Europa (moon) - Wikipedia

Europa /jʊˈroʊpə/ ( listen), or Jupiter II, is the smallest of the four Galilean moons orbiting Jupiter, and the sixth-closest to the planet of all the 80 ... Europa(moon) FromWikipedia,thefreeencyclopedia Jumptonavigation Jumptosearch SmallestGalileanmoonofJupiter "JupiterII"redirectshere.Forthespaceshipinthe1960stelevisionseriesLostinSpace,seeJupiter2. EuropaEuropa'strailinghemisphereinfalsecolour(violet,green,andinfraredasred,greenandbluechannel).TheprominentcraterinthelowerrightisPwyllandthedarkerregionsareareaswhereEuropa'sprimarilywatericesurfacehasahighermineralcontent.Imagedon7September1996byGalileospacecraft.DiscoveryDiscovered byGalileoGalileiSimonMariusDiscovery date8January1610[1]DesignationsPronunciation/jʊˈroʊpə/[2]NamedafterΕυρώπηEyrōpēAlternativenamesJupiterIIAdjectivesEuropan/jʊˈroʊpən/[3][4]Orbitalcharacteristics[7]Epoch8January2004Periapsis664862 km[a]Apoapsis676938 km[b]Meanorbitradius670900 km[5]Eccentricity0.009[5]Orbitalperiod(sidereal)3.551181 d[5]Averageorbitalspeed13743.36 m/s[6]Inclination0.470°(toJupiter'sequator)1.791°(totheecliptic)[5]Satellite ofJupiterGroupGalileanmoonPhysicalcharacteristicsMeanradius1560.8±0.5 km(0.245Earths)[8]Surfacearea3.09×107 km2(0.061Earths)[c]Volume1.593×1010 km3(0.015Earths)[d]Mass(4.799844±0.000013)×1022 kg(0.008Earths)[8]Meandensity3.013±0.005 g/cm3(0.546Earths)[8]Surfacegravity1.314 m/s2(0.134g)[e]Momentofinertiafactor0.346±0.005[9](estimate)Escapevelocity2.025 km/s[f]SynodicrotationperiodSynchronous[10]Axialtilt0.1°[11]Albedo0.67 ± 0.03[8] Surfacetemp. min mean max Surface ≈ 50K[12] 102 K(−171 °C) 125 K Apparentmagnitude5.29(opposition)[8]AtmosphereSurfacepressure0.1µPa(10−12bar)[13] Europa/jʊˈroʊpə/(listen),orJupiterII,isthesmallestofthefourGalileanmoonsorbitingJupiter,andthesixth-closesttotheplanetofallthe80knownmoonsofJupiter.Itisalsothesixth-largestmoonintheSolarSystem.Europawasdiscoveredin1610byGalileoGalilei[1]andwasnamedafterEuropa,thePhoenicianmotherofKingMinosofCreteandloverofZeus(theGreekequivalentoftheRomangodJupiter). SlightlysmallerthanEarth'sMoon,Europaisprimarilymadeofsilicaterockandhasawater-icecrust[14]andprobablyaniron–nickelcore.Ithasaverythinatmosphere,composedprimarilyofoxygen.Itswhite-beigesurfaceisstriatedbylighttancracksandstreaks,butcratersarerelativelyfew.InadditiontoEarth-boundtelescopeobservations,Europahasbeenexaminedbyasuccessionofspace-probeflybys,thefirstoccurringintheearly1970s. EuropahasthesmoothestsurfaceofanyknownsolidobjectintheSolarSystem.Theapparentyouthandsmoothnessofthesurfacehaveledtothehypothesisthatawateroceanexistsbeneaththesurface,whichcouldconceivablyharborextraterrestriallife.[15]Thepredominantmodelsuggeststhatheatfromtidalflexingcausestheoceantoremainliquidanddrivesicemovementsimilartoplatetectonics,absorbingchemicalsfromthesurfaceintotheoceanbelow.[16][17]SeasaltfromasubsurfaceoceanmaybecoatingsomegeologicalfeaturesonEuropa,suggestingthattheoceanisinteractingwiththeseafloor.ThismaybeimportantindeterminingwhetherEuropacouldbehabitable.[18]Inaddition,theHubbleSpaceTelescopedetectedwatervaporplumessimilartothoseobservedonSaturn'smoonEnceladus,whicharethoughttobecausedbyeruptingcryogeysers.[19]InMay2018,astronomersprovidedsupportingevidenceofwaterplumeactivityonEuropa,basedonanupdatedanalysisofdataobtainedfromtheGalileospaceprobe,whichorbitedJupiterfrom1995to2003.SuchplumeactivitycouldhelpresearchersinasearchforlifefromthesubsurfaceEuropanoceanwithouthavingtolandonthemoon.[20][21][22][23] TheGalileomission,launchedin1989,providesthebulkofcurrentdataonEuropa.NospacecrafthasyetlandedonEuropa,althoughtherehavebeenseveralproposedexplorationmissions.TheEuropeanSpaceAgency'sJupiterIcyMoonExplorer(JUICE)isamissiontoGanymedethatisduetolaunchin2023andwillincludetwoflybysofEuropa.[24][25]NASA'splannedEuropaClippershouldbelaunchedin2024.[26] Contents 1Discoveryandnaming 2Orbitandrotation 3Physicalcharacteristics 3.1Internalstructure 3.2Surfacefeatures 3.2.1Lineae 3.2.2Chaosandlenticulae 3.3Subsurfaceocean 3.3.1Composition 3.3.2Sourcesofheat 3.3.2.1Tidalfriction 3.3.2.2Tidalflexing 3.3.2.3Radioactivedecay 3.3.3Plumes 3.4Atmosphere 3.4.1DiscoveryofAtmosphere 3.4.2ClimateandWeather 4Exploration 4.1Futuremissions 4.2Oldproposals 5Habitabilitypotential 6Seealso 7Notes 8References 8.1Furtherreading 9Externallinks Discoveryandnaming[edit] Europa,alongwithJupiter'sthreeotherlargemoons,Io,Ganymede,andCallisto,wasdiscoveredbyGalileoGalileion8January1610,[1]andpossiblyindependentlybySimonMarius.ThefirstreportedobservationofIoandEuropawasmadebyGalileoon7January1610usinga20×-magnificationrefractingtelescopeattheUniversityofPadua.However,inthatobservation,GalileocouldnotseparateIoandEuropaduetothelowmagnificationofhistelescope,sothatthetwowererecordedasasinglepointoflight.Thefollowingday,8January1610(usedasthediscoverydateforEuropabytheIAU),IoandEuropawereseenforthefirsttimeasseparatebodiesduringGalileo'sobservationsoftheJupitersystem.[1] EuropaisthenamesakeofEuropa,daughterofthekingofTyre,aPhoeniciannoblewomaninGreekmythology.LikealltheGalileansatellites,EuropaisnamedafteraloverofZeus,theGreekcounterpartofJupiter.EuropawascourtedbyZeusandbecamethequeenofCrete.[27]ThenamingschemewassuggestedbySimonMarius,[28]whoattributedtheproposaltoJohannesKepler:[28][29] ...InprimisautemcelebranturtresfœminæVirgines,quarumfurtivoamoreIupitercaptus&positusest...EuropaAgenorisfilia...àmevocatur...SecundusEuropa...[Io,]Europa,Ganimedespuer,atqueCalisto,lascivonimiumperplacuereJovi. ...First,threeyoungwomenwhowerecapturedbyJupiterforsecretloveshallbehonoured,[including]Europa,thedaughterofAgenor...Thesecond[moon]iscalledbymeEuropa...Io,Europa,theboyGanymede,andCallistogreatlypleasedlustfulJupiter.[30] Thenamesfelloutoffavorforaconsiderabletimeandwerenotrevivedingeneraluseuntilthemid-20thcentury.[31]Inmuchoftheearlierastronomicalliterature,EuropaissimplyreferredtobyitsRomannumeraldesignationasJupiterII(asystemalsointroducedbyGalileo)orasthe"secondsatelliteofJupiter".In1892,thediscoveryofAmalthea,whoseorbitlayclosertoJupiterthanthoseoftheGalileanmoons,pushedEuropatothethirdposition.TheVoyagerprobesdiscoveredthreemoreinnersatellitesin1979,soEuropaisnowcountedasJupiter'ssixthsatellite,thoughitisstillreferredtoasJupiterII.[31] TheadjectivalformhasstabilizedasEuropan.[4][32] Orbitandrotation[edit] AnimationoftheLaplaceresonanceofIo,EuropaandGanymede(conjunctionsarehighlightedbycolorchanges) EuropaorbitsJupiterinjustoverthreeandahalfdays,withanorbitalradiusofabout670,900 km.Withanorbitaleccentricityofonly0.009,theorbititselfisnearlycircular,andtheorbitalinclinationrelativetoJupiter'sequatorialplaneissmall,at0.470°.[33]LikeitsfellowGalileansatellites,EuropaistidallylockedtoJupiter,withonehemisphereofEuropaconstantlyfacingJupiter.Becauseofthis,thereisasub-JovianpointonEuropa'ssurface,fromwhichJupiterwouldappeartohangdirectlyoverhead.Europa'sprimemeridianisalinepassingthroughthispoint.