Biological methane production under putative Enceladus-like conditions

Area of Science:

• Astrobiology
• Geochemistry
• Microbiology

Background:

• Enceladus exhibits hydrothermal activity and has water and organic molecules in its plume.
• Methanogenic archaea are potential candidates for life on Enceladus due to detected molecular hydrogen (H2) and methane (CH4).

Purpose of the Study:

• To investigate the potential for methanogenic archaea to produce methane under Enceladus's extrapolated physicochemical conditions.
• To assess the viability of Methanothermococcus okinawensis as a methane producer in Enceladus's environment.

Main Methods:

• Culturing Methanothermococcus okinawensis under simulated Enceladus conditions (50 bar pressure).
• Measuring carbon dioxide to methane conversion rates.
• Performing kinetic and thermodynamic computations for low-temperature serpentinization to estimate H2 production.

Main Results:

• Methanothermococcus okinawensis achieved up to 72% CO2 to CH4 conversion under simulated Enceladus conditions, even with inhibitors.
• Computational modeling suggests sufficient H2 production via serpentinization to support methanogenesis on Enceladus.

Conclusions:

• Methanogens, like Methanothermococcus okinawensis, could theoretically produce methane on Enceladus.
• The detected methane in Enceladus's plume may originate from microbial methanogenesis.