Prebiotic Organic Synthesis Research Articles

Formation of Glyoxylic Acid in Interstellar Ices: A Key Entry Point for Prebiotic Chemistry.

With nearly 200 molecules detected in interstellar and circumstellar environments, the identification of the biologically relevant α-keto carboxylic acid, glyoxylic acid (HCOCOOH), is still elusive. Herein, the formation of glyoxylic acid via cosmic-ray driven, non-equilibrium chemistry in polar interstellar ices of carbon monoxide (CO) and water (H2 O) at 5 K via barrierless recombination of formyl (HCO) and hydroxycarbonyl radicals (HOCO) is reported. In temperature-programmed desorption experiments, the subliming neutral molecules were selectively photoionized and identified based on the ionization energy and distinct mass-to-charge ratios in combination with isotopically labeled experiments exploiting reflectron time-of-flight mass spectrometry. These studies unravel a key reaction path to glyoxylic acid, an organic molecule formed in interstellar ices before subliming in star-forming regions like SgrB2(N), thus providing a critical entry point to prebiotic organic synthesis.

Formation of Glyoxylic Acid in Interstellar Ices: A Key Entry Point for Prebiotic Chemistry

AbstractWith nearly 200 molecules detected in interstellar and circumstellar environments, the identification of the biologically relevant α‐keto carboxylic acid, glyoxylic acid (HCOCOOH), is still elusive. Herein, the formation of glyoxylic acid via cosmic‐ray driven, non‐equilibrium chemistry in polar interstellar ices of carbon monoxide (CO) and water (H2O) at 5 K via barrierless recombination of formyl (HCO) and hydroxycarbonyl radicals (HOCO) is reported. In temperature‐programmed desorption experiments, the subliming neutral molecules were selectively photoionized and identified based on the ionization energy and distinct mass‐to‐charge ratios in combination with isotopically labeled experiments exploiting reflectron time‐of‐flight mass spectrometry. These studies unravel a key reaction path to glyoxylic acid, an organic molecule formed in interstellar ices before subliming in star‐forming regions like SgrB2(N), thus providing a critical entry point to prebiotic organic synthesis.

Chemical Diversity of Metal Sulfide Minerals and Its Implications for the Origin of Life.

Prebiotic organic synthesis catalyzed by Earth-abundant metal sulfides is a key process for understanding the evolution of biochemistry from inorganic molecules, yet the catalytic functions of sulfides have remained poorly explored in the context of the origin of life. Past studies on prebiotic chemistry have mostly focused on a few types of metal sulfide catalysts, such as FeS or NiS, which form limited types of products with inferior activity and selectivity. To explore the potential of metal sulfides on catalyzing prebiotic chemical reactions, here, the chemical diversity (variations in chemical composition and phase structure) of 304 natural metal sulfide minerals in a mineralogy database was surveyed. Approaches to rationally predict the catalytic functions of metal sulfides are discussed based on advanced theories and analytical tools of electrocatalysis such as proton-coupled electron transfer, structural comparisons between enzymes and minerals, and in situ spectroscopy. To this end, we introduce a model of geoelectrochemistry driven prebiotic synthesis for chemical evolution, as it helps us to predict kinetics and selectivity of targeted prebiotic chemistry under “chemically messy conditions”. We expect that combining the data-mining of mineral databases with experimental methods, theories, and machine-learning approaches developed in the field of electrocatalysis will facilitate the prediction and verification of catalytic performance under a wide range of pH and Eh conditions, and will aid in the rational screening of mineral catalysts involved in the origin of life.

A new family of extraterrestrial amino acids in the Murchison meteorite

The occurrence of extraterrestrial organic compounds is a key for understanding prebiotic organic synthesis in the universe. In particular, amino acids have been studied in carbonaceous meteorites for almost 50 years. Here we report ten new amino acids identified in the Murchison meteorite, including a new family of nine hydroxy amino acids. The discovery of mostly C3 and C4 structural isomers of hydroxy amino acids provides insight into the mechanisms of extraterrestrial synthesis of organic compounds. A complementary experiment suggests that these compounds could be produced from aldehydes and ammonia on the meteorite parent body. This study indicates that the meteoritic amino acids could be synthesized by mechanisms in addition to the Strecker reaction, which has been proposed to be the main synthetic pathway to produce amino acids.

