Early Earth Research Articles

Exploring the secondary mineral products generated by microbial iron respiration in Archean ocean simulations.

Marine chemical sedimentary deposits known as Banded Iron Formations (BIFs) archive Archean ocean chemistry and, potentially, signs of ancient microbial life. BIFs contain a diversity of iron- and silica-rich minerals in disequilibrium, and thus many interpretations of these phases suggest they formed secondarily during early diagenetic processes. One such hypothesis posits that the early diagenetic microbial respiration of primary iron(III) oxides in BIFs resulted in the formation of other iron phases, including the iron-rich silicates, carbonates, and magnetite common in BIF assemblages. Here, we simulated this proposed pathway in laboratory incubations combining a model dissimilatory iron-reducing (DIR) bacterium, Shewanella putrefaciens CN32, and the ferric oxyhydroxide mineral ferrihydrite under conditions mimicking the predicted Archean seawater geochemistry. We assessed the impact of dissolved silica, calcium, and magnesium on the bioreduced precipitates. After harvesting the solid products from these experiments, we analyzed the reduced mineral phases using Raman spectroscopy, electron microscopy, powder x-ray diffraction, and spectrophotometric techniques to identify mineral precipitates and track the bulk distributions of Fe(II) and Fe(III). These techniques detected a diverse range of calcium carbonate morphologies and polymorphism in incubations with calcium, as well as secondary ferric oxide phases like goethite in silica-free experiments. We also identified aggregates of curling, iron- and silica-rich amorphous precipitates in all incubations amended with silica. Although ferric oxides persist even in our electron acceptor-limited incubations, our observations indicate that microbial iron reduction of ferrihydrite is a viable pathway for the formation of early iron silicate phases. This finding allows us to draw parallels between our experimental proto-silicates and the recently characterized iron silicate nanoinclusions in BIF chert deposits, suggesting that early iron silicates could possibly be signatures of iron-reducing metabolisms on early Earth.

Characterization and Geological Implications of Precambrian Calcite‐Hosted Phosphate

AbstractConstraints on marine phosphate availability and cycling directly inform our understanding of long‐term biological evolution. However, early Earth phosphate records are sparse, biased toward siliciclastic samples, and susceptible to post‐depositional modification. Well‐preserved shallow marine inorganic carbonate precipitates provide a complementary yet understudied record of phosphate cycling. We combined micro‐X‐ray fluorescence mapping, X‐ray absorption, and Nuclear Magnetic Resonance spectroscopy on samples of Precambrian syndepositional herringbone calcite (HBC) and microspar to characterize phosphorus speciation and distribution in these carbonate fabrics. Phosphorus spectroscopy from synthetic calcite, HBC, and microspar, is qualitatively consistent with a disordered distribution of phosphate. These characteristics are diagnostic of calcite‐hosted phosphate, which is pervasive at low concentrations in HBC and microspar. This study provides evidence that ancient, well‐preserved carbonate fabrics retain phosphate sourced from seawater and highlights the potential for an unaltered archive of marine phosphate concentration over geologic time.

Prebiotic synthesis of noncanonical nucleobases under plausible alkaline hydrothermal conditions

Herein, the potential of alkaline hydrothermal environments for the synthesis of possible ancestral pre-RNA nucleobases using cyanide as a primary source of carbon and nitrogen is described. Water cyanide polymerizations were assisted by microwave radiation to obtain high temperature and a relatively high pressure (MWR, 180 °C, 15 bar) and were also carried out using a conventional thermal system (CTS, 80 °C, 1 bar) to simulate subaerial and aerial hydrothermal conditions, respectively, on the early Earth. For these syntheses, the initial concentration of cyanide and the diffusion effects were studied. In addition, it is well known that hydrolysis conditions are directly related to the amount and diversity of organic molecules released from cyanide polymers. Thus, as a first step, we studied the effect of several hydrolysis procedures, generally used in prebiotic chemistry, on some of the potential pre-RNA nucleobases of interest, together with some of their isomers and/or deamination products, also presumably formed in these complex reactions. The results show that the alkaline hydrothermal scenarios with a relatively constant pH are good geological scenarios for the generation of noncanonical nucleobases using cyanide as a prebiotic precursor.

