astrrobiology lesson 8mackie/astrobio/files/abl8.pdf · the interstellar medium – the cradle of...

Astrobiology

Lesson8Discussion

Astrobiologyinanutshell

AcompletecourseinAstrobiologydealswiththefollowingitems:

-  Ancientideas,Copernicanrevolu?on,Enlightenmentvsreligion-  LifebeyondtheEarth,-  LifeinthesolarsystemvslifeintheUniverseasawhole.-  Fundamentalques?onsconcerningtheoriginandevolu?onoflife

onEarthandtheimplica?onsforlifeintheUniverse -  WhereandhowdowesearchforlifeoutsidetheEarth?-  IntelligentLife(SETI)

Butmostimportant:Whyshouldwebeinterestedin“LifeintheUniverse?”AOerall,WealreadyknowthatlifeexistintheUniverse!Sowhatisthebigdeal?(Actualquote)

Well....

•  Dowehaveneighbors?Itisinteres?ngifsomebodylivesacrossthehallway....

•  WedonotknowhowlifearoseonEarth....•  Wasitaneasyprocess–andthereforealikelyoutcomeofthecondi?ons?

•  Orwasitadifficultprocess–andthereforeunlikelytohappen

•  Astrobiologyisanewscience–thisishowitestablishitself?

ArewealoneintheUniverse?

The birth of the belief in other worlds

“Thereareinfiniteworldsbothlikeandunlikethisworldofours…withlifelikaandunlike”Epicurus(c300BC)

“…falseanddamnable…”G.Galiliei(born1564)

“Therearecountlesssunsandcountlessearthsallrota?ngaroundtheirsunsinexactlythesamewayasthesevenplanetsofoursystem…ThecountlessworldsintheuniversearenoworseandnolessinhabitedthanourEarth”GiordanoBruno,1584inDeL'infinitoUniversoEMondi

ButAristotelearguedthatthiswasNOTthecase

Today

•  “Some?mesIthinktheUniverseisfulloflifeandsome?mesIdonot.Eitherwayisequallyamazing”–ArthurC.Clarke

•  “Theremustbebillionsandbillionsofworldswherelifearose.Some?mesIthinkthereisanEncyclopediaGalac?caouttherewhichwehavenotyetbecomepartof....”–CarlSagan

Thishasledtotheaskingof‘BigQues?ons’like....

“WhatistheuniquenessofourownEarth?”

“Arewe(lifeforms)alone?”

“Whatisourpast&future?”-Theforma?onofplanets-Theevolu?onofplanetarysystems

Cosmic Vision is centered around four Grand Themes: 1.  What are the conditions for planet formation and

the emergence of life?

•  From gas and dust to stars and planets

•  From exo-planets to biomarkers

•  Life and habitability in the Solar System

2.  How does the Solar system work?

3.  What are the Fundamental Physical Laws of the Universe?

4.  How did the Universe originate and what is it made of?

Cosmic Vision is centered around four Grand Themes: 1.  What are the conditions for planet formation and

the emergence of life?

•  From gas and dust to stars and planets

•  From exo-planets to biomarkers

•  Life and habitability in the Solar System

2.  How does the Solar system work?

3.  What are the Fundamental Physical Laws of the Universe?

4.  How did the Universe originate and what is it made of?

First: In-depth analysis of terrestrial planets. Next: Understanding the conditions for star & planet formation, and the origin of life. Later: Census of Earth-sized planets, exploration of Jupiter’s moon Europa. Finally: Image terrestrial exoplanet.

Therealisa?onthatforthefirst?meinhistorywecandomorethanspeculate

LifebeyondtheEarth?

•  Thereisagreatgeneralinterestintheques?on:–  Viz.Films,TV,UFO’s,PersistentrumoursaboutArea51,etc.

•  Butalsoscien?stsareinterestedforanumberofreasons:– WedonotreallyknowhowlifearoseontheEarth– WedonotknowwhattheroleoflifeintheUniverseis– Wedonotknowmanyoftheevolu?onarystagesonEarth

•  ItisclearthatthediscoveryofanykindoflifeoutsidetheEarthwouldhaveanenormousimpact

LifebeyondtheEarth?

•  Sowhatarewegoingtolookfor:–  TheintelligentlifeportrayedinfilmslikeStartrek?Orourselves?

