'C_A_A_C_T_A_'_'_9_81~,_N_O_S_P_"~--------
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O_C_E_A_NO
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LO
_G
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•
An hypothesis concermng
the relationship
•
between submarine hot spnngs
and the origin of life on Earth
Subm~ r inc
Archcan f oss Îl s
hydrOl hcrmal SYS l ems
Origin of life
Mid-ocCHr\ ridges
Fos~ ile~ archéens
Sources hydrOlhennale s so us-mar ines
Origine de la vje
DorSllles miu-océ;w iqu e~
1. B. Corli ss, 1. A. Baross. S. E. Horrm,Jn
Sdool of Ûceanogruphy , O rego n S iaie Uni ve rsity , Con -allis . Oregon 97331, USA.
ABS TRA CT
A diverse se l of obscr valÎons fro m ArchHean fo ssiJ-bearing roc ks . modern s obmarinc
hyd ro thermal Systems. experimental and Iheoretical work On the abiotic s ynthesis of orga nic
rnoJec ules and primiti ve organizcd structures. and on wate r-rock interac tions suggests Iha!
submarinc ho t s prings wcrc t he site for the synthcsis of organic compounds Icading to the first
living o rganisms o n e arth. These system s are c haracterized by high flu xes of thermal energy.
highly reducing conditions, abunda nt a nd appro prillte catalytic s urface areas (Fe Mg clay
mine ra Is). sig nifieant concentra tio ns of C H,. N H J , H2' metals, etc., and a continuous
conve cti ve flow whic h removes products from the site of reac tion upward throug h a mi xi ng
gr<idie nt of temperature a nd compos ition . We hypothesize th <i t the sequence o r react!ons C H, .
NH J • Hl - ami no acids -- proteins -- co mple x pol ymers""" metabolizing o rganized s truc tures ...... living o rgauisms could occur within a nd/or adjacent 10 these s ystems. Mieroorga nisms
round in cardull y preserved samples of s ulfide c him neys from the Eas t Pacifie Rise may bc
modern counterparts of Arc haea n fo ss il o rgani sms. This hypothes is s uggests a nurnber of
critieal obse r vations to be made. both in labora tory experimellta l systems and on a ctive
s ubmarine syste ms.
Ocew lOl. A cta. 1981 . Proccedings 26,h l nter nation.al Geolo!!ical Congress . Geology of oceans
symposi um. Paris . J uly 7-17. 1980. 59-69.
RÉSUMÉ
Une hypolh èse pOrla nl sur la rel atio n entre les so urces hyd rothermales
sous-marine s el l'origi ne de la vie sur terre .
Une sé rie très va riéc d 'observations fai tes s ur les roc hes foss ili fères d 'âge Arc hée n et s ur les
sOlJrces hyd rothermales sous- marines conte mpontines. à l' occas ion de tra vaux expérimentaux
e t théoriques concernant la s ynthèse a biotique de moléc ules o rganiq ues et struc ture s
org;tnisées primitives. et les réactions roc hes-eaux . indique que les s ources h ydro thermales
sous· marines o nt pu être les s ites de la s ynt hèse de composés organiques qui donnère nt
naissance a ux premiers organismes viva nts de la te rre. Ces systèmes sous-marins sont
caractérisés par de h;tuts fl ux d 'éne rgie the rma le . de conditions rortement réduc tr ices. UC l>
s urfaces catalytiques abondantes et a ppropriées (argiles de Fe e t Mg). d'impo rtantes
concentrations de C H,. NH). H2' méta ux. e tc .. aussi bien q ue par un courant conti nuel de
convection qui déplace les produits de leur site de réaction ve rs le h ~lU t. par l'i ntermédiaire
d'un gradient co ntinu de température et de composés c himiques e n éta t perpétuel de mélange .
Nou ... propo"'ons que la c haîne de réac tio ns CH,. N l-l J , H I .-. ac ides a minés --. protéines -- po lymè res complexes __ stru cturcs ordonnées e t métabol isa ntes ...... organ is mc l>
vivfln ts. ail pu prendre place à l'intérieur o u a u VOisinage de ces s ys tèmes sous-mari ns. Les
micro-o rganis mes trou vés da ns les éch:.mtillo ns so igne usement prése r vés des c heminées de
s ul rures provenan t de la Dorsale Est-Pac irique, pourr:lie nt bie n être les représ enl;tnts
59
J. 8. CORLlSS, J . A. 8AROSS. S. E. HOFFMAN
modernes d'organismes foss iles trouvés da ns les roches de l'A rchéen. Cem: hypothèse
suggère un no mbre très important d·observa tions. qui pourraien t ètre effect uées à la fois en
l<lbor<ltoire et sur les sys tème~ hydrothermaux ~ous-marins contempora ins.
Ocewwl. ACIlI. 1981. Actes 26< Congrès International de Géologie. colloque Géologie des
oçéans. Paris. 7·17 juil. 19S0. 59-69.
conlributing s ignificant ma s~ 10 Ihe early Earth . Ii is
possible Ihat as much as one-fifth of the earlh's !Ilall~ was
acquired in this period of giant impacting (Smith . 1976).
The enormous energies released through the proceslIes of
giant impacting and the decay of s hort-Jjved radionuclides
would bc sufficient to me! t the surface of the planet.
covering il wilh a hot silica te mngma (S haw . 1976). The
magma would be convecting vigo rous)y. dega.~s ing vola tiles
to form a primevlll secondary :Hmosphere (Fanll1c. 1971)
and radiating heat inlo that atmosphere. T he atmos phere
ihelf would be convecling ;md rad iating heal inlo ~pace .
As impacts diminished ove r lime and as heal radiated iOlo
space. Ihe s urface of the planet evcntually would have
cooled s ufficiently to permit thin crustal fragment s to rorm.
With continued cooling. rafts of solid s ilkate~ would
coalesce to form a conti nuous. Ihough thio and hrÎnle shell.
insulating the atmosphcre from the magma. Conti nued
cooling by radiation into space would then allow liquid
w;ller to condense from the atmo~phere. and ra ins wo uld
begin o n the primitive Earth (Wal ke r. 1976).
Shaw (1976) propo~es th~lt h'tcflll inhomo~eneitie s in the
composition o f Ihis carly crUM would be produced by
magmatic differe ntiation and convection. The Jess dense.
isoslllticlllly higher protocru~1 would rorm the primitive
continenlal areas while ocean basin~ would rorm in :ucas of
denser. isostatically lower protoeruSL The thin ~ubocea nic
c rU ~ 1 would be subjected to both lidal and isostatic body
forces and to s urface dra g from the underlying convecting
magma. leading il to fracture. resulting in s ubmarine volcanism <lnalogous 10 thal al pre ~en t da y s pre,lding centers.
Once ocean waters came into contact wÎth ocean f100r
voJcanism. be it through individual volcanic centers or
Ihro ugh rift zone processes. hydrothcrmal aCli vity would
commence. The~e hydrolhermal systems extracl both the
heat and dissol ved gases from the magma and transport
them inlO the oceans: the flux of both was prc:sumably
s ignificantl y grealer in the firs t oceans.
The critical point for our model is thal eruption of mllgma
inlo the oceans and the cooling of this magma by hydrOlhermal circulai ion is the process required for the origin of Iife
on Earth. and that thi s process has bcen a promincnt feature
of Ihe oceans since they fiTSI formed.
INT RODUCTIO N
We propose that submarine hot springs reeently discovere<l
and explored lIlong mi<l-oceanic rift systems (Corliss el ai ..
1979 a) provide ail of the conditions necessary for the
çrention of life on Earth _ There is a paralleJ bctwcen the
conditions in the ven ts and the conditions used in the
experimental abiotie synthes is of high molec ular weight
o rgll nic polymers a nd pri mitive organized s truc ture s (Fox.