Coupling and decoupling CH stretching vibration of methylene and methine in serine conformers

In the molecules of the early Earth, as a building block of proteins, serine has enormous chemical and biological significance. The vibrational spectroscopy of CH bonds plays an important role in probing biomolecules. Whether the CH stretching vibration bands can be accurately assigned will affect the accuracy of the detection results. In this study, we employed the MP2/cc-pVTZ method to calculate the Raman spectra of 85 serine conformers and the corresponding species with deuterium in the CH stretching region from 2800 cm−1 to 3050 cm−1 and then recorded the movement of each atom and the dihedral angles, CH bond lengths, and Raman shifts before and after deuterium for each conformer. We directly observed that the stretching vibration of two CH bonds in the methylene group decoupled to vibrate independently in some conformers, and the stretching vibrations of methylene and methine could be strongly coupled in some conformers. Those results are inconsistent with the traditional understanding, which is generally believed that the CH stretching vibrations are mutually coupled in a single methyl or methylene group to generate symmetric and antisymmetric stretching vibrations, while for different methyl, methylene or methine groups, the CH stretching vibrations cannot be mutually coupled. Through the statistical analysis between several factors, we found that the level of local coupling in serine methylene was correlated with the bond length difference between two CH bonds. Our work provides a new understanding of the vibrational modes of hydrocarbon bonds and the coupling between different hydrocarbon groups.

The thermal–orbital evolution of the Earth–Moon system with a subsurface magma ocean and fossil figure

Various theories have been proposed to explain the Moon’s current inclined orbit. We test the viability of these theories by reconstructing the thermal–orbital history of the Moon. We build on past thermal–orbital models and incorporate the evolution of the lunar figure including a fossil figure component. Obliquity tidal heating in the lunar magma ocean would have produced rapid inclination damping, making it difficult for an early inclination to survive to the present-day. An early inclination is preserved only if the solid-body of the early Moon were less dissipative than at present. If instabilities at the Laplace plane transition were the source of the inclination, then the Moon had to recede slowly, which is consistent with previous findings of a weakly dissipative early Earth. If collisionless encounters with planetesimals up to 140 Myr after Moon formation excited the inclination, then the Moon had to migrate quickly to pass through the Cassini state transition at 33 Earth radii and reach a period of limited inclination damping. The fossil figure was likely established before 16 Earth radii to match the present-day degree-2 gravity field observations.

Marine phosphate availability and the chemical origins of life on Earth

Prebiotic systems chemistry suggests that high phosphate concentrations were necessary to synthesise molecular building blocks and sustain primitive cellular systems. However, current understanding of mineral solubility predicts negligible phosphate concentrations for most natural waters, yet the role of Fe2+, ubiquitous on early Earth, is poorly quantified. Here we determine the solubility of Fe(II)-phosphate in synthetic seawater as a function of pH and ionic strength, integrate these observations into a thermodynamic model that predicts phosphate concentrations across a range of aquatic conditions, and validate these predictions against modern anoxic sediment pore waters. Experiments and models show that Fe2+ significantly increases the solubility of all phosphate minerals in anoxic systems, suggesting that Hadean and Archean seawater featured phosphate concentrations ~103–104 times higher than currently estimated. This suggests that seawater readily met the phosphorus requirements of emergent cellular systems and early microbial life, perhaps fueling primary production during the advent of oxygenic photosynthesis.

