Primeval Earth Research Articles

The astrochemical evolutionary traits of phospholipid membrane homochirality.

Compartmentalization is crucial for the evolution of life. Present-day phospholipid membranes exhibit a high level of complexity and species-dependent homochirality, the so-called lipid divide. It is possible that less stable, yet more dynamic systems, promoting out-of-equilibrium environments, facilitated the evolution of life at its early stages. The composition of the preceding primitive membranes and the evolutionary route towards complexity and homochirality remain unexplained. Organics-rich carbonaceous chondrites are evidence of the ample diversity of interstellar chemistry, which may have enriched the prebiotic milieu on early Earth. This Review evaluates the detections of simple amphiphiles - likely ancestors of membrane phospholipids - in extraterrestrial samples and analogues, along with potential pathways to form primitive compartments on primeval Earth. The chiroptical properties of the chiral backbones of phospholipids provide a guide for future investigations into the origins of phospholipid membrane homochirality. We highlight a plausible common pathway towards homochirality of lipids, amino acids, and sugars starting from enantioenriched monomers. Finally, given their high recalcitrance and resistance to degradation, lipids are among the best candidate biomarkers in exobiology.

Micro-Inclusions in Corundum from Puesto La Peña Complex Ouachitites, Mendoza, Argentina: A Window to the Mantle

Abstract Corundum xenocrysts from ouachititic dikes related to the ultrapotassic Puesto La Peña Complex, Mendoza, Argentina, contain inclusions of oxides, silicides, and silicates. Oxides identified are hibonite, carmeltazite, and as yet unnamed minerals consisting of ZrTiO3, (Al,Ti,Zr) oxide, and (Mn,REE) oxide. An unnamed Ti2(Mn,Fe)4Si5 phase was also recognized. Silicates include wodegongjieite and grossmanite. All minerals are enriched in rare earth elements. The formation of these mineral inclusions under extreme P-T conditions would have occurred in the primeval Earth, preserved in the lithospheric mantle and protected from oxidation by crystallization of corundum through the introduction of mantle-derived magma-transported fluids. The corundum crystals would have been transported by a rising plume in a back-arc extensional setting during the Miocene and incorporated as xenocrysts in an alkaline ouachititic magma, conferring its peraluminous signature.

Building the uracil skeleton in primitive ponds at the origins of life: carbamoylation of aspartic acid

A large set of nucleobases and amino acids is found in meteorites, implying that several chemical reservoirs are present in the solar system. The “geochemical continuity” hypothesis explores how protometabolic paths developed from so-called “bricks” in an enzyme-free prebiotic world and how they affected the origins of life. In the living cell, the second step of synthesizing uridine and cytidine RNA monomers is a carbamoyl transfer from a carbamoyl donor to aspartic acid. Here we compare two enzyme-free scenarios: aqueous and mineral surface scenarios in a thermal range up to 250 °C. Both processes could have happened in ponds under open atmosphere on the primeval Earth. Carbamoylation of aspartic acid with cyanate in aqueous solutions at 25 °C gives high N-carbamoyl aspartic acid yields within 16 h. It is important to stress that, while various molecules could be efficient carbamoylating agents according to thermodynamics, kinetics plays a determining role in selecting prebiotically possible pathways.

On the synthesis of N–O bearing species in astrophysical ices – an infrared spectroscopic study using heavy-ion irradiation of solid N2:CO samples

ABSTRACT The interstellar chemistry of nitrogen is considerably less understood than the chemistry of other common elements, such as carbon and oxygen. Even though a relatively large number of species containing nitrogen atoms have already been detected in the interstellar medium, only six of them bear a nitrogen–oxygen (N–O) bond. Some astrophysical and primeval Earth models suggest that N–O species, such as hydroxylamine (NH2OH), are potential precursors of prebiotic amino acids, and even peptides. In this work, we have analyzed an apolar ice mixture of N2:CO of astrophysical interest to investigate possible formation mechanisms of N–O bearing molecules due to processing of the sample by 64Ni24+ 538 MeV ions (8.4 MeV/u) at 14 K. The results show the formation of simple nitrogen oxides ($\rm {N_{1 - 2}}{O_y})$, but no CN–O species of any kind. We have also determined the formation cross-sections of some of the products, as well as the destruction cross-sections of precursors and products. The results presented here are discussed in light of our previous work on the processing of a NH3:CO ice mixture, which have found no N–O bearing molecules at all.

