scholarly journals The Cosmochemical Record of Carbonaceous Meteorites: An Evolutionary Story

2019 ◽  
Vol 53 (4) ◽  
Author(s):  
Sandra Pizzarello
Keyword(s):  
Amino Acids ◽  
Water Soluble ◽  
Early Earth ◽  
The Earth ◽  
Terrestrial Environments ◽  
Extraterrestrial Origin ◽  
Exogenous Delivery ◽  
The Origin Of Life ◽  
The Rich ◽  
Evolutionary Story

This account traces a lecture given to El Colegio Nacional last March during a Conference “On the origin of life on the Earth” organized to celebrate Darwin’s Bicentennial. It reports on the extraterrestrial organic materials found in carbon-containing meteorites, their composition, likely origin and possible prebiotic contribution to early terrestrial environments. Overall, this abiotic chemistry displaysstructures as diverse as kerogen-like macromolecules and simpler soluble compounds, such as amino acids, amines and polyols, and show an isotopic composition that verifies their extraterrestrial origin and lineage to cosmochemical synthetic regimes. Some meteoritic compounds have identical counterpart in the biosphere and encourage the proposal that their exogenous delivery to the early Earth might havefostered molecular evolution. Particularly suggestive in this regard are the unique l-asymmetry of a number of amino acids in some meteorites as well as the rich and almost exclusively water-soluble compositions discovered for other meteorite types.

Autocatalytic chemical networks preceded proteins and RNA in evolution

2019 ◽  
Author(s):  
Joana C. Xavier ◽  
Wim Hordijk ◽  
Stuart Kauffman ◽  
Mike Steel ◽  
William F. Martin
Keyword(s):  
Amino Acids ◽  
Origin Of Life ◽  
Small Molecule ◽  
Metabolic Networks ◽  
Early Earth ◽  
Prebiotic Evolution ◽  
Biochemical Evolution ◽  
The Origin Of Life ◽  
Acids And Bases ◽  
Open Question

AbstractModern cells embody metabolic networks containing thousands of elements and form autocatalytic molecule sets that produce copies of themselves. How the first self-sustaining metabolic networks arose at life’ s origin is a major open question. Autocatalytic molecule sets smaller than metabolic networks were proposed as transitory intermediates at the origin of life, but evidence for their role in prebiotic evolution is lacking. Here we identify reflexively autocatalytic food-generated networks (RAFs)—self-sustaining networks that collectively catalyze all their reactions—embedded within microbial metabolism. RAFs in the metabolism of ancient anaerobic autotrophs that live from H2 and CO2 generate amino acids and bases, the monomeric components of protein and RNA, and acetyl-CoA, but amino acids and bases do not generate metabolic RAFs, indicating that small-molecule catalysis preceded polymers in biochemical evolution. RAFs uncover intermediate stages in the origin of metabolic networks, narrowing the gaps between early-Earth chemistry and life.

scholarly journals Synthesis and Preservation of Organic Molecules with Homochiral Excess by Adsorption on Carbon in Carbonaceous Chondrites

2021 ◽  
pp. 46-53
Author(s):  
V. M. Zhmakin
Keyword(s):  
Carbon Dioxide ◽  
Amino Acids ◽  
Carbon Monoxide ◽  
Lactic Acid ◽  
Organic Synthesis ◽  
Organic Molecules ◽  
Early Earth ◽  
Carbonaceous Chondrites ◽  
Abiogenic Synthesis ◽  
Extraterrestrial Origin

