gold - the deep hot biosphere, the myth of fossil fuels

8/12/2019 Gold - The Deep Hot Biosphere, The Myth of Fossil Fuels

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Praise for Thomas Gold... "Goldis one of America's most iconoclasticscientists."

-Stephen Jay Gould

"Thomas Goldis one of the world's most originalminds."

-The Times, London

"Thomas Gold might have grown tired of tiltingatwindmills long ago had he not destroyed so many."

-USA Today

"What if someone told you that [the oil crisis]wasall wrong and that the hydrocarbons that make uppetroleum are constantly refillingreservoirs.Interested? Well, you should read this book....Gold presents his evidence skillfully. You may notagree with him, but you haveto appreciate hisfresh and comprehensive approach to these majorareas of Earth science.... [This book]demonstrates that scientific debate is alive and

well. Science is hypothesis-led and thrives oncontroversy-and few people are morecontroversial than Thomas Gold."

-Nature

.. Thomas Gold, a respected astronomer and

professor emeritus at Cornell University in Ithaca,N.Y., has held for years that oilis actuallyarenewable, primordial syrupcontinuallymanufactured by the Earth under ultrahotconditions and pressures."

-The Wall Street Journal

"Most scientists think the oil we drill forcomesfrom decomposed prehistoric plants. Goldbelieves it has been there since the Earth'sformation, that it supports its own ecosystem farunderground and that life there preceded life on


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the Earth's surface.... If Gold is right, the planet's oil


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reserves are ar arger an po cyma ers expec ,and earthquake prediction procedures require ashakeup; moreover, astronomers hoping forextraterrestrial contacts might want to stopseeking life on other planets and inquire about lifein them."

-Publishers Weekly

"Gold's theories are always original,alwaysimportant, and usually right. Itis my belief, basedon fifty years of observation of Gold asa friendand colleague, that The Deep Hot Biosphere is all

of the above: original, important, controversial,andright."

-Freeman Dyson

"Whatever the status of the upwelling gas theory,many of Gold's ideas deserve to be takenseriously.... The existence of [a deep hotbiosphere] could prove to be one of themonumental discoveries of our age. This bookserves to set the record straight."

-Physics World

"My knowledge and experience of naturalgas,gained from drilling and operating many oftheworld's deepest and highest pressure natural gaswells, lends more credence to your ideas than theconventional theories of thebiological/thermogenic origin of natural gas.Your

theory explains best what we actually encounteredin deep drillingoperations."

-Robert A. Hefner III, The GHK Companies,Oklahoma City, Oklahoma; Froma letter to the

author

"Within the scientific community, Gold hasareputation as a brilliantly clever renegade,havingput forward radical theories in fields rangingfrom cosmology to physiology."

-The Sunday Telegraph, London

"I Th D H Bi h [G ld] l


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"In The Deep Hot Biosphere, [Gold]revealsevidence supporting a subterranean biosphereand speculates on how energy may be producedina region void of photosynthesis. He speculateson the ramifications his concepts could have inpredicting earthquakes, deciphering Earth'sorigins, and finding extraterrestriallife."

-Science News

"Gold's theory, as explained in The Deep HotBiosphere, offers new and radical ideas to ourincomplete notions of what causes earthquakesand where we would look for life in outerspace:not on planets, but in them."

-Ithaca Times

"[The Deep Hot Biosphere] now seems to besupported by a growing body ofevidence."

-Journal of PetroleumTechnology

"Gold knows experts are pooh-poohing hisbelief.It happens to Gold consistently. He hasdeveloped a reputation as someone who takeson a long-held assumption, advances a new ideaand gets rewarded when time-a decade or two-proves him right."

-The Juneau Empire

"Thomas Gold has questioned the very

foundations of the entrenched conventionalmodels.... [The Deep Hot Biosphere] is evidentlyone of the most controversial of allbookspublished in recent history. Itis bound to causemuch debate, and, if found correct, is likelytorevolutionize the face ofscience."

-Current Science "[Thomas Gold]is one of the few who, despite theattacks of mediocrities, is courageous enough tothink ina scientifically unconventional way....[His]courage and original ideas are rays of hope on the

or zon o sc ence


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or zon o sc ence.

-Prof. Dr. Alfred Barth, The European AcademyofSciences and Arts, Paris


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Thomas Gold

Witha Foreword by Freeman Dyson


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Fo reword


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Fo r ewor d by Freeman Dyson

he first time I met Tommy Gold was in1946, when I served as a guinea pig in anexperiment that he was doing on the capabilities ofthe human ear. Humans have a remarkable abilitytodiscriminate the pitch of musical sounds. We caneasily tell the difference when the frequency of apure tone wobbles by as littleas 1 percent. How dowe do it? This was the question that Gold wasdetermined to answer. There were twopossible answers. Either the inner ear contains aset of finely tuned resonators that vibrate inresponse to incident sounds, or the ear does notresonate but merely translates the incidentsounds directly into neural signals that are thenanalyzed into pure tones by some unknown neural

process inside our brains. In1946, experts in the anatomy and physiologyof theear believed that the second answer must becorrect: that the discrimination of pitch happens inour brains, not in our ears. They rejected the firstanswer because they knew that the inner ear is a

small cavity filled with flabby fleshand water. Theycould not imagine the flabby little membranes in theear resonating like the strings of a harp or a piano.

Gold designed his experiment to prove theexperts wrong. The experiment was simple, elegant,and original. During World War II he had beenworking for the Royal Navy on radio communicationsand radar. He built his apparatus out of warsurplus Navy electronics and headphones. He fedinto the headphones a signal consisting of shortpulses of a pure tone, separated by intervals of

silence. The silent intervals were at least ten times


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longer than the

per o o e pure one. e puses were a esame shape but they had phases that could be


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same shape, but they had phases that could bereversed independently. To reverse the phase of apulse means to reverse the movement of thespeaker in the headphone. The speaker in areversed pulse is pushing the air outward when the

speaker in an unreversed pulse is pulling the airinward. Sometimes Gold gave all the pulses thesame phase, and sometimes he alternated thephases so that the even pulses had one phase andthe odd pulses had the opposite phase. All I had todo was sit with the headphones on my ears and

listen while Gold fed in signals with either constantoralternating phases. Then I had to tell him, from thesound, whether the phase was constant oralternating.

When the silent interval between pulses was tentimes the period of the pure tone, it was easy to tellthe difference. I heard a noise like a mosquito, ahum and a buzz sounding together, and the quality ofthe hum changed noticeably when the phases werechanged from constant to alternating. We repeatedthe trials with longer silent intervals. I could still detectthe difference, even when the silent interval was aslong as thirty periods. I was not the only guinea pig.Several other friends of Gold listened to the signalsand reported similar results. The experiment showedthat the human ear can remember the phase of asignal, after the signal stops, for thirty times theperiod of the signal. To be able to remember phase,

the ear must contain finely tuned resonators thatcontinue to vibrate during the intervals of silence.T h e result of the experiment proved thatpitch discrimination is done mainly in the ear, notin the brain.

Besides having experimental proof that the earcan resonate, Gold also had a theory to explain howa finely tuned resonator can be built out of flabbyanddissipative materials. His theory was that the innerear contains an electrical feedback system. Themechanical resonators are coupled to electrically

powere sensors an r vers, so a e com ne electromechanical system workslike a finelytuned


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electromechanical system works like a finelytunedamplifier. The positive feedback provided by theelectrical components counteracts the dampingproduced by the flabbiness of the mechanicalcomponents. Gold's experience as an electrical

engineer made this theory seem plausible to him,although he could not identify the anatomicalstructures in the ear that functioned as sensors anddrivers. In 1948 he published two papers, onereporting the results of the experiment and the otherdescribing the theory.

Having myself participated in the experiment andhaving listened to Gold explainingthe theory, I neverhad any doubt that he was right. But the professionalauditory physiologists were equally sure that he waswrong. They found the theory implausible and theexperiment unconvincing. They regarded Goldas anignorant outsider intrudinginto a field where he hadno training and no credentials. For years his work onhearing was ignored, and he moved on to otherthings.

Thirty years later, a new generation of auditory

physiologists began to explore the ear with far moresophisticated tools. They discovered that everythingGold had said in 1948 was true. The electricalsensors and drivers in the inner ear were identified.They are two differentkinds of hair cells, and theyfunction in the way Gold said they should. The

community of physiologists finally recognized theimportance ofhis work, forty years after it waspublished.

Gold's study of the mechanism of hearing istypical of the way he has worked throughout his life.

