Mineral Radioactivity in Sands as a Mechanism for Fixation of Organic Carbon on the Early Earth

Parnell, John

doi:10.1023/b:orig.0000043132.23966.a1

Cited by 23 publications

(19 citation statements)

References 65 publications

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“…However, a "standard model" explaining the emergence of larger and larger molecular assemblies is lacking. Various sources of energy that might have initiated this synthesis have been suggested in the last 60 y, including UV irradiation both in extraterrestrial and terrestrial environments (8)(9)(10)(11), hydrothermal energy from deep sea vents (12,13), shock waves from meteorite impact (14)(15)(16)(17)(18)(19)(20), redox energy in the "iron−sulphur world" hypothesis (21), radioactive emission from uranium accumulation (22), and, of course, electric discharges originated by lightning, which motivated the Miller experiment, and are the inspiration of the present work. Despite the historical importance of Miller's experiments, no attempts have been made to explore the role of the electric field, traditionally considered merely in terms of just another thermal activation.…”

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confidence: 99%

Miller experiments in atomistic computer simulations

Saitta

Saija

2014

Proc. Natl. Acad. Sci. U.S.A.

169

147

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The celebrated Miller experiments reported on the spontaneous formation of amino acids from a mixture of simple molecules reacting under an electric discharge, giving birth to the research field of prebiotic chemistry. However, the chemical reactions involved in those experiments have never been studied at the atomic level. Here we report on, to our knowledge, the first ab initio computer simulations of Miller-like experiments in the condensed phase. Our study, based on the recent method of treatment of aqueous systems under electric fields and on metadynamics analysis of chemical reactions, shows that glycine spontaneously forms from mixtures of simple molecules once an electric field is switched on and identifies formic acid and formamide as key intermediate products of the early steps of the Miller reactions, and the crucible of formation of complex biological molecules.I n 1953, Miller reported (1) the surprising results he had achieved by the application of an electric discharge on a mixture of the gases CH 4 , NH 3 , H 2 O, and H 2 that simulated what was considered at the time as a model atmosphere for the primordial Earth. The result of this experiment was a substantial yield of a mixture of amino acids (2-4). Similarly, Orò demonstrated the spontaneous formation of nucleic acid bases from aqueous hydrogen cyanide subject to heating and/or spark discharges (5). Since then, a number of different hypotheses have been formulated to explain the synthesis, from simple molecules (water, ammonia, methane, carbon oxides), of simple organic molecules (formaldehyde, hydrogen cyanide, formic acid), and from the latter ones to biological monomers (amino acids, purines, pyrimidines) up the ladder of the complexity of life (6, 7). However, a "standard model" explaining the emergence of larger and larger molecular assemblies is lacking. Various sources of energy that might have initiated this synthesis have been suggested in the last 60 y, including UV irradiation both in extraterrestrial and terrestrial environments (8-11), hydrothermal energy from deep sea vents (12, 13), shock waves from meteorite impact (14-20), redox energy in the "iron−sulphur world" hypothesis (21), radioactive emission from uranium accumulation (22), and, of course, electric discharges originated by lightning, which motivated the Miller experiment, and are the inspiration of the present work. Despite the historical importance of Miller's experiments, no attempts have been made to explore the role of the electric field, traditionally considered merely in terms of just another thermal activation.A key aspect of that experiment was the formation of hydrogen cyanide, aldehydes, ketones, and amino acids, suggesting that the compounds were produced by the Strecker cyanohydrin reaction (23). Subsequent Miller-like experiments, run with other types and combinations of gases (24, 25) representing plausible geochemical conditions, produced other classes of basic building block molecules, namely sugars and nucleotides. To date, all of the major classes of...

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confidence: 99%

Miller experiments in atomistic computer simulations

Saitta

Saija

2014

Proc. Natl. Acad. Sci. U.S.A.

169

147

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“…This has been proposed as a mechanism that could have occurred on the early Earth, involving irradiation from radioactive uranium-and thoriumrich minerals (Parnell 2004). Is this a process that can occur in impact structures, which have been suggested as sites for prebiotic chemistry and primitive evolution (Cockell et al 2006)?…”

Section: Aim Of Studymentioning

confidence: 99%

“…The hydrocarbons form coatings around the radioactive mineral, or digest and replace it so that only small grains of the original mineral are preserved (Parnell 2004). Ellsworth (1928) was among the first to describe carbonaceous matter containing thorium and uranium, and referred to this as thucolite.…”

Section: Occurrence and Formation Of Uranium-thorium-rich Bitumen Nodmentioning

confidence: 99%

Formation of uranium‐thorium‐rich bitumen nodules in the Lockne impact structure, Sweden: A mechanism for carbon concentration at impact sites

Lindgren

Parnell

Norman

et al. 2007

Meteorit & Planetary Scien

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Abstract-The Ordovician Lockne impact structure is located in central Sweden. The target lithology consisted of limestone and black unconsolidated shale overlaying a Precambrian crystalline basement. The Precambrian basement is uranium-rich, and the black shale is both uranium-and organic-rich. This circumstance makes Lockne a good candidate for testing the occurrence of U-Thrich bitumen nodules in an impact structure setting. U-Th-rich bitumen nodules are formed through irradiation; hence the increase in the complexity of organic matter by a radioactive (uranium-and thorium-rich) mineral phase. U-Th-rich bitumen nodules were detected in crystalline impact breccia and resurge deposits from the impact structure, but samples of non-impact-affected rocks from outside the impact structure do not contain any U-Th-rich bitumen nodules. This implies that in the Lockne impact structure, the nodules are associated with impact-related processes. U-Th-rich bitumen nodules occur throughout the geological record and are not restricted to an impact structure setting, but our studies at Lockne show that this process of irradiation can readily occur in impact structures where fracturing of rocks and a post-impact hydrothermal system enhances fluid circulation. The irradiation of organic matter by radioactive minerals has previously been proposed as a process for concentration of carbon on the early Earth. Impact structures are suggested as sites for prebiotic chemistry and primitive evolution, and irradiation by radioactive minerals could be an important mechanism for carbon concentration at impact sites.

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“…The polymerization of simple organic molecules to cause an increase in complexity and the concentration of carbon has been suggested as a mechanism that could have occurred on the early Earth, involving irradiation from radioactive (uranium, thorium) minerals (Parnell, 2004). In the terrestrial geological record there are widespread occurrences of solid carbonaceous coatings around uranium and thorium minerals.…”

Section: Irradiation Of Methane To Complex Organic Moleculesmentioning

confidence: 99%