The Systems Chemistry of Nucleic‐acid‐Peptide Networks

AbstractLiving cells use chemical building blocks (biopolymers) to form fascinatingly complex architectures, which in turn display multiple functions necessary for the cell life cycle. The mechanisms and order of events by which forerunners of these extant biopolymers formed on the early earth remains under intensive investigation. Prebiotic chemistry research has recently provided ample evidence that both peptide and nucleic‐acid (NA) precursors could be formed in a primordial environment through common synthetic routes. However, until recently, studies directed at the design of functional supramolecular structures have focused primarily on assemblies made of either peptides or NAs. The emerging discipline of Systems Chemistry now develops dynamic supramolecular interactions to capture the complex emergent properties of reaction networks. Accordingly, we review here recent work that reveals mutualistic nucleic acid/peptide co‐assembly, and approaches toward utility of these architectures as functional materials capable of substrate binding, catalysis, replication, and translation. Many of these new approaches to smart soft biomaterials and functional bio‐nanotechnology provide insight and extend our understanding of the possible origins of living systems.

Petrogenetic and textural classification of kimberlites and lamproites of the Brauna Kimberlitic Field: Implications for potassic/ultrapotassic magmatism in the São Francisco Craton

Kimberlitic rocks are known in the São Francisco Craton, Brazil, since the 1980s when the De Beers started a prospective work in the Itapicuru River Greenstone Belt. However, 40 years later, the scientific knowledge about these occurrences is still very restricted. This paper presents new geological and petrographical data for the pipes of the “Brauna Kimberlitic Field”. These rocks are exposed in a strongly eroded cratonic area of Northeastern São Francisco Craton and as expected, represent the deepest parts of these bodies, showing textural aspects and components typical of coherent volcanic rocks emplaced at deep crustal levels.The kimberlitic magmatic event resulted not only in the emplacement of macrocrystalline hypabyssal olivine archetypal kimberlites, here represented by the B3 (678–682 Ma) and B4 pipes (s.s. Former type 1 kimberlites), but also in hypabyssal macrocrystalline pyroxene-phlogopite- lamproite intrusions, as exposed in the B7 (641 Ma) pipe of the Brauna Field. Both magmas are rich in mantle-xenoliths and have potential for diamond ores. The observed features suggest the presence of multiple magmatic pulses – which acted as deep samplers, recorded in the diversity of xenoliths and xenocrysts – thus demonstrating the potential of these rocks for the comprehension of the first stages of evolution of the Early Earth as well as for understanding the formation of the metasomatized lithospheric mantle below the São Francisco Craton.The new data for these hypabyssal facies, macrocrystic pulse of kimberlitic rocks in the Brauna Field, São Francisco Craton, Brazil, can be used to characterize the petrographic and mineralogical heterogeneities of a Neoproterozoic alkaline-ultrapotassic magmatic event that shows a kimberlite-lamproite transitional nature. The petrogenetic knowledge presented for the São Francisco Craton kimberlites and lamproites – accordingly to the most recent classifications for these rocks – include textural-genetic data, geotectonic environment, and intrusive-spatial context, setting these rocks at the stage 5 of present-day kimberlite classification scheme. Moreover, the integration of such data and the close spatial associations of kimberlites, lamproites, lamprophyres, syenites and shoshonites allowed to create a solid interpretation of the rock formation processes that correlates these Neoproterozoic alkaline ultrapotassic magmas to the reactivation of ancient mantle conduits in a thick lithosphere that overlies a previously metasomatized mantle and intrude a metal-rich craton environment.

Did transit through the galactic spiral arms seed crust production on the early Earth?

Abstract Although there is evidence for periodic geological perturbations driven by regular or semi-regular extra-terrestrial bombardment, the production of Earth's continental crust is generally regarded as a function of planetary differentiation driven by internal processes. We report time series analysis of the Hf isotopic composition of zircon grains from the North Atlantic and Pilbara cratons, the archetypes of Archean plate tectonic and non-plate tectonic settings, respectively. An ~170–200 m.y. frequency is recognized in both cratons that matches the transit of the solar system through the galactic spiral arms, where the density of stars is high. An increase in stellar density is consistent with an enhanced rate of Earth bombardment by comets, the larger of which would have initiated crustal nuclei production via impact-driven decompression melting of the mantle. Hence, the production and preservation of continental crust on the early Earth may have been fundamentally influenced by exogenous processes. A test of this model using oxygen isotopes in zircon from the Pilbara craton reveals correlations between crust with anomalously light isotopic signatures and exit from the Perseus spiral arm and entry into the Norma spiral arm, the latter of which matches the known age of terrestrial spherule beds. Our data support bolide impact, which promoted the growth of crustal nuclei, on solar system transit into and out of the galactic spiral arms.

