Photocatalytic Production of Organic Compounds from CO and H2O in a Simulated Martian Atmosphere

[¹⁴C]CO₂ and [¹⁴C]organic compounds are formed when a mixture of [¹⁴C]CO and water vapor diluted in [¹²C]CO₂ or N₂ is irradiated with ultraviolet light in the presence of soil or pulverized vycor substratum. The [¹⁴C]CO₂ is recoverable from the gas phase, the [¹⁴C]organic products from the substratum. Three organic products have been tentatively identified as formaldehyde, acetaldehyde, and glycolic acid. The relative yields of [¹⁴C]CO₂ and [¹⁴C]organics are wavelength- and surface-dependent. Conversion of CO to CO₂ occurs primarily at wavelengths shorter than 2000 Å, apparently involves the photolysis of water, and is inhibited by increasing amounts of vycor substratum. Organic formation occurs over a broad spectral ranger below 3000 Å and increases with increasing amounts of substratum. It is suggested that organic synthesis results from adsorption of CO and H₂O on surfaces, with excitation of one or both molecules occurring at wavelengths longer than those absorbed by the free gases. This process may occur on Mars and may have been important on the primitive earth.