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Flores J, Ruscitti M, Khani S, Reilly NJ. Electronic Spectrum of α-Hydrofulvenyl Radical (C 6H 7), and a Simple and Accurate Recipe for Predicting Adiabatic Ionization Energies of Resonance-Stabilized Hydrocarbon Radicals. J Phys Chem A 2024. [PMID: 39264134 DOI: 10.1021/acs.jpca.4c04746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/13/2024]
Abstract
Using a combination of resonant two-photon two-color ionization (R2C2PI) and laser-induced fluorescence/dispersed fluorescence spectroscopy, we have examined the A ~ 2A″ ← X ~ 2A″ transition of the resonance-stabilized α-hydrofulvenyl radical, produced from methylcyclopentadiene dimer in a jet-cooled discharge. Like the related 1,4-pentadienyl and cyclohexadienyl radicals, the α-hydrofulvenyl Ã-state lifetime is orders of magnitude shorter than the predicted f-value implies, indicative of rapid nonradiative decay. The transition is fully allowed by symmetry but considerably weakened by transition moment interference. Intensity borrowing among a' modes brings about static (i.e., Condon) and vibronic (i.e., Herzberg-Teller) moments of similar size, the result being a spectrum substantially less origin-dominated than is usually observed for extensively delocalized radicals. Twenty A ~ -state modes and twelve X ~ -state modes are identified with high confidence and assignments for several others are suggested. In addition, from a series of two-color appearance potential scans with the A ~ -state zero-point level serving as an intermediate, we obtain a field-free adiabatic ionization energy (AIE) of 7.012(1) eV. For a set of 21 resonance-stabilized radicals bearing 5 to 11 carbon atoms, it emerges that the field-free AIE obtained by R2C2PI methods under jet-cooled conditions lies very close to the average of B3LYP/6-311G++(d,p) (with harmonic zero-point energy) and CBS-QB3 0 K calculations, with a mean absolute deviation of only 0.010(7) eV (approximately 1 kJ/mol). On average, this represents a nearly 10-fold improvement in accuracy over CBS-QB3 predictions for the same set of radicals.
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Affiliation(s)
- Jonathan Flores
- Department of Chemistry, University of Massachusetts Boston, 100 Morrissey Boulevard, Boston, Massachusetts 02125, United States
| | - Massimo Ruscitti
- Department of Chemistry, University of Massachusetts Boston, 100 Morrissey Boulevard, Boston, Massachusetts 02125, United States
| | - Sima Khani
- Department of Chemistry, University of Massachusetts Boston, 100 Morrissey Boulevard, Boston, Massachusetts 02125, United States
| | - Neil J Reilly
- Department of Chemistry, University of Massachusetts Boston, 100 Morrissey Boulevard, Boston, Massachusetts 02125, United States
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2
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Michaelian K. The Pigment World: Life's Origins as Photon-Dissipating Pigments. Life (Basel) 2024; 14:912. [PMID: 39063667 PMCID: PMC11277707 DOI: 10.3390/life14070912] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2024] [Revised: 07/03/2024] [Accepted: 07/06/2024] [Indexed: 07/28/2024] Open
Abstract
Many of the fundamental molecules of life share extraordinary pigment-like optical properties in the long-wavelength UV-C spectral region. These include strong photon absorption and rapid (sub-pico-second) dissipation of the induced electronic excitation energy into heat through peaked conical intersections. These properties have been attributed to a "natural selection" of molecules resistant to the dangerous UV-C light incident on Earth's surface during the Archean. In contrast, the "thermodynamic dissipation theory for the origin of life" argues that, far from being detrimental, UV-C light was, in fact, the thermodynamic potential driving the dissipative structuring of life at its origin. The optical properties were thus the thermodynamic "design goals" of microscopic dissipative structuring of organic UV-C pigments, today known as the "fundamental molecules of life", from common precursors under this light. This "UV-C Pigment World" evolved towards greater solar photon dissipation through more complex dissipative structuring pathways, eventually producing visible pigments to dissipate less energetic, but higher intensity, visible photons up to wavelengths of the "red edge". The propagation and dispersal of organic pigments, catalyzed by animals, and their coupling with abiotic dissipative processes, such as the water cycle, culminated in the apex photon dissipative structure, today's biosphere.