–  Giraffes,PlatypusorHamsters?–  Simpleonecellularlifelikethatinhabi?ngourEarthformostofitshistory?~4Gyrs

•  Alloftheabove–ThehistoryoflifeonourEarthmakesthatclear.Modeledonourownexperience

•  Caveat:Somehowwewillhavetoaddresstheques?onthatlifecouldbeverydifferent(Oblivion)

Astrobiology

•  SoAstrobiologyisthestudyoftheorigin,evolu?on,distribu?onandfutureoflifeinthewholeUniverse

•  Howcanitbeaddressed?–  BystudytheeventsthattookplaceontheEarth,bysearchingforsignsoflifeontheplanetsintheSolarSystem,bysearchingintherestoftheUniverse

–  ByusingcrossdisciplinarymethodsincludingeverythingfromgeophysicstoSETI

Astrobiologyisanewscience-howdoesitestablishitself?

Astrobiology

•  Byclarifying,eventually,oneofthegreatques?ons:ArewealoneintheUniverse?

�Bydemonstra?ngitsvaluetounderstandlifeonEarthanditsevolu?on

� Bydemonstra?nghowwecanunderstandthepastandfutureevolu?onoftheSolarSystem

LifebeyondtheEarth?

•  ButtheissuesarecenteredwhenconsideringlifeontheEarthitselfanditsorigin

•  WedonotknowwhenorhowlifearoseonEarth•  Weknowverylikleabouttheevolu?onoflifeforthefirst~4Gyrs

•  WedonotknowwhyaOer~4Gyrwehadthe“CambrianExplosion”leadingtoallphylathatexistonEarthtoday

Howcansciencehelpusanswerthefundamentalques?onsconcerningwherelife

comesfromandhowitisformed?

FirstweconsiderlifeontheEarth?

•  Threeimportantques?ons:•  Whatislife?•  WhendidlifebeginontheEarth?•  AndhowdidlifeariseontheEarth?

Whatislife(Clausius,1865)

•  Clausiusformulatedthefirsttwolawsofthermodynamics

•  1:TheenergyoftheUniverseisconstant•  2:Theentropy(degreeofdisorder)oftheUniversetendstoamaximum

•  Boltzmanspeculated:“Thegeneralstrugglefortheexistenceofanimatebeingsisnotastruggleforrawmaterials,norforenergy,butfornega4veentropy,availablebythetransi?onofenergyfromthehotSuntothecoldEarth

WhatislifeSchrödinger’sparadox(1944)

•  Inaworldgovernedbythe2ndlawofthermodynamicsisolatedsystemsareexpectedtotendtoastateofmaximumdisorder.

•  Lifeapproachesandmaintainsahighlyorderedstate–doesthisviolatethe2ndLaw.Aparadox?

•  Lifeisnotanisolatedsystemènoparadox.Whynot?•  Theincreaseoforderinsideanorganismiscompensated

morethanenoughbytheincreaseindisorderoutsidethisorganism.Thehighlyorderedstate,issustainedbycausinganetincreaseindisorderintheUniverse.

•  ThecomplexityonEarthcausedbyliferequiresenergymostlyprovidedbytheSunandsupernova(radioac?vity)èincreasesentropymorethanlifediminishit

WhatislifeSchrödinger’sparadox(1944)

•  Soweliveincloseconnec?onwiththeUniverseandnotseparatefromitinanyway

•  LaterwewillseethisagainwhendiscussingphotosynthesesandhowthisconnectlifeonEarthwiththeSun

•  IstheUniverseintendedforlife?ThisisabigissueinCosmology

•  ParallelUniverseswithdifferentnaturallaws(aninfiniteamount)solvethisissue

Abriefhistoryoflife

•  AlllifeonEarthisprobablyrelatedandgoesbacktoa“firstcell”~4Gyrsago

•  Theoldestfossilsareprobably(thestromatolites)simpleone-cellularwithnonucleus(~3.5Gyr).Procaryotes

•  2Gyrscellswithanucleusevolved.Eucaryotes•  Mul?cellularlifeareknownfrom650–542Myrsago.The

firstsignsarefossilisedtracksofwormlikelife•  542MyrCambrianexplosion(TheBurgessshale)•  Organismswithshellsand(exo-)skeletonsappear•  FirstVertebrates(488-416MyragoOrdovicium),Jawlessfish

Abriefhistoryoflife

•  Firstplantsonlandnotlaterthan444-416Myrago(Silur)•  Firstfrogs416-359Myrago(Devon)•  Firstmammals251-200Myrago(Trias)•  Firstprimates(endofCretaceus)66Myrago•  Separa?ngfromourcousins(Chimpanzees)7-6Myrago•  HomoErectus~1Myr–143Kyrago•  HomoHeidelbergiensis(thebrightestofthelot),

Neanderthalensis,Denisovans800Kyr–40Kyr•  HomoSapiens200Kyr-.....