Ferrocyanide survival under near ultraviolet (300–400 nm) irradiation on early Earth

Prebiotic lake environments containing ferrocyanide could have fostered origins of life chemistry on early Earth. Ferrocyanide can act to concentrate hydrogen cyanide (HCN), a prebiotically important molecule. Additionally, ferrocyanide, coupled with sulfite, can participate in an ultraviolet (UV)-driven photoredox cycle to generate solvated electrons, which can reduce cyanide to form all four major building blocks of life: sugars, amino acids, nucleotides, and lipid precursors. However, longer wavelength UV light (∼300–400 nm) causes photoaquation of ferrocyanide into pentacyanoaquaferrate, Fe(CN)5H2O. This species can either regain cyanide to reform ferrocyanide or ultimately lose cyanide ligands, which removes ferrocyanide from solution. Here, we investigate this near ultraviolet (300–400 nm) UV-driven loss of ferrocyanide. In addition to determining the wavelength dependence of the loss and the implications from the UV environment on early Earth, we also study the effects of pH, temperature, and concentration. We find that in dilute, slightly alkaline solutions, ferrocyanide would degrade significantly on the order of minutes under the near UV radiation expected on early Earth. We further determine that the lifetime of ferrocyanide is extended at more alkaline pH, lower temperatures, and higher concentrations. Under a reasonable set of planetary conditions, we find that ferrocyanide lifetimes in irradiated environments range from minutes to hours, or longer. Our results can help to determine the constraints implied by the UV-driven loss of ferrocyanide in prebiotic environments. We assess the potential environmental limits and circumstances that would allow for successful retention of significant amounts of ferrocyanide in prebiotic lakes; we further evaluate how ferrocyanide photoaquation may fit in to the larger network of reactions potentially occurring throughout prebiotic chemistry. For example, our experiments show that CN- can be released from ferrocyanide evaporite salts by aqueous dissolution and UV light, making it potentially available for prebiotic reactions. These results can aid in the construction of consistent and plausible circumstances for prebiotic chemistry on early Earth.

Sources of Nitrogen-, Sulfur-, and Phosphorus-Containing Feedstocks for Prebiotic Chemistry in the Planetary Environment.

Biochemistry on Earth makes use of the key elements carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur (or CHONPS). Chemically accessible molecules containing these key elements would presumably have been necessary for prebiotic chemistry and the origins of life on Earth. For example, feedstock molecules including fixed nitrogen (e.g., ammonia, nitrite, nitrate), accessible forms of phosphorus (e.g., phosphate, phosphite, etc.), and sources of sulfur (e.g., sulfide, sulfite) may have been necessary for the origins of life, given the biochemistry seen in Earth life today. This review describes potential sources of nitrogen-, sulfur-, and phosphorus-containing molecules in the context of planetary environments. For the early Earth, such considerations may be able to aid in the understanding of our own origins. Additionally, as we learn more about potential environments on other planets (for example, with upcoming next-generation telescope observations or new missions to explore other bodies in our Solar System), evaluating potential sources for elements necessary for life (as we know it) can help constrain the potential habitability of these worlds.

Widespread impact-generated porosity in early planetary crusts

NASA’s Gravity Recovery and Interior Laboratory (GRAIL) spacecraft revealed the crust of the Moon is highly porous, with ~4% porosity at 20 km deep. The deep lying porosity discovered by GRAIL has been difficult to explain, with most current models only able to explain high porosity near the lunar surface (first few kilometers) or inside complex craters. Using hydrocode routines we simulated fracturing and generation of porosity by large impacts in lunar, martian, and Earth crust. Our simulations indicate impacts that produce 100–1000 km scale basins alone are capable of producing all observed porosity within the lunar crust. Simulations under the higher surface gravity of Mars and Earth suggest basin forming impacts can be a primary source of porosity and fracturing of ancient planetary crusts. Thus, we show that impacts could have supported widespread crustal fluid circulation, with important implications for subsurface habitable environments on early Earth and Mars.

