What are gas hydrates?

Gas hydrates are ice-like substances that form in deep-sea sediments.

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During the final dive of the Gulf of Mexico 2017 expedition, Deep Discoverer encountered gas hydrate mounds, ice worms, chemosynthetic communities, and active gas seeps. In this video, you can see droplets of methane coming out of the seafloor that are that encased with methane hydrate. Video courtesy of the NOAA Office of Ocean Exploration and Research, Gulf of Mexico 2017. Download larger version (mp4, 26.2 MB).

Gas hydrates are ice-like crystalline minerals that form when low molecular weight gas (such as methane, ethane, or carbon dioxide) combines with water and freezes into a solid under low temperature and moderate pressure conditions. Most gas hydrates are formed from methane (CH4), which has led to the terms “gas hydrate” and “methane hydrate” often being used interchangeably.

On Earth, gas hydrates occur naturally in some marine sediments and within and beneath permafrost. They are also speculated to form on other planets.

For us, hydrate deposits are important for a variety of reasons:

  • Gas hydrate deposits may contain roughly twice the carbon contained in all reserves of coal, oil, and conventional natural gas combined, making them a potentially valuable energy resource.
  • Their decomposition can release large amounts of methane, which is a greenhouse gas that could impact Earth’s climate.
  • Sudden release of pressurized methane gas may cause submarine landslides, which in turn can trigger tsunamis.
  • Gas hydrates in the ocean can be associated with unusual and possibly unique biological communities that use hydrocarbons or hydrogen sulfide for carbon and energy, via a process known as chemosynthesis.