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.

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.