Primitive Atmosphere Research Articles

A comment on methanogenic bacteria and the primitive ecology.

The phenotype and antiquity of methanogenic bacteria suggest them to have been one of the major factors determining a dynamic balance between CO2 and CH4 in the primitive atmosphere.

Far UV irradiation of model prebiotic atmospheres

UV light has been the most important energy source on the primitive Earth. However, very few experiments have been performed to test directly the possible role of this energy source on the chemical evolution of the primitive atmosphere, mainly on account of experimental difficulties. Experiments are generally performed with other excitations, mainly electric discharge, and it is frequently assumed that UV irradiation would give similar results. As theoretical considerations make this assumption questionable, direct experimental controls have been undertaken: Model primitive atmospheres have been submitted to 147 nm UV light and the gaseous phase has been analysed. Preliminary qualitative results concerning CH4−NH3 atmospheres are reported. Irradiation of pure CH4 gives rise to the synthesis of a large number of hydrocarbons, mainly saturated hydrocarbons but including also unsaturated ones as, C2H2, C2H4, C3H6, C3H4. These insaturated hydrocarbons are synthetized at a very low rate when ammonia is present in the medium. Irradiations of CH4−NH3 mixtures give rise, in addition to hydrocarbons, to important amounts of HCN (about 0.1%) and to lesser amounts of CH3CN and C2H5CN. No unsaturated nitriles such as acrylonitrile and cyanoacetylene have been detected. Search for amines is in progress. These results evidence that UV irradiation may contribute largely to synthesis of HCN in CH4−NH3 atmospheres and, consequently to the synthesis of many biochemical compounds that can be derivated from HCN. However, synthesis of other compounds, such as pyrimidines, which can derivate from other nitriles, such as cyanoacetylene, cannot be initiated only by UV light, contrary to electric discharges. In addition, if electric discharges are very efficient for synthesis of nitriles in CH4−N2 atmospheres, there is not yet evidence that UV light is able to do so.

Addition reactions of malonic nitriles with alkanethiol in aqueous solution: prebiotic synthesis of iminothioesters.

In order to evidence new reactions of prebiotic synthesis in aqueous solution between the S-containing compounds, such as alkanethiols, which can be obtained in gaseous phase during the simulation of the evolution of primitive atmosphere, and the malonic nitriles which are generally considered as important intermediates in the Chemical Evolution, a kinetic study on the eventual reactions of ethanethiol with cyanoacetaldehyde and malononitrile has been carried out.

Reducing greenhouses and the temperature history of Earth and Mars

THE modern theory of stellar evolution implies that the Sun has increased in brightness by several tens of per cent over geological time. Were all other global parameters held constant, this would imply that the mean temperature of the Earth was below the freezing point of seawater about 2×109 yr ago1. There is, however, excellent geological and palaeontological evidence that there were extensive bodies of liquid water on the Earth between 3 and 4×109 yr ago, A possible solution to this puzzle, first postulated by Sagan and Mullen1, is that the Earth's primitive atmosphere contained small quantities of NH3 and other reducing gases which significantly enhanced the global greenhouse effect. NH3 is especially effective in the 8–13 µm window in a CO2—H2O atmosphere. It was argued that plausible changes in other global parameters, such as the infrared emissivity or the Russell–Bond albedo, would have been ineffective. The increase in solar brightness over geological time seems model-invariant even under extreme model perturbation for the solar interior1, as has recently been reconsidered in a straightforward stellar structure scaling argument2, Cosmochemical considerations point strongly to a higher abundance of reduced constituents in the primitive than in the contemporary terrestrial atmosphere; and reduced atmospheric components such as NH3 and CH4 are required to understand the accumulation of prebiological organic compounds necessary for the origin of life in this same period, between 3 and 4×109 yr ago3.

Origin of organic compounds on the primitive earth and in meteorites.

The role and relative contributions of different forms of energy to the synthesis of amino acids and other organic compounds on the primitive earth, in the parent bodies or carbonaceous chondrites, and in the solar nebula are examined. A single source of energy or a single process would not account for all the organic compounds synthesized in the solar system. Electric discharges appear to produce amino acids more efficiently than other sources of energy and the composition of the synthesized amino acids is qualitatively similar to those found in the Murchison meteorite. Ultraviolet light is also likely to have played a major role in prebiotic synthesis. Although the energy in the sun's spectrum that can be absorbed by the major constituents of the primitive atmosphere is not large, reactive trace components such as H2S and formaldehyde absorb at longer wavelengths where greater amounts of energy are available and produce amino acids by reactions involving hot hydrogen atoms. The thermal reaction of CO + H2 + NH3 on Fischer-Tropsch catalysts generates intermediates that lead to amino acids and other organic compounds that have been found in meteorites. However, this synthesis appears to be less efficient than electric discharges and to require a special set of reaction conditions. It should be emphasized that after the reactive organic intermediates are generated by the above processes, the subsequent reactions which produce the more complete biochemical compounds are low temperature homogenous reactions occurring in an aqueous environment.