Cloud Feedback on Earth's Long‐Term Climate Simulated by a Near‐Global Cloud‐Permitting Model

AbstractThe Sun becomes brighter with time, but Earth's climate is roughly temperate for life during its long‐term history; for early Earth, this is known as the faint young Sun problem (FYSP). Besides the carbonate‐silicate feedback, recent researches suggest that a long‐term cloud feedback may partially solve the FYSP. However, the general circulation models they used cannot resolve convection and clouds explicitly. This study re‐investigates the clouds using a near‐global cloud‐permitting model without cumulus convection parameterization. Our results confirm that a stabilizing shortwave cloud feedback does exist, and its magnitude is ≈6 W m−2 or 14% of the energy required to offset a 20% fainter Sun than today, or ≈10 W m−2 or 16% for a 30% fainter Sun. When insolation increases and meanwhile CO2 concentration decreases, low‐level clouds increase, acting to stabilize the climate by raising planetary albedo, and vice versa.

Tectonically-driven oxidant production in the hot biosphere

Genomic reconstructions of the common ancestor to all life have identified genes involved in H2O2 and O2 cycling. Commonly dismissed as an artefact of lateral gene transfer after oxygenic photosynthesis evolved, an alternative is a geological source of H2O2 and O2 on the early Earth. Here, we show that under oxygen-free conditions high concentrations of H2O2 can be released from defects on crushed silicate rocks when water is added and heated to temperatures close to boiling point, but little is released at temperatures <80 °C. This temperature window overlaps the growth ranges of evolutionary ancient heat-loving and oxygen-respiring Bacteria and Archaea near the root of the Universal Tree of Life. We propose that the thermal activation of mineral surface defects during geological fault movements and associated stresses in the Earth’s crust was a source of oxidants that helped drive the (bio)geochemistry of hot fractures where life first evolved.

Palaeoproterozoic arc related supracrustal units from the Tasiilaq Region, SE Greenland: Insights into the convergence of the Rae and North Atlantic Cratons

The Tasiilaq region in SE Greenland contains Palaeoproterozoic supracrustal rocks, which record the collision and suturing of the Rae Craton and North Atlantic Craton during the 1.9 Ga Nagssugtoqidian orogeny. The original mineralogy and textures of the supracrustal rocks have been largely overprinted by amphibolite facies metamorphism, obscuring the original protoliths and complicating the interpretation of the early Earth surface environment in which these rocks formed. Here, we present new major and trace element data for the Schweizerland, Kuummiut and Isertoq Terranes, with the former two representing the Rae craton, and the latter the northern margin of the North Atlantic Craton. Supracrustal lithologies include metapelites, marbles, calc-silicate rocks and mafic to felsic volcanic rocks and/or shallow intrusive rocks. Pelites normalised to Post Archaean Australian shales have (sub)horizontal rare earth element patterns, with La/SmCN: 1.61 – 23.91 and Eu/Eu* 0.34 – 1.83 and Th/Sc 1. The volcanic rocks are enriched relative to the primitive mantle (PM) with parallel to sub parallel PM-normalised heavy rare earth elements. They have a suprasubduction zone signature with distinct Nb-Ta troughs. The amphibolites can be further divided into those that interacted with the crust; back-arc basalts with subtle Nb-Ta troughs; and fore-arc basalts with distinct Nb-Ta and Zr-Hf troughs and negative Ti anomalies. The marbles consist of a Mg-rich dolomite group with δ13C 0.48 to 0.91 ‰ and δ18O −6.13 to −7.57 ‰; and Mg-poor calcitic carbonates with δ13C −0.74 to 0.17 ‰ and δ18O −10.81 to −14.87 ‰. This isotopic composition suggests formation at ∼ 2050 Ma during the low δ13C excursion following the Great Oxidation Event. We propose that the supracrustals of the Tasiilaq region were deposited at 2050 Ma in a series of interconnected basins during dual subduction convergence of the North Atlantic and Rae cratons, with development of an island arc with back arc basin in the north, and a continental arc in the south. These basins were inverted during continental collision, thrust, and folded into the Archaean Kuummiut and Isertoq TTG-dominated terrane basement, before being subjected to the region-wide amphibolite facies metamorphism at ∼ 1840 Ma during the Nagssugtoqidian orogeny.