1971 : Yanagawa el al.. 19110) with many of the characteristics of primitive living organisms . It appea rs from an:llysis
of the events of early Earth history that hydrotherm'II
activi ty con nectcd with seafloor volca nism cornmenct.d
simultaneously wilh the formation of the prime val oceans
and t h ~lt this followed saon after the final aceretion of the
Earth - 3.9 billion years ago. In exam ining Ihe eflrliest
Precamhrian roc k and fossil record il is notable thal cel1 -li ke
structures a nd s imple organisms h:lVe been found in rock
units from 3.5 to 3.8 billion years old whieh we and olhers
interpret as submarine hydrothermal assemblagc~. In thi~
papcr. we synthesize the evidence from experimental biochemistry . micropll]contology. microbiology , planetolo~y .
marine geology. and chcmistry to present a unified model
for the origin of life ou Eanh. Our argument is pre~ented in
the follow ins order :
1) carly Earth history aud the orisin of Ihe ;Itmosphere.
oceans. and crust :
2) the history and res ults of abiotic sy nthe~b experiments :
3) a description of ~ubmarine hydrothernml proce 5se ~ and a
discussion of their potential as sites for the abiotic synthesis
of çom plex organic moleeules and ceJl-l ike st ruclures :
4) Ihe rock and ross i! record of the earlies l Precambrian :
5) the c val uation of the hydrothermal vent hypo the ~ i s in
comparison with other hypolheses for the o ri gin of life ;
6) li description of the postulated firsl organism~.
Wc are aware of two papcrs which have previousl y proposed s ignificanl parb of the mode] proposed here ; lngmanson ;lnd Dowler (1977) and Degens (1979).
EA RLY EARTH HI STO RY
Il is genera!!y a ccepted that the Earth and Ihe other
terrestrial planets accrete<l roughly 4.5 BYBP. The procesS
of acc re tion led 10 the differen tiation of the core from the
mantlt' . This ~Iage of accretion and core-formation proceeded from roughly4.6to4.2 BYBP (Smilh.1979: Ringwood.
1975: Hartmann. 1978: Goodwin. 1976).
Evidence from the 1\l100n indicates Ihal tht: inner Solar
System wa~ bombarded by large planetesimal ohjects
00-100 km in diameler) from 4.2 until about 3.9 BYBP
(Tera fi (II .• 1974 : Wasserburg el al .• 1977 : Kaula. 1979).
The impact of as m;,uy a~ 10) to 10' of these o bjects o nto the
Earth would have led to major volca nÎC activit y as weIl as
AH IOTIC SYNTHES IS EXPERIMENTS
Early rese,lreh on Ihe origin of life was initial1y done by
c hemists and biochemi~I S as experiment s in c10sed laboratory system s (Calvin. 1969). The goal w,, ~ ~y nthe si~ of
s imple o rganic compounds. 5uc h as ami no aeid~. from
ino rganic compounds under conditions eonsidered to exist
on the early Earth . The Iypic<ll procedure involved confining a mixlUre of gases believed to be pre~enl in a prime val
Earth atmosphere in some sort of dis tilling container.
providing ~IO encrgy inpul. and analyzing the resulting
rC,lCtion prod ucts. Il has been argued. e.g. Holland (1962).
60
SUBMARINE HOT SPRINGS AND ORIGIN OF LlFE
t he Earth's oldest rocks (sec below). continues today. The
fi rs l direc t observations of these hyd rothermal systems
along mid-oceanic s preading centers was carried out in carly
1977 along the Galap.1gos Rift (Corliss et al .• 1979 a) us ing
t he deep d iving subme rs ible. Alvin . Researc h on the exten·
sive set of data and samples collected on Ihis expedit ion h.is
a llowed us to c ha racterize t he behavior of the interact ion of
sellWater wilh ncwly c rupted crust in grcu t d e taiJ. More
recent obse r ... a tions from t he Eas l Pac ifie Rist lit 2 1 N
providc addilional s ignificanl information (S piess et al"
1980 : Hekinian et al. , 1980).
t hm the early atmosphere w hich res ulted from ... olc:mic
oUlg:lssing was il redueing one. The gases th o ught 10 have
been pre sent . and often obser ...ed a.\> the products of
volcanic outgassing . are Hl' H}O . CO}' HlS. S. C H,. N H J •
and/o r 50}. Various combinations of these g;lses have been
used in llbiotic sym hesis experiments .
T he re wc re atleas t fi ... e different sources of energy availa·
bic on a primiti ve Eart h : high energy partic les from
radioac tive declly . solar radiatio n (UV ,tnd visible). e lectri·
cal discharges from the almosphere. shock waves (rom
planetesimal impacts. and t hermal energy from volcanis m.
Miller (1955) first demonstrated the abio tic synthes is of
amino aeids in a presumed early Earth en ... ironment by
spark d ischarge in a continuously recycled low tempera ture
mix t ure of red uced gases and wa ter (CH •. NH J • H:. H:O).
s imulating light ning discha rge in a pr imitive al mosphe rc.
Subsequent experîments have shown t hat these reactions
ca n be d ri ven by a vil riety o f encrgy sources (Calvin. 19(9).
Q
Sites of submarine volcanism bring logether in il s ingle
system a unique combination of roc ks. g.1ses, hea l. and
wate r. T he relevant fea lure s of a hydro thcrmal system are
s ummarized in Figure 1. These sites of eruption occur whcn
crustal plates a re spreading apa rt, aIJow ing magma 10 rise in
the c rus t, ap p roac hing closer to the sea floor a nd produeing
il si rong thermal grad ient across the hlyer of pre ... iously
crupted and cooled rock. This layer of rock has undergone
the rmal contra(: IÎon and fra cturÎng and is subject to tensio·
nal cracking re sulting from the spreading of c rustal pla ies.
As a result. the c rus t is permeable and becomes sat uT<lted
wi t h seawater.
"Acti ... e " hydro the r mal circulation is dr iven by Ihe rapid
tr<lns fer of heat from t he magma to the water al the
"cracking fron l" (Lister. 1974). T he wa ter which saturates
The nex t Sleps in the <lbiotic synthesis sequence a re Ihe
condensation reactions s uc h as those nece ssar y to polymerize amino acids to for m complex proteins by extnlction of
water and formation of peptide bonds. Ultimately. the
process must lead to the formation of individ ual entities
w hic h ca n carry OUI Ihe processes which ddi ne a living
o rga nism: t he ab ility to metabolize. re p roduce identically.
and adap t. Fox and his colleagues pioneered the use of
thermal energy for abiotic s ynthesis. and de ...eloped a model
sequence of events : primordial gases -. amino acids -- primiti ...e protein .... a primiti ve organized struClUre . They used
heat 10 dri ...e off water and produce condensation reac tions.
forming " protei noid" mixt ures, which. o n addit ion o f
water. produced " protocells" whic h had "a cellula r type of
ultras truc ture , d ouble layers. abili ties to metabolize. to
grow in s ize, to prol iferale . 10 und ergo selec tion. to bind
polynucleotides. and to retain some macromolecules selec ti...ery" ( Fox . 1971).