About once every five years, he invades a new fieldof research and proposes an outrageous theory thatarouses intense opposition from the professionalexperts in the field. He then works very hardto provethe experts wrong. He does not always succeed.Sometimes it turns out that the experts are right and

e s wrong. e s no a ra o e ng wrong. e wasfamously wrong (orso it is widely believed) whenhe


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famously wrong (orso it is widely believed) whenhepromoted the theory of a steady-state universe inwhich matter is continuously created to keep thedensity constant as the universe expands. He mayhave been wrong when he cautioned that the moon

may present a dangerous surface, being covered bya fine, loose dust. It proved indeed to be so covered,but fortunatelyno hazards were encountered by theastronauts. When he is proved wrong, he concedeswith good humor. Science is no fun, he says, if youare never wrong. His wrong ideas are insignificant

compared with his far more important rightideas. Among his important right ideas was thetheory that pulsars, the regularly pulsing celestialradio-sources discovered by radio-astronomersin 1967, are rotating neutron stars. Unlike most ofhis right ideas, his theory of pulsars wasaccepted almost immediately by the experts.

Another of Gold's right ideas was rejected by theexperts even longer than his theory of hearing. Thiswas his theory of the 90-degree flip of the axis ofrotation of the earth. In 1955, he published arevolutionary paper entitled "Instability of theEarth's Axis of Rotation." He proposed that theearth's axis might occasionally flip over through anangle of 90 degrees within a time on the order of amillion years, so that the old north and south poleswould move to the equator, and two points of theold equator would move to the poles. The flip

would be triggered by movements of mass thatwould cause the old axis of rotation to becomeunstable and the new axis of rotation tobecome stable. For example, a largeaccumulation of ice at the old north and south polesmight cause such an exchange of stability. Gold's

paper was ignored by the experts for forty years. Theexperts at that time were focusing their attentionnarrowlyon the phenomenon of continental drift andthe theory of plate tectonics. Gold's theory hadnothing to do with continental driftor plate tectonics,

so it was of no interest to them. The flip predictedbyGold would occur much more rapidly than continental


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Gold would occur much more rapidly than continental

r , an wou no c ange e pos ons ocontinents relative to one another. The flip would


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pchange the positions of continents only relative to theaxis of rotation.

In 1997, Joseph Kirschvink, an expert on rock

magnetism at the California Institute of Technology,published a paper presenting evidence that a 90-degree flip of the rotation axis actually occurredd ur i ng a geologically short time in the earlyCambrian era. This discovery is of great importancefor the history of life, because the time of the flipappears to coincide withthe time of the "CambrianExplosion," the brief period when all the majorvarieties of higher organisms suddenly appear in thefossil record. It is possible that the flip of the rotationaxis caused profound environmental changes in theoceans and triggered the rapid evolutionof new lifeforms. Kirschvink gives Gold credit for suggestingthe theory that makes sense of his observations. Ifthe theory had not been ignored for forty years, theevidence that confirms it might have been collectedsooner.

Gold's most controversial idea is the non-

biological originof natural gas and oil. He maintainsthat natural gas and oil come from reservoirs deep inthe earth and are relics of the material out ofwhich the earth condensed. The biologicalmolecules found in oil show that the oil iscontaminated by living creatures, not that the oil

was produced by living creatures. This theory, likehis theories of hearing and of polar flip,contradicts the entrenched dogma of the experts.Once again, Gold is regarded as an intruderignorant of the field he is invading. In fact, Gold isan intruder, but he is not ignorant. He knows thedetails of the geology and chemistry of natural gasand oil. His arguments supporting his theory arebased on a wealth of factual information. Perhaps itwill once again take us forty years to decide whetherthe theory is right.Whether the theory of non-

biological origin is ultimately found to be right orwrong, collecting evidence to test it will add greatly


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g, g g y

o our nowe ge o e ear an s s ory.

Fi ll th t t f G ld' l ti


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Finally, the most recent of Gold's revolutionaryproposals, the theory of the deep hot biosphere, isthe subject of this book. The theory says that theentire crust of the earth, down to a depth of several

m i l e s , is populated with living creatures. Thecreatures that we see living on the surface are only asmall part of the biosphere. The greater and moreancient part of the biosphere is deep and hot. Thetheory is supported by a considerable mass ofevidence. I do not need to summarize this evidencehere, because it is clearly presented in the pagesthat follow.I prefer to let Gold speak for himself.Thepurpose of my remarks is onlyto explain how thetheory of the deep hot biosphere fits into the generalpattern of Gold's life andwork.

Gold's theories are always original, always

important, usually controversial-and usually right.It ismy belief, based on fifty years of observation ofGold as a friend and colleague, that thedeep hot biosphere is all of the above:original, important, controversial-and right.


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Fo revVrrd I

Freeman Dyson

Preface xi

(:i ipter t Our(I"11-dell of1111oll

The Narrow Windowfor Surface Life2

Chemical Energy for Subsurface Life4

A Preview of This Book7

(:11aI)t(~r., I,if't, at IIre I~) r(hrs 11

Energy Deep inthe Earth 13

The Ecology of Deep-OceanVent Life19

Other Borderland Ecologies23

Deep Is Desirable 27

Beneath the Borderlands 30

r:r,me 1)~~~I -F trIIi (,,is i,it r. 37

The Origin of Petroleum:Two ConflictingTheories 38

Five Assumptions Underlying the Deep-EarthGas Theory43

01iriter1 Evidence 1'6r I>fv( -F"irtIi (iaS57Petroleum Reservoirs That Refill59

Clues inthe Carbonate Record 61

e ssoc a on o e um w y rocar ons(;har0vr:) H ;s( IV'in$2, th(' P('tr( 1etnrlPar'alll x


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( ) ( ( ( (79

The Deep Hot Biosphere Solution80

Biological Molecules in Non-BiologicalPetroleum 82

The Upwelling Theory of Coal Formation86

Evidence for the Upwelling Theory94

An Exemption for Peat100chapter(;Th' SiI.jan Fxt (Tinlent105

Drilling in SwedishGranite 107

Magnetite and MicrobialGeology114

(:banter Fxten(Iinw;theihI1mry125

The Origin of Diamonds127

A New Explanationfor Concentrated MetalDeposits 131

I~hatikr`~ IIP( hInking I~'Alrth(tuak(s141

Mud Volcanoes 142

A Challenge to Earthquake Theory143

Eyewitness Accounts 145

Earthquake Spots and Earth Mounds 156

Upwelling Deep Gas as the Cause of Earthquakes 159

t;har)tc t) TIw Ori ;in ofLife165

The Habitability of Surface and SubsurfaceRealms 166

e n ance ro a y or e s r g nDarwin's Dilemma176


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(;banter III hal Next'185

MicrobialInvestigations 188

Prospects for Extraterrestrial Surface Life193

Deepening the Search for Extraterrestrial Life201

Independent Beginnings or Panspermia? 205

Afl('rvV( r(lto IIi Iat erlklck F A111011209

Notes 217

Ackn(wl(il;rnents 235

Itl(I('x237


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o scientific subject holds more surprisesfor us than biology. Foremost is the surprise that lifeexists at all. How could lifehave started? Did oneextraordinary chance occurrence in the universeassemble the first primitive living organism, anddideverything else follow fromthat?

What chemical and physical circumstances wereneeded for such an unlikely eventto occur? Did ourearth offer the only nurturing conditions?Or (in whathas come to be known as the "panspermia"hypothesis) did life arise somewhere else,

spreading through astronomical space to take rootin any fertile spot it encountered? Or is lifenotunlikely after all? Perhaps life is an inevitableconsequence of physical laws and is arisingspontaneously in millions ofplaces.

Whatever the answers to these questions, we doknow that life on the surface of the earth spans ahuge variety of forms. These forms range frommicrobes to whales, giant fungi, and enormoustrees. They include unfathomable numbers ofinsects. If we add to our reckoning the life forms thathave died out, then the diversity expands to includedinosaurs, trilobites, and vastlymore.

All this living variety has much in common. Theconstruction of allknown organisms involvescomplex forms of protein molecules. Those, in turn,

are u up rom a se o u ng oc s ca e amino acids, common to all known formsof life.Thechemical configuration of some of these amino

id ld i t f f hi h i th


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acids could occur in two forms, one of which is themirror image of the other. Yet we find that all thehuge variety of life uses only one kind of each

such pair of molecules. There thus appears to be astrong connecting thread running through all thelife forms we know.

No less important than the common constituentsof life are the common conditions under which allknown life forms can develop and survive. Theseconditions include a requirement for water in theli qui d state, a limited range of temperature, andsources of energy that are delivered in (or can beconverted into) chemical form. We tend to assumethat these conditions are best-and perhaps ideally-provided on the surface of our own planet. And we

conclude, sadly perhaps, that these conditions arealmost certainly not present anywhere else in thesolar system. But are these assumptions valid?