Phylogenomic Evidence for the Origin of Obligate Anaerobic Anammox Bacteria Around the Great Oxidation Event.

The anaerobic ammonium oxidation (anammox) bacteria can transform ammonium and nitrite to dinitrogen gas, and this obligate anaerobic process accounts for up to half of the global nitrogen loss in surface environments. Yet its origin and evolution, which may give important insights into the biogeochemistry of early Earth, remain enigmatic. Here, we performed a comprehensive phylogenomic and molecular clock analysis of anammox bacteria within the phylum Planctomycetes. After accommodating the uncertainties and factors influencing time estimates, which include implementing both a traditional cyanobacteria-based and a recently developed mitochondria-based molecular dating approach, we estimated a consistent origin of anammox bacteria at early Proterozoic and most likely around the so-called Great Oxidation Event (GOE; 2.32–2.5 Ga) which fundamentally changed global biogeochemical cycles. We further showed that during the origin of anammox bacteria, genes involved in oxidative stress adaptation, bioenergetics, and anammox granules formation were recruited, which might have contributed to their survival on an increasingly oxic Earth. Our findings suggest the rising levels of atmospheric oxygen, which made nitrite increasingly available, was a potential driving force for the emergence of anammox bacteria. This is one of the first studies that link the GOE to the evolution of obligate anaerobic bacteria.

Archean crust-mantle geodynamic regimes: A review

The crust-mantle dynamic system of the formation and evolution of the early Earth crust is a frontier field in current Earth Science. This paper mainly introduces the popular dynamic models, comprising the stagnant-lid, mantle plume, sagduction, dripping, hot plate subduction and flat plate subduction models. Geological signatures and thermomechanical experiments suggest that the above-mentioned first four dynamic models most likely occurred in the early Archean under high mantle potential temperature and high thermal state conditions although they may have survived in small scales to the late Archean, while the hot- and flat-plate subductions chiefly operated during the late Archean as the mantle potential temperature decreasing although they could have started since the Paleoarchean. The late Mesoarchean is a crucial transition period of the crust-mantle dynamic regimes, the diversified geodynamic regimes can coexist, for example, mantle plume and hot plate subduction, and pre-subduction buckling, sagduction and dripping mechanism. These regimes possibly emerged alternately, affected each other or operated in combination. Therefore, we believe that the Archean geodynamic regime has obvious variations as the mantle potential temperature decreasing from early to late Archean, of which the transition may be an interrelated and gradual evolved process rather than a sudden event.

Late Archean–Paleoproterozoic plate tectonics along the northern margin of the North China craton