Origin of Life: Clues from Relations Between Chemical Compositions of Living Organisms and Natural Environments

When elemental enrichment factors in living organisms are plotted against the ionic potential of the elements, a strikingly similar pattern is found for different groups of organisms; the pattern is also similar, in its general features, to that found in seawater. These relationships support the idea that life began in a water-rich environment interfacing with the primitive atmosphere of the earth.

The Exospheric Temperature of a Primitive Terrestrial Atmosphere with Evolving Oxygen Content

Abstract The evolution of oxygen in a primitive terrestrial atmosphere from the dissociation of water vapor is determined from the production and dissipation of hydrogen. The temperature of the exosphere however is directly related to the absorption of solar radiation by an increasing amount of oxygen. In this paper a simple model of the dependence of the exospheric temperature on the oxygen content is proposed. It is found, in the available range of values of EUV solar flux, that an exospheric temperature up to 0.1 of the present atmospheric level for oxygen (PAL) is low enough for Spitzer–limited flow to he established. The assumption is made that the limiting flux of hydrogen is determined by the total hydrogen mixing ratio at lower heights at various oxygen levels, and escape fluxes are computed for mixing ratios of 10, 102 and 103 ppm. It is argued that if the hydrogen density were not high enough to influence the thermospheric temperature the rise time in the oxygen content produced by photodissocia...

Evolution of the Atmosphere of Venus

Abstract The runaway greenhouse effect provides the most plausible explanation for the divergent evolution of the atmospheres of Venus and Earth. It has not yet been convincingly demonstrated that the atmosphere of Venus is in chemical equilibrium with the surface. Rates of loss of hydrogen from the primitive atmosphere would have been too high to permit the formation of a predominantly water vapor atmosphere on Venus unless degassing rates were very rapid. A transient oxygen atmosphere would have developed on Venus unless the rate of supply of oxidizable material at the surface was exceedingly large.

Photochemical formation of organic compounds from mixtures of simple gases simulating the primitive atmosphere of the earth

Already in the 1938 English edition of his book “The Origin of Life” A. I. Oparin (3) gave strong reasons for the assumption that the primordial or primitive atmosphere of the Earth was a “reducing atmosphere,” consisting mainly of hydrogen, methane, ammonia, water vapour, and noble gases. In addition he presented many facts supporting the assumption that carbon appeared first on the Earth’s surface, not in the oxidized form of carbon dioxide, but in the reduced state in the form of hydrocarbons. He added that nitrogen first appeared, with a high degree of probability, like carbon, also in its reduced state, in the form of ammonia. These assumptions were later on supported by H. C. Urey (4), W. Kuhn (5), J. D. Bernal (6), and others.

The origin of bioluminescence.

Abstract— Primitive luciferases evolved in order to utilize oxygen directly as an electron acceptor at the low oxygen concentrations of the primitive atmosphere. This provided a major selective advantage in the ability to metabolize aromatic molecules and n‐alkanes. These strongly exergonic reactions produce product molecules in electronically excited states, from which light emission is possible. The low‐level luminescence observed from microsomal extracts, from the action of leukocytes on phagocytized bacteria and from rapidly growing tissues is ascribed to these same exergonic hydroxylase reactions, or to the release during these reactions of superoxide radicals which can initiate chemiluminescent reactions. Bioluminescence is a later secondary adaptation of this oxygenase reaction to signaling for sex, food or escape. The similarity of the reaction pathways is shown in the three bioluminescent systems from which the substrates and products have been identified.

Dynamics of the chemical evolution of Earth's primitive atmosphere

The course of evolution of Earth's primitive reducing atmosphere is shown to possibly have been determined to a large extent by the effect of thunder shock waves, which is comparable to the effect of solar uv radiation. The major chemical reactions occurring during a thunderstorm in the troposphere were pyrolysis of hydrocarbons, their oxidation by water vapor and their reaction with molecular nitrogen. These reactions were studied by the single-pulse shock tube technique and their rates as well as their product distributions were determined. The greenhouse effect of water vapor and acetylene enhanced oxidation by water vapor and prevented the accumulation of large graphite and polymer deposits on the Earth's surface. This is in accordance with their absence on the contemporary Earth. Changes in the frequency and power of thunderstorms, within reasonable limits, affected the rate of evolution but caused only small changes in the concentration profiles of HCN and aldehydes, which are essential for further chemical evolution in the oceans. The surface temperature and relative hydrogen concentration are shown to be of prime importance in determining the course and outcome of atmospheric evolution.