The Narrow Window for Surface Lif e


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he universe is a harsh and severe place, arealm of extremes. Most of the universe is virtuallyempty and very cold-to be precise, 2.7 Kelvinor -270.5 Celsius, which is just 2.7C above absolutezero. This vast cold is punctuated by points ofintense heat and lightthe stars-whose surface

temperatures reach millions ofdegrees.Stars do not maintain their brilliance forever, andit

is from them that the constituents of life come. Starsthat have three or more times the mass of the sunwill expire in a frenzy of violence, a supernovaexplosion that may briefly flare with the brightnessofa hundred billion stars. The explosion scatters thestellar materials into space, making the cold cloudsout of which new stars form. The different atomicnuclei created in the core of the star and during itsexplosion supply materials from which planets canform. The same stellar materials provide theelements from which we and all other living creaturesknownto us are constructed.

Life is thus built up from a variety of atoms forgedin nuclear furnaces deep inside giant stars. Moreprecisely, life is constructed from molecules,

clumpings of atoms that are in close enough contactand cool enough for a weak attractive force to holdthem together. The interiors of stars are suitable forelement formation, but their heat is too intense forthe formation of complexmolecules.

Most places in the universe do not allow thechemical action that is conducive to life. The starsare too hot, and most other places are so cold thatsubstances are in the form of a solid or a very low-density gas, whose chemical activity is exceedinglyslow. But we do see some regions in the cosmos in

w c many eren ypes o mo ecu es ave een built up. These are the large gas clouds in interstellarspaces, warmed by stars that are in or nearthem Radio techniques have made it possible to


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them. Radio techniques have made it possible toidentify many different molecules there. Wateris one common component of the gas, as

are hydrocarbons-combinations of hydrogenand carbon. It is from the materials of such cloudsthat o ur and other star systems are believed tohave formed.

For life forms to arise and to persist, moleculesmust be awash in a liquid or a gas, so that gentlecontacts among molecules can build up othermolecules and generate a brew of the kind ofcomplexity we find in biological materials. In all oftheexpressions of life known to us, this mobility isprovided by liquid water. Given the ferocious andunfriendly conditions of the universe-with points of

intense heat and vast expanses of severe cold-onewould think it rare indeed for any place to holdsurface temperatures in the range that would renderwater a liquid. Surface temperatures depend notonly on the solar irradiation intercepted by the planet,and thus on its distance from the sun and on the

sun's size and surface temperature, but also on themass and composition of the planet's atmosphere.

It is the mass and composition of the atmospherethat crucially determines atmospheric pressure.Without a gas pressure, there is no such thing asliquid water. In the absence of substantialatmosphere, water is either a solid or a vapor. Allinall, a planet that offers liquid water on its surface is arare occurrence. Rarer still would be the subset ofsuch places that have given rise to the intricatedesigns that we call "life."

Could there be, in this fierce universe, locationswhere perhaps a little brook runs down a hillside,with trees gently swaying in the wind, and withcreatures sitting by the side, enjoying the view? Itseems a far-fetched fantasy in this forbidding

un verse. n ye we now one suc p ace: our eearth.

How was our planet able to bring forth the


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p genormous abundance of surface life that we seearound us? None of the other planets and none oftheir moons have anything comparable. Indeed,because the surfaces of all other bodies in ourplanetary system offer essentially no possibility forthe existence of liquid water, it is very unlikelythatsurface life exists anywhere in our solar systemother than on the earth. There may be only oneGarden of Eden here for large life forms such asourselves. But living beings small enough topopulate tiny pore spaces may wellexist withinseveral-and perhaps many-other planetary bodies.

Chemical Energy for Subsurface Lif e


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he sun provides two distinct actions.First, it is the source of heat that puts thesurface temperature of the earth into a rangesuitable for the complex chemical reactions ofmolecules, and thus for life. But ambient heatcannot be a source of energy, and the warmth ofour surface surroundings could not constitute anenergy source for surface life. Only a heat flowfrom a hotter body to a cooler one can beconverted into other forms of energy. We havesuch an energy flow from the hot surface of the sunto the cooler earth-the second action that the sunprovides-and energy is taken from this flow andconverted into chemical energy in the process ofphotosynthesis.

Photosynthesis is performed today largely byplants and algae, using sunlight to dissociate

water molecules (H20) and atmospheric carbondioxide (CO2), then reconfiguring the atomsto yield carbohydrates such as C6H12061 whichcan than be oxidized ("burned") as needed,back into H2O and CO2, to yield metabolicenergy. This process then serves as the principalenergy source for all surface life. A planetarysurface that does not possess photosynthetic lifewould be hostile to any of the surface life forms weknow. Below the surface the temperature may besimilar to that at the surface; but over smalldimensions-like the size of living forms there-only quite insignificant energy flow occurs.Therefore, no energy source can exist beneaththe earth's surface.

When we consider life's beginning, however, werealize that a puzzle lurks in this account of energy

transformation. Photosynthesis is an exceedinglycomplex process. The microorganisms that


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eve ope mus ave a rea y possesse n r ca e chemical processing systems before they acquiredthis more advanced ability. The energy source thatthese initial microorganisms drew on must have


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been chemical to begin with. The chemical energyavailable before the advent of photosynthesiscould not have been created by solar energy orby life. It must have been a free gift of thecosmos.

Where exactly did such chemical energy comefrom? I propose that the original source of energy forearthly life was derived not from photosynthesis butfrom the oxidation of hydrocarbons that were alreadypresent, just as they are also present on many otherplanetary bodies and in the original materials thatformed the solar system. Spanning the range fromthe light gas methane to the heaviest petroleum,hydrocarbons are present in the earth today in largeamounts and to great depths-I believe much larger

and deeper than is typically estimated. This view ofthe genesis of hydrocarbons I have called thedeep- earth gas theory.'

I think we have good evidence now that avery significant realm of life has existed, and stillexists, well below the surface biosphere that ishome to humans. This subsurface realm and itsinhabitants constitute what I call the deep hotbiosphere 2-deep because it may extend downto a depth of ten kilometers or more below thesurface of the earth, a n d hot because, as aresult of the natural temperature gradient of theearth, temperatures in much of that realmapproach and even exceed 100C.

The conventional notion is that hydrocarbonspresent within the earth's upper crust are derived

strictlyfrom plant and animal debris transformed bygeological processes-and thus that hydrocarbonscould not possibly have played a role in the originoflife. Butwe shall have reason to question this, alongwith many other assumptions. And as we shall see inChapter 2, an abundance of new discoveries have

con rme e s presence n s crus a rea m anunder conditions seldom before thought tolerable toany form oflife.

Ch i l i l d i h i l


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Chemical energy is released in chemicalreactions. The substances we call fuels in oursurface realm are really onlyone component of theenergy-producing reactions. The other component,oxygen, is so abundant around us that we tend toforget about it. Hydrocarbons, hydrogen, and carbonare fuels for us only because the other componentneeded for the reaction that produces energy isreadily available from the vast store of oxygenpresent in our atmosphere and dissolved inseawater as Oz. This oxygen is largely, but notentirely, created as a residue substance in theprocess of photosynthesis. It, rather than thepetroleum or the coal, represents the fossil fuel leftover from bygone vegetation.

Before photosynthesis was devised by life-andeven now at depths to which atmospheric oxygencannot penetrate-any hydrocarbonusing life musthave depended on other sources of oxygen. Oxygeni s the second most abundant element (after silicon)in the crust of the earth. The rocks therefore haveplenty of oxygen in them, but most of it is too tightlybound to be useful. Clearly, sources of oxygen thatrequi re more energy to free the oxygen from itsattachment in the rocks than the energy gained byoxidizing hydrocarbons with it cannot providemicrobes with an energysupply.

Subsurface life must therefore depend on sourcesof oxygen in which these vital atoms are only weaklybound with other elements. The largest sources ofweakly bound oxygen in the earth's crust are certainkinds of iron oxides and sulfates (oxidized sulfur

compounds). When oxygen is extracted from ironoxides such as ferric iron, that process leavesbehind iron in a lower oxidationstate in which it ismagnetic; examples include the minerals magnetiteand greigite. When oxygen is taken from sulfates,

w a s e e n may e pure su ur or su es such as hydrogen sulfide and iron sulfide. Theexistence of such by-products of metabolic activityinthe subsurface realm helps us identify theb h l h h d h


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biochemical processes that have occurred. Theseby-products also provide a sense of the scale andreach of the deep hot biosphere.

