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



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.




Among many key discoveries and insights:

  • The deep biosphere constitutes a world that can be viewed as a sort of "subterranean Galapagos" and includes members of all three domains of life: bacteria and archaea (microbes with no membrane-bound nucleus), and eukarya (microbes or multicellular organisms with cells that contain a nucleus as well as membrane-bound organelles)
  • Two types of microbes—bacteria and archaea—dominate Deep Earth. Among them are millions of distinct types, most yet to be discovered or characterized. This so-called microbial "dark matter" dramatically expands our perspective on the tree of life. Deep Life scientists say about 70% of Earth's bacteria and archaea live in the subsurface
  • While subsurface differ greatly between environments, certain genera and higher taxonomic groups are ubiquitous—they appear planet-wide
  • Microbial community richness relates to the age of marine sediments where cells are found—suggesting that in older sediments, has declined over time, reducing the microbial community
  • The absolute limits of life on Earth in terms of temperature, pressure, and energy availability have yet to be found. The records continually get broken. A frontrunner for Earth's hottest organism in the natural world is Geogemma barossii, a single-celled organism thriving in hydrothermal vents on the seafloor. Its cells, tiny microscopic spheres, grow and replicate at 121 degrees Celsius (21 degrees hotter than the boiling point of water). Microbial life can survive up to 122°C, the record achieved in a lab culture (by comparison, the record-holding hottest place on Earth's surface, in an uninhabited Iranian desert, is about 71°C—the temperature of well-done steak)

Ever-increasing accuracy and the declining cost of DNA sequencing, coupled with breakthroughs in deep ocean drilling technologies (pioneered on the Japanese scientific vessel Chikyu, designed to ultimately drill far beneath the seabed in some of the planet's most seismically-active regions) made it possible for researchers to take their first detailed look at the composition of the deep biosphere.


Candidatus Desulforudis audaxviator(the purplish, blue rod-shaped cells straddling orange carbon spheres) is a species of bacteria that survives on hydrogen. Scientists found it living within a fluid and gas-filled fracture 2.8 km beneath Earth's surface at a mine near Johannesburg, South Africa. The genus name Desulforudis comes from the Latin for "from sulfur" and "rod," noting its shape and its ability to get energy from sulfates. And audaxviator? From Jules Verne's Journey to the Center of the Earth, and a message in Latin deciphered by Verne's protagonist, Professor Lidenbrock, which read in part: "descend, bold traveler, and attain the center of the Earth." Credit: Greg Wanger, California Institute of Technology, USA, and Gordon Southam University of Queensland, Australia

To estimate the total mass of Earth's subcontinental deep life, for example, scientists compiled data on cell concentration and microbial diversity from locations around the globe.



Says Mitch Sogin of the Marine Biological Laboratory Woods Hole, USA, co-chair of DCO's Deep Life community of more than 300 researchers in 34 countries: "Exploring the deep subsurface is akin to exploring the Amazon rainforest. There is life everywhere, and everywhere there's an awe-inspiring abundance of unexpected and unusual organisms.


"Ten years ago, we knew far less about the physiologies of the bacteria and microbes that dominate the subsurface biosphere," says Karen Lloyd, University of Tennessee at Knoxville, USA. "Today, we know that, in many places, they invest most of their energy to simply maintaining their existence and little into growth, which is a fascinating way to live.


"Our studies of deep biosphere microbes have produced much new knowledge, but also a realization and far greater appreciation of how much we have yet to learn about subsurface life," says Rick Colwell, Oregon State University, USA. "For example, scientists do not yet know all the ways in which deep subsurface life affects surface life and vice versa. And, for now, we can only marvel at the nature of the metabolisms that allow life to survive under the extremely impoverished and forbidding conditions for life in deep Earth."

Species of Methanobacterium, which produces methane. Found in samples from a buried coal bed 2 km below the Pacific Ocean floor off the coast of Japan, this specimen was retrieved during an Integrated Ocean Drilling Program (now the International Ocean Discovery Program) expedition aboard the Drilling Vessel Chikyu. Bar represents 10 μm (micrometers, or 0.0004 inch). Credit: Hiroyuki Imachi (Japan Agency for Marine-Earth Science and Technology (JAMSTEC)

Among the many remaining enigmas of deep life on Earth:




"Discoveries regarding the nature and extent of the deep microbial biosphere are among the crowning achievements of the Deep Carbon Observatory. Deep life researchers have opened our eyes to remarkable vistas—emerging views of life that we never knew existed."says Robert Hazen, senior staff scientist, Geophysical Laboratory, Carnegie Institution for Science, and DCO Executive Director.

"They are not Christmas ornaments, but the tiny balls and tinsel of deep life look they could decorate a tree as well as Swarovski glass. Why would nature make deep beautiful when there is no light, no mirrors?" says Jesse Ausubel of the Rockefeller University, a founder of the DCO.

Explore further

Microorganisms in the subsurface seabed on evolutionary standby

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Citation: Life in deep Earth totals 15 to 23 billion tons of carbon—hundreds of times more than humans (2018, December 10) retrieved 26 May 2019 from https://phys.org/news/2018-12-life-deep-earth-totals-billion.html

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Dec 10, 2018
And so if life ever existed on mars, rest assured it is still there.

Dec 10, 2018
Zombie Bacteria

In CO2
in the earth in their billions
to all those global warmest
tamper with the climate
tamper with the atmosphere
tamper with the earth
as this is where we live and breath
no one alive knows the earth in its totality
no one can fix a wrong
as every wrong
counterbalanced with a right
these zombie bacteria
the moral is
Tamper with this planet at your peril
It is the only one we've got as there is no other

Dec 10, 2018
Martian zombie bacteria

And so to mars
these zombie bacteria
in their zombie bacterial state
miles into the regolith
as to life on mars
now we know it exists
what use
the martian rovers
as they can only scratch the surface
so close and so far
is so deep
no martian probe can reach
all though there is no life on this arid planet
all earthly scratching reveals no life
no atmosphere exists nor water exists
a lifeless barren planet where no life has existed for 4.5billions of years
as when mankind steps foot will die on this lifeless planet
absolutely no life exists
we know
miles deep in its martian crust
zombie bacteria live

This Martian regolith is alive

Dec 11, 2018
Why does anybody care how much carbon is in them? That's silly. The total mass of insects is some 70 times that of humans. Since we're all eukaryotes here, we can estimate they have about as much carbon per kilogram as we do.

But it gets way worse if you start measuring bacteria. They weigh in at over 3000 times as much as humans. In fact, if all the bacteria that infest your body were collected together, they'd weigh as much as three kilograms. Now all say "ewwwwww" together.

Is this meaningful? I think not.

Dec 11, 2018
That is quite a lot, at about 5-6 times the ocean biota carbon cycling of 3 GtC, but still diminutive compared to land plants 450-650 GtC [see fig in https://arstechni...p-again/ ]. Notably the deep biosphere is carbon efficient as it uses ~ 20/4,000 or 0.25 % of the soil/sediment reservoir while ocean biota uses ~ 3/40,000 or 0.075 % of the ocean reservoir.

Biological evidence is that life evolved in hydrothermal vents.

Why does anybody care how much carbon is in them?

It is a convenient measure of carbon utilization (and, by proxy, population sizes). As in how much life do we see and how much could we have seen? It is not carbon that sets the limits as much as phosphorous (generally).