Observations of forming stars demonstrate that this happens in dense clouds of atomic and molecular gas observed in the Milky way and other galaxies

Inordertohavelife,wefirstneedaplanet

Observa?onsshowforma?ononbothgalac?c

Stars, planets and the Interstellar Medium (ISM)

andintergalac?cscales

As far as we know, life must begin with complex organic molecules

The Interstellar medium – the cradle of Planets and life(?)

Such molecules can form on a planetary surface but also in interstellar space

~ 10% of the (visible) mass of the Galaxy consist of gas and dust between the stars and half of this mass is in molecular form

Significant amounts of this gas is found in dense clouds and these are the precursors of stars and planets

Stars and planets thus form embedded in a gas consisting partly of organic molecules – i.e. Molecules built with Carbon atoms


Molecules similar to nucleotides, fatty acids, carbohydrates and amino acids

è Prebiotic molecules are found all over the universe

But processes forming interstellar molecules are different from those occurring on the Earth


Buckminster-Fullerene C60 Crab supernova remnant (1054 A.D.), creating heavy elements, ejecting them into interstellar medium

Starsforminclusters

•  Mostmolecularcloudscontainbetween104and>106solarmassesofgas.

•  Thereisthusenoughtoformalargeamountofstarsineachcloud

In the interstellar gas are found Polycyclic Aromatic Hydrocarbons (PAHs). Consist only of Carbon and Hydrogen in multiple rings


It has been observed that PAH’s in space transform through hydrogenation, oxygenation and hydroxylation è Organics

è Formation of amino acids and nucleotids è may form è Proteins and DNA respectively

But most important è ISM leads to Stars and planets

We know about 145 different molecules that have been detected (almost exclusively in the micro wave region – mm and sub-mm λ) in the interstellar medium

Theforma?onoftheSunandPlanetsintheSolarSystem

•  Firststeptowardslifewastheforma?onoftheEarth•  Condi?onsonEarthatforma?onareimportanttotrytoformapictureofhowlifefirstappeared

•  Thestar?ngpointwasadensemolecularcloudconsis?ngofgasanddust

•  Rela?velyhighdensity•  Rota?ng–containingangularmomentum•  Contrac?ng–conver?ngpoten?alenergytokine?cenergy


•  Theaccre?nggasformedadiskofvaryingcomposi?on•  Forma?onofclumps•  Metalrichelementsformedgrainsofiron,nickel,refractorymaterialsininnerpart

•  Grainsconsis?ngoficesfurtheroutbeyond‘snowline’•  Metalsoriginateinstellarwindofredgiantstarsandin

supernovaexplosions•  Supernovamaybepartofprocessstar?ngcollapseofdenseISMclouds

•  TheSunbecamehokerandhoker•  Highdensity•  Rota?ng–containingangularmomentum•  Contrac?ng–conver?ngpoten?alenergytokine?cenergy


•  AngularmomentumandEnergywasconserved•  Fasterrota?on•  Highertemperature•  Concentra?ontocenter(99.8%ofmass)èForma?onoftheSun

•  TheSunwasnowaT-Tauristar.Variable.Finally,contrac?onèdensityandtemperatureinthecenterarehighenoughfornuclearreac?onstobegin.

•  Largeamountsofenergyreleased•  Contrac?onbalancedbyreleaseofnuclearenergyHèHe•  Sunbecomesstableandthesolarsurfacebecomescooler(~25%coolerthantoday)è“faintyoungSun”.

•  TheSolarradia?onbecomeseventuallystrongerbecausetheSun(itscore)becomesmorecompressedandhokerasthecenterisfilledwithHe


•  Theclumpsinthesurroundingdisknowformtheplanets.•  Clumpsmergeandcontractgrainsèpebblesèbouldersèplanetesimalsèplanets

•  TheEarthnowbecameveryhot(1000K?)throughcontrac?onandsolarradia?on

•  Toohightemperatureforicesandothervola?lesatEarth’sdistancefromtheyoungSun

•  EarthandinnerplanetsforminaregionwithFe,Ni,simpleminerals(refrac?ve)asSiOandMgOçèJustasmallfrac?onofgasdiskmass

•  Furtherout(beyondthe“snowline”)planetsformfromH,He,Ne,H2O,moleculeswithC,Nformlargerplanets(moregaseousmaterialpresent)


•  Timeframeafew?mes107years(?)•  Manymoreplanetsformed–someejected,somemergedwiththeSun?