It is crucial to the theory of subsurface life that theultimate source of up-welling hydrocarbons residesvery much deeper than the lowermost reach ofsubsurface life. The deep hot biosphere may bedeep, but it must not be excessively deep. Why isthis so? The exponential growth rates of microbes(as of all forms of life) mean that wherever liferesides, the source of energy that supports it mustarrive in a metered flow. If the earliest forms ofsubsurface life had not been checked by limits ontheir food supply, the increase in their numbers

would have very rapidly consumed the entire lot inaninstant of geological time, allowing no gradualevolutionto take place.

Hence energy that can be used by life must beavailable, but it must not be available all at once. Themetered energy flow for the surface biosphere isprovided by a sun that takes billions of years toconsume its own finite stores of fuels. The chemicalenergy (such as sugars) forged by photosynthesizinglife forms here on the earth is thus created throughtime in a metered way and only in areas that haveli q ui d water-not in the driest deserts or in theicefields of polar or high mountain regions. Thetransformation from solar to chemical energy nowtakes place at a rate sufficient to feed all the surfacelife we see. But no matter how greedy life may be,organisms simply cannot make the sun radiateenergy any faster. It is energy that supports life, butonlya metered flow of energy sustains life over along period oftime.

Understanding the importance to lifeof a meteredsupply of energy is crucial to delimiting the

poss es or e s or g ns. e o en scusse warm little pond that contained nutrients forged withg r e a t difficulty by surface processes is not acandidate environment, in myopinion, for thet iti f lif t lif S h i t


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transition from non-life to life. Such an environmentwould yield a limited amount of chemical suppliesand energy, not a long-term and continuous meteredsupply. What is needed, rather, is an environmentthat can supply chemical energy in a metered flowover tens or hundreds of millions of years, duringwhich time incomprehensibly large numbers ofmolecular experiments might take place. lies evendeeper. I will argue that photosynthesis developed inoffshoots of subterranean life that had progressedtoward the surface and then evolved a way to usephotons to supply even more chemical energy. Whensurface conditions became favorable to life(with regard to temperature, the presence of liquidwater, the filtering of harsh components of solarradiation, and the termination of devastating asteroidimpacts), a huge amount of surface life was able tospring up.

A Preview of This Boo k


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n the remaining chapters, I shall set forth thetheory that a fully functioning and robust biosphere,feeding on hydrocarbons, exists at depth withintheearth and that a primordial source of hydrocarbons

In retrospect, it is not hard to understand why the

scientific community has typically sought only surfacelife in the heavens. Scientists have been hindered bya sort of "surface chauvinism." And because earthscientists did not recognize the presence ofchemical energy beneath their feet, astronomers andplanetary scientists could not build a subsurface

component into their quests for extraterrestrial life.Unfortunately, this misunderstanding lingers. Theidea that hydrocarbons on earth are the chemicalremains of surface life that has long been buried andpressurecooked into petroleum and natural gas hasbeen exceedingly difficult to unseat. I have beentrying to do so since 1977, and I discoveredalong t h e way that some pioneering Russianscientists were my forebears.3 The reason for thiscontinuing confusion in understanding howhydrocarbons came into being is a story in itself;I shall take it up in Chapter 3.

As long as Western scientists continue to assumea biological origin for all terrestrial hydrocarbons,themajor sources of the earth's chemical energy will notbe recognized. And as long as this substantial foodsupply goes unrecognized, the prospect that a largesubterranean biosphere may indeed exist, and

exist down to great depth, will likewise fail toattract scientific attention. Thus the particularimportance of Chapter 3, in which I will examine theconsiderations that favor the deep-earth gas theory.

Surface evidence for that theory follows in Chapter

4. Most important, I introduce a set of observationsthat cannot be explained at all by a sedimentaryorigin of hydrocarbons-the strong association ofhydrocarbons with a gas that can have no chemicalinteractions either withplant materials or with


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interactions either withplant materials or withhydrocarbons: the inert element helium. Howcanpetroleum have gathered up clearly biologicalmolecules but also an inert gas that is normallysparsely distributed in the rocks? I call thisassociation the "petroleum paradox." Its resolution(in Chapter 5) suggests that multitudes of microbiallife must exist in the pore spaces of the rocks. In myview, hydrocarbons are not biology reworked by

geology (as the traditional view would hold) butrather geology reworked by biology. In otherwords, hydrocarbons are primordial, but as theyupwell into earth's outer crust, microbial lifeinvades.

Chapter 6 presents the striking results of alarge- scale drilling project thatI initiated in Swedento test the deep-earth gas theory and also to lookfor deep microbial life. In Chapters 7 and 8, Iundertake to show how the deep-earth gas theorycan account for concentrated deposits of certainmetal ores in the crust and also for important

features of earthquakes. In Chapters 9 and 10 I use the deep-earth gas and

deep hot biosphere theories to offer newspeculations on what are perhaps the two mostprofound mysteries of the biological sciences: theorigin of earth life and the prospects forextraterrestrial life. As background, I begin with acomparison of the two biospheres. In what majorways might the surface biosphere and the deepbiosphere differ, beyond the simple fact that onedraws on chemical energy and the other on solar? Ithen revisit the question of life's origin, explainingwhy I believe that surface lifeis the descendant of anoriginal form of life that began at depth, rather thanthe other way around.

If this sequence from depth to surface bestexplains the origin and expansion of terrestrial life,


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en su sur ace e on many o er p ane ary o es would seem very probable. There are many bodiesin the solar system whose internal conditions arethought to be similar to those of our earth butwhose surfaces do not offer the extraordinary


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whose surfaces do not offer the extraordinaryadvantages for life that ours has. It would beunlikely indeed for subsurface life to develop just inthe one unique body that could support surface lifeas well. This reasoning led me in 1992 to make thetentative prediction that our own solar systemharbors not one but ten deep hot biospheres.4

We surface creatures may well be alone in thesolar system, but the denizens of the terrestrial deepseem likely to have many-possibly independentlyevolved-peers. Only when we recognize theexistence of a thriving subterranean biosphere withinour own planet willwe learn the right techniques tobegin the search for extraterrestrial life inother

planetary bodies. Some such techniques andfurther suggestions for future research will bepresented in Chapter 10.

Our journey willbegin in the next chapter with alook at the borderland regions between the twobiospheres. Along hydrothermal vents and petroleumseeps of the ocean, and in hot springs and methane-rich caves on land, we encounter some extraordinaryambassadors from the deep hot biosphere. Here wecan also begin to comprehend why deep may, infact, be desirable for life.


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n February and March of 1977, the smalldeep-sea-diving submarine Alvin descended to adepth of 2.6 kilometers along the East PacificRise. This region, northeast of the GalapagosIslands, was known to be a center of sea floor

spreading. A research ship had drawn a cameraover the area the previous year, confirming theexistence of a series of cracks in the ocean floorthat appeared to be volcanicallyactive. But theoccupants of Alvin saw much more.

Far below the deepest possibility forphotosynthetic life, Alvin'ssearchlight revealed apatch of ocean bottom teeming with life, insharpcontrast with the surrounding barrens. This patchwas covered with dense communities of seaanimals-some exceptionally large for their kind.

Anchored to the rocks, these creatures thrived in therich borderland where hot fluids from the earth metthe marine cold. New to science were species oflemon-yellow mussels and white-shelled clams thatapproached a third ofa meter in length. Most strikingof all were the tube worms, which lurk inside verticalwhite stalks of their own making, bright red gills

protruding from the top. Like the tube worms ofshallow waters, these denizens of the deep livec lus te re d together in communities, with tubesoriented outward resembling bristles on a brush. Butunlike their more familiarkin, the tube worms ofthe

eep are g an s, reac ng eng s n excess o wometers.

Further investigations soon revealed that thisstrange and isolated community of life was by nomeans niq e Pop lations of the same organisms


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means unique. Populations of the same organismswere discovered at other points along that ocean rift,a t hydrothermally active vents elsewhere in thePacific, and in the Atlantic and Indian Oceans too.This was clearly a global phenomenon.These unsuspected oases represent an entirely newhabitat for life. Where did these creatures comefrom? What sources of energy and nutrients could

support such astonishing fecundity and insuch a patchwork distribution?

Through the windows of Alvin,the 1977 discoverycrew witnessed not only strange life forms but alsostreams of milky fluids and black "smoke" emerging

from vents in the sea floor. These streams ofhydrothermal fluids, heated and enriched ingases and minerals, are now known to be thesources of chemical energy at the base of the ventcommunity's food chain. Two decades later,however, we have only begun to understand how itallworks.

