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Astrobiology
Lesson4
“LifeonEarthasareference”
Theancientideas
ArewealoneintheUniverse?
ArewealoneintheUniverse?
The sky is always there. We can only speculate in
how , slowly, questions about the lights in the sky
started to be formulated
The Chinese started keeping records 5000
years ago
The Babylonians could both
record and predict eclipses of the
Sun and Moon with precision
Followed by Mayans in central
America a few hundred years
later
ArewealoneintheUniverse?
Thegreekculturebeginstoariseabout800
B.C.Andiswellestablished~500B.C.
Westernphilosophybeginswith
Thales!(Aristotles,BertrandRussel)
Thalespredictedthesolareclipseof
May28,585BC
HealsoaskedthequesPon:“Whatis
theUniversemadeof?
Thales'rejecPonofmythologicalexplanaPons
becameanessenPalideaforthescienPfic
evoluPon
ThalesfromMiletosc.624–
c.546B.C.
EarlyGreekscience
By500B.C.Greeceiswellestablishedatthe
crossroadsbetweenAfrica,AsiaandEurope
Thalescosmologicalviewinvolvedaflat
EarthfloaPnginaninfiniteocean
ThalesledtoPlato428–384B.C.è
Each philosopher introduced new ideas arguing in a
scientific way, without invoking super-natural
phenomena.
Mathematics was introduced in a serious way
WholedtoAristotele384–
322B.C.
EarlyGreekscience
Anaximander,astudentofThales(610–547
B.C.)introducedthecelesPalsphere,based
ontheapparentrotaPonoftheskyaround
thepolestar.
Around500B.C.Pythagoras(560–
480B.C.)taughtthattheEarthis
round
èThegeocentricmodel
The planets had been recognised as special
already before the Greek science appeared (planet
~ “wanderer”
EarlyGreekscience
SunandMooneachhadtheirowncelesPalspheres,
separatefromthestellarone,androtaPngattheirown
velociPesbuttheplanetswerepeculiarwithstrange
movements
Ptolemy(ca100to170A.D.)cameupwithamodelthatwouldlastfor1500years.
Theepicyclicalmodel.
EarlyGreekscience
ThePtolemaianmodelcametobethe
acceptedoneunPl1543A.D.,butalready
around260B.C.,AristarchusofSamos(c.
310–230B.C.)hadcomeupwithamodel
w/oepicyclesèTheSunisthecentre
NobodyknowhowAristarchushitontheideathatthe
Earthtogetherwiththeotherplanetsmovearoundthe
Sun
We know he actually calculated the size of the Sun and
the Moon. He also believed that the stars were other
Suns
EarlyGreekscience
ThegreekscienPficclimatewasveryferPle
andallowedformanyhypotheses.
AlreadyatthePmeofThales,thegreekphilosophers
realisedtheanswerhadimplicaPonsw.r.t.Lifeelsewhere.
Thales student Anaximander imagined that the world was not based
on water, but instead on a “mystic” element called apeiron which
means “infinite”. From the “infinite” other worlds could appear and
disappear. He made no claims about other life but other “Earths”
could exist.
Democritos postulated atoms and since worlds
appeared from random actions of atoms both worlds
and life could appear
This lead to Epicuros idea about:
There are other worlds both like and unlike this world of ours... We must
beieive that in all worlds there are living creatures and plants and other things
we see in this world
•  ButAristotelehadadifferentideabasedonthefour
elements:earth,fire,water,air
•  TheEarthrestedin“thecentralplace”because“firejut
upwardsintotheskyawayfromthecentre”,andearthfellto
thecentre
•  Aristotelediscardedthe“atomists”aroundDemocritos
•  AristoteleconcludedthattheEarthisinthecentreofthe
Universe,andthatallotherbodiesorbitit.Earthbeingunique
couldbetheonlyhomeforlife!Basedonthewrongphysics
thisidealastedcloseto2millennia
•  “Theworldmustbeunique....Therecannotbeseveralworlds”
AninteresPngsideissue....
•  Howmanycorrectideashavebeendiscardedover
theyears?
•  Makingitnecessarytoinventtheconceptsagain?