Molten earth and the origin of prebiological molecules.

Evidence for the molten Earth at its accretion time has been accumulated through the geochemical investigations and the observations of the surfaces of planets by space probes such as Venera 8, Mariner 9, Surveyor, Luna, and Apollo. The primitive terrestrial atmosphere might have been derived from the volcanic gases, as suggested by Rubey, but of a higher temperature than so far assumed. A thermochemical calculation of the composition of the volcanic gas suggests the following possibilities: (1) Large amounts of H2 and CO were present in the primitive atmosphere. This gives a theoretical basis for the HCN-production experiment by Abelson. (2) HCHO and NH3 existed in the primitive oceans, of the amount comparable with the weight of the present biosphere. (3) Plenty of NO3-, SO4, and PO4 were expected in the primitive oceans. The NO3- ions might have been useful for the nitrate respiration advocated by Egami. In an appendix, it is argued, on ;he basis of the observational evidence of the exospheric temperatures of planets by space probes, that a highly reducing atmosphere would (if it existed on the primitive Earth) have disappeared very quickly due to the thermal escape of hydrogen from its exosphere.

Channels on Mars

By showing that parts of equatorial and mid-latitudinal Mars have a variety of channels and channel-like forms, Mariner 9 photographs provide a basis for speculations concerning surface processes, crustal events, climatological environment, and evolutionary history. Some large outflow channels display characteristics suggesting scour and plucking by torrential floods similar to the Spokane and Bonneville events of western United States, although such channels are probably not solely the product of flood action. Other channels with dendritic tributaries suggest runoff fed by seepage and headward growth and enlargement by sapping. Some Martian channels and channel-like forms were probably created or initiated by endogenic processes such as faulting, subsidence, volcanism, fracturing, and crustal extension; others may be due to wind or lava erosion, but the features and relationships of many channels are best accounted for by fluvial action. Reconciliation of fluvial erosion and the current hostile Martian environment may be possible if the channels are as old as 3 b.y. Such an age is suggested by recent re-evaluations of meteoroidal flux impacting Mars, Moon, and Earth and the chronology of lunar maria. A residual primitive atmosphere possibly congenial to running water on Mars may have permitted fluvial erosion 3 to 3.5 b.y. ago. Haphazard scattering of channels and the likelihood of seepage and sapping suggest that water was supplied to the Martian surface from the lithosphere, not the atmosphere.

Prebiotic chemistry and nucleic acid replication

Recent work is reviewed on some reactions that could have occurred on the primitive earth and that could have played a part in the evolution of a self-replicating system. The transition from the primitive atmosphere to the simplest replicating molecules is considered in four stages: (1) the formation of a 'prebiotic soup' of organic precursors, including the purine and pyrimidine bases and the pentose sugars; (2) the condensation of these precursors and inorganic phosphate to form monomeric nucleotides and activated nucleotide derivatives; (3) the polymerization of nucleotide derivatives to oligonucleotides; and (4) the complementary replication of oligonucleotides in a template-directed process that depends on Watson-Crick base pairing.

Dicarboxylic acids from electric discharge

OPARIN1 and Urey2 have suggested that methane, ammonia, hydrogen and water were present in the primitive atmosphere of the Earth. Significant yields of amino, hydroxy, and monocarboxylic acids have been produced by the action of electric discharge on such a primordial gas mixture3,4; and numerous chemical evolution experiments have produced many types of biologically significant molecules5. Apart from the detection of succinic acid3,4,6, no other dicarboxylic acids have been reported in chemical evolution experiments.

Production of Organic Molecules by Proton Irradiation

IN recent years there has been considerable interest in the production of complex organic molecules in primitive atmospheres. The emphasis of most of this work has been on mechanisms for prebiological synthesis of amino acids and related molecules, but the feasibility of producing organic chromophores which may account for the colours observed on planets and satellites in the outer Solar System by these same processes has become a topic of research effort in the past few years.