•  Dynamicalinterac?onbetweenlargeplanets•  Voidsandlargeaggregatesofsmallplanetesimalsinteractandcollide

•  E.g.The“Nicemodel”•  TheNicemodelisascenarioforthedynamicalevolu?onof

theearlySolarSystem•  Itsuggeststhatthemigra?onofthegiantplanetsfroma

morecompactarrangementaOerthedissipa?onofthegasinthesystemleadeventuallytothecurrentconfigura?onwhichisstableofmanybillionsofyears


•  TheNicemodel•  FormulatedbyMorbidelli,Leavisonandco-workers(2006)

•  Dynamicalcalcula?onsexplainhistoricaleventslike

•  theLateHeavyBombardment(+800Myr),•  ThechangeofplacesofNeptuneandUranus(+1Gyr)•  theforma?onoftheOortcloud•  Theforma?onoftheKuiper-Edgeworthbelt•  Theforma?onoftheJupiterandNeptuneTrojans•  Theforma?onofthetrans-NeptunianObjects(Pluto,etc)


•  TheNicemodel

Simulation showing the outer planets and planetesimal belt: a) early configuration, before Jupiter and Saturn reach a 2:1 resonance; b) scattering of planetesimals into the inner Solar System after the orbital shift of Neptune (dark blue) and Uranus (light blue); c) after ejection of planetesimals by planets


•  Theforma?onofEarth’sMoon•  TheMoonisthoughttohaveformednearly4.57billionyearsago,not

longaOerEarth•  ThereareseveralhypothesesbutmostacceptedisthattheMoonformed

fromdebrisoftheimpactonEarthbyaMarssizedbody

This has been observed recently in the case of HD172555


•  Intheouterreachesofthesolarsystemlargenumbersofsmallbodies(totalmassisratherlow)areformedandprobablyejectedhalfwaytotheneareststars(Oortcloud,containingprimoridalmaker)

•  ThesebodiesconsistofH,He,H2OandCH4.•  Therightenvironmenttoformpre-bio?ccompoundswithO,CandN

67P/Churyumov–Gerasimenko

Theevolu?onoftheyoungEarth

•  TheyoungEarthwasbuiltbyminerals(fromdustgrains).•  Originallyitwasveryhotonthesurface(~1000K)buteventuallythe

gravita?onalcontrac?onalongwiththeheatfromradioac?veheavymetalsheatedthecentralparts

•  Thesebecameelas?candeventuallyfluidsuchasitistoday.AllheavyelementschieflyFeandNisanktothecenterandformedacoreèIncreasedthetemperature.

•  Con?nentalplatesmayhaveformedearly(solidrockfloa?ngonanelas?cmedium)

•  Remnantsoftheforma?onoftheSolarSystemcollidedregularlywiththeplanetsandbroughtsubstancesthatdidnotexistoriginallyinourpartofthesolarsystem(WaterandCarboniccompounds)

Further(possible)evolu?onoftheyoungEarth

•  PartoftheancientEarthwouldhavebeendisruptedbytheimpactcrea?ngtheMoonwhichshouldhavecausedmel?ngofoneortwolargeareas.Presentcomposi?ondoesnotmatchcompletemel?nganditishardtocompletelymeltandmixhugerockmasses

•  However,afairfrac?onofmaterialshouldhavebeenvaporizedbythisimpact,crea?ngarockvaporatmospherearoundtheyoungplanet.Therockvaporwouldhavecondensedwithintwothousandyears,leavingbehindhotvola?leswhichprobablyresultedinaheavyCO2atmospherewithHandH2O

•  Liquidwateroceansexisteddespitethesurfacetemperatureof230°CbecauseoftheatmosphericpressureoftheheavyCO2atmosphere(60bar)

•  Ascoolingcon?nued,subduc?onanddissolvinginoceanwaterremovedmostCO

Geological?ming

•  Howcanwedatethestagesintheearlyevolu?onofourplanet?•  Mainlyusingradioac?ves.MostlytheUranium-Leadchainofdecay•  TheUranium-Leadradiometricda?ngschemetodayèanerrormarginin

rocksthat<twoMyrin21/2Gyr•  TherearenorocksonEartholderthan3.8Gyr.Butwhenoneanalyse

Zircon(ZrSiO4crystals)adifferentresultemerges.ZrincorporatesUinitscrystalsbutrejectlead

•  Twochains:1)from238Uto206Pb,withahalf-lifeof4.47Gyrsand2)from235Uto207Pb,withahalf-lifeof704millionyears.