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Affiliation(s)
- Karo Michaelian
- Department of Nuclear Physics and Application of Radiation, Instituto de Física, Universidad Nacional Autónoma de México, Circuito Interior de la Investigación Científica, Cuidad Universitaria, Cuidad de México CP 04510, Mexico
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3
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Christensen M, Adams D, Wong ML, Dunn P, Yung YL. New Estimates of Nitrogen Fixation on Early Earth. Life (Basel) 2024; 14:601. [PMID: 38792622 PMCID: PMC11122333 DOI: 10.3390/life14050601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Revised: 04/10/2024] [Accepted: 04/12/2024] [Indexed: 05/26/2024] Open
Abstract
Fixed nitrogen species generated by the early Earth's atmosphere are thought to be critical to the emergence of life and the sustenance of early metabolisms. A previous study estimated nitrogen fixation in the Hadean Earth's N2/CO2-dominated atmosphere; however, that previous study only considered a limited chemical network that produces NOx species (i.e., no HCN formation) via the thermochemical dissociation of N2 and CO2 in lightning flashes, followed by photochemistry. Here, we present an updated model of nitrogen fixation on Hadean Earth. We use the Chemical Equilibrium with Applications (CEA) thermochemical model to estimate lightning-induced NO and HCN formation and an updated version of KINETICS, the 1-D Caltech/JPL photochemical model, to assess the photochemical production of fixed nitrogen species that rain out into the Earth's early ocean. Our updated photochemical model contains hydrocarbon and nitrile chemistry, and we use a Geant4 simulation platform to consider nitrogen fixation stimulated by solar energetic particle deposition throughout the atmosphere. We study the impact of a novel reaction pathway for generating HCN via HCN2, inspired by the experimental results which suggest that reactions with CH radicals (from CH4 photolysis) may facilitate the incorporation of N into the molecular structure of aerosols. When the HCN2 reactions are added, we find that the HCN rainout rate rises by a factor of five in our 1-bar case and is about the same in our 2- and 12-bar cases. Finally, we estimate the equilibrium concentration of fixed nitrogen species under a kinetic steady state in the Hadean ocean, considering loss by hydrothermal vent circulation, photoreduction, and hydrolysis. These results inform our understanding of environments that may have been relevant to the formation of life on Earth, as well as processes that could lead to the emergence of life elsewhere in the universe.
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Affiliation(s)
- Madeline Christensen
- Bellarmine Preparatory Marine Chemistry Program, Tacoma, WA 98405, USA
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
| | - Danica Adams
- Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA
- NHFP Sagan Fellow, NASA Hubble Fellowship Program, Space Telescope Science Institute, Baltimore, MD 21218, USA
| | - Michael L. Wong
- NHFP Sagan Fellow, NASA Hubble Fellowship Program, Space Telescope Science Institute, Baltimore, MD 21218, USA
- Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC 20015, USA
| | - Patrick Dunn
- Space Sciences Laboratory, University of California, Berkeley, CA 94720, USA;
| | - Yuk L. Yung
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
- NASA Jet Propulsion Laboratory, Pasadena, CA 91109, USA
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4
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Hernández C, Michaelian K. Dissipative Photochemical Abiogenesis of the Purines. ENTROPY (BASEL, SWITZERLAND) 2022; 24:1027. [PMID: 35893007 PMCID: PMC9394256 DOI: 10.3390/e24081027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Revised: 07/21/2022] [Accepted: 07/22/2022] [Indexed: 01/27/2023]
Abstract
We have proposed that the abiogenesis of life around the beginning of the Archean may have been an example of "spontaneous" microscopic dissipative structuring of UV-C pigments under the prevailing surface ultraviolet solar spectrum. The thermodynamic function of these Archean pigments (the "fundamental molecules of life"), as for the visible pigments of today, was to dissipate the incident solar light into heat. We have previously described the non-equilibrium thermodynamics and the photochemical mechanisms which may have been involved in the dissipative structuring of the purines adenine and hypoxanthine from the common precursor molecules of hydrogen cyanide and water under this UV light. In this article, we extend our analysis to include the production of the other two important purines, guanine and xanthine. The photochemical reactions are presumed to occur within a fatty acid vesicle floating on a hot (∼80 ∘C) neutral pH ocean surface exposed to the prevailing UV-C light. Reaction-diffusion equations are resolved under different environmental conditions. Significant amounts of adenine (∼10-5 M) and guanine (∼10-6 M) are obtained within 60 Archean days, starting from realistic concentrations of the precursors hydrogen cyanide and cyanogen (∼10-5 M).
