the amino acid cocktail in Miller’s samples is very similar to that found on the Murchison meteorite , which landed in Australia in 1969.

These are powerful images, so why aren’t people more excited? Echoing many sources I spoke to, Jim Kasting , who studies the evolution of Earth’s atmosphere, said, “I am underwhelmed by it.” The main problem with the study is that Miller was probably wrong about the conditions on early Earth.

By analysing ancient rocks, scientists have since found that Earth was never particularly teeming in hydrogen-rich gases like methane, hydrogen sulphide or hydrogen itself. If you repeat Miller’s experiment with a more realistic mixture – heavy in carbon dioxide and nitrogen, with just trace amounts of other gases – you’d have a hard time finding amino acids in the resulting brew.

Parker accepts the problem, but he suggests that a few specific places on the planet may have had the right conditions. Exploding volcanoes, for example, throw up masses of sulphurous compounds, as well as methane and ammonia. These gases, belched forth into lightning storms , could have produced amino acids that rained out and gathered in tidal pools. But Kasting still isn’t convinced. “Even then the reduced gases would not be as concentrated as they are in this experiment.”

Even if our young planet had the right conditions to produce amino acids, that’s a less impressive feat than it appeared in the 1950s. “Amino acids are old hat and are a million miles from life,” says Nick Lane. Indeed, as Miller’s experiments showed, it’s not difficult to create amino acids. The far bigger challenge is to create nucleic acids – the building blocks of molecules like RNA and DNA. The origin of life lies in the origin of these “replicators”, molecules that can make copies of themselves. Lane says, “Even if you can make amino acids (and nucleic acids) under soup conditions, it has little if any bearing on the origin of life.”

The problem is that replicators don’t spontaneously emerge from a mixture of their building blocks, just as you wouldn’t hope to build a car by throwing some parts into a swimming pool. Nucleic acids are innately “shy”. They need to be strong-armed into forming more complex molecules, and it’s unlikely that the odd bolt of lightning would have been enough. The molecules must have been concentrated in the same place, with a constant supply of energy and catalysts to speed things up. “Without that lot, life will never get started, and a soup can’t provide much if any of that,” says Lane.

Deep-sea vents are a better location for the origins of life. Deep under the ocean’s surface, these rocky chimneys spew out superheated water and hydrogen-rich gases. Their rocky structures contain a labyrinth of small compartments that could have concentrated life’s building blocks into dense crowds, and minerals that would have catalysed their get-togethers. Far away from visions of languid soups, these churning environments are the current best guess for the site of life’s hatchery.

So Miller’s iconic experiment, and its now-completed follow-ups, probably won’t lay out the first steps of life. As Adam Rutherford, who is writing a book on the origin of life, says, “It’s really a historical piece, like finding that Darwin had described a Velociraptor in one of his notebooks.”

If anything, the analysis of Miller’s vials is a testament to the value of meticulous scientific work. Here was a man who prepared his samples so cleanly, who recorded his notes so thoroughly, and who stored everything so carefully, that his contemporaries could pick up where he left off five decades later.

Reference: Parker, Cleaves, Dworkin, Glavin, Callahan, Aubrey, Lazcano & Bada. 2011. Primordial synthesis of amines and amino acids in a 1958 Miller H2S-rich spark discharge experiment. PNAS http://dx.doi.org/10.1073/pnas.1019191108

Photos by Carlos Gutierrez and Marco Fulle

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RESEARCH HIGHLIGHT
22 November 2021

Message in a bottle: revisiting the origin of life

Andrea Gentile

You can also search for this author in PubMed Google Scholar

Leggi in italiano

Artist's impression of the early Earth conditions that the Miller-Urey experiment tried to recreate. Credit: CSIC.

Some of the basic ingredients for life are well known: a dash of water, methane, ammonia, hydrogen and a spark. But a pinch of minerals is also needed, according to a new study 1 by Italian and Spanish researchers that recreated an experiment from 1952, paying attention to a detail that had been overlooked for all these years: the glass pot in which it was performed.

