Biological methane production under putative Enceladus-like conditions

Abstract

The detection of silica-rich dust particles, as an indication for ongoing hydrothermal activity, and the presence of water and organic molecules in the plume of Enceladus, have made Saturn’s icy moon a hot spot in the search for potential extraterrestrial life. Methanogenic archaea are among the organisms that could potentially thrive under the predicted conditions on Enceladus, considering that both molecular hydrogen (H2) and methane (CH4) have been detected in the plume. Here we show that a methanogenic archaeon, Methanothermococcus okinawensis, can produce CH4 under physicochemical conditions extrapolated for Enceladus. Up to 72% carbon dioxide to CH4 conversion is reached at 50 bar in the presence of potential inhibitors. Furthermore, kinetic and thermodynamic computations of low-temperature serpentinization indicate that there may be sufficient H2 gas production to serve as a substrate for CH4 production on Enceladus. We conclude that some of the CH4 detected in the plume of Enceladus might, in principle, be produced by methanogens.

Development of a simultaneous bioreactor system for characterization of gas production kinetics of methanogenic archaea at high pressure

“…2018 described an alternative way to indirectly quantify CH 4 productivity by the turnover rate [h −1 ] (Equation ). This parameter, while neglecting biomass formation, is described by the difference in pressure before and after incubation Δ p , the maximum theoretical pressure difference due to stoichiometry Δ p max , and the time period Δ t of incubation . …”

Living at the Extremes: Extremophiles and the Limits of Life in a Planetary Context

“…Different classification schemes have been published to describe planetary bodies based on their 'habitability' (e.g., Lammer et al, 2009;Noack et al, 2016;Schulze-Makuch et al, 2017). Several studies have also demonstrated the growth of microorganisms under lab-simulated planetary conditions, including Mars-like (Fajardo-Cavazos et al, 2018;Nicholson et al, 2013;Schuerger and Nicholson, 2016) and Enceladus-like (Taubner et al, 2018) conditions. In this context, defining the boundary limits of life on Earth is a crucial step in identifying the conditions likely to originate or support life on other planetary bodies.…”

Multiverse Predictions for Habitability: Number of Potentially Habitable Planets

“…It should be noted that we are restricting our attention here to surface dwelling life on planets orbiting their star. Thus, life in subsurface oceans and/or on icy moons like Enceladus [41], or even more exotic types of life (e.g., [42,43]), are not considered. It is our plan to consider these alternative environments in future work.…”