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Affiliation(s)
- Claudeth Hernández
- Department of Physics, Division of Exact and Natural Sciences, Campus Hermosillo, Universidad de Sonora, Hermosillo C.P. 83067, Mexico;
| | - Karo Michaelian
- Department of Nuclear Physics and Application of Radiation, Instituto de Física, Universidad Nacional Autónoma de México, Circuito Interior de la Investigación Científica, Cuidad Universitaria, Cuidad de México C.P. 04510, Mexico
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5
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Kaiser RI, Zhao L, Lu W, Ahmed M, Zagidullin MV, Azyazov VN, Mebel AM. Formation of Benzene and Naphthalene through Cyclopentadienyl-Mediated Radical-Radical Reactions. J Phys Chem Lett 2022; 13:208-213. [PMID: 34967648 DOI: 10.1021/acs.jpclett.1c03733] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Resonantly stabilized free radicals (RSFRs) have been contemplated as fundamental molecular building blocks and reactive intermediates in molecular mass growth processes leading to polycyclic aromatic hydrocarbons (PAHs) and carbonaceous nanoparticles on Earth and in deep space. By combining molecular beams and computational fluid dynamics simulations, we provide compelling evidence on the formation of benzene via the cyclopentadienyl-methyl reaction and of naphthalene through the cyclopentadienyl self-reaction, respectively. These systems offer benchmarks for the conversion of a five-membered ring to the 6π-aromatic (benzene) and the generation of the simplest 10π-PAH (naphthalene) at elevated temperatures. These results uncover molecular mass growth processes from the "bottom up" via RSFRs in high temperature circumstellar environments and combustion systems expanding our fundamental knowledge of the organic, hydrocarbon chemistry in our universe.
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Affiliation(s)
- Ralf I Kaiser
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
| | - Long Zhao
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
| | - Wenchao Lu
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Musahid Ahmed
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Marsel V Zagidullin
- Lebedev Physical Institute, Samara Branch, Samara 443011, Russian Federation
| | - Valeriy N Azyazov
- Lebedev Physical Institute, Samara Branch, Samara 443011, Russian Federation
| | - Alexander M Mebel
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States
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6
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The Dissipative Photochemical Origin of Life: UVC Abiogenesis of Adenine. ENTROPY 2021; 23:e23020217. [PMID: 33579010 PMCID: PMC7916814 DOI: 10.3390/e23020217] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 01/22/2021] [Accepted: 02/03/2021] [Indexed: 11/21/2022]
Abstract
The non-equilibrium thermodynamics and the photochemical reaction mechanisms are described which may have been involved in the dissipative structuring, proliferation and complexation of the fundamental molecules of life from simpler and more common precursors under the UVC photon flux prevalent at the Earth’s surface at the origin of life. Dissipative structuring of the fundamental molecules is evidenced by their strong and broad wavelength absorption bands in the UVC and rapid radiationless deexcitation. Proliferation arises from the auto- and cross-catalytic nature of the intermediate products. Inherent non-linearity gives rise to numerous stationary states permitting the system to evolve, on amplification of a fluctuation, towards concentration profiles providing generally greater photon dissipation through a thermodynamic selection of dissipative efficacy. An example is given of photochemical dissipative abiogenesis of adenine from the precursor HCN in water solvent within a fatty acid vesicle floating on a hot ocean surface and driven far from equilibrium by the incident UVC light. The kinetic equations for the photochemical reactions with diffusion are resolved under different environmental conditions and the results analyzed within the framework of non-linear Classical Irreversible Thermodynamic theory.