“In science you should take nothing for granted,” says Raffaele Saladino, a professor at Tuscia University and president of the Italian Society of Astrobiology. “Nobody would have guessed that a setting tested hundreds of times could tell us anything more.” In 1952 at the University of Chicago, Stanley Miller and Harold Urey simulated the Earth’s environment 4.6 billion years ago to study abiogenesis, the natural synthesis of organic molecules such as amino acids and nucleobases (the building blocks of proteins and DNA/RNA respectively). In a sealed flask, they recreated the primordial atmosphere along with water, while a spark simulated lightning. Later, they found several amino acids, demonstrating how the precursors of life could emerge in a prebiotic soup. “In some experiments Miller also noted the presence of silica [the main component of glass and some rocks],” says Saladino, “but he didn’t pay much attention to it.” And nobody else investigated its role until now.

In previous studies, the team found that silica and its minerals in a solution similar to Miller’s could facilitate the process. So they decided to test the idea that, in the original experiment, they had been diluted from the flask because of the causticity of the mixture. They repeated the experiment using three containers made of materials with different pHs: borosilicate glass or Pyrex (the same material used by Miller), Teflon, which is an inert material, and Teflon with some borosilicate bits in the solution. The results confirmed that organic matter emerged in every flask independently of the pH, but the Teflon container had the fewest products, followed by the one with glass pieces. The abundance of organic molecules in the Pyrex container – 56 different kinds, amino acids and nucleobases included – was staggering, with some molecules appearing only in the borosilicate glass, revealing the importance of minerals as hidden ingredients for the precursors of life. “It makes sense, if we want to simulate a realistic scenario,” explains Saladino, “because we would have the atmosphere, water, lightning, but what we missed was the rock containing the water.”

A renewed interest in abiogenesis could help the search for life on other planets. “The complexity of a molecule doesn’t guarantee that it was produced by biological processes,” notes Saladino. “If we were able to create such molecular richness with a single experiment, then finding molecules like glycine or phosphine on other planets wouldn’t necessarily imply that they were synthesized by a living organism.” Future studies will test which molecules can emerge in a Miller-Urey setting using different minerals and alien atmospheres. Then, when looking for life on different planets we will better know what molecules to expect and, more importantly, those that are truly unexpected.

doi: https://doi.org/10.1038/d43978-021-00144-0

Criado-Reyes J, Bizzarri BM, García-Ruiz JM, Saladino R & Di Mauro E, Sci. Rep. 11 , 21009 (2021)

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What the famous Miller-Urey experiment got wrong

The famous experiment showed that a mixture of gases and water could produce amino acids and other biomolecular precursors.
However, new research shows that an unexpected factor may have played a major part in the result: glassware.
Complex experiments need good controls, and the Miller-Urey experiment failed in this regard.

Science in the early 20th century was undergoing many simultaneous revolutions . Radiological dating numbered the years of Earth’s existence in the billions, and eons of sediment demonstrated its geological evolution. The biological theory of evolution had become accepted, but mysteries remained about its selection mechanism and the molecular biology of genetics. Remnants of life dated far, far back, beginning with simple organisms. These ideas came to a head with the question of abiogenesis : could the first life have sprung from non-living matter?

In 1952, a graduate student named Stanley Miller, just 22 years old, designed an experiment to test whether the amino acids that form proteins could be created under the conditions thought to exist on the primordial Earth. Working with his Nobel Prize-winning advisor Harold Urey, he performed the experiment, which is now told time and again in textbooks all over the world.

The experiment mixed water and simple gases — methane, ammonia, and hydrogen — and shocked them with artificial lightning within a sealed glass apparatus . Within days, a thick colored substance built up at the bottom of the apparatus. This detritus contained five of the basic molecules common to living creatures. Revising this experiment over the years, Miller claimed to find as many as 11 amino acids. Subsequent work varying the electrical spark, the gases, and the apparatus itself created another dozen or so. After Miller’s death in 2007, the remains of his original experiments were re-examined by his former student . There may have been as many as 20-25 amino acids created even in that primitive original experiment.

The Miller-Urey experiment is a daring example of testing a complex hypothesis. It is also a lesson in drawing more than the most cautious and limited conclusions from it.

Did anyone consider the glassware?

In the years following the original work, several limitations curbed excitement over its result . The simple amino acids did not combine to form more complex proteins or anything resembling primitive life. Further, the exact composition of the young Earth did not match Miller’s conditions. And small details of the setup appear to have affected the results. A new study published last month in Scientific Reports investigates one of those nagging details. It finds that the precise composition of the apparatus housing the experiment is crucial to amino acid formation.