•  AnindicaPonistheAnPkyteramechanism
•  TheAnthikyteramechanismisanancientanalog
computer,thatcanpredictcelesPalbodiesposiPons,
movements,andeclipsesformanycenturies
forwardsandbackwards
•  Itwasrecoveredin1900–01fromashipwreckatthe
GreekislandofAnPkythera
•  ItsconstrucPonisdatedto150–100B.C.
•  Nothinglikeitwouldbeseenfor1600years
Intermission
•  Discussion:Whydomankindstophere?Foralmosta
thousandyears(aherthefirstChrisPanculturalevoluPon)
scienceisthreadingwater.
•  Alexander(theGreat)foundedthelibrary(andthetown)in
Alexandria~330B.C.For700yearsitwastheworldspreeminentuniversity–unPlthemobcameinthe5:thcentury
andburnedittotheground.AnPintellectuanism?Religious
fundamentalism?
•  TheIslamicscholarsduringtheMiddleAgeskeptintouch
withHinduscienPsts,ideasfromChinaèSyntheseofthe
GreekworldwhichwhenEastRomefellin1453movedwest
intoEurope
TheCopernicanrevoluPon,Enlightenmentvs
religion
•  Theknowledge“kept”bytheIslamicscholarsnow
resurfaceinmonestariesandlibrariesacrossEurope
•  CriPcalthoughthadbeenappearingforafew
hundredyearsbutnowitisapproachinga“boiling
point”
•  ItsPmeforarevoluPon
The birth of the belief in other
worlds
Theanciantideasof There
areinfiniteworldsbothlike
andunlikethisworldofours… Epicurus(c300BC)
...andBruno:“Thereare
countlesssunsandcountless
earthsallrotaPngaroundtheir
sunsinexactlythesamewayas
thesevenplanetsofoursystem…
arenowdebatedagainby…Thecountlessworldsinthe
universearenoworseandnoless
falseanddamnable… G.Galiliei(born1564) inhabitedthanourEarth GiordanoBruno,1584
inDeL'infinitoUniversoEMondi
Into this appears Nicholas Copernicus
from Torun (1473 – 1543)
NicholasCopernicus
publisheshisbookDe
revolutionibus orbium
coelestium in 1543
CopernicusstudiedLaw,
MedicineandAstronomyin
PolandandItaly.Heworked
inmanyfieldsincluding
economicsandtranslaPonof
ancienttexts
HeprobablychoseAristarchus
Sun-centeredmodelbecauseit
wassimplerwhentryingtoexplain
theretrogrademoPononthesky
oftheplanets
He also noted the errors in the positions of
stars when comparing observations with
ancient tables
•  ButhewasahesitantrevoluPonary.Inspiteofbeing
givenassuranceshedidnotpublishthe“De
revoluBonibus”unPlwhenhewasalreadydying.
Withoutthesupportofayoungastronomer,
“RhePcus”itmightneverhavebeenpublished
•  Koestlerwhohaswrilenaveryreadablebook
(“Sleepwalkers”)aboutTheancients,Copernicus,
Brahe,KeplerandGalileithinkhewasafraid,notof
theinquisiPon,butofbeingridiculed
•  IttookPme,however,beforehismodelwasadopted
•  Itmadeabigsplashbutwasconsideredjustanother
model
•  Copernicushadonlymade21observaPonsinhis
wholelifeandofverypoorquality
•  HismodelofaSuncenteredsystemwasposiPvely
beggingforbelerdata
•  AndtherewasaDanetoprovideit
Tycho Brahe (1546 – 1601)
DanishNoblemanwhogot
interestedinAstronomywhen
observingapredictedsolar
eclipsein1560
HestudiedinmanyEuropean
UniversiPesincludingRostock
wherehelosthisnoseina
dueltudiedinPolandand
Aherreturninghomehewentto
theislandofVen,builtacastleand
twogiganPcobservatories(the
VLTofitsday)andstarted
observingstarsandplanets.He
discoveredtheSupernovain1572
wasNOTan
atmosphericphenomenon
He became world
famous and made an
adjustment to Copernicus model
Tycho Brahe (1546 – 1601)
Johannes Kepler (1571 – 1630)
Born in Germany. Also Inspired by
astronomical phenomenon (comet of 1577)
and eclipses of the Moon
Studied Religion, mathematics, astronomy
and astrology but was to argumentative to
be a priest so he got the job as
“Mathematicus” in Graz, developed a
model of the Solar System/Universe
