By Michael J Coren

Two miles below the surface of the Earth, life is thriving and we know almost nothing about it. This "deep life"--mostly yet to be discovered species of bacteria and primitive microbes called archea--has become the focus of scientists trying to understand how life evolved on Earth, and its implications for us today. Their efforts are being channeled into the Census of Deep Life (CoDL) mapping millions of unknown microbial species still waiting below the surface.

"A global census of these deep-sea microbes is underway," states Oregon State University, one of the CoDL partners. Enabled by advances in drilling technology and DNA analysis, the global effort will drill miles below continents and oceans to pull up living species among rocks and sequence the genomes of any life found there. This massive strata of life may rival the total biomass of all life on the surface, perhaps even affecting climate and the transport of minerals around the planet's interior. It is hoped this deep life effort, run by the Deep Carbon Observatory (DCO), a scientific effort to examine the Earth's carbon from "crust to core," will reveal the chemical and biological roles of carbon on Earth, as well as interactions on the surface.

So far, the findings suggest life is almost everywhere. Microbes are appearing in deep drill cores and underground mines. One of the most recent discoveries is a microbe known as Candidatus Desulforudis audaxviator, or "bold traveller," living in water filled crevices of a South African gold mine, reports the New Scientist, and an almost identical organism was also found thousands of miles away in a half-mile deep borehole near California's Death Valley.

Perhaps it's not surprising these are unlike almost anything on the surface. As they may have lived for hundreds of millions of years without sunlight, these slow-going organisms derive their energy from chemical bonds in minerals of the rock itself (perhaps dividing as infrequently as once every thousand years). As the deep life census gets under way, we may discover life on Earth assumes a whole new meaning.

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