The highly alkaline chemical broth dissolves a small amount of the borosilicate glass reactor vessel used in the original and subsequent experiments. Dissolved bits of silica permeate the liquid, likely creating and catalyzing reactions . The eroded walls of the glass may also boost catalysis of various reactions. This increases total amino acid production and allows the formation of some chemicals which are not created when the experiment is repeated in an apparatus made of Teflon. But, running the experiment in a Teflon apparatus deliberately contaminated with borosilicate recovered some of the lost amino acid production.

Complex questions need carefully designed experiments

The Miller-Urey experiment was based on a complicated system. Over the years, many variables were tweaked, such as the concentration and composition of gases. For the purpose of demonstrating what might be plausible — that is, whether biomolecules can be created from inorganic materials — it was stunningly successful. But there wasn’t a good control. We now see that might have been a pretty big mistake.

One of the elements of art in science is to divine which of innumerable complexities matter and which do not. Which variables can be accounted for or understood without testing, and which ones can be cleverly elided by experimental design? This is a borderland between hard science and intuitive art. It is certainly not obvious that glass would play a role in the outcome, but it apparently does.

A more certain and careful form of science is to conduct an experiment that varies one and only one variable at a time. This is a slow and laborious process. It can be prohibitively difficult for testing complex hypotheses like, “Could life evolve from non-life on the early Earth?” The authors of the new work performed just such a single-variable test. They ran the entire Miller-Urey experiment multiple times, varying only the presence of silicate glass. The runs performed in as glass vessel produced one set of results, while those using a Teflon apparatus produced another.

Systematically marching through each potential variable, one at a time, might be called “brute force.” But there is art here too, namely, in deciding which single variable out of many possibilities to test and in what way. In this case, we learned that glass silicates played an important role in the Miller-Urey experiment. Perhaps this means that silicate rock formations on the early Earth were necessary to produce life. Maybe.

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A is for abiogenesis —

Scientists recreated classic origin-of-life experiment and made a new discovery, 1952 miller-urey experiment showed organic molecules forming from inorganic precursors..

Jennifer Ouellette - Oct 28, 2021 6:59 pm UTC

Stanley Miller with the original laboratory equipment used in the 1952 Miller-Urey Experiment, which gave credence to the idea that organic molecules could have been created by the conditions of the early Earth's atmosphere.

In 1952, a University of Chicago chemist named Stanley Miller and his adviser, Harold Urey, conducted a famous experiment . Their results, published the following year, provided the first evidence that the complex organic molecules necessary for the emergence of life ( abiogenesis ) could be formed using simpler inorganic precursors, essentially founding the field of prebiotic chemistry. Now a team of Spanish and Italian scientists has recreated that seminal experiment and discovered a contributing factor that Miller and Urey missed. According to a new paper published in the journal Scientific Reports, minerals in the borosilicate glass used to make the tubes and flasks for the experiment speed up the rate at which organic molecules form.

In 1924 and 1929, respectively, Alexander Oparin and J.B.S. Haldane had hypothesized that the conditions on our primitive Earth would have favored the kind of chemical reactions that could synthesize complex organic molecules from simple inorganic precursors—sometimes known as the " primordial soup " hypothesis. Amino acids formed first, becoming the building blocks that, when combined, made more complex polymers.

Miller set up an apparatus to test that hypothesis by simulating what scientists at the time believed Earth's original atmosphere might have been. He sealed methane, ammonia, and hydrogen inside a sterile 5-liter borosilicate glass flask, connected to a second 500-ml flask half-filled with water. Then Miller heated the water, producing vapor, which in turn passed into the larger flask filled with chemicals, creating a mini-primordial atmosphere. There were also continuous electric sparks firing between two electrodes to simulate lighting. Then the "atmosphere" was cooled down, causing the vapor to condense back into water. The water trickled down into a trap at the bottom of the apparatus.

That solution turned pink after one day and deep red after a week. At that point, Miller removed the boiling flask and added barium hydroxide and sulfuric acid to stop the reaction. After evaporating the solution to remove any impurities, Miller tested what remained via paper chromatography. All known life consists of just 20 amino acids. Miller's experiment produced five amino acids, although he was less certain about the results for two of them.