Il is imponantlO point out that these co ndensation reactions
~:tye been shown 10 occur, wilhout drying, in aqueous
solutions suc h a s Ihose in hyd ro t hermal systems. if the
rcac tions are cou pled wi th t he hydrolysis of condensi ng
agen ts such as c yan imide or cya noacetylene derived from
hydrogen cyanide. HCN sho uld bc readily s ynthesized
under hydrothermlll conditions. thiocyanate pre sumabl y
derived from HCN and H,S. has been ue lected in the
h yd rothermally produced Red Sea brines (Dowler . Ingmanson, 1979). MontmorillonilC clays . abundanl in hydrother.
mal syste ms. h .....e nlso been s hown to cnllllyze thesc
condensation reac tions, serviny as ternphlte.\> for protein
sy nthe sis (Degcns. 1979 : Laha .... Chang. 1976 ; Prtec ht·
Ho ro wi tz. 1970: 1978). Rl.:cently , Yamlgami et lIl. (1980)
ha ve succeeded in synthesizing " Fox·like" protocel l struc·
tures by hold ing a mixture of a mino acids in modified sea
waler (with addcd Fe, Mn , Zn. Ni. Co and Mo) under warm .
aeid conditions (105 eC. p H 5.2). Polymers conl .. ining pept ide bond s. with molcc ular weigh ts from 1.800 10
82,000 daltons . were produced in t he inleriors of these
st ru ct ures.
The physical and chemical cond itio ns o f those experimenls
are found in il nal ura l en ... ironment which has been presen t
in the oceans s ince thl.:Y first formed . in hot s prings
associated wit h submarine ... olcanis m.
Figure 1
H yporl!erical modd of tI,t submarine hydro/humal s ystem uS (1
cantinua l/s fla .... and mixing gradie/!/ pudf!d·bed rea eta r far Illt
(lbio/;i' syn tl,u;.~ of liI'lnll org(l1!ism s or /hcir Immedilllt' prUli rSlJr.t.
.u
,_ .--A~32L1;i1,
:tr:
,
,
• ,
J
_~~(i.'
I" ~- :~~
...... ,
.........
_.
- '-_.
-,-
•
'.~
ço,
''''0<'_
~
~
ttTh-,<
'll2_ '
-- -
1
~
_._.
. ~." ',~:;~':::.
.........
~
.
'.
---
.
H t a/ und CO, urt txt1llcted from the mllg l1l(1 al Ihe cruding
fron, ; Ihe redaeed gasts . reda eed Iransi/inn me/ab and OIhu
appropriafe compone/!/s are Inlmdl/ctd daring the "'uterlm d
in/eraclions. t'hese law d ..nsil y. III ... j'Iscosil)' fll/ids. ,ise ru/"dl,
Ihroagh an UnaJtamosing fraCla rt system. fined b)' appmpriate
c ullll)·tic liurfuces. r/!/,uining and mixi,,!: wirlr Ilrt cool sell 14'01'"
sll/urating the surrounding cold mcks. Ali Ill t {luids reac h Ihe j'eu
f/oor u nd m;x rl/piclly Wil /' bol/utll "'/IIt·r. Ihe ~'III}erSlll llra/ed
('O /llIHmenl$ of Il,t J/llid.~ ... /lic h lIre salllrlll ed ill Ih .. battum ,,'lIIer
PUe/pi/III", f",mln H cl1"",rctll sedi"''''' 1$ ('''lIIl1d tI,t ,·ell/ .t .
a .
SU UMAR INE H YD ROTH E RMAL SYSTEMS
T he q ue nching o f newly in je c tcd crust 0 11 the sea floor by
circ ula ling seawatl.:r . w hich we belie ...e is clearly recorded in
61
J . B. CORLISS. J . A. BARQSS . S. E. HOFFMAN
n.
fl OO_
1-< oOO'CI
HeJ/ heal ra tio in several indi vidual ve nts suggc:.h that the
and heat ;Ire eX lracted from the rock in t he same
proçess (Corliss fi al .. 1979 b). In addi tion to these g;lses,
Ihe magma eontains ail o f the nat urillly occ urring clemenls.
As Ihe magma c ryswll izes. the gases a'Id Ihe ·· incompllti ble" elements (lhose not entering the growing cry~ l al
ki ll ices) are fra clionated into Ihe intercryslalline fluid. and
when c rys taIli7..·uion is complete. they occupy Ihe intergranula r spaces. As the rock cools below the ~olidus. the
diffe rentiallhermal contraction of the individual grain!> will
tend to o pen ;In interconnecting network . As a fra clUre
propagates into Ihe viclnil Y. it introduces wmer into the
net work. The wa te r extracls both the gases and ··i ncomp'l tibic'· clements in the intcrgranular spaces. and reac t.. wi t h
solid phases altering them and extrac ting addilional cie ·
ments . incl uding tra nsit ion mctals.
ga~es
:;h
t
(>
t
,
$ ••
III.",
t
_....
...........,_.
1...... ' .." . .... _ . 1
(> •~ +
••••".....".... P,'""··'·.·
(>
...".... "< •••~
<."".n... ~ •••• "
II is di ffir.:uh to estimate Ihe maximum temperalUres this
wate r ca n altai n. The magmn solidifies at - 980·C. L'lç henbruch (1962) has suggested thm s uch frac l ures. once init i;tted. could propagale past the sol idus boundary inlo the area
where res idual f1uid s ;lfe not entirely c rystallized. Il is nOl
unreaso nable to believe Ihal waler could anain lemperaluTes close to the solidus temperature of the magma . Evidence
from Ihe GallLpagos Rift and .he Eas t Pacific Rise ind icates
tha t the wate r reac hes tcmperal ures greater than 350"C
(Spiess et al .. 1980). Waler at these temperatures a nd sea
flooT dcpths has low dens ity and viscosity. leading to ve ry
rapid convec tion a nd Ihe abi lity to readily pene trate into the
rocks. As the fluid s rise . they enter an a n,lstomosing and
expanding set of ff<lclure ~ and fissures. ail Ihe while
incorpora ti ng cooler water which is drawn illlo the rising
plume from the adjacent cool. permeable rocks. Hot ~eawa­
ter inteTacls with the basait. forming saponite, a magnes ium-rich smectile clay which Încorpora tes magnesium from
the seawater. Th is proeess lower.. Ihe pH of the seawatcr by
remo ving OH - and lowers the Eh by oxidizing fe rrou~ iron
in the rocks thro ugh the reduction of SO._ and/or oxygen
from the d issociation of wale r (Bi~choff, Dickson. 1975 ;
H'Ljash, 1975; Seyfricd elll l., 1978: Seyfried. Bischoff.
1977). The flu ids emerging out of the sea floor from ven ts on
the Galapagos Rift and f rom mos t vents o n the East Pacifie
Ri ~e (21 N) had tempera tures in the range of 10-30-C as a
result of the mixing proccss. However . a t ..orne of the 2 1 ~ N
venlS, water emergcd at temperalUres of - 350-C. l'res um;tbly . the rc WOlS a di rec t vertical c ha nnel to sorne depth in Ihe
rock. These high-temperalUre vents precipitate dissolved
melals forming large s ulfide ch imneys ( Hekinian tr al ..
1980).
... ....
~
I-IOOO"CI
b. Tht! propoud st!ql/lnct! of c hemical and biuchtm k al ,,·t'nll
leuding lu lire furmalion and de,·tlopmtrll of ··pro uX'tlls·· ",ollid
O("("lIr a/ong Ihe Ihermal alUllht c hem;co/ SlIbSlrOle COlralt/rfl/iOIl
f,lrlldiml.r ...hiclr exisi ... //Jrln 1I1t! I/p ...elling fil/Id s of tlrese hydmllrtrmil/ ,·nI/)" . Amino (.dds Utld othtr rfu,·/;"t co mpOlUIds SIKh as
hydrogen cyallide ulld ilS dl'riraril'u a/Id formuldt!/I yde cO I/Id be
s)'lr/ htsiztd from tht dino/ ,·td (u,us.lnitially 0/ high ttmperO/JlftS.
AI lo ...er /tmptrUlUrtS oddilionul ml/in n acids and ptp/idts co,,/d he
synlhtsi;;td. ('alulyzed b)' rtuc jj,'t cumpu.mds und d a )' mllluu/s.