The nature of carbon, initial components, molecules of homochiral abiogenic synthesis and their preservation from decay and racemization for more than 4.5 billion years in carbonaceous chondrites has not been established. In the oxygen-free atmospheres of the nebula and early Earth, hydrogen and hydrogen-containing gases were oxidized with carbon monoxide and carbon dioxide to form carbon and water, as well as the intermediates of these reactions, formaldehyde and methane acid. Together with ammonia, they were the initial components of organic synthesis. According to the Rebinder rule, carbon adsorbs hydrogen well, including in organic molecules. In this connection, experiments with the assumed conditions of the early Earth were carried out by adsorption on carbon to obtain R-(rectus, Latin) ribose from formaldehyde, and S-(sinister) serine from formaldehyde, methane acid and ammonia. For other S-amino acids, a stereo chemical justification of their formation based on S-serine is given. For carbonaceous chondrites, the results of the above experiments were confirmed by the correlation of an increase in homochiral excess with an increase in the amount of hydrogen in aldonic acids and lactic acid with a coefficient of 0.94 and 0.85 in amino acids. The justification of the homochiral process will reduce the costs of searching for life on planets, for scientific research, for the production of medicines, perfumes, food, and so on. Doubts about the extraterrestrial origin of homochiral enantiomers in carbonaceous chondrites arise most often due to a lack of understanding of the reasons for their appearance. This work will significantly reduce such skepticism.

The origin of life in comets

2007 ◽  
Vol 6 (4) ◽  
pp. 321-323 ◽  
Author(s):  
W.M. Napier ◽  
J.T. Wickramasinghe ◽  
N.C. Wickramasinghe
Keyword(s):  
Origin Of Life ◽  
Aqueous Phase ◽  
Early Earth ◽  
Habitable Zone ◽  
The Galaxy ◽  
Terrestrial Environments ◽  
Prebiotic Environments ◽  
The Origin Of Life

AbstractMechanisms of interstellar panspermia have recently been identified whereby life, wherever it has originated, will disperse throughout the habitable zone of the Galaxy within a few billion years. This re-opens the question of where life originated. The interiors of comets, during their aqueous phase, seem to provide environments no less favourable for the origin of life than that of the early Earth. Their combined mass throughout the Galaxy overwhelms that of suitable terrestrial environments by about 20 powers of ten, while the lifetimes of friendly prebiotic environments within them exceeds that of localized terrestrial regions by another four or five powers of ten. We propose that the totality of comets around G-dwarf Sun-like stars offers an incomparably more probable setting for the origin of life than any that was available on the early Earth.

scholarly journals The early Earth under a superflare and super-CME attack: prospects for life

2015 ◽  
Vol 11 (S320) ◽  
pp. 409-415 ◽  
Author(s):  
Vladimir Airapetian ◽  
Alex Glocer ◽  
Guillaume Gronoff
Keyword(s):  
Molecular Nitrogen ◽  
Three Dimensional ◽  
Solar Energetic Particle ◽  
Early Earth ◽  
Polar Cap ◽  
Mhd Simulations ◽  
The Earth ◽  
The Origin Of Life ◽  
Mass Ejection ◽  
The Impact

AbstractKepler observations suggest that G-type stars produce powerful flares suggesting that the early Earth may also have been exposed to frequent and energetic solar explosive events generated by the young Sun. We show that powerful coronal mass ejection (CME) events associated with superflares impacting the Earth magnetosphere with a frequency of 1 event/day. What was the impact of superflares, CMEs and associated solar energetic particle (SEPs) events on the atmospheric erosion of the young Earth and habitability? In this paper we discuss our three-dimensional (3D) magnetohydrodynamic (MHD) simulations that show that frequent and energetic CMEs from the early Sun continuously destroyed the sub-solar parts of Earth's magnetosphere at heights < 1.25 RE. This suggests that CME shock accelerated energetic protons are capable of penetrating into the polar cap region and breaking atmospheric molecular nitrogen, the major ingredient of the early Earth atmosphere, into atomic nitrogen. Photo-collisional dissociation of molecular nitrogen and carbon dioxide creates reactive chemistry that efficiently produces nitrous oxide and hydrogen cyanide, the essential molecule in prebiotic life chemistry. This raises an possibility that frequent super-CMEs could serve as a potential catalyst for the origin of life on early Earth.

scholarly journals Astrochemistry as the basics of Astrobiology: from simplest molecules to bioindicatorsonexoplanets surfaces