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7
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On an EUV Atmospheric Simulation Chamber to Study the Photochemical Processes of Titan's Atmosphere. Sci Rep 2020; 10:10009. [PMID: 32561886 PMCID: PMC7305212 DOI: 10.1038/s41598-020-66950-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 06/01/2020] [Indexed: 11/16/2022] Open
Abstract
The in situ exploration of Titan’s atmosphere requires the development of laboratory experiments to understand the molecular growth pathways initiated by photochemistry in the upper layers of the atmosphere. Key species and dominant reaction pathways are used to feed chemical network models that reproduce the chemical and physical processes of this complex environment. Energetic UV photons initiate highly efficient chemistry by forming reactive species in the ionospheres of the satellite. We present here a laboratory experiment based on a new closed and removable photoreactor coupled here to an Extreme Ultraviolet (EUV) irradiation beam produced by the high-order harmonic generation of a femtosecond laser. This type of EUV stable source allow long-term irradiation experiments in which a plethora of individual reactions can take place. In order to demonstrate the validity of our approach, we irradiated for 7 hours at 89.2 nm, a gas mixture based on N2/CH4 (5%). Using only one wavelength, products of the reaction reveal an efficient photochemistry with the formation of large hydrocarbons but especially organic compounds rich in nitrogen similar to Titan. Among these nitrogen compounds, new species had never before been identified in the mass spectra obtained in situ in Titan’s atmosphere. Their production in this experiment, on the opposite, corroborates previous experimental measurements in the literature on the chemical composition of aerosol analogues produced in the laboratory. Diazo-compounds such as dimethyldiazene (C2H6N2), have been observed and are consistent with the large nitrogen incorporation observed by the aerosols collector pyrolysis instrument of the Huygens probe. This work represents an important step forward in the use of a closed cell chamber irradiated by the innovative EUV source for the generation of photochemical analogues of Titan aerosols. This approach allows to better constrain and understand the growth pathways of nitrogen incorporation into organic aerosols in Titan’s atmosphere.
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8
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Ugelow MS, Berry JL, Browne EC, Tolbert MA. The Impact of Molecular Oxygen on Anion Composition in a Hazy Archean Earth Atmosphere. ASTROBIOLOGY 2020; 20:658-669. [PMID: 32159384 DOI: 10.1089/ast.2019.2145] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Atmospheric organic hazes are common in planetary bodies in our solar system and likely exoplanet atmospheres as well. In addition, geochemical data support the existence of an organic haze in the early Earth's atmosphere. Much of what is known about organic haze formation derives from studies of Saturn's moon Titan. It is believed that on Titan ions play an important role in haze formation. It is possible, by using Titan as an analog for the Archean Earth, to consider that an Archean haze could have formed by similar processes. Here, we examine the anion chemistry that occurs during laboratory simulations of early Earth haze formation and measure the composition of gaseous anions as a function of O2 mixing ratio. Gaseous anion composition and relative abundances are measured by an atmospheric pressure interface time-of-flight mass spectrometer and are compared to previous photochemical haze mass loading measurements. Numerous anions are observed spanning from mass-to-charge ratio 26 to 246, with a majority of the identified anions containing carbon, hydrogen, nitrogen, and/or oxygen. A shift in the anion composition occurs with increasing the precursor O2 mixing ratio. With 0-20 ppmv O2 in CH4/CO2/N2 mixtures, ions contain mostly organic nitrogen, with CNO- being the most intense ion peak. As the precursor O2 is increased to 200 and 2000 ppmv, inorganic nitrogen ions become the dominant chemical group, with NO3- having the most intense ion signal. The clear shift in the ionic composition could be indicative of a modification to the gas-phase chemistry that occurs in the transition from an anoxic atmosphere to an oxygen-containing atmosphere, with potential astrobiological significance.
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Affiliation(s)
- Melissa S Ugelow
- Department of Chemistry, University of Colorado, Boulder, Colorado
- Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado
- Now at Astrochemistry Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland
- University Space Research Association, Columbia, Maryland
| | - Jennifer L Berry
- Department of Chemistry, University of Colorado, Boulder, Colorado
- Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado
| | - Eleanor C Browne
- Department of Chemistry, University of Colorado, Boulder, Colorado
- Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado
| | - Margaret A Tolbert
- Department of Chemistry, University of Colorado, Boulder, Colorado
- Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado
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9
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Michaelian K. Microscopic dissipative structuring and proliferation at the origin of life. Heliyon 2017; 3:e00424. [PMID: 29062973 PMCID: PMC5647473 DOI: 10.1016/j.heliyon.2017.e00424] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Revised: 09/01/2017] [Accepted: 10/03/2017] [Indexed: 01/22/2023] Open
Abstract
Some fundamental molecules of life are suggested to have been formed, proliferated, and evolved through photochemical microscopic dissipative structuring and autocatalytic proliferation under the UV-C/UV-B solar environment prevalent at Earth's surface throughout the Archean. Evidence is given in the numerous salient characteristics of these, including their strong absorption in this spectral region and their rapid non-radiative excited state decay through inherent conical intersections. The examples of the dissipative structuring and dissipative proliferation of the purines and of single strand DNA are given. UV-C and UV-B-induced stationary state isomerizations and tautomerizations are shown to be crucial to the formation of the purines from hydrogen cyanide in an aqueous environment under UV-C light, while UV-C induced phosphorylation of nucleosides and denaturing of double helix RNA and DNA are similarly important to the production and proliferation of single strand DNA. This thermodynamic dissipation perspective provides a physical-chemical foundation for understanding the origin and evolution of life.