Because we are surface creatures, we readilyadopt the outlook that surface life is the only possiblekind. We marvel at the exotic life along thedeep- ocean vents. We assume, of course, thatthe vents were originally colonized by

emigrants from a surface ecosystem-pioneers in evolving the adaptations necessaryto subsist on energy drawn f r o m chemicalsources rather than bundled in photons, theunits of energy in which light is delivered. Thistop-down scenario is reasonable for the large

animals. Tube worms and clams surely did migratedown from shallow waters. But no animal of anykind can serve as the base of a food chain. Allanimals depend on chemical energy stored in thebodies of organisms they consume. Something,

therefore, must have already been growing aroundthe ocean vents when the worms and clams arrived.


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In my view, the base of the food chain in the deepocean vents is more likely to have emerged frombelow than to have descended fromabove. Themicrobes (bacteria and archaea) that today supportt h e whole complex enterprise are offspring of


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microbial communities thatlived and still live within

the earth's crust. Whereas the large life forms canexist only where there is considerable space forthem, the micro bial life that feeds them occurs inunits small enough to inhabit minute cracks in therocks of the sea floorand elsewhere throughout theearth's upper crust. The total volume of rock that isaccessible to such microbes is enormous; as weshall see in Chapter 5, the microbial content of theearth's upper crust may well exceed in mass andvolume all surface life. Indeed, microbes from therealm that I call the deep hot biosphere probablyinvaded this borderland between the twoworldsbetween the deep biosphere and the surfacebiosphere-long before photosynthesis evolved onthe surface. In fact, the chemical differencesbetween the two worlds may have been slight priorto the advent of photosynthesis, because it wasphotosynthesis that transformed the earth'ssurface into a zone pervaded by free oxygen-

molecules of OZ.

Energy Deep in the Ear t h


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hotosynthesis is an exceedinglycomplex process for turning the energy of light intochemical energy. But why does the route that energytakes have to include chemical forms? Whycannot the sunlight be made to drive directlyall the processes that the organism requires?

There are some compelling reasons. First, theenergy required to run cellular metabolisms mustbe available in increments no more than a tenthas powerful as that supplied by even a single solarphoton. Expecting a cell to use a photon directlyto synthesize a sugar would be more ludicrous

than expecting a baseball player to field bullets froma machine gun. Rather, life has devised anextremely sophisticated apparatus to perform theinitial task of catching thebullets.

Second, a photon has no patience. Make use of itnow or lose it forever. Sunlight cannot be captured ina jar and stored on a shelf. But its energy can beused to set up molecules such as sugars, that willd e li ve r energy on combining with atmosphericoxygen. Our breathing demonstrates this: we take insuch "reduced" (unoxidized) carbon compounds inour food and we inhale oxygen and exhale carbon

dioxide. This describes the overall metabolic activity,but in fact there are various stages in between, alldependent on the energy provided by the oxidationof the reduced carbon compounds we eat, eventuallyto C02- Sugars or other intermediate molecules canbe stored on the cellularshelf, and the rate of

"combustion" can be controlled. Chemical energythus carries the advantage of availability, offeringanadjusted amount where and when it is needed.

Because photosynthesis is such a complexprocess, and because the energy derived fromphotons must be converted into chemical energy


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before the cell can make use of it, researchers whoprobe the possible origins of earthly life havebecome convinced that the firstliving cells tappednot sunlight but chemical energy present in theenvironment. Where this chemical energy came fromand what it consisted of remain hotly debated


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and what it consisted of remain hotly debated

issues, but the widespread assumption is that eitherthis primordial energy source has long since beenused up or the conditions that produced it billionsofyears ago no longer prevail. I shall return to thisquestion in later chapters. For now it is important toremember only that it would be far more difficulttodesign a living cell that could construct chemicalenergy from photons than it would be to design aliving cell that scavenged chemical energy from itssurroundings.

The cells that perform this complex function ofphotosynthesis must have access to liquid water,as

already noted, and they must have access to carbonand nitrogen for the fabrication of proteins, theprincipal building blocks for their chemicalmachinery. The solar energy is used to "reduce"(unoxidize) compounds that will serve to provideenergy as they are later oxidized again. Oxygen

must therefore also be available, as must catalysts(enzymes) that initiate and control the reaction ratesand thereby the power output.

Life as we know it depends fundamentally on thepresence of carbon; earth life is sometimes referredto as "carbon-based life," to distinguish it from thetheoretically possible (but unknown) "silicon-basedlife." Carbon atoms constitute the skeletal structureof all proteins and of all genetic materials of all thelife forms we know. In the surface biosphere,carbon is provided by carbon dioxide, which ispresent in small proportion in the atmosphere.Each of the several varieties of photosynthesisthat life has evolved begins with carbon dioxide,from which the complex molecules of life arethen forged. In the most common form of

photosynthesis, energetic photons from the sunare employed to dissociate


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wa er an us o ga n access o a oms o y rogen. The hydrogen is next used to "reduce" (take oxygenaway from)the molecule of carbon dioxide. Thismakes available unoxidized carbon, which can thenbe used for construction materials and for a varietyof functional materials such as proteins. Unoxidized


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pcarbon can also be used to construct thevarious sugar-like substances(saccharides and polysaccharides) that providestorable sources of chemical energy.

When the photosynthetic organism dies, andwhen the other organisms that have benefitted

from its products die, microbial decay willreturn to the atmosphere all the materials thathave been taken out. Depending on the type ofmicrobe undertaking the decomposition, the carbonwillbe returned to the atmosphere either as carbondioxide or as methane (CH4). Because the

atmosphere is rich in oxygen, a n y methanereleased into it will spontaneously transform intocarbon dioxide and water on a time scale ofabout ten years. So far as the energy balanceis concerned, no chemical energy derived from theearth has been used up. Carbon dioxide returnsas carbon dioxide, and water returns as water.

It may thus seem that carbon cycles through thesurface biosphere in a complete and closed manner.If the atmosphere and the exposed rocks initiallypossess the volumes of raw materials required bylife,the process should go on for as long as the sun

shines and temperatures allow water to remain in aliquid state. But as we will see in Chapter 4,the paththat carbon follows through the cycle ofphotosynthesis and oxidation is far from aclosed loop. Several times as much carbon as istaken up by living materials is constantly extracted

from the atmosphere and taken out of circulation,as long- lived or permanent carbonate rock.The surface biosphere must therefore have beenkept alive by an ongoing and large supply of

carbon in the form of either methane or CO2 (or,as some observations


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wou n ca e, y a m x o e wo . w e efinal additionto the atmosphere in either case.

In the surface biosphere, all the energy drivingbiochemical transformations ultimatelycomes fromsunlight. Life in the deep hot bio sphere does noth t light th f g


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have access to sunlight, so the source of energycould not work in the same way. But even there,carbon is the basic building blockof life. Whatis thesource of this carbon in the subsurface realm?

The notion, derived from surface biology, thatCO2 is the standard carbon supply for all life has

been applied by some investigators to the deep lifealso. While the ocean water contains plenty of C021it does not have any energy source to reduce this.The reduced carbon that trickles down from thesurface layers would be quite inadequate. No energycan be derived from a process that both starts andends with oxidized carbon. If unoxidized carbonwere available at the outset, in the form ofhydrocarbon molecules migrating upward, thenthese molecules would be the logical candidate fora carbon supply that would also yield an energy-producing sequence, ending up with CO2.

The hot ocean vents are not themselves provincesof the deep hot biosphere; they are borderlandsbetween two worlds, between surface andsubsurface. Nevertheless, their food chains aredriven by processes so different from that of thesurface realm that they are a good place to begin

our explorations of deep hot biosphere energy. Theamounts of carbon that sink down from oceansurface life are quite inadequate to supply theexceptionally fertile ocean vent biology. The volcanicro c k s of the sea floor contain only a very smallfraction of carbon-about 200 parts per million (ppm).To extract carbon from this source would be difficultand very energy-consuming. There is, however, amuch larger carbon source in all these communities:hydrocarbons. Methane (CH4) is generally the mostabundant, but the heavier members of the series,

suc as e ane an a e way up o o sconstituted of twentyto thirty carbon atoms, are alsofound along the same fault lines, though in regionswhere less volcanic heat is in evidence. As the nexttwo chapters will show, these hydrocarbon fluidsshow many features that suggest they have come upf h d i


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from much deeper regions.