2018 ◽  
Vol 2 (1) ◽  
pp. 33-64
Author(s):  
A.G. Yeghikyan ◽  
Keyword(s):  
Amino Acids ◽  
Origin Of Life ◽  
Biological Evolution ◽  
Complex Compounds ◽  
Optically Active ◽  
Point Of View ◽  
Heavy Hydrocarbons ◽  
The Earth ◽  
Other Substances ◽  
The Origin Of Life

The problem of the origin of Life is discussed from the astrophysical point of view. Most biologists and geologists up to the present time believe that Life was originated on the Earth in some initial natural chemical pre-reactors, where a mixture of water, ammonia, methane containing species and some other substances, under the influence of an energy source like, e.g. lightning, turned into quite complex compounds such as amino acids and complex hydrocarbons. In fact, under conditions of the primordial Earth, it is not possible to obtain such pre-biological molecules by not-bio-chemical methods, as discussed in this paper. Instead, an astrophysical view of the problem of the origin of Life on the Earth is proposed and it is recalled that the biological evolution on the Earth was preceded by the chemical evolution of complex chemical compounds, mostly under extraterrestrial conditions, where it is only possible to form optically active amino acids, sugars and heavy hydrocarbons necessary for constructing the first pre-biomolecules. Then, according to a widespread point of view, they were brought to Earth by comets and dust between 4.5 and 3.8 billion years ago. Some part of the matter of comets landed unchanged during grazing collisions. Prebiotic complexes on the surface of the planet participate in the formation of a specific cover with a reflective spectrum (or color index), whose characteristic details can be tried to reveal by observation. The most promising bio-indicators at present are optically active amino acids and their derivatives, however, the existing observational capabilities are insufficient to identify them. More promising as (pre)biomarkers are the heavy hydrocarbons discussed in this article, in particular bitumen and isoprene hydrocarbons.

Amino acid cosmogeochemistry

1991 ◽  
Vol 333 (1268) ◽  
pp. 349-358 ◽  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Cosmic Dust ◽  
Dust Particles ◽  
Early Earth ◽  
The Earth ◽  
Racemic Mixtures ◽  
Protein Amino Acids ◽  
Living Organisms ◽  
Diagenetic Reactions

Amino acids are ubiquitous components of living organisms and as a result they are widely distributed on the surface of the Earth. Whereas only 20 amino acids are found in proteins, a much more diverse mixture of amino acids has been detected in carbonaceous meteorites. Amino acids in living organisms consist exclusively of the L-enantiomers, but in meteorites, amino acids with chiral carbons are present as racemic mixtures. Protein amino acids undergo a variety of diagenetic reactions that produce some other amino acids but not the unique amino acids present in meteorites. Nevertheless, trace quantities of meteoritic amino acids may occur on the Earth, either as a result of bolide impact or from the capture of cosmic dust particles. The ensemble of amino acids present on the early Earth before life existed was probably similar to those in prebiotic experiments and meteorites. This generates a question about why the L-amino acids on which life is based were selected.

scholarly journals Autocatalytic chemical networks at the origin of metabolism

2020 ◽  
Vol 287 (1922) ◽  
pp. 20192377 ◽  
Author(s):  
Joana C. Xavier ◽  
Wim Hordijk ◽  
Stuart Kauffman ◽  
Mike Steel ◽  
William F. Martin
Keyword(s):  
Amino Acids ◽  
Origin Of Life ◽  
Small Molecule ◽  
Metabolic Networks ◽  
Early Earth ◽  
Prebiotic Evolution ◽  
Autocatalytic Sets ◽  
The Origin Of Life ◽  
Acids And Bases ◽  
Open Question