[34]Researchsuggeststhatthetidallockingmaynotbefull,asanon-synchronousrotationhasbeenproposed:Europaspinsfasterthanitorbits,oratleastdidsointhepast.Thissuggestsanasymmetryininternalmassdistributionandthatalayerofsubsurfaceliquidseparatestheicycrustfromtherockyinterior.[10] TheslighteccentricityofEuropa'sorbit,maintainedbythegravitationaldisturbancesfromtheotherGalileans,causesEuropa'ssub-Jovianpointtooscillatearoundameanposition.AsEuropacomesslightlynearertoJupiter,Jupiter'sgravitationalattractionincreases,causingEuropatoelongatetowardsandawayfromit.AsEuropamovesslightlyawayfromJupiter,Jupiter'sgravitationalforcedecreases,causingEuropatorelaxbackintoamoresphericalshape,andcreatingtidesinitsocean.TheorbitaleccentricityofEuropaiscontinuouslypumpedbyitsmean-motionresonancewithIo.[35]Thus,thetidalflexingkneadsEuropa'sinteriorandgivesitasourceofheat,possiblyallowingitsoceantostayliquidwhiledrivingsubsurfacegeologicalprocesses.[16][35]TheultimatesourceofthisenergyisJupiter'srotation,whichistappedbyIothroughthetidesitraisesonJupiterandistransferredtoEuropaandGanymedebytheorbitalresonance.[35][36] AnalysisoftheuniquecracksliningEuropayieldedevidencethatitlikelyspunaroundatiltedaxisatsomepointintime.Ifcorrect,thiswouldexplainmanyofEuropa'sfeatures.Europa'simmensenetworkofcrisscrossingcracksservesasarecordofthestressescausedbymassivetidesinitsglobalocean.Europa'stiltcouldinfluencecalculationsofhowmuchofitshistoryisrecordedinitsfrozenshell,howmuchheatisgeneratedbytidesinitsocean,andevenhowlongtheoceanhasbeenliquid.Itsicelayermuststretchtoaccommodatethesechanges.Whenthereistoomuchstress,itcracks.AtiltinEuropa'saxiscouldsuggestthatitscracksmaybemuchmorerecentthanpreviouslythought.Thereasonforthisisthatthedirectionofthespinpolemaychangebyasmuchasafewdegreesperday,completingoneprecessionperiodoverseveralmonths.AtiltcouldalsoaffecttheestimatesoftheageofEuropa'socean.TidalforcesarethoughttogeneratetheheatthatkeepsEuropa'soceanliquid,andatiltinthespinaxiswouldcausemoreheattobegeneratedbytidalforces.Suchadditionalheatwouldhaveallowedtheoceantoremainliquidforalongertime.However,ithasnotyetbeendeterminedwhenthishypothesizedshiftinthespinaxismighthaveoccurred.[37] Physicalcharacteristics[edit] SizecomparisonofEuropa(lowerleft)withtheMoon(topleft)andEarth(right) EuropaisslightlysmallerthantheMoon.Atjustover3,100kilometres(1,900 mi)indiameter,itisthesixth-largestmoonandfifteenth-largestobjectintheSolarSystem.ThoughbyawidemargintheleastmassiveoftheGalileansatellites,itisnonethelessmoremassivethanallknownmoonsintheSolarSystemsmallerthanitselfcombined.[38]Itsbulkdensitysuggeststhatitissimilarincompositiontotheterrestrialplanets,beingprimarilycomposedofsilicaterock.[39] Internalstructure[edit] ItisestimatedthatEuropahasanouterlayerofwateraround100 km(62 mi)thick;apartfrozenasitscrust,andapartasaliquidoceanunderneaththeice.Recentmagnetic-fielddatafromtheGalileoorbitershowedthatEuropahasaninducedmagneticfieldthroughinteractionwithJupiter's,whichsuggeststhepresenceofasubsurfaceconductivelayer.[40]Thislayerislikelytobeasaltyliquid-waterocean.Portionsofthecrustareestimatedtohaveundergonearotationofnearly80°,nearlyflippingover(seetruepolarwander),whichwouldbeunlikelyiftheiceweresolidlyattachedtothemantle.[41]Europaprobablycontainsametallicironcore.[42][43] Surfacefeatures[edit] Falsecolor(left)andfalsecolorwithenhancedcontrast(right)madebyRGBsynthesisofnearinfrared,greenandvioletluminancedata.Galileoviewofleadinghemisphere EuropaisthesmoothestknownobjectintheSolarSystem,lackinglarge-scalefeaturessuchasmountainsandcraters.[44]However,accordingtoonestudy,Europa'sequatormaybecoveredinicyspikescalledpenitentes,whichmaybeupto15 metershigh,duetodirectoverheadsunlightontheequator,causingtheicetosublime,formingverticalcracks.[45][46][47]AlthoughtheimagingavailablefromtheGalileoorbiterdoesnothavetheresolutionneededtoconfirmthis,radarandthermaldataareconsistentwiththisinterpretation.[47]TheprominentmarkingscrisscrossingEuropaappeartobemainlyalbedofeaturesthatemphasizelowtopography.TherearefewcratersonEuropa,becauseitssurfaceistectonicallytooactiveandthereforeyoung.[48][49]Europa'sicycrusthasanalbedo(lightreflectivity)of0.64,oneofthehighestofallmoons.[33][49]Thisindicatesayoungandactivesurface:basedonestimatesofthefrequencyofcometarybombardmentthatEuropaexperiences,thesurfaceisabout20to180millionyearsold.[50]ThereiscurrentlynofullscientificconsensusamongthesometimescontradictoryexplanationsforthesurfacefeaturesofEuropa.[51] TheionizingradiationlevelatthesurfaceofEuropaisequivalenttoadoseofabout5.4 Sv(540 rem)perday,[52]anamountthatwouldcausesevereillnessordeathinhumanbeingsexposedforasingleEarth-day(24hours).[53]ThedurationofaEuropandayisapproximately3.5timesthatofadayonEarth,resultingin3.5timesmoreionizingradiationexposure.[54] Lineae[edit] Seealso:ListoflineaeonEuropa FalsecolorGalileomosaicofEuropa'santi-Jovianhemisphereshowingnumerouslineae. Saturated,falsecolorviewshowingtheintricatepatternoflinearfracturesonEuropa'ssurface Europa'smoststrikingsurfacefeaturesareaseriesofdarkstreakscrisscrossingtheentireglobe,calledlineae(English:lines).CloseexaminationshowsthattheedgesofEuropa'scrustoneithersideofthecrackshavemovedrelativetoeachother.Thelargerbandsaremorethan20 km(12 mi)across,oftenwithdark,diffuseouteredges,regularstriations,andacentralbandoflightermaterial.[55] ThemostlikelyhypothesisisthatthelineaeonEuropawereproducedbyaseriesoferuptionsofwarmiceastheEuropancrustspreadopentoexposewarmerlayersbeneath.[56]TheeffectwouldhavebeensimilartothatseeninEarth'soceanicridges.ThesevariousfracturesarethoughttohavebeencausedinlargepartbythetidalflexingexertedbyJupiter.BecauseEuropaistidallylockedtoJupiter,andthereforealwaysmaintainsapproximatelythesameorientationtowardsJupiter,thestresspatternsshouldformadistinctiveandpredictablepattern.However,onlytheyoungestofEuropa'sfracturesconformtothepredictedpattern;otherfracturesappeartooccuratincreasinglydifferentorientationstheoldertheyare.ThiscouldbeexplainedifEuropa'ssurfacerotatesslightlyfasterthanitsinterior,aneffectthatispossibleduetothesubsurfaceoceanmechanicallydecouplingEuropa'ssurfacefromitsrockymantleandtheeffectsofJupiter'sgravitytuggingonEuropa'soutericecrust.[57]ComparisonsofVoyagerandGalileospacecraftphotosservetoputanupperlimitonthishypotheticalslippage.AfullrevolutionoftheouterrigidshellrelativetotheinteriorofEuropatakesatleast12,000years.[58]StudiesofVoyagerandGalileoimageshaverevealedevidenceofsubductiononEuropa'ssurface,suggestingthat,justasthecracksareanalogoustooceanridges,[59][60]soplatesoficycrustanalogoustotectonicplatesonEartharerecycledintothemolteninterior.Thisevidenceofbothcrustalspreadingatbands[59]andconvergenceatothersites[60]suggeststhatEuropamayhaveactiveplatetectonics,similartoEarth.[17]However,thephysicsdrivingtheseplatetectonicsarenotlikelytoresemblethosedrivingterrestrialplatetectonics,astheforcesresistingpotentialEarth-likeplatemotionsinEuropa'scrustaresignificantlystrongerthantheforcesthatcoulddrivethem.