··Pr%cel/"· fo rmollOIl cOllld (}Ccur ,.'ill,ill Ilris s rodit"t JUrJt r tht
appropriOle tempera/ure. pH and (l/hu clrf'mical IIlId plrYJicu/
ct/ndlrlons (/or example. Yunugu ..·u 11'1 al .. 1980). Tllnt' "prowal/s·' pro"ide Il pro/tc/t d ",icroen t"irolllntnl bOllltd in rooUnll
h ydra/ humai fillids (.Ind/ar bo/tom "'O/ers cOIi/(ûninll redl/ad
trurlSiti(J n melUls. diu/J/!"ed rtul·,i,·e guses Ulrd othu compo"enfS
... hi,·h Ira,·t httn sho,,'" la he appropriatt fa, lire ahiotie spI/lresis of
po/ypf'plidf's a/Id poly/Uu·/eo /ides. Till' ··pr%Cills·· CO I/Id ht! deposi/td lI/onll ...itlr silicli prer/pilO/ed from lire .fl/pt'fmlllrllled Irydm _
Ihermu/ /I,lid.< /0
cur/w IIIJ ceUlU' cherl ~. clJlllain;ng or;;llIIl:ell
o'lIlIIlic SirI/CIUfi'S SI/cil Q$ fo und ill Ille lsl/Q rocks .
Tht asterik co mpQll t ll/5 hm·t bUll dntclt d i" m odem hydrQlh~mral
s}".!/fm.l (Go rdon. Lille>'. pt'fs. <"Omm.]. Iht s/ orrtJ ,''''''POlrtnb
h(lI'e hte,1 rfpo n t d ill Rtd Sfa brillt5 (l'igma l/ soll. Do .. ler. 1979 ;
II l1d Do,,·lu. Inllmansoll. I!1SQ).
f,"'"
Q
the cold. permeabl~ rock ··au ack,,·· the magma body in .1
conlinuous cycle:
cool ing ....,. crack propagation __ water penetration ......
convec tion ...... cooling.
Wilhin Ihe magma body , removal of heat from t he upper
s urface leads to plating of the c rys tallizing minerai pha~e ~
onto the roof of the magma c hambcr. forming fi zone of
çryslall ine mus h which grade ~ upward into solid rock. Heat
f rom the magma i!> conduc ted across Ihis interface up to the
··çracking front" · where il is eXlraeted by circulati ng waler.
This interface is th~ site whcre a significant fnlet ion of the
cooling and degassing o f the Earth has occurred. Gordon
and Lille y (pers. comm.) ha\e .. hown that signifieant
qu:mtities of CO!, N B ), and H2 arc present in the hydrothermal fluids at the Galapagos Rift . O'Neil (pers. comm.) ha,
analyzed the carbon isotope eo mpo~i tion of COz in these
s amples and found SC U va lues of 5. 1 to - 5.3 . es tablishing
it a ~ primordial carbon. Primordial He J is also prc sent in the
G'llapagos f1uid s (Jellkins et al .. 1978). The eonstancy of the
lt appears 10 us that ~ ubmarine hydrolhermal systems arc
ideal reaç t or~ fo r nbiotic synthesis. The s tases of the
process whieh we arc proposins ;Lre shown in Fig ure 1 b.
The raw mate rials are extracted from Ihe magma in the
vicinity o f the cT<lcking front. Low molecu lar weigh l organic
compounds could be synthes ized at hiSh temperatures and
then mpidly mo ved upw:lrd along a gradient of continuously
decreasing tempera ture a nd concentratio n. The expo~ ed
surface area in the fractures a nd inter s ti c e ~ b coated ..... ilh
alte ralio n minerah, dominanlJy saponite. a Mg-montmoril lonite. Montmorillonites ha ve been demonstrated to bc
effecti ve catalyslS fo r 3biotic synthesis rc ac lion ~. Thro ugh
clay catalysis a nd condens ing ;Igenb Ihe low molecular
weight organic compounds could he polymerized into more
complex conlpounds and plate o ut onto t he wall ~ of the
fraclUres. evenlually forming protocell s. The ~e interiors of
these protocell s form a protec ted microen vi ronrllent in
whic h fu rther a biotic synthes is could proceed . The rising
62
SUBMARINE HOT SPRINGS AND ORIGIN OF LlFE
Anhaeusser et (II. described a sequence of metamorphosed
basic lavas with interlayered sil iceous sediments, occasional
th in carbonaceous chert horizons. and bands and lenses of
serpentinized ultramaric rocks. De Wi t and Stern no ted the
s imilarities in melamorphic textures and mineralogies to the
s hee ted dike complexes and flanking pi1low lavas of Phanerozoie ophiolites. The extensive hydration of the Onverwac ht minerais they feel is bes t explained by metamorphis m at
u spreading ridge. Evidence for this interpretlltion is '1lso
found in the prese nce of b.mded iron format ion, rich
metallogenic sediment s. barile, car bonates, and c heriS. Si.
Ba. Ca. and Fe lire dominent components of greenschist bel t
c hcmical sediments (Rid ler . 1976) and s ubmarine hydrothermal systems are a s ignifieant or dominant source of these
elements into t he ocean today (Corliss et al .. 1979 a :
Edmond et (/1 .. 1979 a. b). S i, Ha and Ca are presently
maintained near saturation by biological mediated precipitation. I n the Archaean oceun. hydrot he rmal input must have
slltunlled Ihe oceans in Ihese components , leading to rapid
precipitation in areas of submarine vo[canism. Vezeir (1979)
desc ribes c hemical and isotopic data for Archaean sedimen ts, ,Ill of whie h lire consistent with a s ingle assumption
that the seawa ter-oceanÎC crust cxc hange was exceptionall y
hig h 'd ur ing the Arc haean. Fe·oxides are the dom inant
component of metalliferous sediments associated with
hydrothcrmal ac tivity along modern mid-ocean ridges
(Dymond . 19K1).
Il is a ve r y in triguing fac t that a number of workèrs ha ve
isolated fossi l form s from the Onverwacht Series. Engel
et al. (1968) "isollited both siliceous and carbonllf;:eous
particies and carbO/wceoll s filaments" from chens. argillites and carbonate beds in the O nve rwacht. Furthermore ,
"the s pheroids within the carbonaceous Onverwacht sedi-
f1uids would wash t he protocells off t he s urfaces a nd
tra nsport t hem upwa rd , depo$i ting them in cooler environments in the vent sys tem or on the adjacent seil floor.
Continuous s upply in a limited area could result in s ignificant accumu lations of these protocells.
EVIDENCE FROM THE OL DEST ROCKS
The evide nce for this statement can he found in the three
oldest dated se ries of rocks on the Earth (Table 1). T hey arc
Archaean greenslone belts containing sequences of rock
t hH t have ail the major characteristics of modern sea fl oor
hydrothermal environments and/or of preserved sea floor
hydro t hermal environments round throughout the geological record younger than the Archaean. They contain
sequences of hydrothermally metamorphosed tholeiitic
mafic and ultramafic rocks induding pillow basait sequences, overillin by and overlying bedded sediments (silicate.
car bonate, sulfide. o:o;ide and reduced car bon facie s). Ridler
(1970 ; 1976) has named Ihese hydro t hermal chcmiclll sediments. common in Archllean greenstone belts, the " ex halile" facies.
The Onverwac ht Series is a 3.5 billion year old (Hamilton
el al .. 1979) rock assemblage in the Barberton Mountain
land of South Africa. The Onverwacht Series form s the
base of the Swazil;lnd System . Directly above the Onverwac hi Series is the Fig Tree Series. A synthes is and re vicw of
the earlier fie ld work in Ihis are'l was presented by
Anhaeusscr el al. (1968). Rece ntl y, de Wit el al. (1980) have
reinterpreted the entire Swaziland System in light of present-day knowledge of s ubmarinc hydrothcrmal processes.
