258 research outputs found
Prebiotic Organic Microstructures
Micro- and sub-micrometer spheres, tubules and fiber-filament soft structures have been synthesized in our experiments conducted with 3 MeV proton irradiations of a mixture of simple inorganic constituents, CO, N2 and H2O. We analysed the irradiation products, with scanning electron microscopy (SEM) and atomic force microscopy (AFM). These laboratory organic structures produced wide variety of proteinous and non-proteinous amino acids after HCl hydrolysis. The enantiomer analysis for D-, L- alanine confirmed that the amino acids were abiotically synthesized during the laboratory experiment. Considering hydrothermal activity, the presence of CO2 and H2, of a ferromagnesian silicate mineral environment, of an Earth magnetic field which was much less intense during Archean times than nowadays and consequently of a proton excitation source which was much more abundant, we propose that our laboratory organic microstructures might be synthesized during Archean times. We show similarities in morphology and in formation with some terrestrial Archean microstructures and we suggest that some of the observed Archean carbon spherical and filamentous microstructures might be composed of abiogenic organic molecules. We further propose a search for such prebiotic organic signatures on Mars. This article has been posted on Nature precedings on 21 July 2010 [1]. Extinct radionuclides as source of excitation have been replaced by cosmic radiations which were much more intense 3.5 Ga ago because of a much less intense Earth magnetic field. The new version of the article has been presented at the ORIGINS conference in Montpellier in july 2011 [2] and has since been published in Origins of Life and Evolution of Biospheres 42 (4) 307-316, 2012. 
DOI: 10.1007/s11084-012-9290-5 


Formation of H2 and CH4 by weathering of olivine at temperatures between 30 and 70°C
Hydrocarbons such as CH4 are known to be formed through the Fischer-Tropsch or Sabatier type reactions in hydrothermal systems usually at temperatures above 100°C. Weathering of olivine is sometimes suggested to account for abiotic formation of CH4 through its redox lowering and water splitting properties. Knowledge about the CH4 and H2 formation processes at low temperatures is important for the research about the origin and cause of early Earth and Martian CH4 and for CO2 sequestration. We have conducted a series of low temperature, long-term weathering experiments in which we have tested the CH4 and H2 formation potential of forsteritic olivine
A primordial origin for the atmospheric methane of Saturn's moon Titan
The origin of Titan's atmospheric methane is a key issue for understanding
the origin of the Saturnian satellite system. It has been proposed that
serpentinization reactions in Titan's interior could lead to the formation of
the observed methane. Meanwhile, alternative scenarios suggest that methane was
incorporated in Titan's planetesimals before its formation. Here, we point out
that serpentinization reactions in Titan's interior are not able to reproduce
the deuterium over hydrogen (D/H) ratio observed at present in methane in its
atmosphere, and would require a maximum D/H ratio in Titan's water ice 30%
lower than the value likely acquired by the satellite during its formation,
based on Cassini observations at Enceladus. Alternatively, production of
methane in Titan's interior via radiolytic reactions with water can be
envisaged but the associated production rates remain uncertain. On the other
hand, a mechanism that easily explains the presence of large amounts of methane
trapped in Titan in a way consistent with its measured atmospheric D/H ratio is
its direct capture in the satellite's planetesimals at the time of their
formation in the solar nebula. In this case, the mass of methane trapped in
Titan's interior can be up to 1,300 times the current mass of atmospheric
methane.Comment: Accepted for publication in Icaru
Bio-inspired CO₂ conversion by iron sulfide catalysts under sustainable conditions
The mineral greigite presents similar surface structures to the active sites found in many modern-day enzymes. We show that particles of greigite can reduce CO2 under ambient conditions into chemicals such as methanol, formic, acetic and pyruvic acid. Our results also lend support to the Origin of Life theory on alkaline hydrothermal vents
Selection for Replicases in Protocells
PMCID: PMC3649988This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Comparative Investigation of Microbial Communities Associated with Hydrothermal Activities in the Okinawa Trough
Geogenic and atmospheric sources for volatile organic compounds in fumarolic emissions from Mt. Etna and Vulcano Island (Sicily, Italy)
In this paper, fluid source(s) and processes controlling the chemical composition of volatile organic compounds (VOCs) in gas discharges from Mt. Etna and Vulcano Island(Sicily, Italy) were investigated. The main composition of the Etnean and Volcano gas emissions is produced by mixing, to various degrees, of magmatic and hydrothermal components. VOCs are dominated by alkanes, alkenes and aromatics, with minor, though significant, concentrations of O-, S- and Cl(F)-substituted compounds. The main mechanism for the production of alkanes is likely related to pyrolysis of organic-matterbearing sediments that interact with the ascending magmatic fluids. Alkanes are then converted to alkene and aromatic compounds via catalytic reactions (dehydrogenation and dehydroaromatization, respectively). Nevertheless, an abiogenic origin for the light hydrocarbons cannot be ruled out. Oxidative processes of hydrocarbons at relatively high temperatures and oxidizing conditions, typical of these volcanic-hydrothermal fluids, may explain the production of alcohols, esters, aldehydes, as well as O- and S-bearing heterocycles. By comparing the concentrations of hydrochlorofluorocarbons (HCFCs) in the fumarolic discharges with respect to those of background air, it is possible to highlight that they have a geogenic origin likely due to halogenation of both methane and alkenes. Finally, chlorofluorocarbon (CFC) abundances appear to be consistent with background air, although the strong air contamination that affects the Mt. Etna fumaroles may mask a possible geogenic contribution for these compounds. On the other hand, no CFCs were detected in the Vulcano gases, which are characterized by low air contribution. Nevertheless, a geogenic source for these compounds cannot be excluded on the basis of the present data
Experimental Hydrogen Production in Hydrothermal and Fault Systems: Significance for Habitability of Subseafloor H2 Chemoautotroph Microbial Ecosystems
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