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Affiliation(s)
- Karo Michaelian
- Department of Nuclear Physics and Application of Radiations, Instituto de Física, Universidad Nacional Autónoma de México, Apartado Postal 20–364, Cuidad de México, Mexico
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10
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Kobayashi K, Geppert WD, Carrasco N, Holm NG, Mousis O, Palumbo ME, Waite JH, Watanabe N, Ziurys LM. Laboratory Studies of Methane and Its Relationship to Prebiotic Chemistry. ASTROBIOLOGY 2017; 17:786-812. [PMID: 28727932 DOI: 10.1089/ast.2016.1492] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
To examine how prebiotic chemical evolution took place on Earth prior to the emergence of life, laboratory experiments have been conducted since the 1950s. Methane has been one of the key molecules in these investigations. In earlier studies, strongly reducing gas mixtures containing methane and ammonia were used to simulate possible reactions in the primitive atmosphere of Earth, producing amino acids and other organic compounds. Since Earth's early atmosphere is now considered to be less reducing, the contribution of extraterrestrial organics to chemical evolution has taken on an important role. Such organic molecules may have come from molecular clouds and regions of star formation that created protoplanetary disks, planets, asteroids, and comets. The interstellar origin of organics has been examined both experimentally and theoretically, including laboratory investigations that simulate interstellar molecular reactions. Endogenous and exogenous organics could also have been supplied to the primitive ocean, making submarine hydrothermal systems plausible sites of the generation of life. Experiments that simulate such hydrothermal systems where methane played an important role have consequently been conducted. Processes that occur in other Solar System bodies offer clues to the prebiotic chemistry of Earth. Titan and other icy bodies, where methane plays significant roles, are especially good targets. In the case of Titan, methane is both in the atmosphere and in liquidospheres that are composed of methane and other hydrocarbons, and these have been studied in simulation experiments. Here, we review the wide range of experimental work in which these various terrestrial and extraterrestrial environments have been modeled, and we examine the possible role of methane in chemical evolution. Key Words: Methane-Interstellar environments-Submarine hydrothermal systems-Titan-Origin of life. Astrobiology 17, 786-812.
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Affiliation(s)
- Kensei Kobayashi
- 1 Department of Chemistry, Yokohama National University , Yokohama, Japan
| | - Wolf D Geppert
- 2 Department of Geological Sciences, Stockholm University , Stockholm, Sweden
| | - Nathalie Carrasco
- 3 LATMOS, Université Versailles St-Quentin , UPMC, CNRS, Guyancourt, France
| | - Nils G Holm
- 2 Department of Geological Sciences, Stockholm University , Stockholm, Sweden
| | - Olivier Mousis
- 4 Aix Marseille Université , CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, Marseille, France
| | | | - J Hunter Waite
- 6 Southwest Research Institute , San Antonio, Texas, USA
| | - Naoki Watanabe
- 7 Institute of Low Temperature Science, Hokkaido University , Sapporo, Japan
| | - Lucy M Ziurys
- 8 Department of Astronomy, Department of Chemistry and Biochemistry, and Steward Observatory, University of Arizona , Tucson, Arizona, USA
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Arney G, Domagal-Goldman SD, Meadows VS, Wolf ET, Schwieterman E, Charnay B, Claire M, Hébrard E, Trainer MG. The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth. ASTROBIOLOGY 2016; 16:873-899. [PMID: 27792417 PMCID: PMC5148108 DOI: 10.1089/ast.2015.1422] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Accepted: 07/13/2016] [Indexed: 05/21/2023]
Abstract
Recognizing whether a planet can support life is a primary goal of future exoplanet spectral characterization missions, but past research on habitability assessment has largely ignored the vastly different conditions that have existed in our planet's long habitable history. This study presents simulations of a habitable yet dramatically different phase of Earth's history, when the atmosphere contained a Titan-like, organic-rich haze. Prior work has claimed a haze-rich Archean Earth (3.8-2.5 billion years ago) would be frozen due to the haze's cooling effects. However, no previous studies have self-consistently taken into account climate, photochemistry, and fractal hazes. Here, we demonstrate using coupled climate-photochemical-microphysical simulations that hazes can cool the planet's surface by about 20 K, but habitable conditions with liquid surface water could be maintained with a relatively thick haze layer (τ ∼ 5 at 200 nm) even with the fainter young Sun. We find that optically thicker hazes are self-limiting due to their self-shielding properties, preventing catastrophic cooling of the planet. Hazes may even enhance planetary habitability through UV shielding, reducing surface UV flux by about 97% compared to a haze-free planet and potentially allowing survival of land-based organisms 2.7-2.6 billion years ago. The broad UV absorption signature produced by this haze may be visible across interstellar distances, allowing characterization of similar hazy exoplanets. The haze in Archean Earth's atmosphere was strongly dependent on biologically produced methane, and we propose that hydrocarbon haze may be a novel type of spectral biosignature on planets with substantial levels of CO2. Hazy Archean Earth is the most alien world for which we have geochemical constraints on environmental conditions, providing a useful analogue for similar habitable, anoxic exoplanets. Key Words: Haze-Archean Earth-Exoplanets-Spectra-Biosignatures-Planetary habitability. Astrobiology 16, 873-899.