[61] Chaosandlenticulae[edit] Seealso:ListofgeologicalfeaturesonEuropaLeft:surfacefeaturesindicativeoftidalflexing:lineae,lenticulaeandtheConamaraChaosregion(close-up,right)wherecraggy,250 mhighpeaksandsmoothplatesarejumbledtogether OtherfeaturespresentonEuropaarecircularandellipticallenticulae(Latinfor"freckles").Manyaredomes,somearepitsandsomearesmooth,darkspots.Othershaveajumbledorroughtexture.Thedometopslooklikepiecesoftheolderplainsaroundthem,suggestingthatthedomesformedwhentheplainswerepushedupfrombelow.[62] Onehypothesisstatesthattheselenticulaewereformedbydiapirsofwarmicerisingupthroughthecoldericeoftheoutercrust,muchlikemagmachambersinEarth'scrust.[62]Thesmooth,darkspotscouldbeformedbymeltwaterreleasedwhenthewarmicebreaksthroughthesurface.Therough,jumbledlenticulae(calledregionsof"chaos";forexample,ConamaraChaos)wouldthenbeformedfrommanysmallfragmentsofcrust,embeddedinhummocky,darkmaterial,appearinglikeicebergsinafrozensea.[63] Analternativehypothesissuggestthatlenticulaeareactuallysmallareasofchaosandthattheclaimedpits,spotsanddomesareartefactsresultingfromover-interpretationofearly,low-resolutionGalileoimages.Theimplicationisthattheiceistoothintosupporttheconvectivediapirmodeloffeatureformation.[64][65] InNovember2011,ateamofresearchersfromtheUniversityofTexasatAustinandelsewherepresentedevidenceinthejournalNaturesuggestingthatmany"chaosterrain"featuresonEuropasitatopvastlakesofliquidwater.[66][67]TheselakeswouldbeentirelyencasedinEuropa'sicyoutershellanddistinctfromaliquidoceanthoughttoexistfartherdownbeneaththeiceshell.Fullconfirmationofthelakes'existencewillrequireaspacemissiondesignedtoprobetheiceshelleitherphysicallyorindirectly,forexample,usingradar.[67] WorkpublishedbyresearchersfromWilliamsCollegesuggeststhatchaosterrainmayrepresentsiteswhereimpactingcometspenetratedthroughtheicecrustandintoanunderlyingocean.[68][69] Subsurfaceocean[edit] TwopossiblemodelsofEuropa Europa-internalstructure(artwork;25May2021) Scientists'consensusisthatalayerofliquidwaterexistsbeneathEuropa'ssurface,andthatheatfromtidalflexingallowsthesubsurfaceoceantoremainliquid.[16][70]Europa'ssurfacetemperatureaveragesabout110 K(−160 °C;−260 °F)attheequatorandonly50 K(−220 °C;−370 °F)atthepoles,keepingEuropa'sicycrustashardasgranite.[12]Thefirsthintsofasubsurfaceoceancamefromtheoreticalconsiderationsoftidalheating(aconsequenceofEuropa'sslightlyeccentricorbitandorbitalresonancewiththeotherGalileanmoons).GalileoimagingteammembersarguefortheexistenceofasubsurfaceoceanfromanalysisofVoyagerandGalileoimages.[70]Themostdramaticexampleis"chaosterrain",acommonfeatureonEuropa'ssurfacethatsomeinterpretasaregionwherethesubsurfaceoceanhasmeltedthroughtheicycrust.Thisinterpretationiscontroversial.MostgeologistswhohavestudiedEuropafavorwhatiscommonlycalledthe"thickice"model,inwhichtheoceanhasrarely,ifever,directlyinteractedwiththepresentsurface.[71]Thebestevidenceforthethick-icemodelisastudyofEuropa'slargecraters.Thelargestimpactstructuresaresurroundedbyconcentricringsandappeartobefilledwithrelativelyflat,freshice;basedonthisandonthecalculatedamountofheatgeneratedbyEuropantides,itisestimatedthattheoutercrustofsolidiceisapproximately10–30 km(6–19 mi)thick,[72]includingaductile"warmice"layer,whichcouldmeanthattheliquidoceanunderneathmaybeabout100 km(60 mi)deep.[73]ThisleadstoavolumeofEuropa'soceansof3 × 1018 m3,betweentwoorthreetimesthevolumeofEarth'soceans.[74][75] Thethin-icemodelsuggeststhatEuropa'siceshellmaybeonlyafewkilometersthick.However,mostplanetaryscientistsconcludethatthismodelconsidersonlythosetopmostlayersofEuropa'scrustthatbehaveelasticallywhenaffectedbyJupiter'stides.[citationneeded]Oneexampleisflexureanalysis,inwhichEuropa'scrustismodeledasaplaneorsphereweightedandflexedbyaheavyload.Modelssuchasthissuggesttheouterelasticportionoftheicecrustcouldbeasthinas200metres(660 ft).IftheiceshellofEuropaisreallyonlyafewkilometersthick,this"thinice"modelwouldmeanthatregularcontactoftheliquidinteriorwiththesurfacecouldoccurthroughopenridges,causingtheformationofareasofchaoticterrain.[76]Largeimpactsgoingfullythroughtheicecrustwouldalsobeawaythatthesubsurfaceoceancouldbeexposed.[68][69] Composition[edit] CloseupviewsofEuropaobtainedon26September1998;imagesclockwisefromupperleftshowlocationsfromnorthtosouthasindicatedatlowerleft. TheGalileoorbiterfoundthatEuropahasaweakmagneticmoment,whichisinducedbythevaryingpartoftheJovianmagneticfield.Thefieldstrengthatthemagneticequator(about120nT)createdbythismagneticmomentisaboutone-sixththestrengthofGanymede'sfieldandsixtimesthevalueofCallisto's.[77]TheexistenceoftheinducedmomentrequiresalayerofahighlyelectricallyconductivematerialinEuropa'sinterior.Themostplausiblecandidateforthisroleisalargesubsurfaceoceanofliquidsaltwater.[42] SincetheVoyagerspacecraftflewpastEuropain1979,scientistshaveworkedtounderstandthecompositionofthereddish-brownmaterialthatcoatsfracturesandothergeologicallyyouthfulfeaturesonEuropa'ssurface.[78]Spectrographicevidencesuggeststhatthedarker,reddishstreaksandfeaturesonEuropa'ssurfacemayberichinsaltssuchasmagnesiumsulfate,depositedbyevaporatingwaterthatemergedfromwithin.[79]Sulfuricacidhydrateisanotherpossibleexplanationforthecontaminantobservedspectroscopically.[80]Ineithercase,becausethesematerialsarecolorlessorwhitewhenpure,someothermaterialmustalsobepresenttoaccountforthereddishcolor,andsulfurcompoundsaresuspected.[81] Anotherhypothesisforthecoloredregionsisthattheyarecomposedofabioticorganiccompoundscollectivelycalledtholins.[82][83][84]ThemorphologyofEuropa'simpactcratersandridgesissuggestiveoffluidizedmaterialwellingupfromthefractureswherepyrolysisandradiolysistakeplace.InordertogeneratecoloredtholinsonEuropatheremustbeasourceofmaterials(carbon,nitrogen,andwater)andasourceofenergytomakethereactionsoccur.ImpuritiesinthewatericecrustofEuropaarepresumedbothtoemergefromtheinteriorascryovolcaniceventsthatresurfacethebody,andtoaccumulatefromspaceasinterplanetarydust.[82]Tholinsbringimportantastrobiologicalimplications,astheymayplayaroleinprebioticchemistryandabiogenesis.[85][86][87] Thepresenceofsodiumchlorideintheinternaloceanhasbeensuggestedbya450 nmabsorptionfeature,characteristicofirradiatedNaClcrystals,thathasbeenspottedinHSTobservationsofthechaosregions,presumedtobeareasofrecentsubsurfaceupwelling.[88] Sourcesofheat[edit] Tidalheatingoccursthroughthetidalfrictionandtidalflexingprocessescausedbytidalacceleration:orbitalandrotationalenergyaredissipatedasheatinthecoreofthemoon,theinternalocean,andtheicecrust.[89] Tidalfriction[edit] Oceantidesareconvertedtoheatbyfrictionallossesintheoceansandtheirinteractionwiththesolidbottomandwiththetopicecrust.Inlate2008,itwassuggestedJupitermaykeepEuropa'soceanswarmbygeneratinglargeplanetarytidalwavesonEuropabecauseofitssmallbutnon-zeroobliquity.Thisgeneratesso-calledRossbywavesthattravelquiteslowly,atjustafewkilometersperday,butcangeneratesignificantkineticenergy.Forthecurrentaxialtiltestimateof0.1degree,theresonancefromRossbywaveswouldcontain7.3×1018Jofkineticenergy,whichistwothousandtimeslargerthanthatoftheflowexcitedbythedominanttidalforces.