The chemical energy supply, we might thensuspect, is driven by the oxidation of thesehydrocarbons. Starting out with hydrocarbonsavoids the first and energetically most demandingstep in the surface energy cycle. The chemical

energy that is made available at the ocean vents isvery similar to that made available by burningnatural gas (which is largely methane) and turning itinto water and carbon dioxide. There is one snag,however. When methane is burned in a furnace,there is an unlimited amount of oxygen from the

atmosphere available all the time. In the oceanvents, a borderland between the surface a n d thedeep biospheres, there may be someatmospheric oxygen available that was carried downin solution in the cold ocean water. If this weresufficient for converting all the methane suppliedfrom the vents into carbon dioxide and water, thenthis borderland province would be dependent onsurface biological processes, and it would notbe anoutpost of what I suggest is an independent realm oflife stretching down into the rocks below. It seemsdoubtful that the prolific life at these concentratedlocations on the ocean floor could receive enoughwaterborne atmospheric oxygen, but a firm answeris not yet known. However, this issue is not ofcentral importance. We now know of many caseswhere we can probe so far down into the deepbiosphere that atmospheric oxygen has absolutelyno access, and we observe generally similar

metabolic processes taking place there. Wheredoes the necessary oxygen come from?

There is plenty of oxygen bound in the rocks, asnoted earlier, but most of it is so strongly bound that

more energy would be required to remove itthan


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cou e er ve y us ng su sequen y o ox ze hydrocarbons. There are just two commonsubstances in which oxygen atoms are boundloosely enough that more energy would be obtainedfrom using oxygen so acquired than is spent inacquiring it. These two common substances arehighly oxidized iron (Fe2O3 and associated


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highly oxidized iron (Fe2O3 and associatedcompounds) and oxidized sulfur (such as SO2 andHZSO4 in compounds that are called sulfates). Ifmicrobes at or beneath the ocean vents secure theiroxygen needs from ferric iron oxides, what willremain is a less oxidized form of iron-magnetite orgreigite. Microbial actionleaves a clear fingerprint

behind: The crystals of these products are muchsmaller than those of the same substances that havefrozen out in the cooling of rocks from liquidto solidform.

The water of the oceans includes the second

source of lightly bound oxygen, sulfate, in greatquantities. Sulfate (SO4) is the second mostabundant ion of negative charge in seawater. Theamount of oxygen that could be derived from marinesulfate ions may well exceed the convectedatmospheric oxygen available at the ocean vents. Ifoxygen is, in fact, primarily availablenear the ventsin the form of sulfate, then the microbes that makeuse of the hydrocarbons willbe in an ideal situation:The chemical transformations for extracting thechemical energy from upwelling hydrocarbons willnot run by themselves, because an initial energysupply is required for the first step of freeing oxygenatoms from sulfate. The microbes will be amplycompensated for this energy-demanding step,however, when the second step is taken.

The task of brokering such transactions is left tothe world of microbes. Here, it is important to

remember that a chemical fuel is useless to life if itcombusts spontaneously. Dinner would do you nogood if the food burst into flames on your plate. Forasubstance to qualify as "food," it must becomeoxidized only withthe help of a catalyst created and

ep oye y e. s s a un amen a requ remen both for the organisms at the base of the foodchains of the surface and deep biospheres andalso for all organisms that stand later in line.

The removal of oxygen from sulfates at the oceanvents would produce either pure (elemental) sulfur or


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ve ts wou d p oduce e t e pu e (e e e ta ) su u o

sulfides, which are unoxidized sulfur compounds.The large quantities of metal sulfides that are foundheaped up at the edges of ocean vents suggeststhat such biologically facilitated transformationsareindeed taking place.

A further requirement for the construction oforganisms-be they inhabitants of the surfacebiosphere or the subsurface biosphere-is a supply ofvarious metals required in the protein moleculesknown as enzymes that catalyze chemical reactions.

Also required for biological constructionor chemicalprocessing are some reactive molecules thatcontain elements such as sulfur, phosphorus, andchlorine. The required quantities of these aresmall enough that the upper crust of the earth canusually supply them. The deep biosphere andthe land portions of the surface biosphere arethus adequately nourished. But the surface watersof the open oceans may be impoverished,particularlywith respect to phosphorus and iron.

In summary, there are important differences andimportant similarities between the two biospheres.The surface biosphere runs on solar energy

converted into chemical energy; the deep biospherebegins with chemical energy freely supplied fromthedepths of the earth. Bothbiospheres rely onunoxidized carbon as the building block of life, butsurface life extracts it initially, with the help ofsunlight, from carbon dioxide in the atmosphere,whereas deep life extracts it from the samesubstances used as the energy source:hydrocarbons. Oxygen is a requirement in bothrealms, since chemical energy is provided only intheprocess of oxidation. For surface creatures, oxygen

s ava a e arge y n e orm o pure, mo ecu ar oxygen. Inhabitants of the subsurface must workharder to gain their supply, extracting oxygenatoms that are loosely bound in iron oxides andsulfates.


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The Ecology of Deep-Ocean Vent Lif e


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ecause we are surface creatures, we areinclined to regard an ecosystem based on chemicalenergy rather than photosynthetic energy as astrange, if wonderful, adaptation of life. We marvela t the ecology of the deep ocean vents as a deftadjustment of surface life to an inhospitable realm.

The evidence argues otherwise. Microbes andeven animals are thriving at these vents; growthrates are thought to exceed those in even the mostproductive surface realms. If the theory of thedeep hot biosphere is correct, we wouldinfer that the m i cro b i a l pioneers invaded frombelow. Many viewpoints would have to bechanged as a consequence.

The communities of life at the deep ocean ventsdiffer from other marine ecosystems not so much intheir garish macrofauna but in their unseenmicrobes-the bacteria and archaea at the base of

the food web. Two decades of studies haverevealed that these microbes feed on moleculesgushing from the vents: hydrogen (H2), hydrogensulfide (1-12S), and methane (CH4), each of whichcan supply energy only if oxygen is available.' Noknown animal can feed on any of these chemicals

directly, but animals can feed on microbes that do.What is particularly remarkable about the deep-ocean vent communities is that many of themacrofauna seem to be dependent on symbioticpartnerships with the microbes.

Clams and mussels have entered into symbioticpartnerships withmicrobes bound in their gilltissues. The giant tube worm species, however, hastaken partnership to a new dimension. Its interiorguests are so skilled in producing food forthemselves and their host that coevolution has

atrophied the worm's digestive system and deprivedit of a mouth. Utterly dependent now on the excessproduction of its symbionts, the tube worm hasevolved a large and specialized organ deepinside its body for the microbes to inhabit.The worm supplies its microbes with the materialsthey need by employing feathery red gills to filter


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they need by employing feathery red gills to filteruseful molecules out of seawater. Then it volunteersits own circulatory system to deliver what the gillshave gathered.

The greatest challenge to organisms alonghydrothermal vents is posed by the risk of beingswept out of range of the vent and thereby losing thechemical supplies and the temperature range theyrequire. The bivalves and tube worms solve theproblem by anchoring themselves in place.Crabs and shrimps and snails that live amongthe fixed organisms can, of course, creep and

clutch as needed. The microbes that constitutethe primary step in the food chain have found waysto hold their place, too. The most heat-adaptedvarieties can live very close to (and even inside of)the vent. Wherever it is too hot for animal grazerssuch as snails to intrude, microbes cling to the

rocks in communal mats of slime. Those that taketo the water column above the venting fluidspossess a whip-like flagellum by whichtolocomote, sensing temperature or chemicalstimuli to guide their directional movements andthus staying within or next to the vent stream. Themost audacious bacterial entrepreneurs are thosethat have made themselves welcome guestswithin the very tissues of the bivalves and tubeworms. There they are protected from prowlinggrazers as well as errant currents.

The hydrogen, hydrogen sulfide, and methane

fuels consumed by both free-living and symbioticmicrobes in the vent communities are exploited bymicrobes that access oxygen atoms loosely boundin ferric iron oxide carriedup from the depths in ventfluids, oxygen derived from sulfate that pervades

seawater, and perhaps also free oxygen in theseawater.


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whence the macrofauna derive their oxygen. But,as we shall discuss in the next section,


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many m cro a commun es ave een en ethat certainly have no access to atmospheric oxygen.

Life thrivesat the ocean vents because these aresites at the borders between two worlds. Anabundance of chemical energy can be extractedfrom the chemicals that meet there and that had no


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opportu nity to reach equilibrium with one another.Upwelling fluids from the world below are rich in"reduced" molecules, such as hydrogen andmethane. Hydrogen sulfide is also present, but wedo not yet know whether this is a primary fluid fromthe depths of the earth or a product of microbes as

they utilizea combination of hydrogen and sulfate forenergy needs.

Of the three major sources that provide energywhen reacted withoxygen (hydrogen, hydrogensulfide, and methane), hydrogen sulfide hasattracted the most research interest, because itseems to be the fuelon which the microbialsymbionts of the giant tube worms and clamsdepend. But the carbon atoms that form the core ofall organic molecules must be obtained elsewhere.The presence of methane in the output of oceanvents thus assumes particular importance; it can bethe source of the required carbon as well as thesource of chemical energy.