•  ThisgivesanageoftheEarth’sZrcrystalsof4.4Gyrs•  TheMoonislesschangedthantheEarthè4.57Gyrwhichissimilarto

meteoritesorigina?ngintheasteroidbelt

Geological?ming

•  WethereforedividetheearlyphasesoftheEarth’shistoryinto•  1.Hadeanfromthebeginningun?l~3.8Gyr•  2.TheArcheanfrom3.8Gyrun?l~2.4Gyr•  TheLunarlandingsinthe1970:?esbroughtin-situmeasurementsofthe

Moon.Itwasfoundthatthe“Mare”thelargelavaplainsontheMoonwereallformedbyheavycollisions~4Gyrsago.Theconclusionwasthatanumberofbodies>100kmindiametercollidedwiththeMoonduringthisepoch(seetheNicemodelforexplana?on)

•  TheEarth,beingbigger,musthavebeenhitmuchmoreandeachcollisionislargeenoughsothatmostoftherockssurfaceoftheearthwouldhavemeltedoreventurnedintogas.MostofthewatermusthaveturnedintosteamèTheimplica?onsforlifeifithasformedalreadyarenotgood.

•  Theseinterpreta?onsarenottotallyaccepted!•  Whatisclearisthatrocksdatedat3.8Gyrsdemonstratethatthe

collisionsceasedthen.

StructureoftheyoungEarth

TheearlyphasesoftheEarthwasviolentevenwhenthebombardmenthadceasedMajor movements in the crust, tectonics, as well as severe volcanic activity

Large amounts of radioactivity è heating + contraction + latent heat left from the merger of the planetesimals. + the bombardment

This led to a stratification that remains to this day

Crust (~ 35km – thinner under the oceans, thicker under land) + Mantle (3000km) consisting of MgO+ Core (Fe+Ni) down to 6400km

Under the mantle is the Magma which is liquid

Volcanic activity takes place at the border between different tectonic plates, where magma can reach the surface

Tectonicplates

TracesofearlylifeonEarth

•  WecannotreallyexpecttofindtracesofthefirstlifeonEarthsinceitwasverysimpleandprimi?veandourplanethavebeenre-cycled

•  Earlyevolu?onappear,however,tohaveproducedmicroorganismsthatusedSunlightgavetracesinthefossilrecordthatcanbefoundaOer3Gyr.

•  CyanobacteriaformedveryearlyanddominatedtheEarthforatleast1Gyr.TheyproducedfreeoxygenandthuschangedtheEarth’satmosphere

•  SomeresearchersclaimthatfossiltracesofStromatolitesexistthatare3500millionyearsold.Thesearecoloniesofcyanobacteriawhichproducemineralisedmatsthats?llexist

Fossilised stromatolite

EarlyLifeontheEarth?–Whatdoweknow

•  TheEarthformedabout4.54Gyrago•  Earliestundisputed(almost)signsoflifearefossilmicrobialmats(Stromatolites)from3.48Gyr(Australia)

•  Biogenic(?)Graphiteinsedimentary?3.7GyroldrocksinGreenland

•  Twootherstudiesfindsigns(fromfossil12C/13Cra?os)from4.25and4.4Gyr

•  èLifearoseEarly?Implica?ons?

TheatmosphereoftheyoungEarth

•  AOerthenuclearreac?onslitofinsidetheSunitsluminosity,LO,dropped.Observa?onsofT-TauristarsindicatetheLOmayhavegonedownby25-35%

•  TheZirconeanalysisindicateearlyliquidwaterontheEarthèamuchdenseratmospherewith“greenhousegases”(CO,CH4)

•  Theatmosphereprobablyoriginatedinplanetesimals/cometsfallingdownontoEarth,butalsooutgassing(volcanos)sincesuchcomponentsmusthavebeenpartoftheforma?onèHcombiningwithO,C,NèH2O,CH4,NH3

•  Thisisareducingatmospherewithcompletelydifferentproper?esthaninourpresentatmospherewhichisoxidizing.

•  Reducingatmospheredoesnotformoxides(e.g.RustwithFe),C+HdoesnotexplodebutinsteadformCH4.