[90][91]DissipationofthisenergycouldbetheprincipalheatsourceofEuropa'socean.[90][91] Tidalflexing[edit] TidalflexingkneadsEuropa'sinteriorandiceshell,whichbecomesasourceofheat.[92]Dependingontheamountoftilt,theheatgeneratedbytheoceanflowcouldbe100tothousandsoftimesgreaterthantheheatgeneratedbytheflexingofEuropa'srockycoreinresponsetogravitationalpullfromJupiterandtheothermoonscirclingthatplanet.[93]Europa'sseafloorcouldbeheatedbythemoon'sconstantflexing,drivinghydrothermalactivitysimilartounderseavolcanoesinEarth'soceans.[89] Experimentsandicemodelingpublishedin2016,indicatethattidalflexingdissipationcangenerateoneorderofmagnitudemoreheatinEuropa'sicethanscientistshadpreviouslyassumed.[94][95]Theirresultsindicatethatmostoftheheatgeneratedbytheiceactuallycomesfromtheice'scrystallinestructure(lattice)asaresultofdeformation,andnotfrictionbetweentheicegrains.[94][95]Thegreaterthedeformationoftheicesheet,themoreheatisgenerated. Radioactivedecay[edit] Inadditiontotidalheating,theinteriorofEuropacouldalsobeheatedbythedecayofradioactivematerial(radiogenicheating)withintherockymantle.[89][96]Butthemodelsandvaluesobservedareonehundredtimeshigherthanthosethatcouldbeproducedbyradiogenicheatingalone,[97]thusimplyingthattidalheatinghasaleadingroleinEuropa.[98] Plumes[edit] WaterplumesonEuropadetectedbytheGalileospaceprobe[20][22][23][99] PhotocompositeofsuspectedwaterplumesonEuropa[100] TheHubbleSpaceTelescopeacquiredanimageofEuropain2012thatwasinterpretedtobeaplumeofwatervapoureruptingfromnearitssouthpole.[101][100]Theimagesuggeststheplumemaybe200 km(120 mi)high,ormorethan20timestheheightofMt.Everest.[19][102][103],thoughrecentobservationsandmodelingsuggestthattypicalEuropeanplumesmaybemuchsmaller.[104][105][106]Ithasbeensuggestedthatifplumesexist,theyareepisodic[107]andlikelytoappearwhenEuropaisatitsfarthestpointfromJupiter,inagreementwithtidalforcemodelingpredictions.[108]AdditionalimagingevidencefromtheHubbleSpaceTelescopewaspresentedinSeptember2016.[109][110] InMay2018,astronomersprovidedsupportingevidenceofwaterplumeactivityonEuropa,basedonanupdatedcriticalanalysisofdataobtainedfromtheGalileospaceprobe,whichorbitedJupiterbetween1995and2003.GalileoflewbyEuropain1997within206 km(128 mi)ofthemoon'ssurfaceandtheresearcherssuggestitmayhaveflownthroughawaterplume.[20][21][22][23]SuchplumeactivitycouldhelpresearchersinasearchforlifefromthesubsurfaceEuropanoceanwithouthavingtolandonthemoon.[20] Thetidalforcesareabout1,000timesstrongerthantheMoon'seffectonEarth.TheonlyothermoonintheSolarSystemexhibitingwatervaporplumesisEnceladus.[19]TheestimatederuptionrateatEuropaisabout7000 kg/s[108]comparedtoabout200 kg/sfortheplumesofEnceladus.[111][112]Ifconfirmed,itwouldopenthepossibilityofaflybythroughtheplumeandobtainasampletoanalyzeinsituwithouthavingtousealanderanddrillthroughkilometresofice.[109][113][114] InNovember2020,astudywaspublishedinthepeer-reviewedscientificjournalGeophysicalResearchLetterssuggestingthattheplumesmayoriginatefromwaterwithinthecrustofEuropaasopposedtoitssubsurfaceocean.Thestudy'smodel,usingimagesfromtheGalileospaceprobe,proposedthatacombinationoffreezingandpressurizationmayresultinatleastsomeofthecryovolcanicactivity.Thepressuregeneratedbymigratingbrinywaterpocketswouldthus,eventually,burstthroughthecrusttherebycreatingtheseplumes.ThetheorythatcryovolcanismonEuropacouldbetriggeredbyfreezingandpressurizationofliquidpocketsintheicycrustwasfirstproposedbyresearchersattheUniversityofHawai'iatMānoain2003,whowerethefirsttomodelthisprocess.[115]ApressreleasefromNASA'sJetPropulsionLaboratoryreferencingtheNovember2020studysuggestedthatplumessourcedfrommigratingliquidpocketscouldpotentiallybelesshospitabletolife.Thisisduetoalackofsubstantialenergyfororganismstothriveoffof,unlikeproposedhydrothermalventsonthesubsurfaceoceanfloor.[116][117] Atmosphere[edit] TheatmosphereofEuropacanbecategorizedasathin,tenuousatmosphere(oftencalledanexosphere),primarilycomposedofoxygenandtraceamountsofwatervapor.[118]However,thisquantityofoxygenisproducedinanon-biologicalmanner.GiventhatEuropa’ssurfaceisicy,andsubsequentlyverycold;assolarultravioletradiationandchargedparticles(ionsandelectrons)fromtheJovianmagnetosphericenvironmentcollidewithEuropa'ssurface,watervaporiscreatedandinstantaneouslyseparatedintooxygenandhydrogenconstituents.Asitcontinuestomove,thehydrogenislightenoughtopassthroughthesurfacegravityoftheatmosphereleavingbehindonlyoxygen.[119]Thesurface-boundedatmosphereformsthroughradiolysis,thedissociationofmoleculesthroughradiation.[120]Thisaccumulatedoxygenatmospherecangettoaheightof125milesabovethesurfaceofEuropa.Molecularoxygenisthedensestcomponentoftheatmospherebecauseithasalonglifetime;afterreturningtothesurface,itdoesnotstick(freeze)likeawaterorhydrogenperoxidemoleculebutratherdesorbsfromthesurfaceandstartsanotherballisticarc.Molecularhydrogenneverreachesthesurface,asitislightenoughtoescapeEuropa'ssurfacegravity.[121][122]Europaisoneoftheonlymoonsinoursolarsystemwithaquantifiableatmosphere,nexttoTitan,Io,Triton,GanymedeandCallisto.Europaisalsooneofthethreeformations,amongplanetsandmoons,tocontainoxygenwithinitsatmosphere.[123]Europaisalsooneofseveralmoonsinoursolarsystemwithverylargequantitiesofice(volatiles),otherwiseknownas"icymoons."[124]MagneticfieldaroundEuropa.TheredlineshowsatrajectoryoftheGalileospacecraftduringatypicalflyby(E4orE14).Europaisalsoconsideredtobegeologicallyactiveduetotheconstantreleaseofhydrogen-oxygenmixtureintospace.Asaresultofthemoon’sparticleventing,theatmosphererequirescontinuousreplenishment.[119]Europaalsocontainsasmallmagnetosphere(approximately25%ofGanymede’s).However,thismagnetospherevariesinsizeasEuropaorbitsthroughJupiter'smagneticfield.Thisconfirmsthataconductiveelement,suchasalargeocean,likelyliesbelowitsicysurface.[125]AsmultiplestudieshavebeenconductedoverEuropa’satmosphere,severalfindingsconcludethatnotalloxygenmoleculesarereleasedintotheatmosphere.Thisunknownpercentageofoxygenmaybeabsorbedintothesurfaceandsinkintothesubsurface.Becausethesurfacemayinteractwiththesubsurfaceocean(consideringthegeologicaldiscussionabove),thismolecularoxygenmaymakeitswaytotheocean,whereitcouldaidinbiologicalprocesses.[126][127]Oneestimatesuggeststhat,giventheturnoverrateinferredfromtheapparent~0.5GyrmaximumageofEuropa'ssurfaceice,subductionofradiolyticallygeneratedoxidizingspeciesmightwellleadtooceanicfreeoxygenconcentrationsthatarecomparabletothoseinterrestrialdeepoceans.[128] Throughtheslowreleaseofoxygenandhydrogen,aneutraltorusaroundEuropa’sorbitalplaneisformed.This"neutralcloud"hasbeendetectedbyboththeCassiniandGalileospacecraft,andhasagreatercontent(numberofatomsandmolecules)thantheneutralcloudsurroundingJupiter'sinnermoonIo.