| Summary: | <p>Abstract</p> <p>Hydrocarbons such as CH<sub>4 </sub>are known to be formed through the Fischer-Tropsch or Sabatier type reactions in hydrothermal systems usually at temperatures above 100°C. Weathering of olivine is sometimes suggested to account for abiotic formation of CH<sub>4 </sub>through its redox lowering and water splitting properties. Knowledge about the CH<sub>4 </sub>and H<sub>2 </sub>formation processes at low temperatures is important for the research about the origin and cause of early Earth and Martian CH<sub>4 </sub>and for CO<sub>2 </sub>sequestration. We have conducted a series of low temperature, long-term weathering experiments in which we have tested the CH<sub>4 </sub>and H<sub>2 </sub>formation potential of forsteritic olivine.</p> <p>The results show low temperature CH<sub>4 </sub>production that is probably influenced by chromite and magnetite as catalysts. Extensive analyses of a potential CH<sub>4 </sub>source trapped in the crystal structure of the olivine showed no signs of incorporated CH<sub>4</sub>. Also, the available sources of organic carbon were not enough to support the total amount of CH<sub>4 </sub>detected in our experiments. There was also a linear relationship between silica release into solution and the net CH<sub>4 </sub>accumulation into the incubation bottle headspaces suggesting that CH<sub>4 </sub>formation under these conditions could be a qualitative indicator of olivine dissolution.</p> <p>It is likely that minerals such as magnetite, chromite and other metal-rich minerals found on the olivine surface catalyze the formation of CH<sub>4</sub>, because of the low temperature of the system. This may expand the range of environments plausible for abiotic CH<sub>4 </sub>formation both on Earth and on other terrestrial bodies.</p>
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