A Universal Geochemical Scenario for Formamide Condensation and Prebiotic Chemistry

Abstract

The condensation of formamide has been shown to be a robust chemical pathway affording molecules necessary for the origin of life. It has been experimentally demonstrated that condensation reactions of formamide are catalyzed by a number of minerals, including silicates, phosphates, sulfides, zirconia, and borates, and by cosmic dusts and meteorites. However, a critical discussion of the catalytic power of the tested minerals, and the geochemical conditions under which the condensation would occur, is still missing. We show here that mineral self-assembled structures forming under alkaline silica-rich solutions are excellent catalysts for the condensation of formamide with respect to other minerals. We also propose that these structures were likely forming as early as 4.4 billion years ago when the whole earth surface was a reactor, a global scale factory, releasing large amounts of organic compounds. Our experimental results suggest that the conditions required for the synthesis of the molecular bricks from which life self-assembles, rather than being local and bizarre, appears to be universal and geologically rather conventional.

Keywords: biomorphs; formamide; geochemistry; origin of life; prebiotic chemistry; serpentinization.

Figure 1

The biologically more relevant compounds obtained by reacting NH₂CHO in the presence of various minerals. A: nucleobases. B: nucleosides and acyclonucleosides. C: sugars. D: carboxylic acids. E: amino acids, condensing agents, and HCN oligomers.

Figure 2

4400 Million years ago, water condensed on the first solid crust of the planet, which was made of peridotites and ultramafic rocks. The reaction of water with the mineral olivine triggers serpentinization reaction at large scale and creates the reduced environment required for the formation of organic compounds of geological origin. Alkaline pH and subsequent enrichment in silica allows the formation of mineral self‐organized structures, such as silica/carbonate biomorphs and mineral vesicles, which are illustrated. Scale bar of silica/carbonate biomorphs: 25 microns; Scale bar of mineral vesicles: 300 microns.