Putative mechanism of the sugar formation on prebiotic Earth initiated by UV-radiation

UV-irradiation of neutral aqueous formaldehyde solutions leads to the formation of a number of products. CO, CH4, CO2 and H2 are the main products detected in the gas phase over the solutions. In the liquid phase, glycolaldehyde and glyceraldehyde are among the products with the maximum yields of 4.2% and 0.18%, respectively. These aldehydes are shown to be the most active initiators of the formose reaction in the dark to synthesize monosaccharides from formaldehyde. The amounts of the photolytically formed initiators are sufficient for the initiating the formose reaction.