Initial indications of abiotic formation of hydrocarbons in the Rainbow ultramafic hydrothermal system, Mid-Atlantic Ridge

In the presence of water, olivine of ultramafic rock is oxidized during the process referred to as 'serpentinization'. Water in contact with the olivi ne is reduced to molecular hydrogen (H-2) with the concomitant oxidation of Fe(II). The molecular hydrogen formed may be used as an energy source by l ithotrophic bacteria, but may, at high temperature, also be combined with C O2 for the abiotic formation of organic compounds such as hydrocarbons and fatty acids through Fischer-Tropsch type (FTT) synthesis. Our analyses of f luids from the peridotite-hosted Rainbow hydrothermal field on the Mid-Atla ntic Ridge indicate de novo synthesis of linear saturated hydrocarbons. The chain length of the hydrocarbons is between 16 and 29 carbon atoms. The di scovery of FTT reactions in ultramafic hydrothermal systems on Earth provid es an alternative pathway for the formation of early membranes and the orig in of life. (C) 2001 Elsevier Science BN. All rights reserved.