Carbon sheds fresh light on origin of life

New findings have revealed long unknown details about carbon deep beneath the Earth's surface, suggesting ways this carbon might have influenced the history of life on the planet.

The Johns Hopkins University-led team also developed a related theory about how diamonds form in the Earth's mantle.

"It is a very exciting possibility that deep fluids beneath the Earth's surface might transport building blocks for life into the shallow Earth. This may be a key to the origin of life itself," said geochemist Dimitri Sverjensky, professor in department of earth and planetary sciences.

Sverjensky's theoretical model called the "Deep Earth Water" model allowed the team to determine the chemical makeup of fluids in the Earth's mantle, expelled from descending tectonic plates.

Some of the fluids at 100 miles below the Earth's surface contained the expected carbon dioxide and methane.

But others, those in equilibrium with diamonds, contained dissolved organic carbon species including a vinegar-like acetic acid.

"These high concentrations of dissolved carbon species, previously unknown at great depth in the Earth, suggest they are helping to ferry large amounts of carbon from into the overlying mantle wedge where they are likely to alter the mantle and affect the cycling of elements back into the Earth's atmosphere," explained Sverjensky.

Sverjensky and his team demonstrate that in addition to the carbon dioxide and methane, there exists a rich variety of organic carbon species that could spark the formation of diamonds and perhaps even become food for microbial life.

"These mantle fluids with dissolved organic carbon species could be creating diamonds in a previously unknown way," the authors said.

Scientists have long believed diamond formation resulted through chemical reactions starting with either carbon dioxide or methane.

The article was published in the journal Nature Geoscience.