Hydrogen and carbon isotopic ratios of polycyclic aromatic compounds in two CM2 carbonaceous chondrites and implications for prebiotic organic synthesis

Study of meteoritic organic compounds offers a unique opportunity to understand the origins of the organic matter in the early Solar System. Meteoritic polycyclic aromatic hydrocarbons (PAHs) and heteropolycyclic aromatic compounds (HACs) have been studied for over fifty years, however; their hydrogen stable isotopic ratios (δD) have never been reported. Compound-specific δD measurements of PAHs and HACs are important, in part because the carbon isotopic ratios (δC13) of various meteoritic PAHs cannot be readily distinguished from their terrestrial counterparts and it is difficult to rule out terrestrial contamination based on carbon isotopic ratios alone. In this study, we have extracted and identified more than sixty PAHs and HACs present in two CM2 carbonaceous chondrites Murchison and LON 94101. Their carbon and hydrogen stable isotopic ratios (δC13 and δD) were measured and used to discuss about their synthetic environments and formation mechanisms. The concentration of aromatic compounds is ∼30% higher in Murchison than in the Antarctic meteorite LON 94101, but both samples contained similar suites of PAHs and HACs. All PAHs and HACs found exhibited positive δD values (up to 1100‰) consistent with an extraterrestrial origin, indicating the relatively low δC13 values are indeed an inherent feature of the meteoritic aromatic compounds. The hydrogen isotopic data suggest aromatic compounds in carbonaceous chondrites were mainly formed in the cold interstellar environments. Molecular level variations in hydrogen and carbon isotopic values offer new insights to the formation pathways for the aromatic compounds in carbonaceous chondrites.

PREBIOTIC HYDROCARBON SYNTHESIS IN IMPACTING REDUCED ASTROPHYSICAL ICY MIXTURES

We present results of prebiotic organic synthesis in shock-compressed reducing mixtures of simple ices from quantum molecular dynamics simulations extended to close to chemical equilibrium timescales. Given the relative abundance of carbon in reduced forms in astrophysical ices as well as the tendency of these mixtures to form complex hydrocarbons under the presence of external stimuli, it is possible that cometary impacts on a planetary surface could have yielded a larger array of prebiotic organic compounds than previously investigated. We find that the high pressures and temperatures due to shock compression yield a large assortment of carbon- and nitrogen-bonded extended structures that are highly reactive with short molecular lifetimes. Expansion and cooling causes these materials to break apart and form a wide variety of stable, potentially life-building compounds, including long-chain linear and branched hydrocarbons, large heterocyclic compounds, and a variety of different amines and exotic amino acids. Our results help provide a bottom-up understanding of hydrocarbon impact synthesis on the early Earth and its role in producing life-building molecules from simple starting materials.

Chirality of meteoritic free and IOM-derived monocarboxylic acids and implications for prebiotic organic synthesis

The origin of homochirality and its role in the development of life on Earth are among the most intriguing questions in science. It has been suggested that carbonaceous chondrites seeded primitive Earth with the initial organic compounds necessary for the origin of life. One of the strongest pieces of evidence supporting this theory is that certain amino acids in carbonaceous chondrites display a significant l-enantiomeric excess (ee), similar to those use by terrestrial life. Analyses of ee in meteoritic molecules other than amino acids would shed more light on the origins of homochirality. In this study we investigated the stereochemistry of two groups of compounds: (1) free monocarboxylic acids (MCAs) from CM2 meteorites LON 94101 and Murchison; and (2) the aliphatic side chains present in the insoluble organic matter (IOM) and extracted in the form of monocarboxylic acids (MCAs) from EET 87770 (CR2) and Orgueil (CI1). Contrary to the well-known ee observed for amino acids in meteorites, we found that meteoritic branched free and IOM-derived MCAs with 5–8 carbon atoms are essentially racemic. The racemic nature of these compounds is used to discuss the possible influence of ultraviolet circularly polarized light (UVCPL) and aqueous alterations on the parent body on chirality observed in in carbonaceous chondrites.

Miller-Urey and Beyond: What Have We Learned About Prebiotic Organic Synthesis Reactions in the Past 60 Years?