based on hocus pocus of the Greek 5
solid figures
He wrote about science and started an
exchange of ideas with Brahe and Galileo
Johannes Kepler (1571 – 1630)
Born in Germany. Also Inspired by
astronomical phenomenon (comet of 1577)
and eclipses of the Moon
Studied Religion, mathematics, astronomy
and astrology but was to argumentative to
be a priest so he got the job as
“Mathematicus” in Graz, developed a
model of the Solar System/Universe
based on hocus pocus of the Greek 5
solid figures
He wrote about science and started an
exchange of ideas with Brahe and Galileo
AherjoiningBrahewhohadmovedtoPrague,hereplacedhimas
imperialastronomer/mathemaPcianatBrahe’sdeathin1601
Kepler now becomes the first modern astronomer. He uses
Brahes exquisite observations to formulate the Keplerian laws
1.  The orbit of the planets are ellipses with the Sun in one focus
2.  As a planet moves around the Sun its radius vector sweep out equal areas in
equal time
3.  The square of the orbital period equals the cube of the distance of the planet to
the Sun
Galileos physical laws of motion is the final weapon
overturning Aristotele and Ptolemaios. His observations of
Venus phases, the Jupiter moons, as well as sunspots and
lunar craters makes way for Isaac Newton and the modern
times have arrived. He found that the stars are at great
distances
Now,slowlybutcertainlyenlightenmentbringsback“Astrobiology”
AlreadyKeplerwritesascienceficPonnovelaboutatriptothe
Moon
WilliamHerschel(1738-1822)claimedthattheplanetswere
inhabited
AndPercivalLowelltogetherwithmanyotherstowardstheendof
the19:thcenturywereconvincedthatMarswasinhabited
Lowellgoeswildwithastrobiology
FromhisprivateobservatoryinFlaggstaffArizonaheobserves
Mars...
Hediscoversanextensivenetworkofcanalsacrossthesurfaceand
interpretthisas....
Theengineeringtriumphbyanancientracecarryingwaterfrom
thepolesofadyingworldtowardstheequatorregions
ButhehadatoocreaPveeyesight....Whathesawwasthisè
The period of enlightenment is a period of great freedom of thought and the
strong leadership of the churches is weakening.
Revolution takes place in many countries
At the same time we find the concept of the central place of mankind as well as
the earth is diminishing.
The Sun is an ordinary star, in an ordinary system of stars with an ordinary group
of planets orbiting it. This must mean that we are also ordinary as life and that
the Universe must be full of life
But is this proven by anything we have said?
And why did one change from the “Earth centric” to “the Earth is just a
common grain of dust in an infinitely large Universe”
Astrobiology turns into a science.
Astrobiology
•  Whatisastrobiology?
–  Astrobiologyisthestudyoftheorigin,evoluPon,
distribuPonandfutureoflifeinthewholeUniverse
•  Howcanitbeaddressed?
–  BystudytheeventsontheEarth,bysearchingforsignsof
lifeontheplanetsintheSolarSystem,bysearchinginthe
restoftheUniverse
–  Byusingacrossdisciplinarymethodincludingeverything
fromgeophysicstoSETI
–  AstrobiologyaddressesahostofquesPons.Some
examples:
FormulaPonofAstrobiologicalQuesPons
•  TheEarth
–  BaselineforunderstandingtheoriginandevoluPonoflife
–  HowistheEarthchangingwithPmenowandinthefuture?
•  TheSun
–  OriginandevoluPonoftheSun
–  HowdoestheSun’sfluxvarywithPme
–  WhataretheimpactsonlifeontheEarthandtheSolarSystem
•  TheSolarsystem
–  Howdidthesun'sfamilyofplanetsandminorbodiesoriginate?
–  Howdidthesolarsystemevolvetoitscurrentdiversestate?
–  HowdidlifebeginandevolveonEarth,andhasitevolvedelsewhere
intheSolarSystem?