[129]ThistoruswasofficiallyconfirmedusingEnergeticNeutralAtom(ENA)imaging.Europa’storusionizesthroughtheprocessofneutralparticlesexchangingelectronswithitschargedparticles.SinceEuropa’smagneticfieldrotatesfasterthanitsorbitvelocity,theseionsareleftinthepathofitsmagneticfieldtrajectory,formingaplasma.IthasbeentheorizedthattheseionsareresponsiblefortheplasmawithinJupiter'smagnetosphere.[130] DiscoveryofAtmosphere[edit] TheatmosphereofEuropawasfirstdiscoveredin1995byHallAl.andtheGoddardHighResolutionSpectrographoftheHubbletelescope.Thisobservationwasthenconfirmedin1997bytheGalileoprobewhichwasbuiltbyHughesAircraftCompanyandoperatedbyNASA.TheGalileoprobeflewonlythreemilesabovetheestimatedmaximumatmosphericline(128milesfromEuropa'ssurface),butthenchangedcoursetocollidewithJupiter'satmosphereinordertopreventunwantedimpactwithEuropa'ssurface.IthasbeenspeculatedthattherewillbeseveralmorefuturemissionstoEuropainhopestofurtherstudytheatmosphere,chemicalcomposition,andpossibilityofextraterrestriallifebelowtheicysurface.[131] ClimateandWeather[edit] Despitethepresenceofagastorus,Europahasnoweatherproducingclouds.Asawhole,Europahasnowind,precipitation,orpresenceofskycolorduetothelowpresenceofgravity.Europa’sgravityisapproximately13%ofearth's.ThetemperatureonEuropavariesfrom-160°Cattheequatorialline,to-220°Cateitherofitspoles.[132]Europa'ssubsurfaceoceanisthoughttobesubsequentlywarmhowever.Itistheorizedthatbecauseofradioactiveandtidalheating(asmentionedinthesectionsabove),therearepointsinthedepthsofEuropa'soceanthatmayonlybeslightlycoolerthanthatofearth'soceans.StudieshavealsoconcludedthatEuropa’soceanwouldhavebeenratheracidicatfirst,withlargeconcentrationsofsulfate,calcium,andcarbondioxide.Butoverthecourseof4.5billionyears,itbecamefullof chloride,thusresemblingour1.94%chlorideoceansonEarth. Exploration[edit] In1973Pioneer10madethefirstcloseupimagesofEuropa–howevertheprobewastoofarawaytoobtainmoredetailedimagesEuropaseenindetailin1979byVoyager2 ExplorationofEuropabeganwiththeJupiterflybysofPioneer10and11in1973and1974respectively.Thefirstcloseupphotoswereoflowresolutioncomparedtolatermissions.ThetwoVoyagerprobestraveledthroughtheJoviansystemin1979,providingmore-detailedimagesofEuropa'sicysurface.Theimagescausedmanyscientiststospeculateaboutthepossibilityofaliquidoceanunderneath. Startingin1995,theGalileospaceprobeorbitedJupiterforeightyears,until2003,andprovidedthemostdetailedexaminationoftheGalileanmoonstodate.Itincludedthe"GalileoEuropaMission"and"GalileoMillenniumMission",withnumerouscloseflybysofEuropa.[133]In2007,NewHorizonsimagedEuropa,asitflewbytheJoviansystemwhileonitswaytoPluto.[134] Futuremissions[edit] ConjecturesregardingextraterrestriallifehaveensuredahighprofileforEuropaandhaveledtosteadylobbyingforfuturemissions.[135][136]TheaimsofthesemissionshaverangedfromexaminingEuropa'schemicalcompositiontosearchingforextraterrestriallifeinitshypothesizedsubsurfaceoceans.[137][138]RoboticmissionstoEuropaneedtoendurethehigh-radiationenvironmentaroundJupiter.[136]BecauseitisdeeplyembeddedwithinJupiter'smagnetosphere,Europareceivesabout5.40Svofradiationperday.[139] In2011,aEuropamissionwasrecommendedbytheU.S.PlanetaryScienceDecadalSurvey.[140]Inresponse,NASAcommissionedEuropalanderconceptstudiesin2011,alongwithconceptsforaEuropaflyby(EuropaClipper),andaEuropaorbiter.[141][142]Theorbiterelementoptionconcentratesonthe"ocean"science,whilethemultiple-flybyelement(Clipper)concentratesonthechemistryandenergyscience.On13January2014,theHouseAppropriationsCommitteeannouncedanewbipartisanbillthatincludes$80millionfundingtocontinuetheEuropamissionconceptstudies.[143][144] In2012,JupiterIcyMoonExplorer(JUICE)wasselectedbytheEuropeanSpaceAgency(ESA)asaplannedmission.[25][145]Thatmissionincludes2flybysofEuropa,butismorefocusedonGanymede.[146] EuropaClipper–InJuly2013anupdatedconceptforaflybyEuropamissioncalledEuropaClipperwaspresentedbytheJetPropulsionLaboratory(JPL)andtheAppliedPhysicsLaboratory(APL).[147]InMay2015,NASAannouncedthatithadaccepteddevelopmentoftheEuropaClippermission,andrevealedtheinstrumentsitwilluse.[148]TheaimofEuropaClipperistoexploreEuropainordertoinvestigateitshabitability,andtoaidselectingsitesforafuturelander.TheEuropaClipperwouldnotorbitEuropa,butinsteadorbitJupiterandconduct45low-altitudeflybysofEuropaduringitsenvisionedmission.Theprobewouldcarryanice-penetratingradar,short-waveinfraredspectrometer,topographicalimager,andanion-andneutral-massspectrometer. EuropaLander(NASA)isarecentconceptmissionunderstudy.2018researchsuggestsEuropamaybecoveredintall,jaggedicespikes,presentingaproblemforanypotentiallandingonitssurface.[149][150] Oldproposals[edit] Left:artist'sconceptofthecryobotanditsdeployed"hydrobot"submersible.Right:EuropaLanderMissionconcept,NASA2005.[151] Intheearly2000s,JupiterEuropaOrbiterledbyNASAandtheJupiterGanymedeOrbiterledbytheESAwereproposedtogetherasanOuterPlanetFlagshipMissiontoJupiter'sicymoonscalledEuropaJupiterSystemMission,withaplannedlaunchin2020.[152]In2009itwasgivenpriorityoverTitanSaturnSystemMission.[153]Atthattime,therewascompetitionfromotherproposals.[154]JapanproposedJupiterMagnetosphericOrbiter. JovianEuropaOrbiterwasanESACosmicVisionconceptstudyfrom2007.AnotherconceptwasIceClipper,[155]whichwouldhaveusedanimpactorsimilartotheDeepImpactmission—itwouldmakeacontrolledcrashintothesurfaceofEuropa,generatingaplumeofdebristhatwouldthenbecollectedbyasmallspacecraftflyingthroughtheplume.[155][156] JupiterIcyMoonsOrbiter(JIMO)wasapartiallydevelopedfission-poweredspacecraftwithionthrustersthatwascancelledin2006.[136][157]ItwaspartofProjectPrometheus.[157]TheEuropaLanderMissionproposedasmallnuclear-poweredEuropalanderforJIMO.[158]Itwouldtravelwiththeorbiter,whichwouldalsofunctionasacommunicationrelaytoEarth.[158] EuropaOrbiter–Itsobjectivewouldbetocharacterizetheextentoftheoceananditsrelationtothedeeperinterior.Instrumentpayloadcouldincludearadiosubsystem,laseraltimeter,magnetometer,Langmuirprobe,andamappingcamera.[159][160]TheEuropaOrbiterreceivedago-aheadin1999butwascanceledin2002.Thisorbiterfeaturedaspecialice-penetratingradarthatwouldallowittoscanbelowthesurface.[44] Moreambitiousideashavebeenputforwardincludinganimpactorincombinationwithathermaldrilltosearchforbiosignaturesthatmightbefrozenintheshallowsubsurface.[161][162] Anotherproposalputforwardin2001callsforalargenuclear-powered"meltprobe"(cryobot)thatwouldmeltthroughtheiceuntilitreachedanoceanbelow.[136][163]Onceitreachedthewater,itwoulddeployanautonomousunderwatervehicle(hydrobot)thatwouldgatherinformationandsenditbacktoEarth.[164]BoththecryobotandthehydrobotwouldhavetoundergosomeformofextremesterilizationtopreventdetectionofEarthorganismsinsteadofnativelifeandtopreventcontaminationofthesubsurfaceocean.[165]Thissuggestedapproachhasnotyetreachedaformalconceptualplanningstage.