TabLe
1
Ag<
ISUA
- 3.8 b.y. n.p.
lMoorbalh. 1973J
ONVE RWACIIT
- 3.5 b.y.b.p.
[Jahll and Shih, 19741
WARRAWOONA
- 3.5 b.y.b.p.
ISangsler and Brook .
MID-OCEAN
1977 ;
[RIDGE]
MODERN
t'idgcon. 1977J
Igneous and Melamor·
phic
1'i!lrology
- amphibolitcs (layered,
massive and dikes) (Brid·
gcwalër. 1973);
- melabasalls
with
major ele menl distribu·
lion ill good accord wilh ...
ocean·ridge
modern
basalls (Appel. 1979).
- ophiotite
comple~
consisting of shecled ree·
de r dike cOm:r'cx, cdrusive unilS fe by dikes.
magmalic
cumulates
spreading ridge mClamo rphism (deWit .., al.. 1980).
- " basalt lavas, cornmonly pillowed wilh imer·
calated cheri horiwns"
( Lipple. 1974).
- Iholeiitic pillow basalts
and inlrusives, hydro·
thermally metamorphoscd
cruSI. grecllsch ist and
amphibolite facies.
Chernicat
Sediments
- cheTlS. banded iron
formation.
- "submarine exhaltive
sulfides in Iron formations" (Appel. 1979).
- ballded Iron forma- - concordant
bcdded
tion, manganeS<! ric h sedi- chen-barite
within
a
menlS, claslic and chemi- sequence of carbonated
cal chens barite (deWil (1 and silicified metabasalts
af.. 1980),
(Dunlop (1 al., 1978).
- carbonaceous chens.
mClalliferous sedi·
ments. massive sulfides,
biogenic silica and carbonate sediments. hydro·
thermal sulfides.
Organk Compounds,
Structures and FossiJs
- carbonizcd
organie
maltcr and este rs in rossil
cclIs ( l'nug. JaeschkeBoyer. 1979).
- unicells.
filaments.
and ccli colonies with
laminar walls ( l'n ug.
- keroge n bcaving sphe· - " microfossils with a - complex chemosynthe·
riods and filaments in car- wide range of morpholo- lie balcriological and ani·
bonaceous chen (Engel gies, including 50titary mal communities (Corliss
.., of.• 1968).
spheroids, spheroids wilh el al., 1979 Il: Karl el al.,
- "'fossil microorg3 1lisms splits, paired spheroids 1980),
arresled and prescrved in and rare chains of sphc- - filaments,
org3nic
the midst of biological roids" (Dulliop el al.. debris, sulfide chim neys
actÎvitey" (KllolI Bar- 1978),
(Fig. 2 and 3).
- slrOmatOlilÎC
(abric
ghoorn. 1977).
(Walter el 01., 1980).
1978).
- " nuid
inclusions"
( IJridgewaler l'lof .. 198 1).
63
J . B. COALlSS, J , A. BAROSS, S, E, HOFFMAN
menu not o n[ y have the morphologies of fossils, but also
arc intimate!y associated with the kerogen·bearing C;lrbonaceous s ubs tances which appear to form parts of their walls
and interiors. They are a[so closely associa ted with keropell'
bearill g, fi/amelllOl/S forms ",Meil IWI't.' Ihe appt.'armlce of
microfossUs" .
Knoll and Barghoorn (1971) ha ve also deseribed popUlf\tions
of organic walled micros tructures from the Swartkoppie
which they concludc arc fossil organisms, in which "various
stages of binary di vision are clear!y recorded ", They also
conclude that the foss il-bearing cherts were depos ited in
~ hallow water, citing t he presence of oolites, cross.bedding
a nd f[at·pebble cong[omerates.
Engel el al. commen ted upon the difficulties of Interpreta·
tion of the car bomlceous fiJ:lmenlS. reporting thal the
filamenlous layers in 1he c;ubonaceous argillie cherI are of a
di verse morphology 110d rem;lrkably lifel ike . T hey çoncl u·
ded tha t "many a ppear to be truc fossils, although [ess
well·preserved than those round in younger PrecambrÎ:lO
sediments". There is a n interesling correlation between
these rossil descriptions from 3.5 billion years old hydrothermal sediments and the a ppeaTance of complex filamen·
tous o rganic s truClUres in scanning eJectronmicrognlphs of
c himney rock samples from 21"N, One of Ihese micrograph':>
is reproduced here as Figure 2.
Figure 3
Scanning electrolllllicrograph sho ...in/; Ihe sur{aus I»f illor/;wric
crys/als c(n'ertd ,.'ifh dt!posilS of or8anie dthris alld m k roorga·
nisms ",hich hu.,t bun tmi/lt!d (rom" black s/IIoktr " chim/lt)'s al
Z, oN and hOl,t stlll~d on Iht sllr/arts of Ih~ chimllt)'l' und Iht
sUl'TOundinR rocks and animais , Th t! samplu ,.·t!U pr~partd as
dt!scribtd in Figll1t Z. Phow mURllifitd 400 x.
Once agnin, there is a sequence of mafic and ultramafic
cxtrusives, pil10w basalts, çherts, and other volcanic rocks
intercalated with pyroclastics and probable turbidite depo·
SilS, which ind icatcs extensive submarine volca nis m and
conseque nt hydrothermal llctivit y and ev idence of Il high
eoergy depos ition<l[ e nvironment interpreted as indicati ve of
sh<lllow water,
Even more interesting in lerms of o ur modeJ is a group of
rocks which o utcrop in sout hwcst Grcenland at the edge of
the Greenland ice C;lp. This is the Is ua supracrusta[ succcs·
s io n, which includes the o ldeSI sedimen!:lry rock~ yel dated.
The s tratigraphy and petrology of the Is ua succession are
described by Bridgwater et al. (1976) and Alla<lrt (1976), The
rocks are basic and ultrabasic greenschist. metamorphosed
sediments and quartz fel dspathic rocks with many s imilari·
ties to yo unger green~chist bclts. They have been metamor·
phosed 10 the amphÎbo[i te facies, and sorne units have
retrogresscd 10 Ihe greenschis l facies. The rocks form a
[ayered series. Incl uded in t he l uccession is the Isua
ironstone, li fine[y banded ~equence of magnetite and
quartz·riçh layers. The iro nSlones have been dated by
Pb - Pb at 3.76 ~ ,07 BYBP ( Moorbath. 1973). Bridgwater
el al, inte rprel these s iliceous rocks as chemical sediments ,
They are interlayered with chlorite·rich basic rocks inler·
preted as sills, We interpret this sequence of rocks a':>
s ubmarine lava f[ows (lOd relalcd hydrothermally-deri ved
s i[ica and iron oxide~,
Appel (1979) has noled that the major element distribution
o f the Isua met~lbasa[ts is in good accordance wilh the
patter ns of modern ocean ridge basa[ ts a nd Tha! the massive
amphibo[jtes in thc hua ~ u ccess i on probably represent
basaltic lava f1ow~ and intrusive s ills. Appel concludes that
"a submarine exalitive source of the copper and iron
seems .. , more plausible" because of the ocçurrençe of the
sulfides in distinct layeTS concordant with the banding o f the
Iron formation and the layering of the amp hibolites. Overall,
the ltratigraphic rc[a lionships of the sulfide [ayer~ to the
irons tones and the amp hiboJites, Appel believes, exclude
the po~sibility of a replacement process, We be[ieve that
Appel's observ;i1ions suggest that t he Isua sediment s werc
precipitated from the hydrotherma[ solutions which cooled
and metamorphosed the basaltic precursors of the amphibo·
lites.
hgure 2
Scunning t!1t!clronmicrogruph sho ...illg Ihin unrOI'~/jn8 Slfunds of
orgunir o ~ possiblr inorganir shtmh! ,,'hieh " 't!rt f~tqut!n,l)' found
0 11 hOI ('himnt!)' rock surfuus fmm Z' ~N. Th~St SIfUCluru 1ts~mbl~,
II» sumt U l M/' Iht fouil Slru ClllrtS obstrwd in uncitnl fO('l!.3 (su
lUI). HM is 10 l'm, Tilt sumplu ,,'ere fixtd in surilt arlifidul
St!U"'tIltr con/aininX Z Si> Rlultraldthydt! ...ilhin minultl alltr Ih,
Al,'in surfaud. Sieril~ Itchniqllts "'tre ustd "'lIh 0/1 specimtns, Tht!