–  WhatarethecharacterisPcsoftheSolarSystemthatleadtothe
originsoflife?
TheEarth’sclimate
•  Earth’sclimatehasbeenconstantlychanging
essenPallysincethebeginning!
–  E.g.TheEarthhasexperiencednumerousice-agesinterspersedwith
warmperiodsinthelastmillionyears
–  E.gTheEarthexperiencedasignificantwarmerclimateduringmostof
Trias,JuraandtheCretaceous(maybe+10to15degCelcius)
•  TodaythetemperatureoftheEarthiswarmingup
again
–  0.6degCinlastcentury
–  Thiscouldbefasterthaneverbefore
–  Humansappeartobethereason
TheEarth’sclimate
•  TheEarthmayhavebeencompletelyfrozen–manyPmes
–  650MyrsagoasevidencedbyglacialdepositsattropicallaPtudes
–  PaleomagnePsmèwherelandmasseswere~650Myrsago
–  Neoproterozoic(1Gyrto541Myr)lowlaPtudelayersindicateglacial
deposits
–  Openseadeposits(depthsof5-6000m)
–  BandedIronFormaPons(BIF:formonlyonanoxicoceans)
•  Triggermechanism:SomethingdeplePngthegreenhouse
gasesintheEarth’satmosphere
•  ThiscoolstheEarthandincreasesthereflecPonofSunlight
intospace
•  TheglaciaPonsmayhaveclearedthewayforthenextstep
During the Neoproterozoic the Earth’s rotation rate decreased and day = 22h, the
Sun’s luminosity went from 94% to 95% of today
Most dramatic events: two great
glaciations—the Sturtian at 720 Myrs
and the Marinoan at 635 Myrs
Metazoan life (multi-cell,
specified organs, internal
cavities) arise at end of
Neoproterozoic è Cambrian
Explosion 541 Myrs ago
Metazoan life (multi-cell, specified organs, internal cavities) arise at end of
Neoproterozoic è Cambrian Explosion 541 Myrs ago
The "Cambrian explosion" consist of
two phases of metazoan expansion
into empty niches:
first, an unprecedented rise in
diversity as animals explored niches
on the bottom of the sea,
a second expansion in the early
Cambrian as metazoan life becomes
established in the water column
The rate of diversification seen in the
Cambrian phase of the explosion is
unparalleled among marine animals
Cambrian explosion, about 541
million years ago. Animals are
divided into various sub-groups,
some of which are: vertebrates
(birds, mammals, amphibians,
reptiles, fish); molluscs (clams,
oysters, octopuses, squid, snails);
arthropods (millipedes, centipedes,
insects, spiders, scorpions, crabs,
lobsters, shrimp); annelids
(earthworms, leeches); sponges; and
jellyfish.
LifebeyondtheEarth?
•  WedonotknowwhenorhowlifearoseonEarth
•  WeknowverylilleabouttheevoluPonoflifeforthe
first~4Gyrs
•  Wedonotknowwhyaher~4Gyrwehadthe
“CambrianExplosion”
ModernScience
•  Astrobiologymustconformtotheprinciplesof
modernscience
•  Thestoryhowwewentfrompurephilosophyto
modernscienceduring2000yearsshouldbeour
lesson
•  WemustbecarefulwithspeculaPonandonlyletus
beguidedbyspeculaPon–CarefullystaPngwhatis
knowledgeandwhatisspeculaPon
Make observation
Ask a question
Suggest a hypotheses
Make a prediction
Test prediction
Test does not support
hypotheses è
Revise hypoteses
Test supports hypotheses è
Make additional predictions,
test
Hallmarksofscience
Progressesthrough
creaPonandtesPngof
modelsthatexplain
observaPons(as
simplyaspossible)
SeekexplanaPonsthat
relyonlyonnatural
causes
Science
Makestestable
predicPonsabout
naturalphenomena.If
predicPonsdoesnot
testoutmodelmustbe
revisedorabandoned
Occamsrazor
IfscienPstshadonlyevaluatedCopernicusmodelquanPtaPvelythey
shouldhavediscardedit
InsteaditwasnotedthatitexplainedthingsliketheretrogrademoPon
whichappealedtoscienPstsunPlKeplerfixeduptheinputdataofthe
observaPons
ScienPstscouldhavemadeamodelwithepicyclesthatfitCopernicus
databutitwouldhavebeenextremelycomplex
WilliamofOccam(1285–1349)formulatedtheideathatscienPsts
shouldprefer(first)thesimpleroftwomodels.Thisiscalled“Occams
razor”
VerifiableObservaPons
•  WhatisacorrectobservaPon?