•  HistolighttostayintheEarth’satmosphere.H2OandNH3aredissociatedbyUVlightandtheHescapestospacewhichleadstoanatmospheredominatedbyN(78.09%today),(+20.95%O,0.93%Ar,0.039%CO2).

DifferencesbetweenayoungEarthandayoungVenus

•  Thetwoplanetsareverysimilarinsizeandincomposi?onbutVenushasatemperature~600K,whiletheEarthisbetween273Kand370K(average287.3Kin2013).

–  TheblackbodytemperatureofEarthis254Kor-19degreesC.ITisthegreenhouseeffectthatkeepEarthfrombeingasnowballagain

•  ThecurrentdensityofVenusatmosphereis90?meshigherthantheEarth’s

•  Theiratmosphereswereverylikelysimilartostartoutwith....ButVenuswasalwayshokerthantheEarthèVenuslostmoreofitswaterandthereforenevergotplatetectonics.TheHescapedandOreactedwithCH4andformedCO2whichmadetheplanethoker.AllitsCistodayintheatmosphere

•  OnEarthmostoftheCO2formedinthiswayisdissolvedintotheoceans,andtogetherwithCagoesoutofsolu?onascarbonates.

StanleyMiller’sexperiment

•  A.Oparin(1894-1980)suggestedin1920:?esthatareducingatmospherewithHandhydrogenatedmoleculestogetherwithelectricdischargesandUvradia?onèchemicalreac?onsimportantforthechemistryoflife.

•  HaroldUrey(1893-1981,Nobelprizein1934,discoveryofD)suggestedanexperimenttohisstudentStanleyMiller(1930-2007)whichhecarriedoutin1953

•  Hecreatedreducingatmospheresinthelabandpassedelectricdischargesthroughit

•  AOerafewdayshefoundsomeblackgoointhetestvessel:–  Aspar?cacidandButyricacid–nosurprisesthere.–  Thesecondmostcommonsubstance,however,wasglycinthesimplestaminoacid–  Andnumber4wasalaninanotherimportantaminoacid+somemoreaminoacidsin

significantamounts

And amino acids are the building blocks of proteins! è Biochemestry!

StanleyMiller’sexperiment

•  ProblemisofcoursethatwealreadyfoundthattheEarthwouldloseitsH,H2andrapidlygetanatmosphereofN2andCO2whichdoesnotallowtheresultsofMiller’sexperiment

•  Millercon?nuedtoworkfortherestofhislifeandotherideashavebeentested:

–  MethaneejectedfromvolcanosintoaCO2richatmospheregivessomeaminoacidsbutnotinsuchgreatamounts

–  Moderncalcula?onsindicatethattheEarthwouldhavebeenlosingitsHmuchslowerthanpreviouslysuggestedèLifecouldhavehad?metostart

•  Areducingatmosphereandcoldseas/oceansseemtobeastar?ngpointforcrea?nganenvironmentintowhichthebuildingblocksoflifecouldhavebeenformed.AlotofCH4isalsorequiredplussuitableenergysources

•  Comparedtootheralterna?vesincludingthepresentEarth,thesecondi?onscouldbesearchedforaroundexoplanetswithadvancedinstrumentsanditwouldhelpiftheplanetwaslargerthantheEarth(moreHandH2isretained)èSuperEarth

HowdidthefirstlifeariseonEarth?

•  Summary:Itisatleastpossiblethatthecondi?onsofMiller’sexperiment,togetherwithcoldoceansofH2Ocouldhaveexistedforasignificant?me

Lifeoritsbuildingblocksarrivingfromspace?

•  TheMurchisonmeteoritefellindaylightoverMurchison,Victoria,Australiaon28/91969.Itwaswidelyobservedasafireball,breakingintoatleast3fragmentsasitwasobservedandanimpacttremorwasfelt

•  100kgofmasswascollectedinfragmentsofupto7kgoveranareaof13km2includingoneinsideabarn

•  Over15aminoacidsplusahostofotherorganiccomponentshavebeeniden?fied.AmountsaresimilartothosefoundintheMillerexperiment

•  Sofarnoorganiccompoundshavebeenretrievedfromacomet,butobserva?onsofHalley’sandothercometshavedemonstratedthepresenceofcarboniccompoundssuchashydrogencyanideandformaldehyde.Alsoadenine,oneofthebasesinnucleicacids(likeDNA)wasseeninHalley

•  Injustafewweeks,ESAwillreleasedatafromalaboratorylandedonthecomet67P/Churyumov–Gerasimenko

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