Hydrocarbons bear a structural resemblance tofoods we eat that are derived fromphotosynthesizers. For example, the only material

difference between a molecule of hexane (a six-carbon form of petroleum) and a molecule of glucose(a six-carbon sugar, common in foods at the surface)is that hydrogen atoms surround the chain of carboni n hexane, whereas water molecules surround thechain of carbon in the sugar. The hexane C6H14 is ahydrocarbon, whereas the sugar C6H1206 is acarbohydrate. The terminological differenceis subtlebut important. For us animals the carbohydrate isfood, the hydrocarbon poison. Nevertheless, thebiological idiosyncrasies of our own tribe of complex

e s ou no e a owe o cons ra n our u gmen as to the possibilities-indeed preferences-amongthe multi-talented microbes. They mightwell have ametabolism that requires an input ofpetroleum.

Microbes that utilize methane as a source ofenergy in the presence of oxygen, and also as a


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source of carbon, are known to be present in thehydrothermal vent communities. Suchmethanotrophs ("methane eaters") have beenidentified as symbionts withinthe macrofauna- thusfar, only in mussels-but they are presumably free-living as well.2They can consume heavier

hydrocarbons, too. Are the methanotrophs of the deep-ocean vents

ambassadors from this other, deeper, and perhapsindependent world? We know that clams and wormsdo not venture any deeper than the thin skin ofsurface rock and sediments. But what about thebacteria and archaea? If microbial slimes on therocks near and within the vents thrive on methaneand sulfide gases that rise up from below, might theynot also find suitable habitat within cracks and porespaces deep below the crustal surface?

Other Borderland Ecolog ie s

h h h d d


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ithin the past three decades, manya n d various borderland ecosystems have beendiscovered and their secrets probed. First tocapture scientific attention was a type that had longbeen enjoyed by crowds of tourists: the microbialcommunities that colorfully coatthe rocks withinhotpools of Yellowstone National Park. Serious studyofthe metabolisms of Yellowstone's thermophilic(heat-loving) microbes began in the mid-1960s.3 Itwas here that scientists first came to appreciate theextraordinary talents of the earth's seeminglysimplest forms of life. For example, one bacteriumdiscovered in Yellowstone's hot pools, Therm usaquaticus, provided the enzyme that launched themolecular biology industry by making DNAreplication fast and easy. Today, Yellowstone's hotsprings offer rich prospecting for scientists seekingto add new names to the list of microbes classifiedin the taxonomic domain of Archaea.

In 1977 the exciting exotica we have alreadydiscussed were discovered beneath the sea-theelaborate assemblages of microbes and animals atthe edges of hot springs on the ocean floor. In 1984came the discovery of more assemblages of

symbiotic microbes, tube worms, and bivalves-not,this time, in the abyssal depths but on themuch shallower continental shelves.4 Similar inform, but taxonomically differentat the species oreven genus level, tube worms and bivalves onthe continental shelves were making their livingin "cold seep" regions, where crude oil andhydrocarbon volatiles seep up through thesediments. No hot springs or other hydrothermalaction is associated with these se e p s . Unlikethe hydrothermal vents, which are point sourcesrestricted in size, cold petroleum

seeps o er mar ne e c em ca energy overvastexpanses of the continental shelves that are toodeep to support photosynthesis. (In even the clearestocean waters, photosynthesis is impossible anydeeper than about 200 meters beneath the oceansurface, and continental shelves often sink to a depth

f kil ) G h i h i


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of a kilometer or more.) Growth rates in the regionsof hydrocarbon seeps are not, however, as high asthey are at the actively venting rift zonesof the deepocean.

On land, too, an ecosystem border realm hascaptured scientificand public attention. In 1986 acave in Romania-until then, isolated from theatmosphere-was discovered and found to contain athriving ecosystem based on the chemical energy ofreduced gases emanating from below. Ten yearslater, when its biological inventorywas published,this cave habitat was touted by the media as the firstinstance of a terrestrial ecology that was not basedon photosynthesis and yet was able to support not

just microbes but land animals as well.5 Feeding onthe bacterial base of the food web are more thanforty species of cavedwelling invertebrate animals,including spiders, millipedes, centipedes, pillbugs,

springtails, scorpions, and leeches. Thirty-three arenew to science. As with the deep-ocean venthabitat, hydrogen sulfide was identified as thereduced gas supporting the base of the foodchain in this cave, though I suspect that methanealso plays a role. Indeed, methane consumers

may wellbe generating hydrogen sulfide as a wasteproduct when sulfate is used to oxidize methane,in which case the sulfide consumers would be anotch up from the base of the fo o d chain. Hydrogensulfide, converted by water into sulfuric acid,probably carved out the limestone cave.

In 1997 another cave ecosystem based entirely onchemical energy was explored in southern Mexico.That cave, too, appears to have been carved out oflimestone by a flowof sulfuric acid.The acid fumesi n this cave are so intense that scientists were able

o ven ure a m e n o s unne s ony w eassistance of breathing masks. Microbial lifeis soprolific throughout that the walls are shrouded inslime.' Feasting on the microbes is a community ofinvertebrates, but this ecosystem also supportsvertebrates: tiny fishes in the waist-deep water thatoccupies the tunnel system.


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Also very recently, Russian scientists have beenpreparing to explore a vast lake-as large as LakeOntario-that was discovered in central Antarcticabeneath four kilometers of ice.' Lake Vostok owesi t s existence to the entrapment of heat upwelling

everywhere within the earth. The thick glacial ice,strangely enough, acts as a thermal insulator,segregating the heat from the intense cold of

Antarctic air. Remote sensors indicate a water depthof perhaps 600 meters in some places, underlain bysediments 100 meters thick. Drilling was halted 250meters above the water line, pendingimplementation of procedures that could ensuresterile contact. If life is present down there, it willunquestionably be based on chemical energy wellingup from below. To test that possibility, it isimperative to prevent contamination of the pristinelake by surface microbes. NASA has expressedinterest in fostering technologies for sterileexploration of Lake Vostok, which would probablyhappen no sooner than 2001. One reason forNASA's interest is that a subglacial lake offers anextraordinary analog for the subsurface environmentof Europa, a moon of Jupiter that is covered with a

thick layer of ice and may have liquid waterunderneath that.'

An important discovery of very large amounts ofmethane was made in the last two decades.Methane hydrates, crystals of water ice that entrapmethane molecules within their lattices, exist in greatquantities on many areas of the ocean floor. Thepresence of methane raises the freezing point ofwater by an amount depending on the ambientpressure, and therefore this ice can form in regions

w ere wa er s supp e n qu orm an enfreezes where methane is added.

For methane hydrates to form, temperatures mustbe no greater than about 7C and pressures no lessthan about 50 atmospheres. This means thatmuch of the sea floor that is outside of volcanic

zones and covered by water to a depth of 500


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zones and covered by water to a depth of 500meters or more could support methane hydrates.`'Within the past two decades we have learned,both by remote sensing and by directsampling, that methane hydrates do indeed existin great quantities in many areas of the ocean floor.

They produce a clear and unique signature onsonar and are remotely sensed as a distinct layerin ocean muds, sometimes lying directly on thebedrock of the ocean floor. A large area of thecontinental shelf has been surveyed in this fashion.Results indicate that methane hydrates may, infact, be present in all areas where thepressure and temperature allow them to form.10 Ithas been estimated that methane hydrates (thosewithin the Arctic permafrost layer as well as thoseunder the sea) contain more unoxidized carbonthan all other deposits of unoxidized carbon knownin the crust, such as crude oil, natural gas, and coal."

Often there is more carbon in the methane atomstrapped in a deposit of hydrate than in all of thesediments associated with that deposit. Insuch instances the conventional explanation of itssource (biological materials buried with the

sediments) cannot account for the productionof so much methane. The methane embedded inthe ice lattices must have risen from below,through innumerable cracks in the bedrock. Once athin, capping layer of the solid forms, the genesisof more such hydrate underneath becomes aninevitability, provided methane continues to upwell.

This conclusion-that the source of methane liesbeneath, not within, the crustal sediments-isstrengthened by evidence of pockets of freemethane gas beneath some regions of hydrate

ce an a so enea perma ros ayers o rc c tundra.13 In these regions, downward migration ofmethane gas from overlying sediments does notseem conceivable. Gases, after all, do not migratedownward in a liquidof greater density. If there isany flow, itis in the reverse direction.

Lake Vostok which we have just discussed willb id l l h k h i f


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Lake Vostok, which we have just discussed, willbe an ideal place to check on the quantity ofhydrocarbons that have come up from below sincethe ice cover formed. The quantities of methanehydrates contained there may be very large,they may even represent the major componentof the lake.