A Bit of Sugar on TiO2: Quantum Chemical Insights on the Interfacial Interaction of Glycolaldehyde over Titanium Dioxide

Among 200 molecules discovered up to now in the interstellar and circumstellar space, glycolaldehyde (GA) represents the smallest monosaccharide detected in those places. This detection comes with important clues about the origins of life in the Universe and in a primeval Earth, as GA is one of the intermediates in the formose reaction leading to ribose. Mineral surfaces, such as TiO2, have a primary role in processing simple molecules toward more complex prebiotic species. In the present work, the adsorption of GA over the surface of TiO2 anatase (1 0 1) is investigated by quantum chemical simulations, being this the first step involved in the series of reactive steps mediated by the surface. Six adsorption configurations are modeled by periodic density functional theory (DFT) calculations, and for each of them structural, energetic and vibrational properties are calculated. The results of the theoretical study are supported with measurements of the GA adsorption on TiO2 by diffuse reflectance infrared F...

Comparison of fundamental physical properties of the model cells (protocells) and the living cells reveals the need in protophysiology

AbstractA hypothesis is proposed about potassium ponds being the cradles of life enriches the gamut of ideas about the possible conditions of pre-biological evolution on the primeval Earth, but does not bring us closer to solving the real problem of the origin of life. The gist of the matter lies in the mechanism of making a delimitation between two environments – the intracellular environment and the habitat of protocells. Since the sodium–potassium pump (Na+/K+-ATPase) was discovered, no molecular model has been proposed for a predecessor of the modern sodium pump. This has brought into life the idea of the potassium pond, wherein protocells would not need a sodium pump. However, current notions of the operation of living cells come into conflict with even physical laws when trying to use them to explain the origin and functioning of protocells. Thus, habitual explanations of the physical properties of living cells have become inapplicable to explain the corresponding properties of Sidney Fox's microspheres. Likewise, existing approaches to solving the problem of the origin of life do not see the need for the comparative study of living cells and cell models, assemblies of biological and artificial small molecules and macromolecules under physical conditions conducive to the origin of life. The time has come to conduct comprehensive research into the fundamental physical properties of protocells and create a new discipline – protocell physiology or protophysiology – which should bring us much closer to solving the problem of the origin of life.

Investigation of the presence of an aliphatic biopolymer in cyanobacteria: Implications for kerogen formation

Algaenan has been suggested to be one of the main precursors of certain kerogens. It is a non-hydrolysable and insoluble biomolecule of high molecular weight. It has been found in a limited number of microalgae species. There is considerable uncertainty about its formation and preservation, as well as its role in kerogen formation and the implications for the global C cycle. We tested whether the cyanobacterium Chlorogloeopsis fritschii can synthesise a biomacromolecule similar to algaenan with potential to contribute to kerogen via selective preservation. Two freshwater green microalgae, Pseudochoricystis ellipsoidea and Scenedesmus obliquus, as well as C. fritschii, were subjected to harsh solvent extraction and hydrolysis steps to obtain an insoluble and non-hydrolysable macromolecule. The residues from all three species were analysed using pyrolysis–gas chromatography–mass spectrometry and solid-state nuclear magnetic resonance spectroscopy. The analysis revealed that C. fritschii indeed contains a resistant biomacromolecule exhibiting the characteristic aliphatic structure of algaenan, similar to the algaenan residues from the two microalgae. Due to the robust nature of Chlorogloeopsis compared with eukaryotes, it can prevail in extreme environmental conditions such as freezing, thawing, desiccation and overheating – conditions prevalent on the primeval earth. The presence of a resistant aliphatic biopolymer in Chlorogloeopsis suggests that cyanobacteria could have contributed to kerogen via selective preservation.

