Life in deep Earth totals 15 to 23 billion tons of carbon—hundreds of times more than humans

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Barely living "zombie" bacteria and other forms of life constitute an immense amount of carbon deep within Earth's subsurface—245 to 385 times greater than the carbon mass of all humans on the surface, according to scientists nearing the end of a 10-year international collaboration to reveal Earth's innermost secrets.

On the eve of the American Geophysical Union's annual meeting, scientists with the Deep Carbon Observatory today reported several transformational discoveries, including how much and what kinds of life exist in the deep subsurface under the greatest extremes of pressure, temperature, and low nutrient availability.

Drilling 2.5 kilometers into the seafloor, and sampling microbes from continental mines and boreholes more than 5 km deep, scientists have used the results to construct models of the ecosystem deep within the planet.

With insights from now hundreds of sites under the continents and seas, they have approximated the size of the deep biosphere—2 to 2.3 billion cubic km (almost twice the volume of all oceans) - as well as the carbon mass of deep life: 15 to 23 billion tonnes (an average of at least 7.5 tonnes of carbon per cu km subsurface).

The work also helps determine types of extraterrestrial environments that could support life.



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Carbon

6 protons
6 neutrons
6 electrons

makes up 99.9% of everything on earth