In the domain of high methane hydrates there isalso macro-life, just as at the ocean vents. Littleworms are found there that plough through themethane hydrates and the overlying water.14 Theirexistence indicates that such methane hydrateshave been there long enough to allow life to adaptto the strange circumstances. Most probablysymbiotic microbes inside the worms use energyderived from t he oxidation of methane. Thecarbohydrates and other biological molecules themicrobes produce are then shared with their animal

hosts.Hydrates made up with CO2 rather than methane

can exist also, though over a smaller stabilityrange of temperature and pressure than methanehydrates. Nevertheless, there are substantial areasof ocean floor that could support CO2 hydrates, butfew-if any- such samples have been found. Theconclusion must be that the "gentle" butwidespread addition of carbon to the atmosphereis a global phenomenon o f diffusion from theground of methane and other hydrocarbons, nodoubt at different rates at different locations and atdifferent times. The dominance of CO2 overmethane from volcanoes is the exception and notthe rule. This conclusion then agrees with the findingthat methane is far more abundant than CO2 in

wellbores (to the good fortune of the petroleumindustry), and also with the evidence from meteorites


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a y rocar ons an no -pro uc ng compounds will have been the principal input ofcarbon in the forming earth. (Chapters 3 and 4 willexplore these points in detail).


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Deep Is De s ir able

n light of the discoveries of thrivingchemicalbased ecosystems associated with


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g gchemicalbased ecosystems associated withme tha ne hydrates, hot ocean vents, andcold petroleum seeps on the ocean floor, along withthose associated with hot springs and gas-richcaves on land, we can conclude that methane,hydrogen sulfide, and other energy-rich gases(those that could provide large amounts of energyif combined with supplies of oxygen) are attractiveto life forms that span a wide range of temperature.Very close to the hot ocean vents, however, andwherever hot springs on land are more thanmerely warm-above, say, 45C-these habitats do notsupport animals. But heat-loving (thermophilic)microbes are abundant in these places.

As temperatures rise even more, thermophilesdrop out, but hyperthermophiles-microbes that growbest at 80C or higher15-go about their business

unperturbed. The waxy cell membranescharacteristic of hyperthermophiles facilitatematerial exchange at temperatures at which fattymembranes like our own would simply melt.16 Hyperthermophiles can grow and reproduce only atsuch high temperatures. At lower temperatures their

membranes stiffen to the point where materials canno longer pass through as needed. Moleculescalled heat-shock proteins enshroud the DNA andregular proteins of hyperthermophiles,guarding the intricately folded structuresagainst the unraveling that such high heat wouldotherwise bringabout.

What are the highest temperatures thathyperthermophiles can tolerate? We are stilluncertain. But we do know that temperature alone is

no more determinative of an environment's livabilitythan it is determinative of a fluid's boiling point.One


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more factor must be considered: pressure.

Although the boiling point of wateris 100C at sealevel, it rises to a full 300C at a depth of just 876meters. At that depth, the water column exerts apressure of 87 atmospheres, which means 87 timesmore than the pressure exerted by the atmosphereat the surface of the sea. This pressure is sufficientto prevent water molecules at even 299C


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to prevent water molecules at even 299Cfrom expanding into a vapor phase. Deeper still,at a depth of 2.25 kilometers, the "criticalpoint" is reached. Here the pressure is sogreat that no matter what the temperature, there is

no longer any distinction between vapor andliquid. Rather, it is more appropriate to refer towater beyond the critical point as existing as afluid-specifically,a "supercritical"fluid.

Now consider that the first community ofhydrothermal vent organisms ever witnessed in theabyssal realm of the sea was found at a depth of 2.6kilometers. Here water is a supercritical fluid.Waterat temperatures of about 300C has been detectedissuing from the vents, but it is cooled quicklyas aresult of mixing with surrounding water. Boilingis notan issue for organisms at that depth, because watercannot boil there. Melting of membranes andunraveling of proteins, rather, may become thelimiting factors for life at hightemperatures."

Because of the effect of pressure, if one mustcope with temperatures approaching or exceeding

100C, then deep is certainly desirable. Howwidespread are zones of such high temperature?Hot springswhether on the sea floor or on land-arefar from the norm. They occur where heat generateddeep within the planet finds a rapid escape route tothe surface, by way of fluids buoyed up from below.These are active volcanic zones. Far more commonare non-volcanic regions, such as those over whichyou and I are probably sitting rightnow.

The earth generates its own heat from

compress on, grav a ona sor ng, an ra oac ve decay deep within its core and mantle. In a non-volcanic region the temperature of the rock,beginning at the surface, increases steadily withdepth and at a rate fairly uniform over the entireglobe. This phenomenon is referred to as earth'sthermal gradient. The temperature of the crust near

its contact with the atmosphere is approximately 20C over most of the area The temperature


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20 C over most of the area. The temperatureincreases at a rate of between 15C and 30C perkilometer of depth in nonvolcanicregions.

Hyperthermophiles are known that can grow attemperatures of 110C. This means that, on averageand provided that the necessary chemical resourcesare present, life as we know it could survive downtoa depth of six kilometers in regions of crust thatexhibit the low temperature gradient (15C perkilometer or less) and three kilometers where thetemperature gradient is high (30C per kilometer).Itis not yet clear whether hyperthermophiles exist thatcan tolerate higher temperatures still. Somemicrobiologists consider that the temperature limitfor microbiallife may be as high as 150C.18 In thatcase, lifemight extend to deeper levels, in somecool areas possibly to a depth of ten kilometers.

It is crucial to remember that because of thesteady rise in pressure with depth, nowhere withinthe earth's crust (with the exception of volcaniczones) does the combination of temperature andpressure ever permit water to boil. What

about methane, the lightest and hence quickest toboil of all hydrocarbons? Moving downward alongany thermal gradient, methane becomes denser atthe greater pressures of increasing depths, even asit remains a vapor. What does this increase indensity mean for subterranean life forms that feedon methane?

For one thing, the greater density means thatmethane is actually easier for lifeto access at depth.

At a depth of six kilometers, for example, methanewould be 400 times as dense as it would be on the

s ur a c e a a mosp er c pressure. so, g er temperatures that coincide withgreater depthsescalate the rate at which methane molecules collidewith the cell membranes of microbes. Both factorsenhance the rate at which methane would beexpected to diffuse across cell membranes. Deep isthus desirable not only to ease some of the

biological problems created by high temperaturesbut also to assist methane consumers in accessing


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but also to assist methane consumers in accessingtheir food.

Up here in the surface biosphere, where methaneexists only as a diffuse gas, methane consumers area curious group. But methanotrophs may be far fromtangential members of the food web in the deepbiosphere. Indeed, they may be the foundation ofthat system.

Beneath the Bor de r lands

o study the deep hot biosphere andsample its inhabitants, we must probe far beneath


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sa p e ts ab ta ts, we ust p obe a be eatthe borderland regions of hot springs, hydrothermalvents, oil seeps, methane hydrates, and gas-richcaves. We must peer into the bottom of deep wellsdrilled into the earth'scrust.

When I began developing the deep hot biosphereidea in the early 1980s, and when my "Deep, HotBiosphere" paper was published in 1992,19 apersistent criticism was that microbes brought up insamples from the depths of oil and gas wells werenot native inhabitants but opportunists introducedfrom the surface in biologically contaminateddrillingfluids.20 This contamination argument was at firstdifficultto refute. But in 1995 a key paper publishedin one of the top scientific journals demonstrated thatmicrobes discovered at a depth of 1.6 kilometers inFrance were truly "members of a deep indigenousthermophilic community."21 The following yearanother report of indigenous microbes, this timefrom an oil well in Alaska, established active biologyat a depth of 4.2 kilometers and a temperature of110C.22 In 1997 the discovery of microbial fossilsembedded in granitic rockat a depth of 200 meters

confirmed the indigenous interpretation; fossilscannot be introduced by drilling fluids into solidgranite.23

Thus far, the deepest indication of active biologywas detected in 1991, at a depth of 5.2 kilometers inSweden, as we will see in Chapter 6.24Significantly,the well in which these microbes weredetected had been drilled into solid granitic bedrock,not the sedimentary strata that generally attractpetroleum prospectors. A sample that had been

a en an sea e a ep an en rawn up wascultured in the laboratory. It yielded previouslyunknown strains of anaerobic microbes thatreproduced only in the temperature range from whichthey had been sampled, 60C to 700C.

The term I coined, deep hot biosphere, is

sometimes mentioned in scientific papers ormedia coverage interpreting such findings ofb l l f d d d h f

8/12/2019 Gold - The D

gold - the deep hot biosphere, the myth of fossil fuels

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