Gas: A recent scientific discovery has helped to solve an old geological mystery and given new knowledge and insight into the rise of life on Earth and possibly other planets.
This enigma is directly linked to an enormous reservoir of methane scientists discovered deep beneath the ocean floor.
Methane is usually stored in the atmosphere where the gas is produced by living organisms. This new discovery of abiotic methane is created in chemical reactions caused by geology.
Although it has long been known to exist submerged in the seabed and released from deep-sea vents, the gas’s source in this underwater environment has not been fully understood, until now.
The story was first published by Woods Hole Oceanographic Institution (WHOI) in the Proceedings of the National Academy of Sciences on August 19th, 2019.
Seewald is a scientist of Marine Chemistry and Geochemistry at WHOI and one of the lead authors in the published paper. He explains that this study points to methane-rich inclusions being common in olivine-bearing rocks. Those rocks may be the main source of abiotic (physical, non-biological) methane on the planet.
Science Alert explains that the quantity of methane in the olivine-bearing rock pockets is enormous, perhaps more than that in Earth’s atmosphere pre-industrial revolution.
In a study to better understand the source of the methane in the ocean, Seewald and fellow WHOI researchers collected and analyzed rock samples.
They collected a total of 160 pieces of rock from ocean ridges, subduction zones, and ophiolites or uplifted sections of oceanic crust.
The samples were tested with spectroscopy and microscopy techniques. Microscopy is using microscopes to examine small objects and structures. Spectroscopy involves the absorption and emission of light and other radiation by matter.
The tests showed that the rocks, often along with hydrogen, contained pockets of methane.
The research and study led scientists to a bigger question. How were the pockets of methane produced?
Solving the Mystery
Researchers say the pockets of methane are produced as seawater moves through deep oceanic crust. It then becomes trapped in hot olivine, a rock forming mineral and the primary component of Earth’s upper mantle.
The mineral cools as time passes, allowing the stored water to go through serpentinisation, a chemical reaction that produces hydrogen and methane. The methane and hydrogen can remain sealed within the rock for eons after formation until the rock deteriorates or fractures.
Researchers say this discovery is important for learning about methane on Earth and other planets.
Scientists know that methane exists in places other than Earth, such as Mars. New findings help to explain how it might exist in places where liquid water or hydrothermal activity is lacking.
Frieder Klein, Niya G. Grozeva, and Jeffrey S. Seewald, the authors of the published paper write, “Because fluid inclusions may form in olivine-rich rocks that interact with water on celestial bodies elsewhere in our Solar System, their formation may have key implications for the maintenance of microbial life beyond Earth.”
They explain that escape of these gases from rocks could sustain life forms. The release of these gasses may provide the hydrogen and methane that is necessary to supply microbial ecosystems with electron donors in natural environments. In other situations the formations of these gases would not be favorable.
It is possible that this cycle of chemical production and release might have been an important element in the survival of terrestrial, sea-dwelling life forms on Earth since the beginning of time.
Researchers believe that the cycle has been taking place since plate tectonics started. They also suggest the process may have assisted microbial ecosystems in geological environments.
Though the team of scientists provide an explanation of how and why this distribution of methane exists, it is still somewhat speculative.
The origin of the trapped fluids cannot be explained precisely. However, they say that the chemicals within the rocks are consistent with an ocean like fluid source.
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It is anticipated that further study will answer much and lead to even more questions.