When Miller showed his results to Urey, the latter suggested a paper should be published as soon as possible. (Urey was senior but generously declined to be listed as co-author, lest this lead to Miller getting little to no credit for the work.) The paper appeared in 1953 in the journal Science. "Just turning on the spark in a basic pre-biotic experiment will yield 11 out of 20 amino acids," Miller said in a 1996 interview . The original apparatus has been on display at the Denver Museum of Nature and Science since 2013.

Miller died in 2007. Shortly before he passed, one of his students, Jeffrey Bada, now at the University of San Diego, inherited all his mentor's original equipment. This included several boxes filled with vials of dried residues from the original experiment. Those 1952 samples were re-analyzed the following year using the latest chromatography methods, revealing that the original experiment actually produced even more compounds (25) than had been reported at the time.

Miller had also performed additional experiments simulating conditions similar to those of a water-vapor-rich volcanic eruption, which involved spraying steam from a nozzle at the spark discharge. Bada and several colleagues re-analyzed the original samples from those experiments, too, and found this environment produced 22 amino acids, five amines, and several hydroxylated molecules. So the original experiments were even more successful than Miller and Urey realized.

There have been many, many more experiments on abiogenesis over the ensuing decades, but co-author Joaquin Criado-Reyes of the Universidad de Granada in Spain and his collaborators thought that one potential factor had been overlooked: the role of the borosilicate glass that comprised the flasks and tubes Miller had used. They noted that Miller's simulated atmosphere was highly alkaline, which should cause the silica to dissolve. "Therefore, it could be expected that upon contact of the alkaline water with the inner wall of the borosilicate flask, even this reinforced glass will slightly dissolve, releasing silica and traces of other metal oxides [into the vapor]," the authors wrote.

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Chemische Evolution

Du fragst dich, was die chemische Evolution ist? Hier im Beitrag und im Video erklären wir es dir!

Chemische Evolution — einfach erklärt

Miller-urey-experiment .

Die Abiogenese oder chemische Evolution ist ein Prozess, durch den Leben aus nicht-lebenden Materien entstand . Vor etwa 4 Milliarden Jahren gab es auf der Erde nur eine „Ursuppe“ aus verschiedenen chemischen Verbindungen.

Durch Blitzschläge oder vulkanische Aktivität fanden chemische Reaktionen statt. Daraus entstanden immer komplexere Moleküle , wie Aminosäuren, Zucker und Fette. Diese Moleküle sind die Grundbausteine des Lebens , da sie die Grundlage für Proteine, DNA und RNA bilden.

Die Abiogenese , auch chemische Evolution genannt, ist der Prozess, durch den aus anorganischem Material organische Moleküle entstanden sind. Diese organischen Moleküle sind die Grundlage allen Lebens, da sie die Bausteine von Proteinen, DNA und anderen lebenswichtigen Molekülen sind.

Es gibt viele Hypothesen darüber, wie die chemische Evolution genau abgelaufen sein könnte. Das Miller-Urey-Experiment ist eine der bekanntesten Methoden , um diese Hypothesen zu testen.

1953 führten die Wissenschaftler Stanley Miller und Harold Urey ein Experiment durch, um die Bedingungen der Urerde im Labor nachzustellen . Dabei erhitzten sie eine Mischung aus Wasser, Methan, Ammoniak und Wasserstoff in einem Glaskolben. Den setzten sie zusätzlich elektrischen Funken aus. Das sollte die Blitze in der frühen Atmosphäre der Erde simulieren. Nach nur einer Woche fanden sie organische Verbindungen wie Aminosäuren in der Lösung — die Bausteine von Proteinen und somit des Lebens.

abiogenese, chemische evolution, abiogenese einfach erklärt, chemische evolution einfach erklärt

Das Miller-Urey-Experiment liefert starke Hinweise darauf, dass die ersten Lebensformen auf der Erde aus einfachen, organischen Molekülen entstanden sind. Das Experiment ist aber nur eine Simulation der frühen Erde. Die tatsächlichen Bedingungen waren möglicherweise etwas anders.

Super! Jetzt weißt du, dass die chemische Evolution die Grundlage für das Leben geschaffen hat. Sie ist quasi die „Vorgeschichte“ zur biologischen Evolution . Wenn du mehr darüber erfahren möchtest, dann schau dir unseren Beitrag dazu an!