The synthesis of amino acids in the Miller-Urey spark-discharge experiments in the early 1950s inspired a strong interest in experimental studies of prebiotic organic chemistry that continues today. Over the years, many of the basic building blocks of life as we know it have been synthesized in the laboratory from simple ingredients, including amino acids, sugars, nucleobases, and membrane-forming lipids. Questions remain, however, concerning whether the conditions that allow synthesis of these compounds in the laboratory accurately simulate those that might have been present on the early Earth, and a closer convergence between plausible prebiotic conditions and laboratory simulations remains a challenge for experimentalists.

Prebiotic Chemistry within a Simple Impacting Icy Mixture

We present results of prebiotic organic synthesis in shock compressed mixtures of simple ices from quantum molecular dynamics (MD) simulations extended to close to equilibrium time scales. Given the likelihood of an inhospitable prebiotic atmosphere on early Earth, it is possible that impact processes of comets or other icy bodies were a source of prebiotic chemical compounds on the primitive planet. We observe that moderate shock pressures and temperatures within a CO2-rich icy mixture (36 GPa and 2800 K) produce a number of nitrogen containing heterocycles, which dissociate to form functionalized aromatic hydrocarbons upon expansion and cooling to ambient conditions. In contrast, higher shock conditions (48-60 GPa, 3700-4800 K) resulted in the synthesis of long carbon-chain molecules, CH4, and formaldehyde. All shock compression simulations at these conditions have produced significant quantities of simple C-N bonded compounds such as HCN, HNC, and HNCO upon expansion and cooling to ambient conditions. Our results elucidate a mechanism for impact synthesis of prebiotic molecules at realistic impact conditions that is independent of external constraints such as the presence of a catalyst, illuminating UV radiation, or pre-existing conditions on a planet.

Themes and Variations in Complex Systems

Research Article| February 01, 2010 Themes and Variations in Complex Systems Robert M. Hazen; Robert M. Hazen 1Geophysical Laboratory, Carnegie Institution of Washington 5251 Broad Branch Road NW, Washington, DC 20015, USA E-mail: rhazen@ciw.edu Search for other works by this author on: GSW Google Scholar Niles Eldredge Niles Eldredge 2Division of Paleontology, American Museum of Natural History New York, NY 10024, USA E-mail: epunkeek@amnh.org Search for other works by this author on: GSW Google Scholar Author and Article Information Robert M. Hazen 1Geophysical Laboratory, Carnegie Institution of Washington 5251 Broad Branch Road NW, Washington, DC 20015, USA E-mail: rhazen@ciw.edu Niles Eldredge 2Division of Paleontology, American Museum of Natural History New York, NY 10024, USA E-mail: epunkeek@amnh.org Publisher: Mineralogical Society of America First Online: 09 Mar 2017 Online ISSN: 1811-5217 Print ISSN: 1811-5209 © 2010 by the Mineralogical Society of America Elements (2010) 6 (1): 43–46. https://doi.org/10.2113/gselements.6.1.43 Article history First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Robert M. Hazen, Niles Eldredge; Themes and Variations in Complex Systems. Elements 2010;; 6 (1): 43–46. doi: https://doi.org/10.2113/gselements.6.1.43 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyElements Search Advanced Search Abstract Complex systems display diversification in type, patterning, and behavior over time through varied selective mechanisms. Such systems are observed in numerous natural and cultural contexts, including nucleosynthesis, minerals, prebiotic organic synthesis, languages, material culture, and cellular life. These systems possess such qualitatively similar characteristics as diversification into new environments (radiation), episodic periods of innovation (punctuation), and loss of types (extinction). Comparisons among these varied systems thus point to general principles of complexification. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Changeable hydrothermal media as potential cradle of life on a planet