{i.I'ed sU/llples ...tre dried br Iht crilicul method, Ihell lIIoullled on
allUliimllll stilbs and coat~d undtr Il ,'ueuum ... illl a la)'tr "f go/d
10·20 IIm in thicknt!Ss. The SUlllt/ln ,,'Ut ,'ie ...td USin8 U/I inll'fIIU/ro_
11/1/ l'cicntifi,' inslr/mIC/11S mini·SEM, modt/ MSM·2, JcU/millR
eleClfon microscope.
Recently, a new suite of Arc haean microfossiJs has been
found in a 3.5 billion ycar old terrain in WeSlern Australia,
the Warrawoona Group of the e;ISlern Pilbara B[ock (Dunlop l't al.. 1978). The organisnls were discovered in stroma·
lolitic structures (Lowe, 1980: Walter et al .. 1980) which
form a part of the North Pole dome, a major grecnltone
dome co nsisl În~ of pîllow basali~, cherts, and felsic vo[ea·
nics ( Hickman, 1972 ; Lipple, 1974). A remarkable simi la·
rit y bctwecn the Onvcrwacht succeslion and the Warn;·
wooml Group has a[ ready been nOled (Barle y et al .. 1979),
64
SUBMARINE HOT SPRINGS AND ORIGIN OF LlFE
the inpui o f UV radiation o r lightning dise harges which
somehow reaCI 10 form large r molecu les. Eventually these
la rger molee ules are fo rmed into "coacervatcs" o r " protoeells" that acquire th e capacity to "transport" organie
compounds th rough a highly orgll nized membrane and to
ca rr y on m:idat ion/red uct ion and s ynthetie rea ctions. These
quasi-heterotrophs. as a res ult o f continued expos ure 10
ultraviole t light. devclop olher s truc tures. incl uding pholonabsorbing porph yrins.
ln the c hen y layers o f the !sua quartzi te. Pflug (1978) found
cell-!ike inclus io ns occurring as indi vidu:t! uni cell s . filaments, or ceJl colonies . He describes the structu res as
surro unded b y multilaminate s heaths enclos ing a more or
Jess glo bular hollow partially filled wi th urgan ic matter.
Raman laser mo lecular micro pro be .. nalyse s o f these
objects (Pflug. JlIeschke- Boyer. 1979) produced IWO kinds
of spectra : the ccII walls a nd (jllings co ns!s l of cMboni zed
a nd gra philized organic malerial whiJe cell vac uoles conla ined esters and aliphatic hydrocarbons. They point o ut the
s imilarities with Fox's prolocelJs but a ssert Iha t Ihe Isua
objec ts are fossils of li ving organisms.
T his "organic so up " hypothesis pred ic ts thal. befo re the
fo rmlltion of biochemically acti ve "protocells". a protoenvironmen t would ha ve to be formed whic h contained a high
concentra ti on of a mino acid s and o thcr organic eompounds.
Ir s ue h a n envi ro nment had cxis ted , ve r y ancient sediment s
s hould conlllin signifiea nt le ve L~ of these aotino add s a nd
o rganic compounds. This Îs nO I the ca se. Ins tead. in Ihe
o ldes t rocks known to e xis!. w hich formed s hortl y arler the
cessatio n of giHnt impacting , s truc tures ha ve been round
wh ich stron gly rese m ble the buddin g " protocells" described as resulting from expcriments us ing th ermal energy,
There is no detectable sedimenlllr y eviden ce for a pre-exÎsting " organic SOU,)" . It i5 a lso important 10 point out that . in
an oeeanic environment. the concentrations o f orgnnic
compounds would be quite dilute except at the site o f
synthes is _ and heterot rophic organis ms eo uld not sur vive
under these conditions. Consequently , the sugge stion that
the fi rs! protist was helerotrophic docs not scem 10 be
supportable.
Bridgwater el al. (l98t ) c ite evidenee that the rocks ha ve
been exposed 10 high lemperatures in pos t.dcpositional
metamorp h ic e vents which they s ugges! th e fossils could
not have s ur vived . They a lso present Ihe results of their
microscopic stu d ies o f Ihese objects and conclude Ihal the
PfJug microstructures are non-biogenic. They ac know1cdge
the presence of graph itic earbo n;tceous matte r in the Isu a
mClasedimenls . bUI a sse rl Ihal "il rem;lins (Q be eSlablished
whethe r th is is biogenic or abiogenic in nature and to wh;1I
extent it ma y be post-de po ~ i tion a l rather than solel y syngenetic in origio".
Our model s uggests that carbonaceous microstru c tures s uc h
a s those desc ri bed by Pfl ug co uld be re adily produeed
abiogcnicall y within t he s ubmarine hyd rothermal systems
whic h produced the l'iliea in whÎc h these mic ro stru c tures
a re found. In the On ve rwllc ht a nd Wa rrawoona roc ks . Ihe
carbona cc o us mic ros iructu re s. in what we in te rprcl a s
hydrothcrmally d eposited c herts. ha ve been widcly aceeptcd as fossil living organis ms. The question o f the origin of
the Is ua micros truc tures requires furthe r clarificat ion.
AnOl her probJe m wi th the "org;tni c soup" model Îs that it is
know n that the conditions nccessary fo r the fo rmation of
amino ac ids and of low molecular weight reactive organic
eompounds ,Ife d iffe re nt from the cond itio ns required for
the formation of macrorn o lecules and " pro tocell s". The
"organic soup" hypothes is has ail these proeesse s taking
place in the same vat under the samc cond it ions. However.
in our model for the o r igin o f life in sub marine hydrot hermal
s ystems. the rap iù and continuous upward flow of fJuid s
crea le s gradienls of temperature, p H , an d chcmical concen·
tration in whic h ail of the synthetic rea c tions needed for the
cre a lion of li fe could take place.
A COMPARI SON OF HYPOTHES ES FOR TH E OR IGIN
OF Ll FE
Ali of the Olher curre ntl y favored mode!s for Ihe o rigin of
life lac k one o r many of the conditions neccssa ry tO ma ke
the transitio n from the synthes is o f s imple organic
compound s to the formatio n of "pro tocell" struc tures and
eomple x biopolyrners. Table 2 o ffers li comparison o f our
model wÎth Ihe mod el of Oparin (1957 ; 1977) . the theory of
panspermi" (C rick , O rgel, 1973). Many models. including
Oparin ·s. pielUre an aqua ti c environmenl whic h cOntains
high concentrati ons o f o rg;IOie compound s formed Ihrough
T~ b le
Ma ny biochemically acti ve mac romolee ules eontain va rious
melals. particularly iron. molybdenu m . mang,mese, co pper . ete .. as part of their Slruclllre. MoJybde!lllm , for
example . is important in vnrious bioe hemicaJ proce sses
incl ud ing the fixation of ni lrogen and the rcduction of
nitrate. Il has bee n hYPOlhe sized t ha t carly in the e vol ut ioo
2
Co mpariw" of 1/1/.' prO{lt.'ffiu inht'fl!/U in 1111.' vur;ow, hypo/lrcSI!s fo r Il.t.' oriS;I1 uf life.
l lypolhcsis
Early
Atmosphcre
OpMin mode!.