•  Mostwitnessesarealoneinobservinganevent–yetitworks
incourt!
•  Ontheotherhand,literallythousandsofpeoplehaveseen
flyingsaucersandotherUFO’s
•  NeitherisascienPficobservaPonunlessitisverifiable
•  ToparaphraseSpiderman“Extraordinarystatementsneed
extraordinaryevidence
•  AscienPficallyverifiableobservaPonfitsthebill
Issuesofastrobiology
• 
• 
• 
• 
• 
• 
Whatislife?
Cellsandthechemistryoflife
RNAandDNAlife
Extremophiles–dotheytellussomething?
Couldlifebeverydifferent?
Howlikelyislifetoarise?
Abriefhistoryoflife
•  AlllifeonEarthisprobablyrelatedandgoesbacktoa“first
cell”~4Gyrsago
•  Theoldestfossilsareprobably(thestromatolites)simpleonecellularmicrobes(Cyanobacteria)agowithnonucleus(~3.5
Gyr).Procaryotes.DominatethePre-Cambrian(super-Eon)
•  2Gyrscellswithanucleusevolved.Eucaryotes
•  MulPcellularlifeareknownfrom650–542Myrsago.The
firstsignsarefossilisedtracksofwormlikelife
•  542MyrCambrianexplosion(TheBurgessshalefossils)
•  Organismswithshellsand(exo-)skeletonsappear
•  FirstVertebrates(488-416MyragoOrdovicium),Jawlessfish
Abriefhistoryoflife
Firstplantsonlandnotlaterthan444-416Myrago(Silur)
Firstfrogs416-359Myrago(Devon)
Firstmammals251-200Myrago(Trias)
Firstprimates(endofCretaceus)66Myrago
SeparaPngfromourcousins(Chimpanzees)7-6Myrago
HomoErectus~1Myr–143Kyrago
HomoHeidelbergiensis,Neanderthalensis,Denisovans800Kyr
–40Kyr
•  HomoSapiens200Kyr-.....
• 
• 
• 
• 
• 
• 
• 
Lifeoritsbuildingblocksarrivingfromspace
•  TheMurchisonmeteoritefellindaylightoverMurchison,Victoria,
Australiaon28/91969.Itwaswidelyobservedasafireball,breakinginto
atleast3fragmentsasitwasobservedandanimpacttremorwasfelt
•  100kgofmasswascollectedinfragmentsofupto7kgoveranareaof13
km2includingoneinsideabarn
•  Over15aminoacidsplusahostofotherorganiccomponentshavebeen
idenPfied.AmountsaresimilartothosefoundintheMillerexperiment
•  Sofarnoorganiccompoundshavebeenretrievedfromacomet,but
observaPonsofHalley’sandothercometshavedemonstratedthe
presenceofcarboniccompoundssuchashydrogencyanideand
formaldehyde.Alsoadenine,oneofthebasesinnucleicacids(likeDNA)
wasseeninHalley
•  Injustafewweeks,ESAwillalempttolandalaboratoryonthecomet
67P/Churyumov–Gerasimenko
TracesofearlylifeonEarth
•  WecannotreallyexpecttofindtracesofthefirstlifeonEarthsinceitwas
verysimpleandprimiPveandourplanethavebeenre-cycled
•  EarlyevoluPonappear,however,tohaveproducedmicroorganismsthat
usedSunlightgavetracesinthefossilrecordthatcanbefoundaher3Gyr.