Beliebte Inhalte aus dem Bereich Evolutionsbiologie

Geschlechtliche Fortpflanzung Dauer: 05:06
Ungeschlechtliche Fortpflanzung Dauer: 03:48
Bestäubung und Befruchtung Dauer: 05:18

Weitere Inhalte: Evolutionsbiologie

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Origin-of-Life Experiment: Going from Bad to Worse

Stanley L. Miller’s legendary spark-discharge experiments, conducted in the 1950s, were considered the first experimental validation of chemical evolutionary scenarios for the origin of life. But since that time a number of scientists have raised concerns that question the relevance of the Miller-Urey experiment. Things have now gone from bad to worse. New work by scientists from Japan identifies yet another problem for the Miller-Urey experiment as an explanation for life’s origin.

Truth be told, I love The Three Stooges . While living in Cincinnati, I would get together with my friend John D. and watch episode after episode. Without fail, I found myself laughing as things invariably went from bad to worse whenever Larry, Moe, and Curly were on the job.

Though not a laughing matter, things continue to go wrong when it comes to the famous Miller-Urey experiment and its significance for the origin-of-life question. A recent study by researchers from Japan raises the concern that efforts to revitalize the Miller-Urey experiment have produced misleading results, 1 thus dealing yet another “poke in the eyes” at attempts to construct a naturalistic origin-of-life scenario.

A Promising Start

Textbook origin-of-life scenarios claim that chemical reactions in early Earth’s atmosphere produced small organic molecules (prebiotic compounds) that accumulated in oceans to form the so-called “primordial soup.” The prebiotic compounds within the soup reacted to generate life’s building blocks—key steps in the origin-of-life pathway. Stanley L. Miller’s famous spark-discharge experiments, first conducted in the 1950s, provided the impetus for this idea.

The 22-year-old graduate student ostensibly showed that energy discharges passing through early Earth’s atmosphere could have sparked the formation of building blocks such as amino acids and other organic compounds. Miller’s work launched countless prebiotic simulation experiments, and they all seemed to indicate that life’s building blocks could form in a primordial soup, sans Creator.

At the time, scientists believed early Earth’s atmosphere had been composed of hydrogen, methane, ammonia, and water vapor; and as Miller demonstrated, this gas mixture readily yields amino acids. But further insights into our planet’s primordial atmosphere spelled the end of the experiment’s importance.

Going from Bad to Worse

Most origin-of-life researchers now consider Miller’s experiments irrelevant because the consensus view of early Earth’s atmospheric constituents has changed since the 1950s. Scientists now believe the initial atmosphere was composed of carbon dioxide, nitrogen, and water. This gas mixture does not readily produce organic compounds in prebiotic simulation experiments (see “ Biology Textbooks Get it Wrong on Life’s Origin ”).

Still, a few researchers have tried to elevate the Miller-Urey experiment to renewed prominence. Many scientists think the carbon dioxide-nitrogen-water atmosphere’s failure to generate amino acids stems from the gas mixture’s oxidative properties. However, in recent years, others have suggested that the oxidative potential originates in the laboratory setting when the spark discharge produces nitrite and nitrate. These two compounds have been directly observed breaking down the amino acid precursors, and some people argue this breakdown reduces the reaction yield.

To test this idea more fully, some researchers have added ascorbic acid to the Miller-Urey experiment (employing a carbon dioxide-nitrogen-water mixture). The addition provides an antioxidant compound that counters the effects of the nitrite and nitrate species and increases the yield of amino acids by a factor of several hundred, just as predicted. Other antioxidants, like pyrite and ferrous sulfate, also increase amino acid yields, but only by a slight amount.

These results imply that the Miller-Urey experiment may not be irrelevant after all. Failure to produce amino acids from a carbon dioxide-nitrogen-water mixture may stem from nothing more than an artifact of the experimental design (which unintentionally generates nitrate and nitrite). In other words, this finding improves the likelihood that amino acids (and other organics) would have formed on early Earth via chemical processes taking place in the atmosphere.