Kcduci ng
(gases).
l'anspcrmia.
l-I yd rOlhcrmal mode!.
O~idi zing.
ErIVironmem
" Tcrrestrial" so up.
Ene rgy
Kinds of
Gradients
UV . clectrie dis- None .
charges.
Early
Mieroorga nism
Anaerobie
tTOphs.
l'ime to
Evolve Active
''l'rotocells''
hctero- > Hf yellT.
Direclcd or non· Moot.
di rcetcd
oosmic
source.
T only.
I-I yd rothermal gra- Heal.
die nt in seawaler.
T , pH. chemical Anaerobie ehemo- - instanlancous
ooncemration .
aUlotTOphs.
reaclion trom redu·
ced gascs 10 "protoeells",
65
Anaerobie hctcTO- Preformcd _
trophs or phololrophs,
J. B. CQRLISS. J . A. BARQSS. S. E. HOFFMAN
of cells or cell-like s tructures. metallo-proteins. including
enzymes. were formed from s imple polypeplides and Iha!
these carly macromnlecules were active. although ineHi·
denl when eompared to present analogous compound ~
(Ochai. 1978; Eg;lmi. 1975). The importance of molybde·
num in biot.:hem iclii processes and the apparen t scardty of
this metal in terre <; trial environmenls has been used tO
s upporl Ihe hypothesis th:lt the first microorganisms on
Earth originllted frorn an extralerrestrial source where
molybdenum WM abundant (Crick. Orgel. 1973). However.
the concentratinn<; of molybdenum and other biochemically
active metals are not rimiting in the present ocean .•lOd it i~
generall y lIccepted thal Ihis WllS also Ihe case in the early
ocean (Holland . 1962). Hydrotherrnal al teration of oceanic
erust has becn the primary source of thesc transition metals
to both the 'Incient Hnd Ihe present oceans.
lures lower than 101re. the presence ofpolyphos phoric aeid
ean initiate polymerization ( Harada , Fox . 19(4). In the fOA
reeipe for the format ion of " protocclls", amino acids musl
he healed to ZOO" or 300'C under dehyd ralÎng condition~.
However . in addition to Ihe dehydration reaclion de<;cTÏbed
by Fox, il is possible 10 effectively remo ve water from
amino aeids and (orm peptides through the use of various
reaclive compound~. ~ uch a~ cyanamides and carbodiimide~
(Ponnumperu ma, 1978). These compounds ha ve been
shown tO initiate the condensation of amino acids to
peptide ~ .lnd of certain purines lInd pyrimidines to nucleotides. Altho ugh Ihere arc no published reports on the po~sibJc
existence of co ndens i n~ compounds in hydrolhermal envimnmentS, the necessary reducing g:lses ~Ire prese nt in the
requi red concentratinns in order fnr the syn thc sis of these
co mp ound ~ 10 rcadily lake place.
The synlhes is of lImino ltcids from gases by thermal energy
has been repeatedly demons trated in the labonllory ( Lemmon , 1970). The faet thal very high temperatures (MOO tn
1 .1)()()~C) are required to form amino adds has becn a
criticism of the hypothesis that life could have origimilcd in
high tcmperalure environments. This i ~ bec<lu~e the conlinued expo~ure of both low molecular weighl organic
compounds and polymers to high temperatures afler forma tion leads to their rapid decomposition. It would take only
minutes to denature eomplex protein ~ Iru e !ure s allempem·
tures grealer Ih"n 100"C. The lemperature gnldienl of
hydrolhermal environmenl~ provides a nalural sol ution to
this problern .
TIiE F IR ST O RGAN ISMS
Earlier in this paper wc diseussed how ··p rotocell~" containing hydrolhermally-derived organic com pounds courd ha ve
formed in very high numbers within the ve nts and would
ha ve been carried out into cooler ocean waters by circulaling hydrothermal fluids. In the present venlS. the mos!
abundanl groups of e hemoaUlolrophic bilcleria isolated
(rom both thc Gahlpllgos and 21 ~N have a tempe rature range
fo r ~rowlh from a minimum of 10 10 ZlfC to over 7WC (the
higher minimum and maximum growth temperatures a re
from bllcleria isolated from 21 °N samples) (Baross. unpublishcd results). Since the lImbie nt waler tempe rai ure
around Ihe ve nts b approxima tel y Z' C these oocteria would
be incapable of growth outside of the vents propcr. The fact
that a s i.tmifieant portion of the primary prooueers in these
environments is round within the ven ts dennitely under~co­
res the efficiency of hydrUlhermal gradienls in s us taining
lifc.
ln li hydro thermal sy~ le n1. it is highly probable thm most of
Ihe amino acids and other organk compounds would he
condensed into polymers and "protoceHs·· ~ horlJy after
their synlhesis . Consequently, il does nQI seem likely tha!
Iherc would be an ul:cumull"llion of sol uble organics as in the
Oparin mode!. In~lead . wilh in the newly·formed protocells.
the synthes is of high molecular weight compo und~ would
probably conlin ue due 10 the inclu~ion of low molecular
weighl organic conde l'I sing compounds. react ive gases and
reduced melals, Any high molecular weight s ubs tances
internally s ynthes ized would he unable to pllSS OUI of the
carly cclls. This ~t rongl y implies thal the fiTSI protocells and
ultimatdy the fiht proli ~ l s were Q/wtrQbic clu!l7l()(lfuntft)plis, organisms which could u!ilize the hydrothermally
delivered gases such as COl' H1' NH J • H)S (and pcrhaps
sulfale or somc other oxidized form of s uif ur). lInd HCN
with the reduced melab 10 carry OUt internai
oxidalionfred uclion re action~. EventlUilly . biochemically
active macromolecules and energy lransforming compound~
<; uc h a <; NAD and ATP could be formed .
The use of inorianic gases and mel:lls as energy ~ource~ in
these carly o rganism~ would ~olve one o f Ihe mlljor problem~ in current n:: ~earc h into Ihe origin of lige : expillining
Ihe fo rm'ltion of the complex membrane required by hetcrolrophic organisms for the transport of organic compounds.
It would Hlso explain how Ihese carly microorganis ms would
s urvive in an oceanic environmenl where organic
compounds would be quile di IUle and how they could
perpetuale before evolving the complex macromolecures
It b aho possible Ihal many of Ihe amino acids, paTliculllrl y
with row moleeurar weights. <Ire formed al much lower
temperatures. given appropria le c hemical conditions. It has
been demonstrated. for examplc. that if. beside~ Ihe pre ·
~e nec of Ihe IIslIal iltscs. reac ti vc compounds 5uch a~
hydrogen cyanide and formaldehyde are 3vailable. lImino
acids can be sy nthcsizcd a t tcmpcratures belween 80~ and
lOO' C (Lem mon. 1970). Amino acids have also been synthesized from formaldchyde .md hydroxy hlmi ne al 105w C in
~e .. w.. ler (Oth'li. 1978). Thb proce~~ wa~ round 10 be
sreatly influenced by Ihe concentration of molytx1enum in
a rtificial seawatcr, ln addition. as previously discussed.
Yanagawa a nd Egami synthcs ized ··protoccW · stru ctu rc ~ in
a ··modified ~eawale r '· medium re ~emb ling hydrolhermlll
tho~e
fluid ~.