Chemical reaction networks as a model to describe UVC- and radiolytically-induced reactions of simple compounds

When a chemical system is submitted to high energy sources (UV, ionizing radiation, plasma sparks, etc.), as is expected to be the case of prebiotic chemistry studies, a plethora of reactive intermediates could form. If oxygen is present in excess, carbon dioxide and water are the major products. More interesting is the case of reducing conditions where synthetic pathways are also possible. This article examines the theoretical modeling of such systems with random-generated chemical networks. Four types of random-generated chemical networks were considered that originated from a combination of two connection topologies (viz., Poisson and scale-free) with reversible and irreversible chemical reactions. The results were analyzed taking into account the number of the most abundant products required for reaching 50% of the total number of moles of compounds at equilibrium, as this may be related to an actual problem of complex mixture analysis. The model accounts for multi-component reaction systems with no a priori knowledge of reacting species and the intermediates involved if system components are sufficiently interconnected. The approach taken is relevant to an earlier study on reactions that may have occurred in prebiotic systems where only a few compounds were detected. A validation of the model was attained on the basis of results of UVC and radiolytic reactions of prebiotic mixtures of low molecular weight compounds likely present on the primeval Earth.

First ecosystems on Earth

Theories attempting to explain the origin of life on Earth should be based on the assumption that habitability precedes habitation. The hypotheses of the first organism should be based on the evaluation of its possible life-supporting ecosystem. The ecosystem should necessarily include primary autotrophic producers, and hydrogenotrophy appears to be an adequate physiological type for primitive ecosystems. Consideration of life on Earth should differentiate between the origin of organisms in situ and the transportation of organisms from outside with cosmic bodies in the framework of life as a widespread phenomenon of the Universe. In the case of transport of life with cosmic bodies, there are no limitations on the transfer of a community rather than an individual cell. In the case of the transport of the community with a large piece of “dirty ice,” the problem lies in the correspondence between the community and its ecosystem on the parent body and the conditions on the primeval Earth rather than functional divergence from a primary ancestor. Subsequent events are within the framework of paleontologically observed evolution and can be described as biogeochemical succession without any additional speculations.

Early Earth closely surrounded by young stars

Knowledge of the physical and chemical conditions on the primeval Earth is important for the study of the origin of the biosphere. This paper discusses the latest modification of the theory of the origin of the Earth and other planets. Possible consequences of the formation of the Sun in the area of the star formation closely surrounded by neighboring young stars are considered. The classical problem of the rate of accretion of Earth and other planets is generalized with new estimates allowing the correlation of the results from long-lived (U-Pb) and short-lived (Hf-W) space-chronometers. A model of the early evolution of the Earth, based on both dynamic estimates and the latest geochemical data (earliest Australian zircons, relict xenon pleiad) is discussed. The problems of the theory of early Earth’s evolution, which so far cannot be adequately solved, are discussed.

Prebiotic chemical kinetics imprint on positional codon usage

Over one million exons across the three Domains of Life have been analyzed and a significant excess of first codons containing identical bases in their first two positions has been found in Eubacteria and Archaea genomes. This frequency is observed to be much lower in the genome of Eukarya. This discrepancy is proposed to depend on the kinetics of oligoribotide/oligoribotide-like growth in the primeval Earth, toned down during further evolution.

On the origin of life in the zinc world. 2. Validation of the hypothesis on the photosynthesizing zinc sulfide edifices as cradles of life on Earth.

