Gas Hydrates

Gas hydrate is a solid substance composed of water and natural gas (predominantly methane). Methane hydrate deposits occur worldwide where they are commonly found along active and inactive continental margins and in high latitudes. Typically these deposits occur where bottom temperatures are ~ 0°C and at depths of ~>300 m to < 2000 m. In recent years there has been intense interest in these deposits because they potentially represent a huge reservoir for natural gas; current estimates indicate that they contain ~10^19 g of methane carbon. These deposits are also of significant interest, however, because of their potential for significantly impacting the global climate (methane is a greenhouse gas) and stability of slopes, and because these are important to understanding carbon cycling. They also host novel macrofaunal and microbial communities.

Neptune is uniquely well located to address problems critical to understanding gas hydrate formation and biogeochemical coupling, and the episodic release of methane into the hydrosphere. The Cascadia margin off of Oregon, Washington, and Vancouver Island, British Columbia contains enormous quantities of methane hydrate and some of the best-studied systems in the world. It has been extensively studied by the Ocean Drilling Program at Sites 889 (ODP Leg 146 and IODP Leg 311) on the northern Cascadia margin and numerous sites at Hydrate Ridge drilled on Leg 204.