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Grosch EG, McLoughlin N, Whitehouse M. Multiple sulphur isotope record of Paleoarchean sedimentary rocks across the Onverwacht Group, Barberton Greenstone Belt, South Africa. GEOBIOLOGY 2023; 21:153-167. [PMID: 36571166 DOI: 10.1111/gbi.12542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 12/01/2022] [Accepted: 12/12/2022] [Indexed: 06/17/2023]
Abstract
This study presents multiple sulphur isotope (32 S, 33 S, 34 S, 36 S) data on pyrites from silicified volcano-sedimentary rocks of the Paleoarchean Onverwacht Group of the Barberton greenstone belt, South Africa. These rocks include seafloor cherts and felsic conglomerates that were deposited in shallow marine environments preserving a record of atmospheric and biogeochemical conditions on the early Earth. A strong variation in mass independent sulphur isotope fractionation (MIF-S) anomalies is found in the cherts, with Δ33 S ranging between -0.26‰ and 3.42‰. We explore possible depositional and preservational factors that could explain some of this variation seen in MIF-S. Evidence for microbial activity is recorded by the c. 3.45 Ga Hooggenoeg Formation Chert (HC4) preserving a contribution of microbial sulphate reduction (-Δ33 S and -δ34 S), and a c. 3.33 Ga Kromberg Formation Chert (KC5) recording a possible contribution of microbial elemental sulphur disproportionation (+Δ33 S and -δ34 S). Pyrites from a rhyo-dacitic conglomerate of the Noisy Formation do not plot along a previously proposed global Felsic Volcanic Array, and this excludes short-lived pulses of intense felsic volcanic gas emissions as the dominant control on Archean MIF-S. Rather, we suggest that the MIF-S signals measured reflect dilution during marine deposition, early diagenetic modification, and mixing with volcanic/hydrothermal S sources. Given the expanded stratigraphic interval (3.47-3.22 Ga) now sampled from across the Barberton Supergroup, we conclude that large MIF-S exceeding >4‰ is atypical of Paleoarchean near-surface environments on the Kaapvaal Craton.
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Affiliation(s)
- Eugene G Grosch
- Geology Department, Rhodes University, Makhanda/Grahamstown, South Africa
| | - Nicola McLoughlin
- Geology Department, Rhodes University, Makhanda/Grahamstown, South Africa
| | - Martin Whitehouse
- NORDSIMS Laboratory, Swedish Museum of Natural History, Stockholm, Sweden
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2
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A Few Experimental Suggestions Using Minerals to Obtain Peptides with a High Concentration of L-Amino Acids and Protein Amino Acids. Symmetry (Basel) 2020. [DOI: 10.3390/sym12122046] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The peptides/proteins of all living beings on our planet are mostly made up of 19 L-amino acids and glycine, an achiral amino acid. Arising from endogenous and exogenous sources, the seas of the prebiotic Earth could have contained a huge diversity of biomolecules (including amino acids), and precursors of biomolecules. Thus, how were these amino acids selected from the huge number of available amino acids and other molecules? What were the peptides of prebiotic Earth made up of? How were these peptides synthesized? Minerals have been considered for this task, since they can preconcentrate amino acids from dilute solutions, catalyze their polymerization, and even make the chiral selection of them. However, until now, this problem has only been studied in compartmentalized experiments. There are separate experiments showing that minerals preconcentrate amino acids by adsorption or catalyze their polymerization, or separate L-amino acids from D-amino acids. Based on the [GADV]-protein world hypothesis, as well as the relative abundance of amino acids on prebiotic Earth obtained by Zaia, several experiments are suggested. The main goal of these experiments is to show that using minerals it is possible, at least, to obtain peptides whose composition includes a high quantity of L-amino acids and protein amino acids (PAAs). These experiments should be performed using hydrothermal environments and wet/dry cycles. In addition, for hydrothermal environment experiments, it is very important to use one of the suggested artificial seawaters, and for wet/dry environments, it is important to perform the experiments in distilled water and diluted salt solutions. Finally, from these experiments, we suggest that, without an RNA world or even a pre genetic world, a small peptide set could emerge that better resembles modern proteins.
