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GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L11202, doi:10.1029/2006GL029156, 2007

Salinity-induced hydrate dissociation: A mechanism for recent CH4 release on Mars

M. E. Elwood Madden

Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA


S. M. Ulrich

Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA


T. C. Onstott

Department of Geosciences, Princeton University, Princeton, New Jersey, USA


T. J. Phelps

Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA


Abstract

Recent observations of CH4 in the Martian atmosphere suggest that CH4 has been added relatively recently. Several mechanisms for recent CH4 release have been proposed including subsurface biological methanogenesis, abiogenic hydrothermal and/or volcanic activity, dissociation of CH4 hydrates, atmospheric photolysis, or addition of organics via bolide impact. This study examines the effects of increasing salinity on gas hydrate stability and compares estimates of the Martian geothermal gradient to CH4 and CO2 hydrate stability fields in the presence of high salinity brines. The results demonstrate that salinity increases alone result in a significant decrease in the predicted hydrate stability zone within the Martian subsurface and may be a driving force in CH4 hydrate destabilization. Active thermal and/or pressure fluctuations are not required in order for CH4 hydrates to be the source of atmospheric CH4.

Received 20 December 2006; accepted 7 May 2007; published 8 June 2007.

Keywords: Mars; methane; hydrate.

Index Terms: 1060 Geochemistry: Planetary geochemistry (5405, 5410, 5704, 5709, 6005, 6008); 3004 Marine Geology and Geophysics: Gas and hydrate systems; 5210 Planetary Sciences: Astrobiology: Planetary atmospheres, clouds, and hazes (0343); 5220 Planetary Sciences: Astrobiology: Hydrothermal systems and weathering on other planets; 6225 Planetary Sciences: Solar System Objects: Mars.

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Citation: Elwood Madden, M. E., S. M. Ulrich, T. C. Onstott, and T. J. Phelps (2007), Salinity-induced hydrate dissociation: A mechanism for recent CH4 release on Mars, Geophys. Res. Lett., 34, L11202, doi:10.1029/2006GL029156.