According to the elaborated systemic concept, a prebiotic microsystem has a chance to be transformed into primary living unit (probiont) only under nonequilibrium oscillating conditions. This transition proceeds through three successive kinds of transformations. First, a prebiotic microsystem must acquire the specific critical properties being at the unstable state of the bifurcate transition. Then it should be relatively stabilized due to balanced oscillations between the initial and the forward states (there appears the paradoxical state of ‘stabilized instability’). The decisive transformation to the living state is connected with the inversion of the ratio of ‘free energy to entropy contribution’ when the free energy input in the microsystem becomes higher than the entropy input. Changeable nonequilibrium conditions are most typical to hydrothermal systems in comparison with other aqueous media of the Earth. In this context the hydrothermal medium seems very suitable to be considered as a potential cradle of life on a planet. To characterize a scale of the thermodynamic and physico-chemical fluctuations some hydrothermal systems in Kamchatka peninsula were explored. The period of the pressure microoscillations in Mutnovsky and Pauzhetsky hydrothermal systems range from 10 to 30 min, and the amplitude is 0.2–0.7 bar. From time to time the amplitude of the fluctuations significantly rises due to spontaneous increase of activity of the nearest volcanoes. Similar results were obtained during the exploration of thermodynamic and chemical fluctuations in Mura hydrothermal field in Slovenia: the period of the water pressure oscillations is 60–70 min, and the average amplitude about 0.5 bar. Temperature and some chemical parameters oscillate in this field with the same period. These data can be used to conduct advanced laboratory experiments on prebiotic organic synthesis under nonequilibrium oscillating conditions. Some universal aspects of this concept may allow us to better understand the origin-of-life process in the Universe.

A reassessment of prebiotic organic synthesis in neutral planetary atmospheres.

The action of an electric discharge on reduced gas mixtures such as H(2)O, CH(4) and NH(3) (or N(2)) results in the production of several biologically important organic compounds including amino acids. However, it is now generally held that the early Earth's atmosphere was likely not reducing, but was dominated by N(2) and CO(2). The synthesis of organic compounds by the action of electric discharges on neutral gas mixtures has been shown to be much less efficient. We show here that contrary to previous reports, significant amounts of amino acids are produced from neutral gas mixtures. The low yields previously reported appear to be the outcome of oxidation of the organic compounds during hydrolytic workup by nitrite and nitrate produced in the reactions. The yield of amino acids is greatly increased when oxidation inhibitors, such as ferrous iron, are added prior to hydrolysis. Organic synthesis from neutral atmospheres may have depended on the oceanic availability of oxidation inhibitors as well as on the nature of the primitive atmosphere itself. The results reported here suggest that endogenous synthesis from neutral atmospheres may be more important than previously thought.

Prebiotic organic synthesis in early Earth and Mars atmospheres: Laboratory experiments with quantitative determination of products formed in a cold plasma flow reactor

The goal of this study was to explore prebiotic chemistry in a range of plausible early Earth and Mars atmospheres. To achieve this laboratory continuous flow plasma irradiation experiments were performed on N 2/H 2/CO/CO 2 gas mixtures chosen to represent mildly reducing early Earth and Mars atmospheres derived from a secondary volcanic outgassing of volatiles in chemical equilibrium with magmas near present day oxidation state. Under mildly reducing conditions (91.79% N 2, 5.89% H 2, 2.21% CO, and 0.11% CO 2), simple nitriles are produced in the gas phase with yield ( G in molecules per 100 eV), for the key prebiotic marker molecule HCN at G ∼ 1 × 10 −3 (0.1 nmol J −1). In this atmosphere localized HCN concentrations possibly could approach the 10 −2 M needed for HCN oligomerization. Yields under mildly oxidizing conditions (45.5% N 2, 0.1% H 2, 27.2% CO, 27.2% CO 2) are significantly less as expected, with HCN at G ∼ 3 × 10 −5 ( 3 × 10 −3 nmol J −1 ). Yields in a Triton atmosphere which can be plausibly extrapolated to represent what might be produced in trace CH 4 conditions (99.9% N 2, 0.1% CH 4) are significant with HCN at G ∼ 1 × 10 −2 (1 nmol J −1) and tholins produced. Recently higher methane abundance atmospheres have been examined for their greenhouse warming potential, and higher abundance hydrogen atmospheres have been proposed based on a low early Earth exosphere temperature. A reducing (64.04% N 2, 28.8% H 2, 3.60% CO 2, and 3.56% CH 4), representing a high CH 4 and H 2 abundance early Earth atmosphere had HCN yields of G ∼ 5 × 10 −3 (0.5 nmol J −1). Tholins generated in high methane hydrogen gas mixtures is much less than in a similar mixture without hydrogen. The same mixture with the oxidizing component CO 2 removed (66.43% N 2, 29.88% H 2, 0% CO 2, and 3.69% CH 4) had HCN yields of G ∼ 1 × 10 −3 (0.1 nmol J −1) but more significant tholin yields.