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Li Y, Li Y, Liu Y, Wu Y, Wu J, Wang B, Ye H, Jia H, Wang X, Li L, Zhu M, Ding H, Lai Y, Wang C, Dick J, Lu A. Photoreduction of inorganic carbon(+IV) by elemental sulfur: Implications for prebiotic synthesis in terrestrial hot springs. SCIENCE ADVANCES 2020; 6:6/47/eabc3687. [PMID: 33208363 PMCID: PMC7673799 DOI: 10.1126/sciadv.abc3687] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 10/05/2020] [Indexed: 06/11/2023]
Abstract
Terrestrial hydrothermal systems have been proposed as alternative birthplaces for early life but lacked reasonable scenarios for the supply of biomolecules. Here, we show that elemental sulfur (S0), as the dominant mineral in terrestrial hot springs, can reduce carbon dioxide (CO2) into formic acid (HCOOH) under ultraviolet (UV) light below 280 nm. The semiconducting S0 is indicated to have a direct bandgap of 4.4 eV. The UV-excited S0 produces photoelectrons with a highly negative potential of -2.34 V (versus NHE, pH 7), which could reduce CO2 after accepting electrons from electron donors such as reducing sulfur species. Simultaneously, UV light breaks sulfur bonds, benefiting the adsorption of charged carbonates onto S0 and assisting their photoreduction. Assuming that terrestrial hot springs covered 1% of primitive Earth's surface, S0 at 10 μM could have produced maximal 109 kg/year HCOOH within 10-cm-thick photic zones, underlying its remarkable contributions to the accumulation of prebiotic biomolecules.
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Affiliation(s)
- Yanzhang Li
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Yan Li
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China.
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Yi Liu
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Yifu Wu
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Junqi Wu
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Bin Wang
- Sinopec Beijing Research Institute of Chemical Industry, Beijing 100013, People's Republic of China
| | - Huan Ye
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Haoning Jia
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Xiao Wang
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Linghui Li
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Meixiang Zhu
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Hongrui Ding
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Yong Lai
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Changqiu Wang
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
| | - Jeffrey Dick
- The Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring, School of Geosciences and Info-Physics, Central South University, Changsha 410083, People's Republic of China
| | - Anhuai Lu
- Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China.
- The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China
- The Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring, School of Geosciences and Info-Physics, Central South University, Changsha 410083, People's Republic of China
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4
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Zaia DAM, de Carvalho PCG, Samulewski RB, de Carvalho Pereira R, Zaia CTBV. Unexpected Thiocyanate Adsorption onto Ferrihydrite Under Prebiotic Chemistry Conditions. ORIGINS LIFE EVOL B 2020; 50:57-76. [PMID: 32266585 DOI: 10.1007/s11084-020-09594-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Accepted: 03/10/2020] [Indexed: 02/02/2023]
Abstract
The most crucial role played by minerals was in the preconcentration of biomolecules or precursors of biomolecules in prebiotic seas. If this step had not occurred, molecular evolution would not have occurred. Thiocyanate is an important molecule in the formation of biomolecules as well as a catalyst for prebiotic reactions. The adsorption of thiocyanate onto ferrihydrite was carried out under pH and ion composition conditions in seawater that resembled those of prebiotic Earth. The seawater used in this work had high Mg2+, Ca2+ and SO42- concentrations. The most important result of this work was that ferrihydrite adsorbed thiocyanateata pH value (7.2 ± 0.2) that usually does not adsorb thiocyanate. The high adsorptivity of Mg2+, Ca2+ and SO42-onto ferrihydrite showed that seawater ions can act as carriers of thiocyanate to the ferrihydrite surface, creating a huge outer-sphere complex. Kinetic adsorption and isotherm experiments showed the best fit for the pseudo-second-order model and an activation energy of 23.8 kJ mol-1forthe Langmuir-Freundlich model, respectively. Thermodynamic data showed positive ΔG values, which apparently contradict the adsorption isotherm data and kinetic data that was obtained. The adsorption of thiocyanate onto ferrihydrite could be explained by coupling with the exergonic SO42- adsorption onto ferrihydrite. The FTIR spectra showed no difference between the C≡N stretching peaks of adsorbed thiocyanate and free thiocyanate, corroborating the formation of an outer-sphere complex. All the results demonstrated the importance of the artificial seawater composition for the adsorption of thiocyanate and for understanding prebiotic chemistry.