In the midst of this seemingly positive turn of events, the research team from Japan raised the possibility that the ascorbic acid, rather than carbon dioxide, may be the carbon source for the amino acid production. To resolve this concern, the team ran two sets of reactions: one with the ascorbic acid labeled with carbon-14 and the other with carbon dioxide labeled with carbon-14, respectively. This distinction allowed them to identify the carbon source for the amino acids. And, sure enough, the experiments demonstrated conclusively that the amino acids derive carbon from the ascorbic acid, not from carbon dioxide. In other words, the addition of ascorbic acid to the Miller-Urey experiment creates artificial success.

To read about other attempts to resurrect the Miller-Urey experiment, check out the following articles:

“ Miller-Urey Redo ”
“A Failed Comeback: Efforts to Reclaim Stanley Miller’s Legacy,” parts 1 and 2
“ Carbon Monoxide Kills Hopes for Primordial Soup ”

The inability to reestablish the relevance of the Miller-Urey experiments exemplifies why every abiogenesis model suffers from fundamental and intractable problems. One of the key ways origin-of-life researchers seek to validate these models is by performing prebiotic simulation experiments, in which they attempt to replicate the conditions of early Earth in the laboratory.

These studies aim to identify and understand the chemical and physical processes that could conceivably contribute to the various stages of chemical evolution. A cursory survey of the scientific literature from the past 60 years indicates that researchers have identified a number of chemical and physical processes that, in principle , could contribute to life’s emergence.

Yet, as in the case for the Miller-Urey experiment, it is questionable if any of this work bears genuine relevancy to the evolutionary processes that would have taken place on early Earth. In many instances, the laboratory conditions used for the prebiotic studies fail to reflect the physicochemical complexity of our planet’s early days. Laboratory conditions are often carefully rigged and precisely controlled to ensure the success of the experiments in question. In other words, these processes are successful in the laboratory simply because they have been unduly influenced by the researcher. And, of course, highly skilled and knowledgeable chemists would not have been present on early Earth to give oversight to the chemical and physical processes required to generate the first life-form.

For a more detailed discussion of this issue check out my book Creating Life in the Lab .

Hideharu Kuwahara et al., “ The Use of Ascorbate as an Oxidation Inhibitor in Prebiotic Amino Acid Synthesis: A Cautionary Note ,” Origins of Life and Evolution of Biospheres 42 (December 2012): 533–41.

Natural Nucleobase Synthesis?

Oxygen Problem for Naturalistic Origin-of-Life Models

What Were Conditions Really Like on Early Earth?

The Miller–Urey experiment was intended to simulate the conditions thought at the time to be present on the early Earth in order to test the chemical origin of life . It was done in 1952 by Stanley Miller , at the University of Chicago , but eventually Harold Urey , from the University of California, San Diego helped. “The experiment used water (H 2 O), methane (CH 4 ), ammonia (NH 3 ), and hydrogen (H 2 ). The chemicals were all sealed inside a sterile 5-liter glass flask connected to a 500 ml flask half-full of liquid water. The liquid water in the smaller flask was heated to induce evaporation , and the water vapour was allowed to enter the larger flask. Continuous electrical sparks were fired between the electrodes to simulate lightning in the water vapour and gaseous mixture, and then the simulated atmosphere was cooled again so that the water condensed and trickled into a U-shaped trap at the bottom of the apparatus.” The two scientist concluded that according to their experiment life could have been naturally formed and since then the experiment is considered the classical scientific example of abiogenesis.