In situ transformation of an aqueous amino acid at high pressures and temperatures

The stability and transformation of aqueous amino acid at high pressures and temperatures are very important in terms of the formation of interstellar organic matter, delivery of organic compounds of meteorolites, and prebiotic organic synthesis. We studied aqueous alanine saturated solid solution at pressures of several gigapascals and temperatures up to 500°C using an external heating hydrothermal diamond anvil cell (HDAC) through in situ observation and Raman spectroscopy. Five samples of initial pressures of 1.23, 1.98, 2.69, 2.78, and 3.67 GPa, which cause transformation from liquid solution to solid phase, are studied. The transformations of aqueous alanine solution are highly reliant on pressure, and with higher initial pressures, the transitions are retarded to higher temperatures. The melted solid alanine solution of the lowest initial pressure separates out a non-eutectic phase which takes on the characteristic of macro-organic matter, which indicates that amino acids can oligomerize or even polymerize at high pressures and temperatures. As for the highest initial pressure, the solid alanine solution remains almost intact up to the highest temperature of 500°C. The results show that pressure should be required to understand many occurrences of amino acids in space and meteorites.

Life in the Universe: from the Miller Experiment to the Search for Life on Other Worlds

Life in the Universe: from the Miller Experiment to the Search for Life on Other Worlds

The potential of photochemical transition metal reactions in prebiotic organic synthesis. I. Observed conversion of methanol into ethylene glycol as possible prototype for sugar alcohol formation.

Photochemical processes involving redox reactions between metal ions and organic substrates possess the versatile potential for having harnessed solar energy for prebiotic organic synthesis. The present study in our Laboratory has shown that ultraviolet irradiation of transition metal ions such as of Ni, Co, Fe, Cu and Ti dissolved in primary or secondary alcohols causes photoreduction of the metal ions with the concomitant oxidation of the alcohol to aldehyde or ketone. An observed accompaniment of this novel 'light' reaction has been the known 'dark' pinacol reaction, whereby the carbonyl derivative underwent bimolecular coupling to the diol by the photogenerated reduced transition metal reagent. These tandem 'light-dark' processes possess the potential for the stepwise synthesis of dimeric 1,2-diols from simpler alcohols under conditions that might have prevailed on the prebiotic earth. Experiments reported here have demonstrated that such a tandem 'light-dark' conversion of methanol into ethylene glycol, via formaldehyde, does in fact occur, when nickel(II) acetylacetonate solutions in methanol undergo prolonged irradiation at 185-254 nm. Since ethylene glycol can be considered as the simplest sugar alcohol, these findings may provide novel insight into the prebiotic oligomerization of formaldehyde into higher sugar alcohols or even sugars.

Biomarkers (molecular fossils) as geochemical indicators of life

Biomarkers (also termed chemical fossils, molecular markers, indicators or organic tracers) are specific organic compounds which are useful in assessing the genetic sources of lipidic or bituminous organic matter. Biomarkers in geological samples on Earth are products derived from biochemical (natural product) precursors by mainly reductive but also oxidative alteration processes (e.g., cholestanes from cholesterol). They have chemical structures which can be related back to their precursor compounds in contemporary or extinct biota. Generally, lipids, pigments and biomembranes are preserved best over longer geological times. Thus the detailed characterization of biomarker structures and mixture compositions permits the assessment of the major contributing source species of extinct and/or extant life. Biomarkers cannot be synthesized by abiological processes and each precursor generally is altered by diagenetic and catagenetic processes to a sequential series of derivative products. The utility of biomarkers as indicators of biogenic, paleoenvironmental and geochemical processes on Earth has been widely accepted. Here I redefine and discuss the application of this concept to extraterrestrial exploration for evidence of life or prebiotic organic synthesis. Nonbiomarkers are also considered in this context.

