A "massive basin" of methane hidden at the bottom of the Earth's surface, discovered by scientists

An enormous source of methane has been discovered at the bottom of the Earth's surface, between the upper mantle and the lower oceanic crust. The discovery is important because it could provide insight into hydrothermal vents that could have helped the first life of the planet to emerge. The researchers also argue that this could be a source of hydrogen and methane on other planets in the solar system – "even on those where liquid water is no longer present".

"Abiotic" methane – methane that does not form with organic matter – has been found trapped in rocks. Researchers at the Massachusetts Woods Hole Oceanographic Institution (WHO) collected 160 samples of hydrothermal sites around the world, including the Mid-Atlantic Ridge, the Guaymas Basin, the East Pacific ascent and the Cayman. After analyzing them with a laser microscope, they discovered that almost all contained pockets of methane.

In their study, published in the journal PNASThe team says it could be the biggest source of abiotic methane in the world. This tank, they explain, could represent more methane than in the Earth 's atmosphere before the beginning of the industrial era.

The methane seems to be formed by reactions between trapped water and olivine, a group of minerals forming rocks present in the basement of the planet. When seawater passes through the deep oceanic crust, it mixes with olivine with magma. When the mineral cools, the water is trapped inside and a chemical reaction occurs, leading to the formation of hydrogen and methane.

Traditionally, we believe that methane – a potent greenhouse gas – is formed when organic matter decomposes. When it is emitted into the atmosphere, it has a warming effect much higher than that of carbon dioxide, although it has a much shorter life span than this and disappears at the end of its life. a decade or so.

However, it is also known that methane exists on the seabed. It is released by mouths of deep water, heated geothermal cracks on the Earth's crust. In 2016, scientists from the Ocean Exploration Trust discovered more than 500 methane outlets off the west coast of the United States.

However, the source of methane from the seabed has remained a mystery. "The identification of an abiotic source of high-seas methane is a problem with which we have been struggling for many years," said in a statement the author of the study, Jeffrey Seewald, Senior Researcher at WHOI.

Lead author Frieder Klein added, "We were totally surprised to find this huge reservoir of abiotic methane in the oceanic crust and mantle, here is a source of chemical energy created by geology."

In addition to helping to explain the origins of methane at the bottom of the Earth's surface, the study could also highlight the presence of methane on other bodies in the solar system. For example, we know that methane exists on the moons Titan and Enceladus of Mars and Saturn.

The researchers say that methane can be produced in the same way on these other worlds "Similar processes involving fluid inclusions can occur elsewhere in the solar system, with important implications for the distribution and maintenance of microbial life beyond beyond the Earth, "they conclude.