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Affiliation(s)
- Dimas A M Zaia
- Departamento de Química, Laboratório de Química Prebiótica-LQP, Universidade Estadual de Londrina, Londrina, PR, CEP 86 057-970, Brazil.
| | - Paulo C G de Carvalho
- Departamento de Química, Laboratório de Química Prebiótica-LQP, Universidade Estadual de Londrina, Londrina, PR, CEP 86 057-970, Brazil
| | - Rafael B Samulewski
- Departamento de Química, Laboratório de Química Prebiótica-LQP, Universidade Estadual de Londrina, Londrina, PR, CEP 86 057-970, Brazil
| | - Rodrigo de Carvalho Pereira
- Departamento de Química, Laboratório de Química Prebiótica-LQP, Universidade Estadual de Londrina, Londrina, PR, CEP 86 057-970, Brazil
| | - Cássia Thaïs B V Zaia
- Departamento de Ciências Fisiológicas, Laboratório de Fisiologia Neuroendocrina--LaFiNen, Universidade Estadual de Londrina, Londrina, PR, CEP 86 057-970, Brazil
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5
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Hicks RK, Day DA, Jimenez JL, Tolbert MA. Follow the Carbon: Isotopic Labeling Studies of Early Earth Aerosol. ASTROBIOLOGY 2016; 16:822-830. [PMID: 27870584 DOI: 10.1089/ast.2015.1436] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Despite the faint young Sun, early Earth might have been kept warm by an atmosphere containing the greenhouse gases CH4 and CO2 in mixing ratios higher than those found on Earth today. Laboratory and modeling studies suggest that an atmosphere containing these trace gases could lead to the formation of organic aerosol haze due to UV photochemistry. Chemical mechanisms proposed to explain haze formation rely on CH4 as the source of carbon and treat CO2 as a source of oxygen only, but this has not previously been verified experimentally. In the present work, we use isotopically labeled precursor gases and unit-mass resolution (UMR) and high-resolution (HR) aerosol mass spectrometry to examine the sources of carbon and oxygen to photochemical aerosol formed in a CH4/CO2/N2 atmosphere. UMR results suggest that CH4 contributes 70-100% of carbon in the aerosol, while HR results constrain the value from 94% to 100%. We also confirm that CO2 contributes approximately 10% of the total mass to the aerosol as oxygen. These results have implications for the geochemical interpretations of inclusions found in Archean rocks on Earth and for the astrobiological potential of other planetary atmospheres. Key Words: Atmosphere-Early Earth-Planetary atmospheres-Carbon dioxide-Methane. Astrobiology 16, 822-830.
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Affiliation(s)
- Raea K Hicks
- Department of Chemistry and Biochemistry, and Cooperative Institute for Research in Environmental Sciences, University of Colorado , Boulder, Colorado
| | - Douglas A Day
- Department of Chemistry and Biochemistry, and Cooperative Institute for Research in Environmental Sciences, University of Colorado , Boulder, Colorado
| | - Jose L Jimenez
- Department of Chemistry and Biochemistry, and Cooperative Institute for Research in Environmental Sciences, University of Colorado , Boulder, Colorado
| | - Margaret A Tolbert
- Department of Chemistry and Biochemistry, and Cooperative Institute for Research in Environmental Sciences, University of Colorado , Boulder, Colorado
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6
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Burcar B, Pasek M, Gull M, Cafferty BJ, Velasco F, Hud NV, Menor‐Salván C. Darwin's Warm Little Pond: A One‐Pot Reaction for Prebiotic Phosphorylation and the Mobilization of Phosphate from Minerals in a Urea‐Based Solvent. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201606239] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Bradley Burcar
- School of Chemistry and Biochemistry Georgia Institute of Technology Atlanta GA 30033 USA
| | - Matthew Pasek
- School of Geosciences University of South Florida Tampa FL USA
| | - Maheen Gull
- School of Geosciences University of South Florida Tampa FL USA
| | - Brian J. Cafferty
- School of Chemistry and Biochemistry Georgia Institute of Technology Atlanta GA 30033 USA
| | - Francisco Velasco
- Department of Mineralogy and Petrology Universidad del País Vasco Campus de Leioa Vizcaya Spain
| | - Nicholas V. Hud
- School of Chemistry and Biochemistry Georgia Institute of Technology Atlanta GA 30033 USA
| | - César Menor‐Salván
- School of Chemistry and Biochemistry Georgia Institute of Technology Atlanta GA 30033 USA
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7
