An international group of scientists at the Deep Carbon Observatory (DCO) announced on Monday that part of the Earth's methane that until now was thought to have a biological origin actually has a mineral origin and is used as food by microbes living at great depths below ground.
The investigation added more elements to the theory that life on Earth may have originated deep within the planet and not on the surface, thanks to the chemical generation of methane.
Until relatively recently, the scientific community had assumed that hydrocarbons at great depths below the Earth's surface had formed organically; that is, they had come from living things like plants or animals buried for millennia.
But over the past 10 years, the DCO scientists have been pursuing a project to study the carbon that exists at great depths within the Earth and that work has begun to explain the formation of hydrocarbons such as methane via abiotic processes, meaning as a result of chemical reactions among minerals and not in a biological way.
Under normal conditions of temperature and pressure, methane - the chemical formula for which is CH4; that is, one carbon atom and four hydrogen atoms - is a colorless and odorless greenhouse gas.
Dr. Isabelle Daniel, one of the scientists from the Claude Bernard Lyon 1 University in Lyon, France, told EFE that the research made public on Monday was aimed at understanding more precisely the way in which "nature produces carbon without the intervention of life, and how much abiotic carbon and methane produced in this way there is on the Earth."
"Right now we don't know the amount of existing methane created in these ways and that is important," Daniel added.
The scientific community is now closer to establishing the amount of abiotic methane on Earth thanks to new instruments and techniques developed in recent years and used by the DCO researchers, Dr. Edward Young, with the University of California Los Angeles (UCLA), told EFE.
Young said that the use of mass spectrometry and spectroscopic absorption techniques are enabling scientists to analyze samples of natural methane to better understand the formation of abiotic methane at great depths.
The key, Young said, is the occasional presence of heavy isotopes in the methane molecules. "The frequency of those heavy isotopes reveals how they formed and at what temperatures," he said.
Daniel added that during the investigation the researchers found that microorganisms living at great depths use hydrocarbons created by chemical reactions between rocks and water as a fuel to sustain themselves.
Benedicte Menez, with the Institut de Physique du Globe in Paris, another of the DCO researchers participating in the study, said that the discovery opens the door to the possibility of a new path for the appearance of life on Earth.
"Now we have a better idea of the conditions, we know that the reaction of rocks can generate different organic components. And if these organic components are allowed to evolve, the small hydrocarbon, which is very simple, can become more complex," she said.
"And with the catalyzation of other organic components, like amino acids, which are the basis for proteins, one gets a small reactor that could lead to protometabolisms that were used by the first living organisms on Earth," she said.
Young said that the investigation has found that the creation of abiotic methane is a much more complicated process than initially thought and that the key to the process is hydrogen.
"Better understanding of how rocks create hydrogen, which permits the appearance of methane, and the speed of that reaction, will allow us to know with precision the quantity of methane that exists on Earth," he said.