[166] Habitabilitypotential[edit] AblacksmokerintheAtlanticOcean.Drivenbygeothermalenergy,thisandothertypesofhydrothermalventscreatechemicaldisequilibriathatcanprovideenergysourcesforlife. Sofar,thereisnoevidencethatlifeexistsonEuropa,butEuropahasemergedasoneofthemostlikelylocationsintheSolarSystemforpotentialhabitability.[128][167]Lifecouldexistinitsunder-iceocean,perhapsinanenvironmentsimilartoEarth'sdeep-oceanhydrothermalvents.[137][168]EvenifEuropalacksvolcanichydrothermalactivity,a2016NASAstudyfoundthatEarth-likelevelsofhydrogenandoxygencouldbeproducedthroughprocessesrelatedtoserpentinizationandice-derivedoxidants,whichdonotdirectlyinvolvevolcanism.[169]In2015,scientistsannouncedthatsaltfromasubsurfaceoceanmaylikelybecoatingsomegeologicalfeaturesonEuropa,suggestingthattheoceanisinteractingwiththeseafloor.ThismaybeimportantindeterminingifEuropacouldbehabitable.[18][170]ThelikelypresenceofliquidwaterincontactwithEuropa'srockymantlehasspurredcallstosendaprobethere.[171] Europa–possibleeffectofradiationonbiosignaturechemicals TheenergyprovidedbytidalforcesdrivesactivegeologicalprocesseswithinEuropa'sinterior,justastheydotoafarmoreobviousdegreeonitssistermoonIo.AlthoughEuropa,liketheEarth,maypossessaninternalenergysourcefromradioactivedecay,theenergygeneratedbytidalflexingwouldbeseveralordersofmagnitudegreaterthananyradiologicalsource.[172]LifeonEuropacouldexistclusteredaroundhydrothermalventsontheoceanfloor,orbelowtheoceanfloor,whereendolithsareknowntoinhabitonEarth.Alternatively,itcouldexistclingingtothelowersurfaceofEuropa'sicelayer,muchlikealgaeandbacteriainEarth'spolarregions,orfloatfreelyinEuropa'socean.[173]IfEuropa'soceanistoocold,biologicalprocessessimilartothoseknownonEarthcouldnottakeplace.Ifitistoosalty,onlyextremehalophilescouldsurviveinthatenvironment.[173]In2010,amodelproposedbyRichardGreenbergoftheUniversityofArizonaproposedthatirradiationoficeonEuropa'ssurfacecouldsaturateitscrustwithoxygenandperoxide,whichcouldthenbetransportedbytectonicprocessesintotheinteriorocean.SuchaprocesscouldrenderEuropa'soceanasoxygenatedasourownwithinjust12millionyears,allowingtheexistenceofcomplex,multicellularlifeforms.[174] EvidencesuggeststheexistenceoflakesofliquidwaterentirelyencasedinEuropa'sicyoutershellanddistinctfromaliquidoceanthoughttoexistfartherdownbeneaththeiceshell,[66][67]aswellaspocketsofwaterthatformMshapediceridgeswhenthewaterfreezesonthesurface-likeinGreenland.[175]Ifconfirmed,thelakesandpocketsofwatercouldbeyetanotherpotentialhabitatforlife.EvidencesuggeststhathydrogenperoxideisabundantacrossmuchofthesurfaceofEuropa.[176]Becausehydrogenperoxidedecaysintooxygenandwaterwhencombinedwithliquidwater,theauthorsarguethatitcouldbeanimportantenergysupplyforsimplelifeforms. Clay-likeminerals(specifically,phyllosilicates),oftenassociatedwithorganicmatteronEarth,havebeendetectedontheicycrustofEuropa.[177]Thepresenceofthemineralsmayhavebeentheresultofacollisionwithanasteroidorcomet.[177]SomescientistshavespeculatedthatlifeonEarthcouldhavebeenblastedintospacebyasteroidcollisionsandarrivedonthemoonsofJupiterinaprocesscalledlithopanspermia.[178] Seealso[edit] solarsystemportal outerspaceportal astronomyportal ColonizationofEuropa Jupiter'smoonsinfiction ListofcratersonEuropa ListofgeologicalfeaturesonEuropa ListoflineaeonEuropa SnowballEarthhypothesis Notes[edit] ^Periapsisisderivedfromthesemimajoraxis(a)andeccentricity(e):a(1 − e). ^Apoapsisisderivedfromthesemimajoraxis(a)andeccentricity(e):a(1 + e). ^Surfaceareaderivedfromtheradius(r):4πr2. ^Volumederivedfromtheradius(r):4/3πr3. ^Surfacegravityderivedfromthemass(m),thegravitationalconstant(G)andtheradius(r):Gm/r2. ^Escapevelocityderivedfromthemass(m),thegravitationalconstant(G)andtheradius(r): 2 G m / r {\displaystyle\textstyle{\sqrt{2Gm/r}}} . 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^PreventingtheForwardContaminationofEuropa.NationalAcademyofSciencesSpaceStudiesBoard.Washington(DC):NationalAcademyPress.2000.ISBN 978-0-309-57554-6.Archivedfromtheoriginalon13February2008. ^Powell,Jesse;Powell,James;Maise,George;Paniagua,John(2005)."NEMO:AmissiontosearchforandreturntoEarthpossiblelifeformsonEuropa".ActaAstronautica.57(2–8):579–593.Bibcode:2005AcAau..57..579P.doi:10.1016/j.actaastro.2005.04.003. ^Schulze‐Makuch,Dirk;Irwin,LouisN.(2001)."AlternativeenergysourcescouldsupportlifeonEuropa".Eos,TransactionsAmericanGeophysicalUnion.82(13):150.Bibcode:2001EOSTr..82..150S.doi:10.1029/EO082i013p00150.Archivedfromtheoriginalon11January2020.Retrieved11January2020. ^Jones,Nicola(11December2001)."BacterialexplanationforEuropa'srosyglow".NewScientist.Archivedfromtheoriginalon27February2015.Retrieved26September2016. ^"Europa'sOceanMayHaveAnEarthlikeChemicalBalance",Jpl.nasa.gov,archivedfromtheoriginalon18May2016,retrieved18May2016 ^Wall,Mike(9June2015)."NASAAimingforMultipleMissionstoJupiterMoonEuropa".Space.com.Archivedfromtheoriginalon11June2015.Retrieved10June2015. ^Phillips,Cynthia(28September2006)TimeforEuropaArchived25November2006attheWaybackMachine,Space.com. ^Wilson,ColinP.(March2007).TidalHeatingonIoandEuropaanditsImplicationsforPlanetaryGeophysics.NortheasternSection-42ndAnnualMeeting.Archivedfromtheoriginalon5September2008.Retrieved21December2007. ^abMarion,GilesM.;Fritsen,ChristianH.;Eicken,Hajo;Payne,MeredithC.(2003)."TheSearchforLifeonEuropa:LimitingEnvironmentalFactors,PotentialHabitats,andEarthAnalogues".Astrobiology.3(4):785–811.Bibcode:2003AsBio...3..785M.doi:10.1089/153110703322736105.PMID 14987483.S2CID 23880085. ^RichardGreenberg(May2010)."TransportRatesofRadiolyticSubstancesintoEuropa'sOcean:ImplicationsforthePotentialOriginandMaintenanceofLife".Astrobiology.10(3):275–283.Bibcode:2010AsBio..10..275G.doi:10.1089/ast.2009.0386.PMID 20446868. ^IcyEuropa'smysteriousdoubleridgesmayhintathiddenpocketsofwaterRahulRao,Space.com.April21,2022 ^NASA–MappingtheChemistryNeededforLifeatEuropa.Archived8April2013attheWaybackMachine.Nasa.gov(4April2013).Retrievedon23July2013. ^abCook,Jia-RuiC.(11December2013)."Clay-LikeMineralsFoundonIcyCrustofEuropa".NASA.Archivedfromtheoriginalon30January2020.Retrieved11December2013. ^Choi,CharlesQ.(8December2013)."LifeCouldHaveHitchedaRidetoOuterPlanetMoons".AstrobiologyMagazine.AstrobiologyWeb.Archivedfromtheoriginalon12December2013.Retrieved12December2013. Furtherreading[edit] Rothery,DavidA.(1999).SatellitesoftheOuterPlanets:WorldsinTheirOwnRight.OxfordUniversityPressUS.ISBN 978-0-19-512555-9. Harland,DavidM.