BackgroundThe accompanying article (A.Y. Mulkidjanian, Biology Direct 4:26) puts forward a detailed hypothesis on the role of zinc sulfide (ZnS) in the origin of life on Earth. The hypothesis suggests that life emerged within compartmentalized, photosynthesizing ZnS formations of hydrothermal origin (the Zn world), assembled in sub-aerial settings on the surface of the primeval Earth.ResultsIf life started within photosynthesizing ZnS compartments, it should have been able to evolve under the conditions of elevated levels of Zn2+ ions, byproducts of the ZnS-mediated photosynthesis. Therefore, the Zn world hypothesis leads to a set of testable predictions regarding the specific roles of Zn2+ ions in modern organisms, particularly in RNA and protein structures related to the procession of RNA and the "evolutionarily old" cellular functions. We checked these predictions using publicly available data and obtained evidence suggesting that the development of the primeval life forms up to the stage of the Last Universal Common Ancestor proceeded in zinc-rich settings. Testing of the hypothesis has revealed the possible supportive role of manganese sulfide in the primeval photosynthesis. In addition, we demonstrate the explanatory power of the Zn world concept by elucidating several points that so far remained without acceptable rationalization. In particular, this concept implies a new scenario for the separation of Bacteria and Archaea and the origin of Eukarya.ConclusionThe ability of the Zn world hypothesis to generate non-trivial veritable predictions and explain previously obscure items gives credence to its key postulate that the development of the first life forms started within zinc-rich formations of hydrothermal origin and was driven by solar UV irradiation. This concept implies that the geochemical conditions conducive to the origin of life may have persisted only as long as the atmospheric CO2 pressure remained above ca. 10 bar. This work envisions the first Earth biotopes as photosynthesizing and habitable areas of porous ZnS and MnS precipitates around primeval hot springs. Further work will be needed to provide details on the life within these communities and to elucidate the primordial (bio)chemical reactions.ReviewersThis article was reviewed by Arcady Mushegian, Eugene Koonin, and Patrick Forterre. For the full reviews, please go to the Reviewers' reports section.

Formation of biomolecule precursors in space?

AbstractThe possibility of an extraterrestrial origin of biomolecule building blocks has been a subject of intense discussions for many years. The detection of amino acids in meteorites opens the possibility of a delivery of biomolecules synthesized in the interstellar medium or star-forming regions to the primeval Earth. Whereas it can be doubted if more complex species like amino acids can survive the strong UV radiation in the early Solar System, this does not necessary hold for more primitive precursor molecules like nitriles. These compounds can also be synthesized very efficiently in methane-nitrogen dominated atmospheres like the one present on Titan and the early ages of Earth. This Contribution focuses on the formation and degradation processes of nitriles in interstellar clouds and planetary atmospheres and on their possible role in the generation of biomolecules.

Melting the Earth: The History of Ideas on Volcanic Eruptions

The last words in the subtitle of this excellent book are somewhat misleading, as this is a history of concepts of magma generation rather than eruption. Haraldur Sigurdsson traces the evolution of ideas on the generation of heat within the Earth, from the ancient view that air in subterranean voids was compressed by ocean waves and tides, through combustion of fossil fuels, remnant heat from a primeval hot Earth, and exothermic reactions, to radioactive decay.In addition to sources of heat, its mechanism of transfer, the process of melting, the identity of the material being melted, and the depths at which magmas were generated were subjects of early inquiry by D'Arezzo, Michell, and Spallanzani, among others. Most 19th century geologists, however, followed Charles Lyell in his reluctance to speculate on causes. This left the field to William Hopkins, Gustav Bischof,and others whose names are not well known to 21st century penologists. The large cast of players in this book also includes the ever‐popular Desmarest, Hamilton, Holmes, Hutton, and Scrope, and an occasional scoundrel. The last chapter, on the source of magmas, makes no mention of contributions from trace element and isotope geochemistry and none concerning high‐pressure minerals that indicate localized deep burial of continental crust and ascent of material from the lower mantle.

Repeats of base oligomers as the primordial coding sequences of the primeval earth and their vestiges in modern genes.

Three outstanding properties uniquely qualify repeats of base oligomers as the primordial coding sequences of all polypeptide chains. First, when compared with randomly generated base sequences in general, they are more likely to have long open reading frames. Second, periodical polypeptide chains specified by such repeats are more likely to assume either alpha-helical or beta-sheet secondary structures than are polypeptide chains of random sequence. Third, provided that the number of bases in the oligomeric unit is not a multiple of 3, these internally repetitious coding sequences are impervious to randomly sustained base substitutions, deletions, and insertions. This is because the recurring periodicity of their polypeptide chains is given by three consecutive copies of the oligomeric unit translated in three different reading frames. Accordingly, when one reading frame is open, the other two are automatically open as well, all three being capable of coding for polypeptide chains of identical periodicity. Under this circumstance, a frame shift due to the deletion or insertion of a number of bases that is not a multiple of 3 fails to alter the down-stream amino acid sequence, and even a base change causing premature chain-termination can silence only one of the three potential coding units. Newly arisen coding sequences in modern organisms are oligomeric repeats, and most of the older genes retain various vestiges of their original internal repetitions. Some of the genes (e.g., oncogenes) have even inherited the property of being impervious to randomly sustained base changes.

