Spark Discharge Experiments Research Articles

Prebiotic cytosine synthesis: a critical analysis and implications for the origin of life.

A number of theories propose that RNA, or an RNA-like substance, played a role in the origin of life. Usually, such hypotheses presume that the Watson-Crick bases were readily available on prebiotic Earth, for spontaneous incorporation into a replicator. Cytosine, however, has not been reported in analyses of meteorites nor is it among the products of electric spark discharge experiments. The reported prebiotic syntheses of cytosine involve the reaction of cyanoacetylene (or its hydrolysis product, cyanoacetaldehyde), with cyanate, cyanogen, or urea. These substances undergo side reactions with common nucleophiles that appear to proceed more rapidly than cytosine formation. To favor cytosine formation, reactant concentrations are required that are implausible in a natural setting. Furthermore, cytosine is consumed by deamination (the half-life for deamination at 25 degrees C is approximately 340 yr) and other reactions. No reactions have been described thus far that would produce cytosine, even in a specialized local setting, at a rate sufficient to compensate for its decomposition. On the basis of this evidence, it appears quite unlikely that cytosine played a role in the origin of life. Theories that involve replicators that function without the Watson-Crick pairs, or no replicator at all, remain as viable alternatives.

Stable isotope analysis at the molecular level: A new approach for determining the origins of amino acids in the Murchison meteorite

A combined gas chromatography/isotope ratio mass spectrometry (GC/IRMS) method has been developed that permits the direct stable carbon isotope analysis of N(O)-trifluoroacetylisopropyl esters of individual amino acids and their respective enantiomers at nanomole abundances. Calculation of the original δ 13C values of the amino acids is accomplished via a correction for the carbon introduced during the derivatization process. Previous GC/IRMS analyses of individual amino acids in the non-hydrolyzed water extract of an interior sample of a Murchison meteorite stone revealed an enrichment in 13C relative to terrestrial organic matter, in agreement with previous findings for bulk extracts. The range of amino acid δ 13C values (+5 to +30 ‰, PDB) suggests possible kinetic effects during synthesis. In this study, an apparent kinetic isotope effect was also observed for the amino acid products of a spark discharge experiment. These preliminary results are supportive of a similar mechanism for the abiotic synthesis of amino acids in the Murchison meteorite.

Abiotic synthesis of organic compounds under the conditions of submarine hydrothermal systems: a perspective

Deep-sea hydrothermal systems have been proposed to be likely environments for chemical evolution and the origin of life on Earth. Recently, experiments have, therefore, been carried out in order to test the hypothesis that amino acids can be synthesized under conditions representing hydrothermally altered oceanic crust. The variety of amino acids that have been detected in such experiments corresponds roughly to that reported previously for electric sparking in reducing gas mixtures. The relative yields of the protein amino acids detected are significantly higher than in electric spark discharge experiments, and the overall yields are about an order of magnitude higher. The amino acids are all racemic.

Gas phase synthesis of organophosphorus compounds and the atmosphere of the giant planets

Experimental studies were carried out on the evolution of CH 4PH 3, CH 4PH 3H 2, CH 4CH 3PH 2, and C 2H 6PH 3 mixtures submitted to spark discharges, and of CH 4PH 3 mixtures submitted to 147-nm UV irradiation. In all these experiments, the only P-organics detected in gas phase are alkylphophines, but with a number of C atoms not higher than that of the starting hydrocarbon. In the spark discharge experiments, the main products obtained from CH 4PH 3 are H 2, CH 3PH 2, and C 2H 6 or P 2H 4, depending on the initial mole fraction (low or high, respectively) of PH 3. Methylphosphine appears much more stable than phosphine. Its rate of formation relative to PH 3 increases dramatically when the initial mole fraction of PH 3 is decreased, and decreases markedly with the addition of large amounts of H 2. In the UV experiments, the main volatile products are H 2 and P 2H 4; the production of organics is very low. Discussion of the mechanisms involved shows the importance of the reaction CH 3 + PH 2 + M → CH 3PH 2 + M in the synthesis of methylphosphine. In the spark discharge experiments, the insertion reaction CH 2 + PH 3 + M → CH 3PH 2 + M cannot be excluded. On the contrary, results of the UV experiments show that the insertion reaction of PH ∗ into CH 4 is negligible. The main reactions of PH ∗ are collisional quenching by PH 3 or CH 4 and energy-transfer-induced decomposition of PH 3: PH ∗ + PH 3 → PH + PH 2 + H . The former must play the most important role, its rate constant appearing approximately 2 and 10 times higher than the rate constant of the reactions PH ∗ + PH 3 → PH + PH 3 and PH ∗ + CH 4 → PH + CH 4 , respectively. Implications of these results for Saturn's atmosphere are presented.

Fiber Optic Signal Transmission to Reduce Radio-Frequency Interference from a High-Voltage Spark Source

The incorporation of fiber optic signal transmission into a high voltage spark discharge experiment to reduce radio-frequency interference is described. Electrical isolation and the elimination of ground loops provided by the fiber optic links allow the use of sensitive CMOS computer logic in control of an electrically noisy spark source experiment. Circuit schematics are given and performance with three optical fiber cable types is described.