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Affiliation(s)
- Giada Arney
- Astronomy Department, University of Washington, Seattle, Washington, USA
- NASA Astrobiology Institute Virtual Planetary Laboratory, University of Washington, Seattle, Washington, USA
- Astrobiology Program, University of Washington, Seattle, Washington, USA
- Now at: NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
- Now at: NASA Postdoctoral Program, Universities Space Research Association, Columbia, Maryland, USA
| | - Shawn D. Domagal-Goldman
- NASA Astrobiology Institute Virtual Planetary Laboratory, University of Washington, Seattle, Washington, USA
- NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
| | - Victoria S. Meadows
- Astronomy Department, University of Washington, Seattle, Washington, USA
- NASA Astrobiology Institute Virtual Planetary Laboratory, University of Washington, Seattle, Washington, USA
- Astrobiology Program, University of Washington, Seattle, Washington, USA
| | - Eric T. Wolf
- Department of Atmospheric and Oceanic Sciences, Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder, Boulder, Colorado, USA
| | - Edward Schwieterman
- Astronomy Department, University of Washington, Seattle, Washington, USA
- NASA Astrobiology Institute Virtual Planetary Laboratory, University of Washington, Seattle, Washington, USA
- Astrobiology Program, University of Washington, Seattle, Washington, USA
- Now at: NASA Postdoctoral Program, Universities Space Research Association, Columbia, Maryland, USA
- Now at: University of California at Riverside, Riverside, California, USA
- Blue Marble Institute of Science, Seattle, Washington, USA
| | - Benjamin Charnay
- Astronomy Department, University of Washington, Seattle, Washington, USA
- NASA Astrobiology Institute Virtual Planetary Laboratory, University of Washington, Seattle, Washington, USA
- Astrobiology Program, University of Washington, Seattle, Washington, USA
- Now at: Paris-Meudon Observatory, Paris, France
| | - Mark Claire
- NASA Astrobiology Institute Virtual Planetary Laboratory, University of Washington, Seattle, Washington, USA
- Blue Marble Institute of Science, Seattle, Washington, USA
- Department of Earth and Environmental Sciences, University of St Andrews, St Andrews, UK
| | - Eric Hébrard
- NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
- University of Exeter, Exeter, Devon, UK
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12
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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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Rodina LL, Galkina OS, Maas G, Platz MS, Nikolaev VA. A New Method for C−H Functionalization of Aliphatic Compounds by an Unusual Photochemical Reaction of Diazoketones without Elimination of Nitrogen. ASIAN J ORG CHEM 2016. [DOI: 10.1002/ajoc.201600050] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Liudmila L. Rodina
- Institute of Chemistry; Saint Petersburg State University; Universitetskii pr. 26, Petrodvorets St. Petersburg 198504 Russia
| | - Olesia S. Galkina
- Institute of Chemistry; Saint Petersburg State University; Universitetskii pr. 26, Petrodvorets St. Petersburg 198504 Russia
| | - Gerhard Maas
- Institut für Organische Chemie I; Universität Ulm; Albert-Einstein-Allee 11 89081 Ulm Germany
| | - Matthew S. Platz
- Department of Chemistry; The Ohio State University; 100 West 18th Avenue Columbus Ohio 43210 USA
| | - Valerij A. Nikolaev
- Institute of Chemistry; Saint Petersburg State University; Universitetskii pr. 26, Petrodvorets St. Petersburg 198504 Russia
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Sebree JA, Stern JC, Mandt KE, Domagal-Goldman SD, Trainer MG. 13C and 15N fractionation of CH 4/N 2 mixtures during photochemical aerosol formation: Relevance to Titan. ICARUS 2015; 270:421-428. [PMID: 31068732 PMCID: PMC6501594 DOI: 10.1016/j.icarus.2015.04.