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Miller-Urey experiment
The experiment. The Miller-Urey experiment (or Miller experiment) was an experiment in chemical synthesis carried out in 1952 that simulated the conditions thought at the time to be present in the atmosphere of the early, prebiotic Earth.It is seen as one of the first successful experiments demonstrating the synthesis of organic compounds from inorganic constituents in an origin of life ...
Miller-Urey experiment
The Miller-Urey experiment was an experimental simulation conducted in 1953 that tested whether organic molecules could be formed from chemical reactions occurring between inorganic molecules thought to have been present early in Earth's history. To test Oparin and Haldane's ideas, Miller and Urey designed a closed experiment in a laboratory.
Miller-Urey Experiment
The Miller-Urey Experiment was a landmark experiment to investigate the chemical conditions that might have led to the origin of life on Earth. The scientist Stanley Miller, under the supervision of the Nobel laureate scientist Harold Urey conducted it in 1952 at the University of Chicago. They tried to recreate the conditions that could have ...
Conducting Miller-Urey Experiments
In 1952, Stanley Miller, then a graduate student at the University of Chicago, approached Harold Urey about doing an experiment to evaluate the possibility that organic compounds important for the origin of life may have been formed abiologically on the early Earth. The experiment was conducted using a custom-built glass apparatus ( Figure 1A ...
What Was The Miller-Urey Experiment?
How did life begin on Earth? Watch this video to learn about the Miller-Urey experiment, a groundbreaking simulation that recreated the conditions of the early planet and produced organic ...
Primordial Soup's On: Scientists Repeat Evolution's Most Famous Experiment
Bada was revisiting the famous experiment first done by his mentor, chemist Stanley Miller, at the University of Chicago in 1953. Miller, along with his colleague Harold Urey, used a sparking ...
Miller Urey Experiment: Hypothesis, Steps, Conclusions, and Limitations
The Miller-Urey experiment, conducted in 1953 by Stanley L. Miller and Harold C. Urey, aimed to simulate early Earth's conditions and test the Oparin-Haldane Hypothesis. Here are the key steps of the experiment: Simulating Early Earth's Atmosphere: The researchers recreated early Earth's atmosphere in a closed system using a mixture of ...
Miller-urey Experiment
A classic experiment in molecular biology and genetics, the Miller-Urey experiment, established that the conditions that existed in Earth ' s primitive atmosphere were able to produce amino acids, the subunits of proteins (complex carbon-containing molecules required by all living organisms). The Miller-Urey experiment fundamentally ...
Miller-Urey experiment
The Miller-Urey experiment (or Urey-Miller experiment) was an experiment that made organic compounds out of Inorganic compounds by applying a form of energy. [1] [2] The idea was to simulate hypothetical conditions thought to be present on the early Earth ( Hadean or early Archaean ). It was a test of the chemical origins of life.
Teach Astronomy
The Miller-Urey experiment. The original apparatus used by Miller and Urey was quite simple compared to today's standards. It essentially consisted of two glass flasks connected by glass tubing. One flask served as the boiling flask, where gases and other molecules could accumulate in a water phase. The other flask (located above the boiling ...
Vials From Miller-Urey Experiment Offer New Hints on Origin of Life
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 ...
What the Famous Miller-Urey Experiment Got Wrong
What the Famous Miller-Urey Experiment Got Wrong. Tom Hartsfield Big Think November 23, 2021. Wikimedia Commons. Science in the early 20th century was undergoing many simultaneous revolutions. Radiological dating numbered the years of Earth's existence in the billions, and eons of sediment demonstrated its geological evolution.
Miller-Urey Revisited
The 1953 Miller-Urey Synthesis had two sibling studies, neither of which was published. Vials containing the products from those experiments were recently recovered and reanalyzed using modern technology. ... Nobelist Harold Urey) actually produced a wider variety of organic molecules than the experiment that made Miller famous. The difference ...
The Miller-Urey Experiment
The Miller-Urey experiment was a simulation of conditions on the early Earth testing the idea that life, or more specifically organic molecules, could have formed by nothing more than simple chemical reactions. Miller's success validated the theoretical ideas of A.I. Oparin and is considered to be the classic experiment investigating the concept of abiogenesis.
Scientists finish a 53-year-old classic experiment on the origins of life
Miller conducted his original 1953 experiment as a graduate student, working with his mentor Harold Urey. It was one of the first to tackle the seemingly insurmountable question of how life began ...
Message in a bottle: revisiting the origin of life
A new version of the famous 1952 Miller-Urey experiment suggests that the glass of the flask may have been a key ingredient for its chemical reactions.
Miller-Urey-Experiment
Im Miller-Urey-Experiment wird ein Gasgemisch, das einer hypothetischen frühen Erdatmosphäre entsprechen soll - Wasser (H 2 O), Methan (CH 4), Ammoniak (NH 3) und Wasserstoff (H 2) - in einem Glaskolben elektrischen Entladungen (Lichtbögen) ausgesetzt.Die Lichtbögen, die Gewitterblitze auf der frühen Erde nachbilden, sollen die Gasmoleküle in hochreaktive freie Radikale aufspalten.
What the famous Miller-Urey experiment got wrong
The Miller-Urey experiment is a daring example of testing a complex hypothesis. It is also a lesson in drawing more than the most cautious and limited conclusions from it.
Scientists recreated classic origin-of-life experiment and made a new
Enlarge / Stanley Miller with the original laboratory equipment used in the 1952 Miller-Urey Experiment, which gave credence to the idea that organic molecules could have been created by the ...
Conducting Miller-Urey Experiments
Conducting Miller-Urey Experiments In 1953, Stanley Miller reported the production of biomolecules from simple gaseous starting materials, using apparatus constructed to simulate the primordial Earth's atmosphere-ocean system. Miller introduced 200 ml of water, 100 mmHg of H2, 200mmHg of CH4, and 200mmHg of NH3 into the apparatus, then subjected this mixture, under reflux, to an electric ...
Chemische Evolution • einfach erklärt · [mit Video]
Es gibt viele Hypothesen darüber, wie die chemische Evolution genau abgelaufen sein könnte. Das Miller-Urey-Experiment ist eine der bekanntesten Methoden, um diese Hypothesen zu testen.. 1953 führten die Wissenschaftler Stanley Miller und Harold Urey ein Experiment durch, um die Bedingungen der Urerde im Labor nachzustellen.Dabei erhitzten sie eine Mischung aus Wasser, Methan, Ammoniak und ...
Origin-of-Life Experiment: Going from Bad to Worse
July 8, 2013. Stanley L. Miller's legendary spark-discharge experiments, conducted in the 1950s, were considered the first experimental validation of chemical evolutionary scenarios for the origin of life. But since that time a number of scientists have raised concerns that question the relevance of the Miller-Urey experiment.
Chapter 90
The Miller-Urey experiment was intended to simulate the conditions thought at the time to be present on the early Earth in order to test the chemical origin of life.It was done in 1952 by Stanley Miller, at the University of Chicago, but eventually Harold Urey, from the University of California, San Diego helped. "The experiment used water (H 2 O), methane (CH 4), ammonia (NH 3), and ...