•  CyanobacteriaformedveryearlyanddominatedtheEarthforatleast1
Gyr.TheyproducedfreeoxygenandthuschangedtheEarth’satmosphere
•  SomeresearchersclaimthatfossiltracesofStromatolitesexistthatare
3500millionyearsold.Thesearecoloniesofcyanobacteriawhichproduce
mineralisedmatsthatsPllexist
Fossilised stromatolite
TracesofearlylifeonEarth
•  Evenolderlifeisindicatedinmetamorphicsedimentaryrocks
(metamorphicmeanschangeofformandthechangeis
causedbyveryhightemperaturesand/orpressure)
•  Nofossilsremainintheserocks
•  Butcarboncompoundsfoundintherocksdemonstratean
isotopicalraPo(C12/C13)thatindicateCarbonbeingingested
fromtheatmospherethroughphotsyntheses.Agesashighas
4.4Gyrhavebeencalculated
•  OldironorescontainlayersofironoxideindicaPnghighlevels
ofoxygenintheoceansveryearlyinEarth’shistory
Consequencesofanoxygenbasedatmosphere
•  TheoxygenproducPoncausedthestrongestchangeofthe
condiPonsonEarth-ever
•  Cyanobacteriaproducedoxygenandcausedthedemiseof
thebiosphereprevioustotheirevoluPon-possiblyeven
themselves
•  ThechangefromCO2toO2inouratmospherediminishedthe
greenhouseeffectandtheEarthbecamecooler–possibly
evencausingaglobaliceage
•  Luckily,thiscoolingwas–inthelongterm–compensatedby
theSun’sincreasingluminosity
Consequencesofanoxygenbasedatmosphere
•  TheproducPonofO2andtheevoluPonofEarth’satmosphere
wasNOTaccompaniedbyextremechangesinthelifeon
Earth
•  WeknowthattherewassimplelifeonEarthforalmost2Gyr
sincetheevoluPonofthecyanobacteria,butnocomplexlife
•  The500-600Myragoaveritableexplosionoflifeappearedon
EarthinarelaPvelyshortPme(tensofMyr)
•  ThereasonforthesuddenradiaPon–calledtheCambrian
explosionorradiaPon–isnotknown.
Consequencesofanoxygenbasedatmosphere
•  Hypothesesincludeglobaliceages“snowballEarth”which
clearedoutecologicalniches,thepossibilitythattheO2+UV
èO3(orOzone)ontopoftheEarth’satmospherecreateda
filteragainsttheharmfulX-rayandUV-radiaPonfromtheSun
allowingthedevelopmentofcomplexlife
•  PriortotheCambrianexplosionmostorganismsweresimple,
composedofindividualcellsoccasionallyorganizedinto
colonies
•  ItisimportantinAstrobiologybecausefindingthecausemay
tellussomethingaboutthePmescaleoftheevoluPonoflife
Whatislife(Clausius,1865)
•  Clausiusformulatedthefirsttwolawsof
thermodynamics
•  1:TheenergyoftheUniverseisconstant
•  2:Theentropy(degreeofdisorder)oftheUniverse
tendstoamaximum
•  Boltzmanspeculated:“Thegeneralstruggleforthe
existenceofanimatebeingsisnotastruggleforraw
materials,norforenergy,butfornegaBveentropy,
availablebythetransiPonofenergyfromthehot
SuntothecoldEarth
StanleyMiller’sexperiment
•  A.Oparin(1894-1980)suggestedin1920:Pesthatareducingatmosphere
withHandhydrogenatedmoleculestogetherwithelectricdischargesand
UvradiaPonèchemicalreacPonsimportantforthechemistryoflife.
•  HaroldUrey(1893-1981,Nobelprizein1934,discoveryofD)suggestedan
experimenttohisstudentStanleyMiller(1930-2007)whichhecarriedout
in1953
•  Hecreatedreducingatmospheresinthelabandpassedelectricdischarges
throughit
•  Aherafewdayshefoundsomeblackgoointhetestvessel:
–  AsparPcacidandButyricacid–nosurprisesthere.
–  Thesecondmostcommonsubstance,however,wasglycinthesimplestaminoacid
–  Andnumber4wasalaninanotherimportantaminoacid+somemoreaminoacidsin
significantamounts
And amino acids are the building blocks of proteins! è Biochemestry!