Modern cells embody metabolic networks containing thousands of elements and form autocatalytic sets of molecules that produce copies of themselves. How the first self-sustaining metabolic networks arose at life's origin is a major open question. Autocatalytic sets smaller than metabolic networks were proposed as transitory intermediates at the origin of life, but evidence for their role in prebiotic evolution is lacking. Here, we identify reflexively autocatalytic food-generated networks (RAFs)—self-sustaining networks that collectively catalyse all their reactions—embedded within microbial metabolism. RAFs in the metabolism of ancient anaerobic autotrophs that live from H 2 and CO 2 provided with small-molecule catalysts generate acetyl-CoA as well as amino acids and bases, the monomeric components of protein and RNA, but amino acids and bases without organic catalysts do not generate metabolic RAFs. This suggests that RAFs identify attributes of biochemical origins conserved in metabolic networks. RAFs are consistent with an autotrophic origin of metabolism and furthermore indicate that autocatalytic chemical networks preceded proteins and RNA in evolution. RAFs uncover intermediate stages in the emergence of metabolic networks, narrowing the gaps between early Earth chemistry and life.

Adsorption of amino acids and nucleic acid bases onto minerals: a few suggestions for prebiotic chemistry experiments

2012 ◽  
Vol 11 (4) ◽  
pp. 229-234 ◽  
Author(s):  
Dimas A.M. Zaia
Keyword(s):  
Amino Acids ◽  
Nucleic Acid ◽  
Origin Of Life ◽  
Prebiotic Chemistry ◽  
Synthesis Methods ◽  
Nucleic Acid Bases ◽  
The Earth ◽  
Protein Amino Acids ◽  
The Origin Of Life ◽  
Living Organisms

AbstractAmino acids and nucleic acid bases are very important for the living organisms. Thus, their protection from decomposition, selection, pre-concentration and formation of biopolymers are important issues for understanding the origin of life on the Earth. Minerals could have played all of these roles. This paper discusses several aspects involving the adsorption of amino acids and nucleic acid bases onto minerals under conditions that could have been found on the prebiotic Earth; in particular, we recommend the use of minerals, amino acids, nucleic acid bases and seawater ions in prebiotic chemistry experiments. Several experiments involving amino acids, nucleic acid bases, minerals and seawater ions are also suggested, including: (a) using well-characterized minerals and the standardization of the mineral synthesis methods; (b) using primary chondrite minerals (olivine, pyroxene, etc.) and clays modified with metals (Cu, Fe, Ni, Mo, Zn, etc.); (c) determination of the possible products of decomposition due to interactions of amino acids and nucleic acid bases with minerals; (d) using minerals with more organophilic characteristics; (e) using seawaters with different concentrations of ions (i.e. Na+, Ca2+, Mg2+, SO42− and Cl−); (f) using non-protein amino acids (AIB, α-ABA, β-ABA, γ-ABA and β-Ala and g) using nucleic acid bases other than adenine, thymine, uracil and cytosine. These experiments could be useful to clarify the role played by minerals in the origin of life on the Earth.

scholarly journals Prebiotic materials from on and off the early Earth

2006 ◽  
Vol 361 (1474) ◽  
pp. 1689-1702 ◽  
Author(s):  
Max Bernstein
Keyword(s):  
Amino Acids ◽  
Solar System ◽  
Oxidation State ◽  
Hydrothermal Vents ◽  
Organic Molecules ◽  
Early Earth ◽  
The Earth ◽  
Evolution Of Life ◽  
Carbon Compounds ◽  
Compare And Contrast

One of the greatest puzzles of all time is how did life arise? It has been universally presumed that life arose in a soup rich in carbon compounds, but from where did these organic molecules come? In this article, I will review proposed terrestrial sources of prebiotic organic molecules, such as Miller–Urey synthesis (including how they would depend on the oxidation state of the atmosphere) and hydrothermal vents and also input from space. While the former is perhaps better known and more commonly taught in school, we now know that comet and asteroid dust deliver tons of organics to the Earth every day, therefore this flux of reduced carbon from space probably also played a role in making the Earth habitable. We will compare and contrast the types and abundances of organics from on and off the Earth given standard assumptions. Perhaps each process provided specific compounds (amino acids, sugars, amphiphiles) that were directly related to the origin or early evolution of life. In any case, whether planetary, nebular or interstellar, we will consider how one might attempt to distinguish between abiotic organic molecules from actual signs of life as part of a robotic search for life in the Solar System.

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