Howe ver. the syn thesis of Ihe hiSh molecular weighl amino
acids. s uc h as tyrosine a nd phenylalanine, from gases
requires temperalures close 10 1.000·C. High temperalures
(600 10 9S0~C) are also required 10 form ~u lrur-con l rlining
amino flcid<; from hydrogen s ulfide (Rauli n. 1978). whieh i~
one of the most abundant gases formed in hydrothermal
ven ts, Although oceanic hydrothcrmal waters ha\'e l'lot becn
analyzed in order to deleci hydrogen cya nide and formalde hyde. Dowler and Ingmanson (1979) recently reported the
di ~cove ry of Ihiocyanate in Red Sea brines .
l n view of Ihese experiment:!1 re~ults, we believe that il is
highl y prolxlble Iha t amino acids are fo rmed in hydrothermal en vironments over a wide tempemture mnge. between
roughly 100' a nd 1.0()(FC (see Fig. 1 hl. These varying
co ndilion~ exi~1 in hydrothermal <;ystems and the spatial
distance of the hydrothermal temperature gradient is relati·
vely s hort.
The fo rma tion of peptide~ and olher orglmic polymer~ from
low molecular weight intermediate eompounds has also
been shown 10 oceur under va rying co ndilion~ .tnd al
lempenllures belween roughly 150' and 200' C. AI tempera·
66
SUBMARINE HOT SPRINGS AND ORIGIN OF LlFE
needed for div ision by binllry fi ssion , Il is possible that the
earliest ccUs "reproduced " as a res ult of "swellings" in
portions of Ihe ccII surface , a mee hanis m that woulcl appear
similar to buclding and would res ult in the distribution of
inte r nally synthesized o rganic compounds. ft is interesting
that " protocclls" s ynthes ized in the labor,Ito ry we re found
to be capllble of buclcling and furrni ng chains of cells (Fox ,
1971 ), and that Pflug and Jaeschke· Boyer (1979) .mcl Knoll
and Barghoorn (1977) found possible fuss il evidence of
budding cells in Ihe ]sua and Onverwac hl rocks.
lt is also 'luite concei vable tha t these carly "protocells"
were capable of reducing COl a nd s ulfale to melhane Hnd
sulfides through the use o f hydrogen. This implies thal the
earl ies l organisms were melhanogcns (Wocse, 1977) .md
related ··arc haeobac leria" . Thc molcc ular analyses of
tR NAs, rRNAs, and ccII wall componenls of va rious
s pecies of methanogens not only ind ieate Ihat Ihcy a rc
dis linctly separHte from most of the other procaryo tes bUl
also Ihal , as a nutritional group. Ihey arc m.trkedly hete rogeneous (8 alch it al .. 1979), They s l'lle IhM the apparent mte
of c hange in the sequence uf RNAs is more rapid in
melhanogens th'ln in othe r gro ups of bacteri:l. s uch as the
·· eubacleria'·. A possihle interpretation of these data, in
keeping with our hypothes is for the origin of life, is that the
methanogens developed somewhm different molec ular
s tr uc tu res and morphologies, becausc they evolved sep;ttately over sorne period of time in different hydrothermaj
environments, Il is conceiva ble Ihal the mos l commo n
present-day group of procaryotes. the "eu bacteria'·, could
have evolved from jus i o ne of the separ;t le groups of
rnethane producers .
The ubiquitous nature of Ihe process pro vidcd an eXlrernely
IMge number of trials.
3) Il is not clear whethe r deep water hot s prings arc
requ ired for the process . The Onverwac ht and Warrawoo ml
fo ssil s are found in rocks with evidence of a hig h e nergy
depos itio n;tl environment with e Vllporile minerais whieh has
been interpreled as il shallow en vironmenl. but it is possible
that a high energy environment and s alt s atuT:Itio n could
occ ur in deeper wate r in the Arc haean oceans. I nte rcsting
q uestions include the effect on abiotie synthesis of hoiling in
shallow s ys tem s and high pressures in deep systems,
The early Earth was a complex , evolving system, T he
system was pro bably d ri ven then , as it is now , by mantle
convec tion th ro ugh a mec hanism of plate teclo nics. T hen.
as now , new crust formed a lo ng submarine rift sys tems and
was cooled , degassed and me tamorp hosed throush reaction
wi th seawater. We bclieve that we have convi nc ingly
demons trated that living org<lnisms could ha ve been c reated
as a resull of th is reactio n.
One of the unavoidable conclusions to be draw n from our
hypothesis is thal the evenls leadi ng to the form;ttion of
eomplell o rganie compounds and "protocell" structures
may still be occurring in present-day oceanic hydrothermal
s ys tems. However. the complex communities of b:lctcria in
modern occanic environments would outcompete :md
consume <lny abiolic ally synthes ized pro tocell s. pre ve nting
the ir evolution into more o rganized entitics. Future ellpeditio ns to occanic hydro therm;tl envÎronments will attempt to
obt;tin evidence bcaring upon our hypo thesis.
Ack nowledgements
CONCLUS IO N
l n this paper we have drawn IUgether data from diverse
scienlific disc iplioes to asse rt thM hydrothermal system .~
provide an idea l e nvironment fo r the the r mal abiotic sy nthes is of comple x orsa nic compounds a nd simple organisms.
Th is hYPolhesis is compatible with the geolugy and pilleonlology of the Arc haean and with the results of abiotie
sy nthes is ellperiments, We are pro posing thm abiotic synthesis occurred as a n intesral part of the origin and
evol ulion of the ;t tmosphere , ocean, and crusl.
S upport for this researc h was provided by the people of the
United States of Ame rica th ro ugh their Nat ional Science
Fo undation: Interna tional Decade of Ocean Exploration
Office Grant OC E75-23352 and OC E77-23978 ( Bruce Mal faÎt , Program Manager) and Oce;tnograp hy Section Gmnt
OCE78-26368 and OCE79-27283 (Neil Andersen. ]lrogram
M;tnager : Robe rt Wall. Section Head), a il made to Oregon
State Uni ve rsity. John Baross recei ved addit ional s upport
from the Office of Nav!!l Rese arch Grant No. NOOO14-79C-
T here a re three additional imeresling cons idemtions regardi ng this model :
OO()4 ,
G. Ross Hea th has provided indis pensable support. C harl e~
Miller re viewed the manuscript and offered pertinent critical advice ,Ind cncour:tgemenl. Jac k Dymond , Jo hn
Edmond , Kathy F i~c h er, Lou Gordon. Ro ge r HrlTl, Vern
Kulm. Marv Lilley. Mitc h Lyle, C hris Moser. Erwin Suess.
and ma ny o t hers provided important insighl. new information. data :t nd s uppo rt. S EH wis hes to thnnk Dr. Raymo nd
Sullivan o f San Francisco Stnle University for introducing
the topie .
Special tha nks to Al Soeldner, Laboratory Manager of the
Elec tronmicroscopy Lab. fo r valuable assis tance in oblaining the electronmicrogntphs.
Elaine S enson. S US,In Harmon, Bonnie Hommel. Nancy
Kn e isel. Regina Tisoo. a nd Pall1 Wegner have been o ur
p;ttient secretaries and typists. Dave Reincr! made the pho to
prints. f>eggy Lo re nce and S,Ill y Kulm drafted the fi gures.
1) A reducing atmos phere is not a prerequbite for Ihe o rigin
of life . An a ppropria le reduCÎng en vi ronment , with sources
for a il of Ihe rcquired mw matcrials and whieh feeds into a
pac ked-bed continous flow gradient re,lc tor lined with
appropriale catalytic s urfaces has bee n present on the fl oor
o f the oceans sincc Ihe y formcd.
2) A long time interval hetween the appea rance of a life
sus tllining e nvirunment (e.g. liquid Willer) and the nppeara nce of the fi rst living organism o n earth may not he
required . There scems to be no reason wh)' pro toce ll
structures wo uld not h;t vc been rapidly produced in these
hot springs as soon as they formed in the Arc hean oceans.
The nellt step. the evolution of protocells to living organisms. is a func tion of probabilities. a n improbable event
hecomes more probable with an increasing nurnber of trials.
67
J. B. COALISS. J. A. BA AOSS. S. E. HOFFMAN
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