StanleyMiller’sexperiment
•  ProblemisofcoursethatwealreadyfoundthattheEarthwouldloseitsH,
H2andrapidlygetanatmosphereofN2andCO2whichdoesnotallowthe
resultsofMiller’sexperiment
•  MillerconPnuedtoworkfortherestofhislifeandotherideashavebeen
tested:
–  MethaneejectedfromvolcanosintoaCO2richatmospheregivessomeaminoacidsbut
notinsuchgreatamounts
–  ModerncalculaPonsindicatethattheEarthwouldhavebeenlosingitsHmuchslower
thanpreviouslysuggestedèLifecouldhavehadPmetostart
•  Areducingatmosphereandcoldseas/oceansseemtobeastarPngpoint
forcreaPnganenvironmentintowhichthebuildingblocksoflifecould
havebeenformed.AlotofCH4isalsorequiredplussuitableenergy
sources
•  ComparedtootheralternaPvesincludingthepresentEarth,these
condiPonscouldbesearchedforaroundexoplanetswithadvanced
instrumentsanditwouldhelpiftheplanetwaslargerthantheEarth
(moreHandH2isretained)èSuperEarth
Whatislife
Schrödinger’sparadox(1944)
•  Inaworldgovernedbythe2ndlawofthermodynamics
isolatedsystemsareexpectedtotendtoastateofmaximum
disorder.
•  Lifeapproachesandmaintainsahighlyorderedstate–does
thisviolatethe2ndLaw.Aparadox?
•  Lifeisnotanisolatedsystemènoparadox.Whynot?
•  Theincreaseoforderinsideanorganismiscompensated
morethanenoughbytheincreaseindisorderoutsidethis
organism.Thehighlyorderedstate,issustainedbycausinga
netincreaseindisorderintheUniverse.
•  ThecomplexityonEarthcausedbyliferequiresenergymostly
providedbytheSunandsupernova(radioacPvity)è
increasesentropymorethanlifediminishit
Whatislife
Schrödinger’sparadox(1944)
•  SoweliveincloseconnecPonwiththeUniverseandnot
separatefromitinanyway
•  Laterwewillseethisagainwhendiscussingphotosyntheses
andhowthisconnectlifeonEarthwiththeSun
•  IstheUniverseintendedforlife?Thisisabigissuein
Cosmology
•  ParallelUniverseswithdifferentnaturallaws(aninfinite
amountsolvethisissue
Biochemistry,moleculargenePcsand
metabolism
•  MoleculesbuildinguplifeonEarthconsistofC
boundtootherCatomswithcovalentbonds
•  AcovalentbondisachemicalbondconsisPngof
sharedelectronpairsbetweenatoms
•  BondsareformedbetweenC=CandwithH,OandN
Biochemistry,moleculargenePcsand
metabolism
Covalentbonds
Waterisauniquemolecule
•  ThebindingsbetweenHandOrestronglypolarized
•  TheanglesbetweenHandOformadipolèH2Ocanform
weakchemicalbondswithchargeddissolvedmoleculesand
inorganicionsçèwaterisaverygoodsolvent
•  ThebondsbetweenindividualH2Omoleculesgivewaterhigh
melPngpoints,boilingpointsandsurfacetension
•  WatercanbeionizedintoH3O+andOH-(oxoniumand
hydroxyl)andbehaveaseitheranacidorabaseandhigh
electricconducPvity
•  LifeisprobablynotpossiblewithoutH2ObutalternaPves
suggestedinclude:
–  Ammonia,NH3
–  Formamide,CH3NO
Waterisauniquemolecule
Ammonia
Formamide
LifebasedonAmmonia,NH3andFormamide,CH3NO
wouldbeverydifferentandhaveacompletely
differentbiochemistry
LifeasweknowitisbasedonCarbon
•  CarbonhasthepropertythatwithH,O,Nitcanform
anenormousamountofdifferentandbothsimple
andcomplexmolecules–organicmolecules
•  Secondly,smallerorganicmolecules(nucleoPdes,
aminoacidsandmonosaccharides=simplesugars)
havethepropertythattheycanformlongchains
•  ExcepBonsareCO2andcarbonatemineralswhicharenot
considertobeorganic
•  E.g.DeoxiribonNucleidAcid(DNA),RiboNucleidAcid
(RNA),proteinsandcarbohydrates
LifeasweknowitisbasedonCarbon
DNA