Primitive xenolithic clasts, often referred to as `` dark clasts", are well known in many regolith breccias. The Sharps H3.4 ordinary chondrite contains unusually large dark clasts up to similar to 1 cm across. Poorly-graphitized carbon (PGC), with Fe, Ni metal and described as `` carbon-rich aggregates", has been reported in these clasts (Brearley, 1990). We report detailed analyses of carbonaceous matter in several identical Sharps clasts using FTIR, Raman, C-XANES, and TEM that provide insight on the extent of thermal processing and possible origin of such clasts. We also prepared acid residues of the clasts using the HCl/HF method and conducted mass spectrometric analysis of the entrained noble gases.

Geometric isomerism in polyacetylene is a basic concept in chemistry textbooks. Polymerization to cis-isomer is kinetically preferred at low temperature, not only in the classic catalytic reaction in solution but also, unexpectedly, in the crystalline phase when it is driven by external pressure without a catalyst. Until now, no perfect reaction route has been proposed for this pressure-induced polymerization. Using in situ neutron diffraction and meta-dynamic simulation, we discovered that under high pressure, acetylene molecules react along a specific crystallographic direction that is perpendicular to those previously proposed. Following this route produces a pure cis-isomer and more surprisingly, predicts that graphane is the final product. Experimentally, polycyclic polymers with a layered structure were identified in the recovered product by solid-state nuclear magnetic resonance and neutron pair distribution functions, which indicates the possibility of synthesizing graphane under high pressure.

Hydrothermal systems may have been favorable environments for the evolution of prebiotic chemistry on early Earth due to the presence of chemical, temperature, and redox gradients that could promote the formation of biomolecules. However, the relevance of these environments in origins of life scenarios has been debated due to rapid decomposition of biologically essential species, such as amino acids, at high temperatures. Little is known about the reactivity of amino acids in the presence of mineral surfaces and reducing conditions, which reflect the geochemical complexities of environments such as serpentinite-hosted hydrothermal vents. We investigated the decomposition of 25 mM aspartate at 200 degrees C and 15.5 bars (P-SAT) in gold capsules both with and without brucite [Mg(OH)(2)], a mineral product of serpentinization, and reducing conditions (NH4Cl and H-2(aq)).We observed that the reaction products of aspartate vary significantly with the initial reaction conditions. Fluids containing aspartate only decomposed to fumarate, maleate, malate, acetate, and trace amounts of succinate and glycine. However, under reducing conditions, the main product was succinate (8 mM) and also approximately 1 mM total of the amino acids glycine, alpha-alanine, and beta-alanine. The amount of a-alanine increased three-fold with brucite. Furthermore, we detected a two-fold decrease in the fumarate concentration, whereas total maleate concentration dramatically decreased over ten-fold and resulted in an overall increase in the trans/cis ratio of these deamination products of aspartate from 0.9 to 4.5 as a function of brucite loading. This net decrease in fumarate and maleate concentration and the five-fold increase in the trans/cis ratio might have been caused by a combination of a pH increase and the formation of magnesite due to increased Mg2+ ion concentration. The results of this study provide evidence that the fundamental properties of a hydrothermal system, including mineral assemblages, reducing conditions, and dissolved species concentrations, will influence the fate of amino acids at high temperature.

Enzymes are biopolymeric complexes that catalyse biochemical reactions and shape metabolic pathways. Enzymes usually work with small molecule cofactors that actively participate in reaction mechanisms and complex, usually globular, polymeric structures capable of specific substrate binding, encapsulation and orientation. Moreover, the globular structures of enzymes possess cavities with modulated microenvironments, facilitating the progression of reaction(s). The globular structure is ensured by long folded protein or RNA strands. Synthesis of such elaborate complexes has proven difficult under prebiotically plausible conditions. We explore here that catalysis may have been performed by alternative polymeric structures, namely hyperbranched polymers. Hyper-branched polymers are relatively complex structures that can be synthesized under prebiotically plausible conditions; their globular structure is ensured by virtue of their architecture rather than folding. In this study, we probe the ability of tertiary amine-bearing hyperbranched polyesters to form hydrophobic pockets as a reaction-promoting medium for the Kemp elimination reaction. Our results show that polyesters formed upon reaction between glycerol, triethanolamine and organic acid containing hydrophobic groups, i.e. adipic and methylsuccinic acid, are capable of increasing the rate of Kemp elimination by a factor of up to 3 over monomeric triethanolamine.

Over the last several hundred years of scientific progress, we have arrived at a deep understanding of the non-living world. We have not yet achieved an analogous, deep understanding of the living world. The origins of life is our best chance at discovering scientific laws governing life, because it marks the point of departure from the predictable physical and chemical world to the novel, history-dependent living world. This theme issue aims to explore ways to build a deeper understanding of the nature of biology, by modelling the origins of life on a sufficiently abstract level, starting from prebiotic conditions on Earth and possibly on other planets and bridging quantitative frameworks approaching universal aspects of life. The aim of the editors is to stimulate new directions for solving the origins of life. The present introduction represents the point of view of the editors on some of the most promising future directions.

Pressure-induced polymerization (PIP) of aromatics is a novel method for constructing sp(3)-carbon frameworks, and nanothreads with diamond-like structures were synthesized by compressing benzene and its derivatives. Here by compressing a benzene-hexafluorobenzene cocrystal (CHCF), H-F-substituted graphane with a layered structure in the PIP product was identified. Based on the crystal structure determined from the in situ neutron diffraction and the intermediate products identified by gas chromatography-mass spectrum, we found that at 20 GPa CHCF forms tilted columns with benzene and hexafluorobenzene stacked alternatively, and leads to a [4+2] polymer, which then transforms to short-range ordered H-F-substituted graphane. The reaction process involves [4+2] Diels-Alder, retro-Diels-Alder, and 1-1' coupling reactions, and the former is the key reaction in the PIP. These studies confirm the elemental reactions of PIP of CHCF for the first time, and provide insight into the PIP of aromatics.

Past studies of the various separable carbonaceous fractions have been unable to account for all of C in primitive chondrites. In particular, up to 20-50% of the C is lost during acid leaching of bulk samples even after the C in carbonates and soluble organic matter is accounted for. To try to better characterize the nature of this missing C, we have compared the bulk infrared (IR) absorption spectra of a number of primitive chondrites with those of their previously reported insoluble organic matter (IOM). The aliphatic C-H stretching bands, in particular, allow us to compare the molecular structures of bulk C with that of IOM. The spectral differences between bulk C and IOM reflect missing C phases that were lost during acid leaching, although we cannot completely exclude the possibility that the OM was modified after demineralization. Comparing IR spectra of bulk meteorite powder and IOM suggests that the missing C varies in its molecular structure, and that mildly thermally metamorphosed type 3 chondrites tend to be richer in an aliphatic fraction with lower CH2/CH3 ratios, relative to IOM, compared to aqueously altered carbonaceous chondrites (CI/CM/CR). The missing C is most likely released from acid-labile functional groups, such as esters, acetals, and amides, during demineralization, although it cannot be ruled out that some fraction of the missing C is in small grains that are difficult to recover from suspension, or in water-soluble compounds trapped in phyllosilicates.