Differentiating biotic from abiotic methane genesis in hydrothermally active planetary surfaces
2012
Oze, Christopher | Jones, L Camille | Goldsmith, Jonas I. | Rosenbauer, Robert J.
Molecular hydrogen (H ₂) is derived from the hydrothermal alteration of olivine-rich planetary crust. Abiotic and biotic processes consume H ₂ to produce methane (CH ₄); however, the extent of either process is unknown. Here, we assess the temporal dependence and limit of abiotic CH ₄ related to the presence and formation of mineral catalysts during olivine hydrolysis (i.e., serpentinization) at 200 °C and 0.03 gigapascal. Results indicate that the rate of CH ₄ production increases to a maximum value related to magnetite catalyzation. By identifying the dynamics of CH ₄ production, we kinetically model how the H ₂ to CH ₄ ratio may be used to assess the origin of CH ₄ in deep subsurface serpentinization systems on Earth and Mars. Based on our model and available field data, low H ₂/CH ₄ ratios (less than approximately 40) indicate that life is likely present and active.
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