AbstractThe North China craton of central Asia is a natural laboratory for investigating early Earth tectonic processes including subduction and large-scale horizontal crustal motions. However, it remains unclear how and when the North China craton formed from the amalgamation of several blocks and orogens including the Archean Western and Eastern blocks, the late Archean Central Orogenic Belt, and the Paleoproterozoic Northern Margin orogen. In this study, we integrated new and existing geological field observations, zircon and baddeleyite U-Pb geochronology, whole-rock geochemistry, and Sr-Nd-C-O isotope analyses along the northern margin of the North China craton to improve our understanding of its late Archean–Paleoproterozoic tectonic evolution. Observations show the Wuchuan ultramafic-mafic complex of the Northern Margin orogen contains a mixture of mylonite gneiss, serpentinized ultramafic blocks, and amphibolite pyroxenite xenoliths. Geochronology and geochemistry results suggest that the ca. 2.55–2.5 Ga development of the Wuchuan ultramafic-mafic complex was associated with subduction, which was followed by ca. 2.39 emplacement of lamprophyre dikes during continental rifting. Subsequent Paleoproterozoic subduction magmatism, continental collision, and post-orogenic rifting between the North China craton and southern margin of the Siberian craton are evidenced by ca. 2.0 Ga arc granitoids, ca. 1.87–1.85 Ga A-type, garnet-bearing granitoids and mafic dikes, and ca. 1.86 carbonatite. Ca. 2.0 Ga collision and ca. 1.87–1.85 Ga rifting were coincident with orogen-normal left-slip shear. Our findings show that the ca. 1.9 Ga North China-Siberia collision was a key event during the assembly of the Columbia supercontinent that occurred via modern plate-tectonic processes.

Tungsten Isotopic Constraints on the Nature of Earth's Accreting Materials

AbstractTungsten isotope is a powerful tracer for the Earth's accreting materials because of the distinct W isotope compositions of the non‐carbonaceous meteorites and carbonaceous meteorites. To better understand the evolution of the early Earth, here we calculated the expected μ183W of the bulk silicate Earth for different assumed compositions of the proto‐Earth's mantle, the Moon‐forming giant impactor, and the late veneer using a Monte Carlo approach. The result shows that the proto‐Earth likely has a non‐carbonaceous composition, while the carbonaceous chondrite‐like materials were delivered to the Earth at the late stages of accretion. The predicted difference in μ183W values between the bulk silicate Earth and the non‐carbonaceous meteorites of the scenarios assuming a pure carbonaceous composition for the giant impactor is slightly bigger than that of the scenarios assuming either a pure non‐carbonaceous or a mixed carbonaceous‐non‐carbonaceous composition for the giant impactor (∼5 ppm versus ∼2 ppm). The ancient mantle reservoir that partially lacks the late veneer with carbonaceous composition should have a negative μ183W value (from –3 to 0). Uncertainties introduced by the cosmogenic effects and mass‐independent fractionation should be concerned during the high precision measurement of μ183W for meteorites and ancient terrestrial samples in further work.

Primitive nucleobases @ sodium 2-Ketooctanoate vesicles with high salt resistance

• PNB@SKO is the strongest salt resistance P-SCA vesicle system to the best of our knowledge. • The rigid planar PNB molecules orientate via hydrogen bonding in the tilted bilayers of SKO. • The morphology, size, and membrane thickness of SKO vesicles are not affected by the PNB combination significantly. Proto-single chain amphiphiles (P-SCAs) vesicles are considered to be a plausible model of the protocell on early Earth due to their primordial relevancy and membrane structure. In this work, we selected P-SCAs sodium 2-ketooctanate (SKO) and proto-nucleobases (PNBs, including cytosine, uracil, adenine, and guanine) as the building constituents of the vesicles. The PNB molecules incorporate into SKO bilayers to form PNB@SKO vesicles with a binding rate of 7% − 12%. The interactions between them increase the solubility of PNB in water obviously while decreasing the critical vesicle concentration of SKO. The morphology, size, and membrane thickness of SKO PRB@SKO vesicles are not affected by the PNB combination significantly. A binding mechanism is proposed based on the results of Fourier transform infrared and small angle X-ray scattering. The rigid planar PNB molecules orientate via hydrogen bonding in the tilted bilayers of SKO, without excessive disruption to the membrane structure. Both ribozyme-catalyzed and non-enzymatic RNA copying reactions require high concentrations of divalent ions, fortunately, the salt resistance of these PNB@SKO vesicles is surprisingly remarkable, one or two orders of magnitude greater than the other typical P-SCAs vesicles systems. We expect that this primitively relevant vesicle system can exert its potential advantages in the proto-membrane mimicry of the origin of life.