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Burcar B, Pasek M, Gull M, Cafferty BJ, Velasco F, Hud NV, Menor‐Salván C. Darwin's Warm Little Pond: A One‐Pot Reaction for Prebiotic Phosphorylation and the Mobilization of Phosphate from Minerals in a Urea‐Based Solvent. Angew Chem Int Ed Engl 2016; 55:13249-13253. [DOI: 10.1002/anie.201606239] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Revised: 07/25/2016] [Indexed: 01/04/2023]
Affiliation(s)
- Bradley Burcar
- School of Chemistry and Biochemistry Georgia Institute of Technology Atlanta GA 30033 USA
| | - Matthew Pasek
- School of Geosciences University of South Florida Tampa FL USA
| | - Maheen Gull
- School of Geosciences University of South Florida Tampa FL USA
| | - Brian J. Cafferty
- School of Chemistry and Biochemistry Georgia Institute of Technology Atlanta GA 30033 USA
| | - Francisco Velasco
- Department of Mineralogy and Petrology Universidad del País Vasco Campus de Leioa Vizcaya Spain
| | - Nicholas V. Hud
- School of Chemistry and Biochemistry Georgia Institute of Technology Atlanta GA 30033 USA
| | - César Menor‐Salván
- School of Chemistry and Biochemistry Georgia Institute of Technology Atlanta GA 30033 USA
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8
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Hicks RK, Day DA, Jimenez JL, Tolbert MA. Elemental Analysis of Complex Organic Aerosol Using Isotopic Labeling and Unit-Resolution Mass Spectrometry. Anal Chem 2015; 87:2741-7. [DOI: 10.1021/ac504014g] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Raea K. Hicks
- Department
of Chemistry and Biochemistry, University of Colorado, 215 UCB, Boulder, Colorado 80309, United States
- Cooperative
Institute for Research in Environmental Sciences, University of Colorado, 216 UCB, Boulder, Colorado 80309, United States
| | - Douglas A. Day
- Department
of Chemistry and Biochemistry, University of Colorado, 215 UCB, Boulder, Colorado 80309, United States
- Cooperative
Institute for Research in Environmental Sciences, University of Colorado, 216 UCB, Boulder, Colorado 80309, United States
| | - Jose L. Jimenez
- Department
of Chemistry and Biochemistry, University of Colorado, 215 UCB, Boulder, Colorado 80309, United States
- Cooperative
Institute for Research in Environmental Sciences, University of Colorado, 216 UCB, Boulder, Colorado 80309, United States
| | - Margaret A. Tolbert
- Department
of Chemistry and Biochemistry, University of Colorado, 215 UCB, Boulder, Colorado 80309, United States
- Cooperative
Institute for Research in Environmental Sciences, University of Colorado, 216 UCB, Boulder, Colorado 80309, United States
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9
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Trainer MG. Atmospheric Prebiotic Chemistry and Organic Hazes. CURR ORG CHEM 2013; 17:1710-1723. [PMID: 24143126 PMCID: PMC3796891 DOI: 10.2174/13852728113179990078] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2011] [Revised: 05/07/2013] [Accepted: 05/12/2013] [Indexed: 02/04/2023]
Abstract
Earth's atmospheric composition at the time of the origin of life is not known, but it has often been suggested that chemical transformation of reactive species in the atmosphere was a significant source of prebiotic organic molecules. Experimental and theoretical studies over the past half century have shown that atmospheric synthesis can yield molecules such as amino acids and nucleobases, but these processes are very sensitive to gas composition and energy source. Abiotic synthesis of organic molecules is more productive in reduced atmospheres, yet the primitive Earth may not have been as reducing as earlier workers assumed, and recent research has reflected this shift in thinking. This work provides a survey of the range of chemical products that can be produced given a set of atmospheric conditions, with a particular focus on recent reports. Intertwined with the discussion of atmospheric synthesis is the consideration of an organic haze layer, which has been suggested as a possible ultraviolet shield on the anoxic early Earth. Since such a haze layer - if formed - would serve as a reservoir for organic molecules, the chemical composition of the aerosol should be closely examined. The results highlighted here show that a variety of products can be formed in mildly reducing or even neutral atmospheres, demonstrating that contributions of atmospheric synthesis to the organic inventory on early Earth should not be discounted. This review intends to bridge current knowledge of the range of possible atmospheric conditions in the prebiotic environment and pathways for synthesis under such conditions by examining the possible products of organic chemistry in the early atmosphere.
