Physics
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufm.p23a0036e&link_type=abstract
American Geophysical Union, Fall Meeting 2006, abstract #P23A-0036
Physics
1011 Thermodynamics (0766, 3611, 8411), 1012 Reactions And Phase Equilibria (3612, 8412), 3004 Gas And Hydrate Systems, 6225 Mars
Scientific paper
Recent observations of atmospheric methane made by the Mars Odyssey spacecraft suggest a relatively recent source of methane. These observations have spurred interest in near-surface methane hydrate deposits as one possible source. While most studies concentrate on measuring the effects of pressure and temperature variations on hydrate stability, salinity changes can also significantly shift the hydrate stability field in pressure-temperature space and may result in hydrate dissociation. Therefore, long-term increases in the salinity of subsurface fluids due to evaporation or freezing may result in the destabilization of hydrates at depth and a gradual release of methane from potential reservoirs. This study integrates the results of ongoing P-T-X experiments conducted in ORNL's 72 L Seafloor Process Simulator (SPS) and data from the literature describing methane hydrate stability in the presence of numerous salts with theoretical estimates of the Martian crust's thermal structure to build a model of recent and potentially ongoing salinity-induced methane hydrate dissociation in the subsurface. Initial calculations suggest that increased salinity may decrease the depth to the base of the hydrate stability zone by up to 4 km. In addition, the rate of salinity-induced methane hydrate dissociation will also be determined experimentally using a variety of salt compositions and ionic strengths. The results of this study suggest that increases in heat flow or large-scale depressurization of hydrate reservoirs are not required for hydrate destabilization in the subsurface. Instead, gradual increases in fluid salinity may cause the dissociation of a small fraction of subsurface hydrates, resulting in the ongoing release of methane into the atmosphere.
Elwood Madden Megan E.
McCallum Scott
Onstott Tussli
Phelps Tommy J.
Szymcek P.
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