Prebiotic organic synthesis under hydrothermal conditions: an overview

Organic compounds which are obviously synthesized from inorganic precursors (e.g., CO) by hydrothermal activity are currently a research topic in prebiotic chemistry leading to the origin of life. However, such de novo products would be overwhelmed in present Earth environments, by an excess of thermal alteration (pyrolysis) products formed from contemporary life (e.g., hydrocarbons, alkanoic acids, etc.). Thus, organic syntheses must be demonstrated and distinguished from organic matter alteration initially in the laboratory and then in the field. Organic synthesis under hydrothermal conditions is theoretically possible and various established industrial processes are used to synthesize organic compounds from inorganic substrates with the aid of catalysts. A set of Strecker-type synthesis experiments has been carried out under hydrothermal conditions (150 °C), producing various amino acids. The formation of lipid compounds during an aqueous organic synthesis (Fischer–Tropsch-type) reaction was reported, using solutions of oxalic acid (also formic acid) as the carbon and hydrogen sources, and heating at discrete temperatures (50° intervals) from 100 to 400 °C. The maximum lipid yield, especially for oxygenated compounds was in the window of 150–250 °C. The compounds range from C 6 to >C 33, including n-alkanols, n-alkanoic acids, n-alkyl formates, n-alkanones, and n-alkanes, all with no carbon number preferences. These lipid compounds, especially the acids, can form lipid bilayers or micelles, potential precursors for membranes. Reductive condensation (i.e., dehydration) reactions also occur under simulated hydrothermal conditions and form amide, nitrile and ester bonds. The chemistry and kinetics of the condensation reactions are under further study and have the potential for oligomerization of acid-amides in aqueous medium. Abiotic organic compounds are not biomarkers per se because they do not originate from biosynthesis. Thus, they should be regarded as a distinctly separate group, termed prebiotic or synthetic organic compounds, in explorations for evidence of life.

MESOBIOTIC EMERGENCE: MOLECULAR AND ENSEMBLE COMPLEXITY IN EARLY EVOLUTION

In addition to the visible complexity expressed in the morphogenesis of multicellular organisms, two levels of microscopic complexity may be discerned within every living cell. The first level is related to covalently bonded structures, namely molecules. The second level has to do with the generation of non-covalent molecular assemblies. Origin of life research has largely focused on the first complexity level, i.e. the appearance of covalent biopolymers. We present a life emergence scenario based mainly on the second complexity level. We argue that homeostatic molecular ensembles, for which we have coined the term "mesobiotic," have assumed a half-way position between prebiotic organic synthesis and full-fledged cellular (biotic) life.

Carbon isotope exchange in the system CO 2-CH 4 at elevated temperatures

Carbon isotope exchange was investigated for the system CO 2-CH 4 at 150 to 600°C in the presence of several potential catalysts by use of isotopically normal or 13C-enriched gases. Silica gel, graphite, molecular sieve Linde 4A, magnetite, and hematite oxidized small amounts of CH 4 in starting CO 2-CH 4 mixtures to CO and CO 2 but failed to enhance the net rate of carbon isotope exchange between CO 2 and CH 4, even after 169 to 1833 h at 400 to 500°C. In contrast, several commercial transition-metal catalysts (Ni, Pd, Rh, and Pt) promoted reactions significantly toward chemical and isotopic equilibrium. With the Ni catalyst, the attainment of carbon isotopic equilibrium between CO 2 and CH 4 was demonstrated for the first time at temperatures from 200 to 600°C by complete isotopic reversal from opposite directions. The experimentally determined carbon isotope fractionation factors between CO 2 and CH 4 (10 3lnα) were similar to, but slightly greater than (0.7–1.1‰, 0.89‰ on average), those of statistical-mechanical calculations by Richet et al. (1977). The experimental results can be described by the following equation between 200 and 600°C only: 10 3lnα(CO 2-CH 4) = 26.70 − 49.137(10 3/T) + 40.828(10 6/T 2) − 7.512(10 9/T 3) (T = 473.15–873.15 K, 1σ = ±0.14‰, n = 44). Alternatively, an equation generated by fitting Richet et al. (1977) data in the temperature range from 0 to 1300°C can be modified by adding +0.89‰ to its constant; 10 3lnα(CO 2-CH 4) = 0.16 + 11.754(10 6/T 2) − 2.3655(10 9/T 3) + 0.2054(10 12/T 4) (T = 273–1573 K, 1σ = ±0.21‰, n = 44). This and other recent experimental studies in the literature demonstrate that transition metals, which are widespread in many natural materials, can catalyze reactions among natural gases at relatively low temperatures (≤200°C). The role of natural catalysts, “geocatalysts,” in the abiogenic formation of methane, hydrocarbons, and simple organic compounds has important implications, ranging from the exploration of hydrocarbon resources to prebiotic organic synthesis.