Our planet is an awesome place. Full of life. Much more than we thought. Far below the scarce surface spaces we inhabit, the planet is filled with an incredibly vast and deep “dark biosphere” of subterranean life forms. The identification of this hidden world has been thanks to the scientists of the Deep Carbon Observatory.
Hidden in this subterranean realm, some of the world’s oldest organisms thrive in places where life shouldn’t even exist, and thanks to this new work, an international team of experts has quantified this deep biosphere of the microbial world like never before. done.
“Now, thanks to ultra-deep sampling, we know that we can find them almost everywhere, although the sampling has obviously reached only an infinitesimally small part of the deep biosphere ,” explains microbiologist Karen Lloyd of the University of Tennessee in Knoxville.
There is a good reason why sampling remains in its early stages.
In a preview of the results of an epic 10-year collaboration by more than 1,000 scientists, Lloyd and other Deep Carbon Observatory researchers estimate that this hidden world of life beneath the Earth’s surface occupies a volume of between 2 -2.300 million cubic kilometers. This is almost twice the volume of all the world’s oceans.
And like the oceans, the deep biosphere is an abundant source of countless forms of life: a population that amounts to between 15 and 23 billion tons of carbon mass (which would represent about 245-385 times more than the equivalent mass of all humans on Earth’s surface).
The findings, which represent numerous studies conducted at hundreds of sites around the world, are based on analyzes of microbes extracted from sediment samples from 2.5 kilometers below the seafloor, and drilled from surface mines and wells to more than 5 kilometers deep.
Hidden at these depths, two forms of microbes (bacteria and archaea) dominate the deep biosphere and are estimated to account for 70% of all bacteria and archaea on Earth.
As for how many types of organisms we are talking about … it is difficult to quantify. Scientists say that there are surely millions of different types of organisms waiting to be discovered.
“Exploring the deep subsurface is similar to exploring the Amazon rainforest,” clarifies microbiologist Mitch Sogin of the Marine Biology Laboratory in Woods Hole, Massachusetts. “There is life everywhere, and everywhere there is an impressive abundance of unexpected and unusual organisms.”
These life forms are not only unusual for their appearance and habitat, but for the actual form in which they are found, with incredibly slow and long life cycles on quasi-geological timescales and, in the absence of sunlight, subsisting in scant quantities. of chemical energy.
Not only does this discovery promote the idea that deep life could exist in other parts of the universe, it also tests our definition of what life really is.
In a sense, the deeper we go, the further we go back in time and in evolutionary history.
“Perhaps we are approaching a nexus where the oldest possible branching patterns could be accessible through deep investigation of life,” concludes Sogin.
Reference: Life in Deep Earth Totals 15 to 23 Billion Tonnes of Carbon — Hundreds of Times More than Humans. Deep Carbon Observatory.
Image credit: Gaetan Borgonie, Extreme Life Isyensya, Belgium