(2000).JupiterOdyssey:TheStoryofNASA'sGalileoMission.Springer.ISBN 978-1-85233-301-0. Externallinks[edit] WikimediaCommonshasmediarelatedtoEuropa(moon). EuropaProfileatNASA EuropaFactsatTheNinePlanets EuropaFactsatViewsoftheSolarSystem PreventingForwardContaminationofEuropa–USASpaceStudiesBoard(2000) ImagesofEuropaatJPL'sPlanetaryPhotojournal MovieofEuropa'srotationfromtheNationalOceanicandAtmosphericAdministration EuropamapwithfeaturenamesfromPlanetaryPhotojournal EuropanomenclatureandEuropamapwithfeaturenamesfromtheUSGSplanetarynomenclaturepage PaulSchenk's3DimagesandflyovervideosofEuropaandotherouterSolarSystemsatellites;seealso Large,high-resolutionGalileoimagemosaicsofEuropanterrainfromJasonPerryatJPL:1,2,3,4,5,6,7 EuropaimagemontagefromGalileospacecraftNASA ViewofEuropafromGalileoflybys GoogleEuropa3D,interactivemapofthemoon High-resolutionanimationbyKevinM.GillofaflyoverofEuropa;seealbumformore vteEuropaGeologyChaoticterrain ConamaraChaos Craters Pwyll Cilix Lists ListoflineaeonEuropa ListofgeologicalfeaturesonEuropa ListofcratersonEuropa ExplorationPast Pioneer10 Pioneer11 Voyager1 Voyager2 Galileo Cassini–Huygens NewHorizons Planned JupiterIcyMoonsExplorer(2023) EuropaClipper(2024) Cancelled/Concepts JupiterEuropaOrbiter EuropaLander EuropaOrbiter JupiterIcyMoonsOrbiter JovianEuropaOrbiter EuropaLander(reroutedtoGanymedeasLaplace-P) Other ColonizationofEuropa Life Europainfiction vteJupiter OutlineofJupiter Geography Atmosphere GreatRedSpot Magnetosphere Rings Jupiter'sNorthPole Jupiter'sSouthPole MoonsInnermoons Metis Adrastea Amalthea Thebe Galileanmoons Io Europa Ganymede Callisto Irregularmoons Himaliagroup Themisto Carpo Valetudo Anankegroup Carmegroup Pasiphaegroup AstronomyGeneral Jupiter-crossingminorplanets Solareclipses Trojans Greekcamp Trojancamp Impactevents CometShoemaker–Levy9 2009Jupiterimpactevent 2010Jupiterimpactevent ExplorationandorbitingmissionsCurrent Juno Past Cassini Galileo NewHorizons Pioneerprogram Pioneer10 Pioneer11 Ulysses Voyagerprogram Voyager1 Voyager2 Future JupiterIcyMoonsExplorer(2023) EuropaClipper(2024) Proposed Laplace-P(2023) InterstellarExpress(2024) IoVolcanoObserver(2026) GanDe(2029) Smara(2030) Related Fiction Mythology Category  SolarSystemportal ArticlesrelatedtoEuropa vteNaturalsatellitesoftheSolarSystemvteMoonsofterrestrialplanetsandasteroidsEarthMarsAsteroidmoons TheMoon Phobos Deimos Binaries List vteMoonsofJupiterListedinincreasingapproximatedistancefromJupiterInnermoons(4) Metis Adrastea Amalthea Thebe Galileanmoons(4) Io Europa Ganymede Callisto Themistogroup(1) Themisto Himaliagroup(7) Leda Ersa Himalia Pandia Lysithea Elara Dia Carpogroup(1) Carpo Valetudogroup(1) Valetudo Anankegroup(22) Euporie JupiterLV Eupheme JupiterLII JupiterLIV Mneme Euanthe S/2003J16 Harpalyke Orthosie Helike Praxidike JupiterLXIV S/2003J12 JupiterLXVIII Thelxinoe Thyone S/2003J2 Ananke Iocaste Hermippe JupiterLXX Carmegroup(23) Pasithee JupiterLXIX S/2003J24 Chaldene JupiterLXIII Isonoe Kallichore Erinome Kale Eirene Aitne Eukelade Arche Taygete JupiterLXXII Carme Herse JupiterLXI JupiterLI S/2003J9 JupiterLXVI Kalyke S/2003J10(?) Pasiphaegroup(17) Philophrosyne Eurydome JupiterLVI S/2003J4 JupiterLXVII Hegemone Pasiphae Sponde Megaclite Cyllene Sinope JupiterLIX Aoede Autonoe Callirrhoe S/2003J23 Kore Seealso RingsofJupiter Jupiter'smoonsinfiction Category vteMoonsofSaturnListedinapproximatelyincreasingdistancefromSaturnRingshepherds S/2009S1 Ringmoonlets Pan Daphnis Atlas Prometheus Pandora Co-orbitals Epimetheus Janus GRing Aegaeon Alkyonides Methone Anthe Pallene Innerlarge(withtrojans) Mimas Enceladus Tethys Telesto Calypso Dione Helene Polydeuces Outerlarge Rhea Titan Hyperion Iapetus Inuitgroup(8) S/2019S1 Kiviuq Ijiraq Paaliaq SaturnLX S/2004S31 Tarqeq Siarnaq Norsegroup(46) Phoebe Skathi S/2004S37 S/2007S2 Skoll S/2004S13 (?) Hyrrokkin Greip Mundilfari S/2006S1 S/2007S3 (?) Gridr Bergelmir Narvi Jarnsaxa S/2004S17 (?) Suttungr Eggther Hati S/2004S12 Bestla Farbauti Thrymr Angrboda Beli Aegir Gerd S/2004S7 (?) Gunnlod Skrymir S/2004S28 Alvaldi Kari Geirrod S/2006S3 Fenrir Surtur Loge Ymir S/2004S21 S/2004S39 S/2004S36 Thiazzi SaturnLXIV Fornjot SaturnLVIII Gallicgroup(4) Albiorix Bebhionn Erriapus Tarvos Progradeoutersatellites S/2004S24 RingsofSaturn Cassini–Huygens Themis Chiron S/2004S6 S/2004S4 S/2004S3 Infiction vteMoonsofUranus ListedinapproximatelyincreasingdistancefromUranus Inner RingsofUranus Cordelia Ophelia Bianca Cressida Desdemona Juliet Portia Rosalind Cupid Belinda Perdita Puck Mab Major(spheroid) Miranda Ariel Umbriel Titania Oberon Outer(irregular) Francisco Caliban Stephano Trinculo Sycorax Margaret Prospero Setebos Ferdinand Geologicalfeatures Arielian KachinaChasmata Yangoor Mirandian VeronaRupes Oberonian Hamlet MommurChasma Puckian Titanian Gertrude MessinaChasmata Ursula RousillonRupes Umbrielian Wunda Vuver Skynd vteMoonsofNeptuneListedinapproximatelyincreasingdistancefromNeptuneRegular(inner) Naiad Thalassa Despina Galatea Larissa Hippocamp Proteus Triton Triton atmosphere geologicalfeatures sky Irregular Nereid Halimede Sao Laomedeia Psamathe Neso Seealso Neptunetrojans RingsofNeptune Category Portal vteMoonsoflikelydwarfplanetsPlutoHaumeaErisMakemakeGonggong Charon Styx Nix Kerberos Hydra ring Namaka Hiʻiaka Dysnomia MK2 Xiangliu QuaoarOrcusSalaciaVarda2013FY27 Weywot Vanth Actaea Ilmarë 2013FY27I vteNaturalsatellitesoftheSolarSystemPlanetarysatellitesof Earth Mars Jupiter Saturn Uranus Neptune Dwarfplanetsatellitesof Orcus Pluto Haumea Quaoar Makemake Gonggong Eris Minor-planetmoons Near-Earth: Florence Didymos(Dimorphos) Moshup(Squannit) 1994CC 2001SN263 Mainbelt: Kalliope(Linus) Euphrosyne Daphne(Peneius) Eugenia(Petit-Prince) Sylvia(Romulus ·Remus) Minerva(Aegis ·Gorgoneion) Camilla Elektra Kleopatra(Alexhelios ·Cleoselene) Ida(Dactyl) Roxane(Olympias) Pulcova Balam Jupitertrojans: Patroclus(Menoetius) Hektor(Skamandrios) Eurybates(Queta) TNOs: Lempo(Hiisi ·Paha) 2002UX25 Sila–Nunam Salacia(Actaea) Varda(Ilmarë) Gǃkúnǁʼhòmdímà(GǃòʼéǃHú) 2013FY27 Rankedbysize Planetary-massmoon Ganymede largest:5268km/0.413Earths Titan Callisto Io Moon Europa Triton Titania Rhea Oberon Iapetus Charon Umbriel Ariel Dione Tethys Dysnomia Enceladus Miranda Vanth Proteus Mimas Ilmarë Nereid Hiʻiaka Actaea Hyperion Phoebe ... Discoverytimeline Innermoons Irregularmoons List Planetary-massmoons Naming Subsatellite Regularmoons Trojanmoons Discoverytimeline Innermoons Irregularmoons List Naming Subsatellite Regularmoons Trojanmoons vteNaturalsatellitesoftheSolarSystemPlanetarysatellitesof Earth Mars Jupiter Saturn Uranus Neptune Dwarfplanetsatellitesof Orcus Pluto Haumea Quaoar Makemake Gonggong Eris Minor-planetmoons Near-Earth: Florence Didymos(Dimorphos) Moshup(Squannit) 1994CC 2001SN263 Mainbelt: Kalliope(Linus) Euphrosyne Daphne(Peneius) Eugenia(Petit-Prince) Sylvia(Romulus ·Remus) Minerva(Aegis ·Gorgoneion) Camilla Elektra Kleopatra(Alexhelios ·Cleoselene) Ida(Dactyl) Roxane(Olympias) Pulcova Balam Jupitertrojans: Patroclus(Menoetius) Hektor(Skamandrios) Eurybates(Queta) TNOs: Lempo(Hiisi ·Paha) 2002UX25 Sila–Nunam Salacia(Actaea) Varda(Ilmarë) Gǃkúnǁʼhòmdímà(GǃòʼéǃHú) 2013FY27 Rankedbysize Planetary-massmoon Ganymede largest:5268km/0.413Earths Titan Callisto Io Moon Europa Triton Titania Rhea Oberon Iapetus Charon Umbriel Ariel Dione Tethys Dysnomia Enceladus Miranda Vanth Proteus Mimas Ilmarë Nereid Hiʻiaka Actaea Hyperion Phoebe ... Discoverytimeline Innermoons Irregularmoons List Planetary-massmoons