Interactions between amino acids and nucleotides in the prebiotic milieu

In the study of chemical evolution we are interested in the path by which nucleic acids and proteins may have arisen under prebiotic conditions giving rise to those interactions which are generally postulated for the threshold of life. Although laboratory experiments have demonstrated that most of the building blocks of life can be generated from the raw material of the primitive atmosphere, in the genesis of polymers, however, the efforts have been less conclusive. It is reasonable to suppose that small peptides and small oligonucleotides may have interacted in the ‘primordial soup’ giving rise to the earliest association between nucleic acids and proteins. The beginnings of these processes could be related to the properties of individual amino acids and nucleotides. The interaction of oligomers with amino acids has been studied by the use of ion exchange and NMR spectroscopy. The observed affinities appear to depend on the given amino acid and the oligonucleotide chain length. The results so far suggest that direct amino-acid nucleotide interactions could have made a contribution to the early evolution of the Genetic Code.

Stable carbon isotopes in selected granitic, mafic, and ultramafic igneous rocks

Noncarbonate (combustion) and carbonate (acid decomposition) carbon were separately analyzed in 18 granitic rocks from a group of related Tertiary intrusions near Crested Butte, Colorado, and 14 mafic and ultramafic rocks from various localities in the western United States. Among the granites, carbonate carbon ranges from nil to 0.76 per cent with δC 13-values from −5.6 to − 9.0‰ (vs PDB); noncarbonate carbon varies from 32–360 ppm with δC 13-values from −19.7 to −26.6‰, The mafic and ultramafic rocks have carbonate carbon contents ranging from 53 ppm to about 2 per cent with δC 13-values from + 2.9 to −10.3‰; noncarbonate carbon varies from 26 to 150 ppm with δC 13-values of −22.2 to − 27.l‰ For these samples, carbonate carbon ranges from 12.0 to 29.4‰ heavier than coexisting noncarbonate carbon. This consistent difference between δC 13 of carbonate and noncarbonate carbon may be an isotopic fractionation effect. Because the specific indigenous form of noncarbonate (combustion) carbon is in doubt, conclusive interpretations regarding isotopic equilibration and fractionation cannot be made. These results have bearing on the assessment of the isotopic composition of mantle carbon and consequently are germane to the question of the origin (source) and history of crustal carbon. If mantle carbon is isotopically similar to noncarbonate (combustion) carbon, i.e. δC 13-values from −19.7 to − 27.1‰, then a simple mantle degassing source for crustal carbon is improbable. Such a result would indicate an additional source of crustal carbon such as from a primitive atmosphere or extra-terrestrial accretion.

Carbon monoxide on the primitive earth

The reaction of CO + OH − in aqueous solution to give formate was studied as a carbon monoxide sink on the primitive earth and in the present ocean. The reaction is first order in OH − and first order in the molar CO concentration. The second order rate constant is given by log k(M −1hr −1) = 15.83−4886/T between 25°C and 60°C. Using the solubility of CO in sea water, and assuming a pH of 8 for a primitive ocean of the present size, the halflife of CO in the atmosphere is calculated to be 12 × 10 6 yr at 0°C and 5.5 × 10 4 yr at 25°C. Three other CO sinks would have been important in the primitive atmosphere: CO + H 2 → H 2CO driven by various energy sources, CO + OH → CO 2 + H, and the Fischer-Tropsch reaction of CO + H 2 → hydrocarbons, etc. It is concluded that the lifetime of a CO atmosphere would have been very short on the geological time scale although the relative importance of these four CO sinks is difficult to estimate. The CO + OH − reaction to give formate is a very minor CO sink on the earth at the present time.

Thermal Synthesis of Amino Acids from a Simulated Primitive Atmosphere

IT has been suggested that thermal energy was readily available for the prebiotic synthesis of organic compounds as evidenced by lava remnants from earlier volcanic activity and by the present widespread occurrence of regions of elevated temperatures on the Earth1,2. In previous chemical evolution thermal experiments, the predominant amino acids reported were those commonly found in present-day protein1,3,4. It was implied from these results that thermal energy may have played an important part in the prebiotic synthesis of protein amino acids. It would certainly be significant if thermal energy could produce only these amino acids and not the unusual amino acids of the type identified in simulated primitive atmosphere discharge experiments5,6 and in meteorite extracts7,8, a presumed extraterrestrial abiotic synthesis. Also, previous studies have relied on the identification of amino acids by ion exchange chromatography1,4 (amino acid analyser) and electrophoresis3, which is not sufficient for the unequivocal identification of an amino acid, particularly when materials other than the common amino acids may be present5,9. For these reasons we have applied the recently developed techniques of gas chromatography (GC) and gas chromatography combined with mass spectrometry (GC–MS) for identification of the compounds produced by thermal synthesis.