Original protocol and results

Miller-Urey experiment

Miller-Urey Experiment

Miller-Urey Experiment And The Primordial Soup Theory

The Miller-Urey Experiment In Support Of Abiogenesis

Miller-Urey Experiment Apparatus and Procedure

Miller-Urey Experiment Animation

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Conducting Miller-Urey Experiments

James H. Cleaves

Aaron S. Burton

Daniel P. Glavin

Jason P. Dworkin

Facundo M. Fernández

Introduction

1. Setting Up a Manifold/Vacuum System

2. Preparation of Reaction Flask

3. Introduction of Gaseous NH 3

4. Introduction of CH 4

5. Introduction of Further Gases ( e.g. N 2 )

6. Beginning the Experiment

7. End of Experiment

8. Collecting Liquid Sample

9. Cleaning the Apparatus

10. Sample Analysis

Representative Results

Disclosures

Acknowledgments

Primordial Soup's On: Scientists Repeat Evolution's Most Famous Experiment

On supporting science journalism

Miller Urey Experiment: Hypothesis, Steps, Conclusions, and Limitations

Oparin-Haldane Hypothesis

Steps of the Miller Urey Experiment

Conclusions of the Miller Urey Experiment

Limitations of the Miller Urey Experiment

Ongoing Debates and Significance

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Chapter 18: Life On Earth

Chapter 2 Early Astronomy

Chapter 3 The Copernican Revolution

Chapter 4 Matter and Energy in the Universe

Chapter 5 The Earth-Moon System

Chapter 6 The Terrestrial Planets

Chapter 7 The Giant Planets and Their Moons

Chapter 8 Interplanetary Bodies

Chapter 9 Planet Formation and Exoplanets

Chapter 10 Detecting Radiation from Space

Chapter 11 Our Sun: The Nearest Star

Chapter 12 Properties of Stars

Chapter 13 Star Birth and Death

Chapter 14 The Milky Way

Chapter 15 Galaxies

Chapter 16 The Expanding Universe

Chapter 17 Cosmology

Chapter 18 Life On Earth

Miller-Urey Experiment

Chapter 19 Life in the Universe

From Old Vials, New Hints on Origin of Life

Miller-Urey Revisited

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The Miller-Urey Experiment – Chemical Evolution

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Scientists finish a 53-year-old classic experiment on the origins of life

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What the famous Miller-Urey experiment got wrong