Abstract-The reaction between kamacite grains and H2 + CO gas mixture has been tested in the laboratory under experimental conditions presumed for interplanetary dust particle (IDP) formation in a nebular-type environment (H2:CO = 250: 1 ; 5 x 10-4 atm total pressure, and 473 K). Carbon deposition, hydrocarbon production in the C1-C4 range, and the formation of an €-carbide phase occur when well-defined model FeNi bcc alloy (kamacite) particles are exposed to a mixture of H2 + CO during 103 h. These results strongly support the idea that gas-solid reactions in the solar nebula during CO hydrogenation represent a plausible scenario for the formation of carbides and carbonaceous materials in IDPs, as well as for the production of hydrocarbons through Fischer-Tropsch-type reactions.