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The ratios of the stable isotopes that comprise each chemical species in Titan's atmosphere provide critical information towards understanding the processes taking place within its modern and ancient atmosphere. Several stable isotope pairs, including 12C/13C and 14N/15N, have been measured in situ or probed spectroscopically by Cassini-borne instruments, space telescopes, or through ground-based observations. Current attempts to model the observed isotope ratios incorporate fractionation resulting from atmospheric diffusion, hydrodynamic escape, and primary photochemical processes. However, the effect of a potentially critical pathway for isotopic fractionation - organic aerosol formation and subsequent deposition onto the surface of Titan - has not been considered due to insufficient data regarding fractionation during aerosol formation. To better understand the nature of this process, we have conducted a laboratory study to measure the isotopic fractionation associated with the formation of Titan aerosol analogs, commonly referred to as 'tholins', via far-UV irradiation of several methane (CH4) and dinitrogen (N2) mixtures. Analysis of the δ13C and δ15N isotopic signatures of the photochemical aerosol products using an isotope ratio mass spectrometer (IRMS) show that fractionation direction and magnitude are dependent on the initial bulk composition of the gas mixture. In general, the aerosols showed enrichment in 13C and 14N, and the observed fractionation trends can provide insight into the chemical mechanisms controlling photochemical aerosol formation.
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Affiliation(s)
- Joshua A. Sebree
- University of Northern Iowa, Department of Chemistry and Biochemistry, Cedar Falls, IA 50614, USA
- NASA Goddard Space Flight Center, Solar System Exploration Division, Greenbelt, MD 20771, USA
| | - Jennifer C. Stern
- NASA Goddard Space Flight Center, Solar System Exploration Division, Greenbelt, MD 20771, USA
| | - Kathleen E. Mandt
- Space Science and Engineering Division, Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78228, USA
| | | | - Melissa G. Trainer
- NASA Goddard Space Flight Center, Solar System Exploration Division, Greenbelt, MD 20771, USA
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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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Li A, Jjunju FPM, Cooks RG. Nucleophilic addition of nitrogen to aryl cations: mimicking Titan chemistry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2013; 24:1745-1754. [PMID: 23982933 DOI: 10.1007/s13361-013-0710-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Revised: 07/08/2013] [Accepted: 07/08/2013] [Indexed: 06/02/2023]
Abstract
The reactivity of aryl cations toward molecular nitrogen is studied systematically in an ion trap mass spectrometer at 10(2) Pascal of nitrogen, the pressure of the Titan main haze layer. Nucleophilic addition of dinitrogen occurs and the nature of aryl group has a significant influence on the reactivity, through inductive effects and by changing the ground state spin multiplicity. The products of nitrogen activation, aryldiazonium ions, react with typical nitriles, aromatic amines, and alkynes (compounds that are relevant as possible Titan atmosphere constituents) to form covalently bonded heterocyclic products. Theoretical calculations at the level [DFT(B3LYP)/6-311++G(d,p)] indicate that the N2 addition reaction is exothermic for the singlet aryl cations but endothermic for their triplet spin isomers. The -OH and -NH2 substituted aryl ions are calculated to have triplet ground states, which is consistent with their decreased nitrogen addition reactivity. The energy needed for the generation of the aryl cations from their protonated precursors (ca. 340 kJ/mol starting with protonated aniline) is far less than that required to directly activate the nitrogen triple bond (the lowest energy excited state of N2 lies ca. 600 kJ/mol above the ground state). The formation of aza-aromatics via arene ionization and subsequent reactions provide a conceivable route to the genesis of nitrogen-containing organic molecules in the interstellar medium and Titan haze layers.
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Affiliation(s)
- Anyin Li
- Chemistry Department, Purdue University, West Lafayette, IN, 47907, USA
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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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