Naming Subsatellite Regularmoons Trojanmoons vteAtmospheresStar Sun Exoplanet HD209458b Kepler-7b Planet Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Dwarfplanet Ceres Pluto Makemake Eris Satellite Moon Io Europa Ganymede Callisto Enceladus Dione Rhea Titan Triton Seealso Prebioticatmosphere Coma Extraterrestrialatmosphere Stellaratmosphere vteExtraterrestriallifeEventsandobjects Shergottymeteorite(1865) Nakhlameteorite(1911) Murchisonmeteorite(1969) Vikinglanderbiologicalexperiments(1976) AllanHills77005(1977) AllanHills84001(1984) Yamato000593(2000) CI1fossils(2011) Polonnaruwameteorite(2012) SignalsofinterestMisidentified CP1919(misidentifiedpulsar) CTA-102(misidentifiedquasar) Stars KIC8462852(unusuallightfluctuations) EPIC204278916(unusuallightfluctuations) VVV-WIT-07(unusuallightfluctuations) HD164595signal(unknownorigin) Other SHGb02+14a(radiosource) Wow!signal(inconclusive) Fastradioburst(unknownorigin) BLC1(radiosignal) LifeintheUniverse Earliestknownlifeforms HabitabilityofEnceladus HabitabilityofEuropa HabitabilityofMars HabitabilityofTitan HabitabilityofVenus Planetaryhabitability CatalogofNearbyHabitableSystems Circumstellarhabitablezone Earthanalog Extraterrestrialliquidwater Galactichabitablezone Habitabilityofbinarystarsystems Habitabilityoforangedwarfsystems Habitabilityofreddwarfsystems Naturalsatellitehabitability Planetaryhabitability Spacemissions Beagle2 BiologicalOxidantandLifeDetection BioSentinel Curiosityrover Darwin Dragonfly EnceladusExplorer EnceladusLifeFinder EuropaClipper ExoMars RosalindFranklinrover ExoLance EXPOSE Foton-M3 IcebreakerLife JourneytoEnceladusandTitan Laplace-P LifeInvestigationForEnceladus LivingInterplanetaryFlightExperiment MarsGeyserHopper Marssample-returnmission Mars2020 NorthernLight Opportunityrover SpaceXRedDragon Spiritrover Tanpopo TitanMareExplorer VenusInSituExplorer Viking1 Viking2 Interstellarcommunication ActiveSETI AllenTelescopeArray Arecibomessage AreciboObservatory BerkeleySETIResearchCenter Bracewellprobe BreakthroughInitiatives BreakthroughListen BreakthroughMessage Communicationwithextraterrestrialintelligence Gauss'sPythagoreanrighttriangleproposal Astrolinguistics Lincoslanguage NIROSETI Pioneerplaque ProjectCyclops ProjectOzma ProjectPhoenix SERENDIP Searchforextraterrestrialintelligence SETI@home setiQuest VoyagerGoldenRecord Waterhole Xenolinguistics Exhibitions TheScienceofAliens Hypotheses Aestivationhypothesis Cosmicpluralism Directedpanspermia Drakeequation Extraterrestrialhypothesis Fermiparadox GreatFilter Hypotheticaltypesofbiochemistry Interplanetarycontamination Kardashevscale Mediocrityprinciple Neocatastrophism Panspermia Planetariumhypothesis RareEarthhypothesis Zoohypothesis Relatedtopics Ancientastronauts Astrobiology Astroecology Biosignature BrookingsReport Planetaryprotection Potentialculturalimpactofextraterrestrialcontact Post-detectionpolicy Exotheology Extraterrestrialsinfiction Extremophile MERMOZ NexusforExoplanetSystemScience Noogenesis SanMarinoScale Technosignature UFOreligion Xenoarchaeology vteAstrobiologyDisciplines Astrochemistry Astrophysics Atmosphericsciences Biochemistry Evolutionarybiology Exoplanetology Geomicrobiology Microbiology Paleontology Planetaryscience Maintopics Abiogenesis AllanHills84001 Biomolecule Biosignature Drakeequation Earliestknownlifeforms Earthanalog Extraterrestriallife Extraterrestrialsamplecuration Extremophiles Hypotheticaltypesofbiochemistry Listofmicroorganismstestedinouterspace Oceanplanet Panspermia Planetaryprotection Searchforextraterrestrialintelligence(SETI) Yamatometeorite Planetaryhabitability Habitabilityofbinarystarsystems HabitabilityofK-typemain-sequencestarsystems Habitabilityofnaturalsatellites Habitabilityofreddwarfsystems Circumstellarhabitablezone Earthanalog Listofpotentiallyhabitableexoplanets Tholin Extraterrestrialliquidwater Galactichabitablezone Superhabitableplanet SpacemissionsEarthorbit BIO BIOCORE Biolab Bion BIOPAN Biosatelliteprogram E-MIST ERA Eu:CROPIS EXOSTACK EXPOSE LunarMicroEcosystem O/OREOS OREOcube Tanpopo VEGGIE Mars Beagle2 Fobos-Grunt MarsScienceLaboratory Curiosityrover Mars2020 Perseverancerover Phoenix Tianwen-1 Zhurongrover TraceGasOrbiter Viking Cometsandasteroids Hayabusa2 OSIRIS-REx Rosetta Planned BioSentinel Dragonfly EuropaClipper ExoMars RosalindFranklinrover Kazachoklander Proposed BreakthroughEnceladus BRUIE CAESAR EnceladusExplorer EnceladusLifeFinder‎ EnceladusLifeSignaturesandHabitability EnceladusOrbilander EuropaLander ExoLance ExplorerofEnceladusandTitan IcebreakerLife JourneytoEnceladusandTitan Laplace-P LifeInvestigationForEnceladus Marssamplereturnmission Oceanus THEO Trident Cancelledandundeveloped AstrobiologyFieldLaboratory Beagle3 BiologicalOxidantandLifeDetection LivingInterplanetaryFlightExperiment MarsAstrobiologyExplorer-Cacher MELOS NorthernLight RedDragon TerrestrialPlanetFinder Institutionsandprograms AstrobiologySocietyofBritain AstrobiologyScienceandTechnologyforExploringPlanets BreakthroughInitiatives BreakthroughListen BreakthroughMessage BreakthroughStarshot CarlSaganInstitute CenterforLifeDetectionScience EuropeanAstrobiologyNetworkAssociation MERMOZ NASAAstrobiologyInstitute NexusforExoplanetSystemScience OceanWorldsExplorationProgram SpanishAstrobiologyCenter‎ Category Commons vteSolarSystem Sun Mercury Venus Earth Mars Ceres Jupiter Saturn Uranus Neptune Orcus Pluto Haumea Quaoar Makemake Gonggong Eris Sedna Planetsanddwarfs Terrestrials Mercury Venus Earth Mars Giants Gas Jupiter Saturn Ice Uranus Neptune Dwarfs Ceres Orcus Pluto Haumea Quaoar Makemake Gonggong Eris Sedna Moons Earth Moon othernear-Earthobjects Mars Phobos Deimos Jupiter Ganymede Callisto Io Europa all80 Saturn Titan Rhea Iapetus Dione Tethys Enceladus Mimas Hyperion Phoebe all83 Uranus Titania Oberon Umbriel Ariel Miranda all27 Neptune Triton Proteus Nereid all14 Orcus Vanth Pluto Charon Nix Hydra Kerberos Styx Haumea Hiʻiaka Namaka Quaoar Weywot Makemake S/2015(136472)1 Gonggong Xiangliu Eris Dysnomia Rings Jovian Saturnian (Rhean) Charikloan Chironean Uranian Neptunian Haumean SmallSolarSystembodies Comets Damocloids Meteoroids Minorplanets namesandmeanings moons Planetesimal Planetaryorbit-crossingminorplanets Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Trojans Venus Earth Mars Jupiter Trojancamp Greekcamp SaturnMoons Uranus Neptune Near-Earthobjects Asteroidbelt Asteroids Ceres Vesta Pallas Hygiea active first1000 families PHA exceptional Kirkwoodgap Cis-Neptunianobjects Centaurs Neptunetrojans Trans-Neptunianobjects Kuiperbelt Cubewanos Plutinos Detachedobjects Sednoids Scattereddisc Oortcloud Hillscloud Hypotheticalobjects Fifthgiant Nemesis Phaeton PlanetNine PlanetV PlanetX Subsatellites Theia Tyche Vulcan Vulcanoids Exploration(outline) Discovery astronomy historicalmodels timeline Spaceprobes timeline list 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