Organic protomolecule assembly in igneous minerals

C-H stretching bands, nu (CH), in the infrared spectrum of single crystals of nominally high purity, of laboratory-grown MgO, and of natural upper man tle olivine, provide an "organic" signature that closely resembles the symm etrical and asymmetrical C-H stretching modes of aliphatic -CH2 units. The nu (CH) bands indicate that H2O and CO2, dissolved in the matrix of these m inerals, converted to form H-2 and chemically reduced C, which in turn form ed C-H entities, probably through segregation into defects such as dislocat ions. Heating causes the C-H bonds to pyrolyze and the nu (CH) hands to dis appear, but annealing at 70 degreesC causes them to reappear within a few d ays or weeks. Modeling dislocations in MgO suggests that the segregation of C can lead to C-x chains, x = 4, with the terminal C atoms anchored to the MgO matrix by bonding to two O-. Allowing H-2 to react with such C-x chain s leads to [O2C(CH2)(2)CO2] or similar precipitates. It is suggested that s uch C-x-H-y-O-z entities represent protomolecules from which derive the sho rt-chain carboxylic and dicarboxylic and the medium-chain fatty acids that have been solvent-extracted from crushed MgO and olivine single crystals, r espectively. Thus, it appears that the hard, dense matrix of igneous minera ls represents a medium in which protomolecular units can be assembled. Duri ng weathering of rocks, the protomolecular units turn into complex organic molecules. These processes may have provided stereochemically constrained o rganics to the early Earth that were crucial to the emergence of life.