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Affiliation(s)
- Melissa G. Trainer
- Planetary Environments Laboratory, NASA Goddard Space Flight Center, Code 699, Greenbelt, MD 20771, USA
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Vibronic origin of sulfur mass-independent isotope effect in photoexcitation of SO2 and the implications to the early earth's atmosphere. Proc Natl Acad Sci U S A 2013; 110:17697-702. [PMID: 23836655 DOI: 10.1073/pnas.1306979110] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Signatures of mass-independent isotope fractionation (MIF) are found in the oxygen ((16)O,(17)O,(18)O) and sulfur ((32)S, (33)S, (34)S, (36)S) isotope systems and serve as important tracers of past and present atmospheric processes. These unique isotope signatures signify the breakdown of the traditional theory of isotope fractionation, but the physical chemistry of these isotope effects remains poorly understood. We report the production of large sulfur isotope MIF, with Δ(33)S up to 78‰ and Δ(36)S up to 110‰, from the broadband excitation of SO2 in the 250-350-nm absorption region. Acetylene is used to selectively trap the triplet-state SO2 ( (3)B1), which results from intersystem crossing from the excited singlet ( (1)A2/ (1)B1) states. The observed MIF signature differs considerably from that predicted by isotopologue-specific absorption cross-sections of SO2 and is insensitive to the wavelength region of excitation (above or below 300 nm), suggesting that the MIF originates not from the initial excitation of SO2 to the singlet states but from an isotope selective spin-orbit interaction between the singlet ( (1)A2/ (1)B1) and triplet ( (3)B1) manifolds. Calculations based on high-level potential energy surfaces of the multiple excited states show a considerable lifetime anomaly for (33)SO2 and (36)SO2 for the low vibrational levels of the (1)A2 state. These results demonstrate that the isotope selectivity of accidental near-resonance interactions between states is of critical importance in understanding the origin of MIF in photochemical systems.
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11
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Production, preservation, and biological processing of mass-independent sulfur isotope fractionation in the Archean surface environment. Proc Natl Acad Sci U S A 2013; 110:17644-9. [PMID: 23572589 DOI: 10.1073/pnas.1213148110] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mass-independent fractionation of sulfur isotopes (S MIF) in Archean and Paleoproterozoic rocks provides strong evidence for an anoxic atmosphere before ~2,400 Ma. However, the origin of this isotopic anomaly remains unclear, as does the identity of the molecules that carried it from the atmosphere to Earth's surface. Irrespective of the origin of S MIF, processes in the biogeochemical sulfur cycle modify the primary signal and strongly influence the S MIF preserved and observed in the geological record. Here, a detailed model of the marine sulfur cycle is used to propagate and distribute atmospherically derived S MIF from its delivery to the ocean to its preservation in the sediment. Bulk pyrite in most sediments carries weak S MIF because of microbial reduction of most sulfur compounds to form isotopically homogeneous sulfide. Locally, differential incorporation of sulfur compounds into pyrite leads to preservation of S MIF, which is predicted to be most highly variable in nonmarine and shallow-water settings. The Archean ocean is efficient in diluting primary atmospheric S MIF in the marine pools of sulfate and elemental sulfur with inputs from SO2 and H2S, respectively. Preservation of S MIF with the observed range of magnitudes requires the S MIF production mechanism to be moderately fractionating ( 20-40‰). Constraints from the marine sulfur cycle allow that either elemental sulfur or organosulfur compounds (or both) carried S MIF to the surface, with opposite sign to S MIF in SO2 and H2SO4. Optimal progress requires observations from nonmarine and shallow-water environments and experimental constraints on the reaction of photoexcited SO2 with atmospheric hydrocarbons.
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12
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Domagal-Goldman SD, Meadows VS, Claire MW, Kasting JF. Using biogenic sulfur gases as remotely detectable biosignatures on anoxic planets. ASTROBIOLOGY 2011; 11:419-41. [PMID: 21663401 PMCID: PMC3133782 DOI: 10.1089/ast.2010.0509] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
We used one-dimensional photochemical and radiative transfer models to study the potential of organic sulfur compounds (CS(2), OCS, CH(3)SH, CH(3)SCH(3), and CH(3)S(2)CH(3)) to act as remotely detectable biosignatures in anoxic exoplanetary atmospheres. Concentrations of organic sulfur gases were predicted for various biogenic sulfur fluxes into anoxic atmospheres and were found to increase with decreasing UV fluxes. Dimethyl sulfide (CH(3)SCH(3), or DMS) and dimethyl disulfide (CH(3)S(2)CH(3), or DMDS) concentrations could increase to remotely detectable levels, but only in cases of extremely low UV fluxes, which may occur in the habitable zone of an inactive M dwarf. The most detectable feature of organic sulfur gases is an indirect one that results from an increase in ethane (C(2)H(6)) over that which would be predicted based on the planet's methane (CH(4)) concentration. Thus, a characterization mission could detect these organic sulfur gases-and therefore the life that produces them-if it could sufficiently quantify the ethane and methane in the exoplanet's atmosphere.
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