The oldest high grade terranes : possible relicts of primeval earth crust

Some of the oldest high-grade terranes developed under very specific conditions that could be there only at the earliest stage of the Earth's evolution, are an important argument in favour of the Pre-Archean age of these terranes (older than 3.5 Ga). The Pre-Archean stage was a period when the primary massive atmosphere of essentially hydrous composiuon existed. The surface temperature was very high (300 ± 100°C). The earliest epoch of this period was specific in its small volume of hydrosphere or its absence due to which lhe lithogenesis of that time was mainly of volcanic nature. The high standing of the geoisotherms resulted in the intensive magma melting at relatively shallow depths, and the quick uplift of nondifferentiated magmas to the surface formed a primitive metabasalt shell. Further development was going on under the conditions of an intensive exogenous differentiation of the basaltic and more acidic volcanic substance coming from the mantle. The temperatures being extremely high as well as the chemical activity of the hydro- and atmosphere. ln this way a thick continental protocrust, of about 40 km, was formed.

The synthesis of some lipid-like structures in simulated primeval earth conditions

Starting from a simple gas mixture rich in methane, suggested as being a model of the primeval atmosphere for a certain time period, we succeeded in synthesizing lipid-like compounds. The hydrophobic nature of the products was demonstrated by IR, NMR, MS, elementary analysis, gel filtration measurements and solubility tests. The hydrophobic products self-assemble in stable, uniformly sized microspheres possessing membrane-like properties. They can selectively retain biologically active compounds. The wall-membrane of the microspheres shows a supra-molecular order.

Biological and biochemical activities of protobiopolymers

AbstractThe biological and biochemical activity of protobiopolymers and their macromolecular aggregates (microspheres) synthesized in simulative primeval Earth conditions has been investigated. In vitro and in vivo experiments were carried out on bovine albumine and Tubifex egg cells, respectively. The activity of trypsin encapsulated microspheres was studied also. Intense biological and biochemical activities of the protobiopolymers and the trypsin encapsulated microspheres have been observed. It is noteworthy that the development and the division of the egg cells are influenced dramatically.

Abiotic synthesis and the properties of some protobiocopolymers

AbstractThe appearance and the properties of protobiocopolymers are critically discussed. Simulating the geologically relevant primeval Earth conditions, i.e., taking into account the early atmosphere, hydrosphere, and available energies, the possibility of simultaneous appearance of some protobiocopolymers is suggested. The self‐assembling of these macromolecules in well‐defined individual systems (microspheres), their special electrical properties, such as membrane potential and semiconductivity, and their stability in rather severe physicochemtcal conditions, e.g., pH, temperature, mechanical stress, and irradiation with UV light, bring forward the “protocell” which could arise on this track on our primitive planet.

Darwin, Lyell, and the Geological Significance of Coral Reefs

In the half century following Cook's entry into the Pacific in 1769, few tropical phenomena excited more attention than coral islands and the corals which evidently built them. In the eighteenth century corals occupied a critical position in the Great Chain of Being. Sometimes interpreted as animals, sometimes as plants, they built large topographic structures of limestone, and thus spanned the gap between the organic and inorganic worlds. ‘The strata which they form are at once living and fossil; we can see them in the act of production, and the mountains grow up to the day before us, new parts of our own earth.’ Towards the end of the century, after Peyssonnel had conclusively shown that corals were animals—variously designated as worms, insects, or molluscous worms—this bridging significance was transferred to the coral islands, new areas of land emerging from the ocean and newly colonized by plants and animals, as an analogue of the primeval earth. This creative process served for some to counterbalance the Huttonian vision of universal degradation: ‘Whatever destroying tendencies … exist on the earth, these renovating powers compensate for them’.