Abiotic Production of Methane in Terrestrial Planets (Astrobiology, 2013)
VPL Authors
Full Citation:
Guzmán-Marmolejo, A., Segura, A., & Escobar-Briones, E. (2013). Abiotic Production of Methane in Terrestrial Planets. Astrobiology, 13(6), 550–559. https://doi.org/10.1089/ast.2012.0817
Abstract:
On Earth, methane is produced mainly by life, and it has been proposed that, under certain conditions, methane detected in an exoplanetary spectrum may be considered a biosignature. Here, we estimate how much methane may be produced in hydrothermal vent systems by serpentinization, its main geological source, using the kinetic properties of the main reactions involved in methane production by serpentinization. Hydrogen production by serpentinization was calculated as a function of the available FeO in the crust, given the current spreading rates. Carbon dioxide is the limiting reactant for methane formation because it is highly depleted in aqueous form in hydrothermal vent systems. We estimated maximum CH4 surface fluxes of 6.8×108 and 1.3×109 molecules cm−2 s−1 for rocky planets with 1 and 5 M⊕, respectively. Using a 1-D photochemical model, we simulated atmospheres with volume mixing ratios of 0.03 and 0.1 CO2 to calculate atmospheric methane concentrations for the maximum production of this compound by serpentinization. The resulting abundances were 2.5 and 2.1 ppmv for 1 M⊕ planets and 4.1 and 3.7 ppmv for 5 M⊕ planets. Therefore, low atmospheric concentrations of methane may be produced by serpentinization. For habitable planets around Sun-like stars with N2-CO2 atmospheres, methane concentrations larger than 10 ppmv may indicate the presence of life. Key Words: Serpentinization—Exoplanets—Biosignatures—Planetary atmospheres. Astrobiology 13, 550–559.
URL:
https://www.liebertpub.com/doi/abs/10.1089/ast.2012.0817?journalCode=ast&journalCode=ast_
VPL Research Tasks:
Task C: The Habitable Planet