In Depth | Europa – NASA Solar System Exploration

Like our planet, Europa is thought to have an iron core, a rocky mantle, and an ocean of salty water. Unlike Earth, however, Europa's ocean lies ... MORE Europa MENU Overview InDepth BytheNumbers Exploration Galleries Overview InDepth BytheNumbers Exploration Galleries Introduction Decadesago,sciencefictionofferedahypotheticalscenario:WhatifalienlifewerethrivinginanoceanbeneaththeicysurfaceofJupiter’smoonEuropa?ThenotionpulledEuropaoutofobscurityandintothelimelightwhereithasremained,stokingtheimaginationsofpeoplebothwithinandoutsidethesciencecommunitywhofantasizeabouthumansdiscoveringlifebeyondEarth.Thatfantasy,however,maybegroundedinreality. Fromground-basedtelescopes,scientistsknewthatEuropa'ssurfaceismostlywaterice,andscientistshavefoundstrongevidencethatbeneaththeicecrustisanoceanofliquidwaterorslushyice.In1979thetwoVoyagerspacecraftpassedthroughtheJoviansystem,providingthefirsthintsthatEuropamightcontainliquidwater.Thenground-basedtelescopesonEarth,alongwiththeGalileospacecraftandspacetelescopes,haveincreasedscientists’confidenceforaEuropanocean. ScientiststhinkEuropa’siceshellis10to15miles(15to25kilometers)thick,floatingonanocean40to100miles(60to150kilometers)deep.SowhileEuropaisonlyone-fourththediameterofEarth,itsoceanmaycontaintwiceasmuchwaterasallofEarth’soceanscombined.Europa’svastandunfathomablydeepoceaniswidelyconsideredthemostpromisingplacetolookforlifebeyondEarth.ApassingspacecraftmightevenbeabletosampleEuropa’soceanwithoutlandingonthemoon’ssurfacebecauseitispossiblethatEuropa’soceanmaybeleakingoutintospace. ResourcePackages JupiterResources OceanWorldsResources WhilenoplumeswereobservedwhiletheGalileospacecraftwasintheJupitersysteminthe1990s,morerecentobservationsfromtelescopessuchastheHubbleSpaceTelescope,aswellasareanalysisofsomedatafromtheGalileospacecraft,havesuggestedthatitispossiblethatthinplumesofwaterarebeingejected100miles(160kilometers)aboveEuropa’ssurface.InNovember2019,aninternationalresearchteamledbyNASAannouncedtheyhaddirectlydetectedwatervaporforthefirsttimeaboveEuropa’ssurface.TheteammeasuredthevaporusingaspectrographattheKeckObservatoryinHawaiithatmeasuresthechemicalcompositionofplanetaryatmospheresthroughtheinfraredlighttheyemitorabsorb. Iftheplumesdoexist,andiftheirsourceislinkedtoEuropa’socean,thenaspacecraftcouldtravelthroughtheplumetosampleandanalyzeitfromorbit,anditwouldessentiallybeanalyzingthemoon’socean(theCassinispacecraftperformedthisfeatatSaturn’smoonEnceladus,whichisknowntohaveanoceansprayingintospace).EvenifEuropaisn’tejectingfreesamplesintospace,a2018studyconcludedthatsamplesofEuropa’soceancouldgetfrozenintothebaseofthemoon’siceshell,wheretheicemakescontactwiththeocean.Astheiceshelldistortsandflexesfromtidalforces,warmerandless-denseicewouldrise,carryingtheoceansamplestothesurfacewhereaspacecraftcouldanalyzeitremotely,usinginfraredandultravioletinstruments,amongothers.Scientistscouldthenstudythematerial’scompositiontodeterminewhetherEuropa’soceanmightbehospitableforsomeformoflife. Namesake Namesake Europaisnamedforawomanwho,inGreekmythology,wasabductedbythegodZeus–JupiterinRomanmythology. A3DmodelofJupiter'smoonEuropa,anicymoonwithahiddensubsurfaceocean.Credit:NASAVisualizationTechnologyApplicationsandDevelopment(VTAD) ›DownloadOptions PotentialforLife PotentialforLife Lifeasweknowitseemstohavethreemainrequirements:liquidwater,theappropriatechemicalelements,andanenergysource. Astrobiologists–scientistswhostudytheorigin,evolution,andfutureoflifeintheuniverse–believeEuropahasabundantwaterandtherightchemicalelements,butanenergysourceonEuropahasbeendifficulttoconfirm.OnEarth,lifeformshavebeenfoundthrivingnearsubterraneanvolcanoes,deep-seavents,andotherextremeenvironments.These“extremophile”lifeformsgivescientistscluesabouthowlifemaybeabletosurvivebeneathEuropa’siceshell. IfweeventuallyfindsomeformoflifeatEuropa(orMarsorEnceladusforthatmatter),itmaylooklikemicrobes,ormaybesomethingmorecomplex.Ifitcanbedemonstratedthatlifeformedindependentlyintwoplacesaroundthesamestar,itwouldthenbereasonabletosuspectthatlifespringsupintheuniversefairlyeasilyoncethenecessaryingredientsarepresent,andthatlifemightbefoundthroughoutourgalaxyandtheuniverse.IflifewerefoundatEuropa,howmightitchangeyourviewofthecosmosandourplaceinit? SizeandDistance SizeandDistance Withanequatorialdiameterof1,940miles(3,100kilometers),Europaisabout90percentthesizeofEarth’sMoon.SoifwereplacedourMoonwithEuropa,itwouldappearroughlythesamesizeintheskyasourMoondoes,butbrighter–much,muchbrighter.Europa’ssurfaceismadeofwatericeandsoitreflects5.5timesthesunlightthanourMoondoes. EuropaorbitsJupiteratabout417,000miles(671,000kilometers)fromtheplanet,whichitselforbitstheSunatadistanceofroughly500millionmiles(780millionkilometers),or5.2astronomicalunits(AU).OneAUisthedistancefromEarthtotheSun.LightfromtheSuntakesabout45minutestoreachEuropa.Becauseofthedistance,sunlightisabout25timesfainteratJupiterandEuropathanatEarth. OrbitandRotation OrbitandRotation EuropaorbitsJupiterevery3.5daysandislockedbygravitytoJupiter,sothesamehemisphereofthemoonalwaysfacestheplanet.Jupitertakesabout4,333Earthdays(orabout12Earthyears)toorbittheSun(aJovianyear).Jupiter’sequator(andtheorbitalplaneofitsmoons)aretiltedwithrespecttoJupiter’sorbitalpatharoundtheSunbyonly3degrees(Earthistilted23.5degrees).ThismeansJupiterspinsnearlyuprightsothattheplanet,aswellasEuropaandJupiter’sotherdozensofmoons,donothaveseasonsasextremeasotherplanetsdo. Jupiter’smoonsIo,Europa,andGanymedeareinwhatiscalledaresonance–everytimeGanymedeorbitsJupiteronce,Europaorbitstwice,andIoorbitsfourtimes.Overtime,theorbitsofmostlargesatellitesorplanetstendtobecomecircular,butinthecaseofthesethreesatellites,theresonanceproducesaforcedeccentricitysincethesatelliteslineupwitheachotheratthesamepointsintheirorbitsoverandover,givingeachotherasmallgravitationaltugthatkeepstheirorbitsfrombecomingcircular. BecauseEuropa'sorbitiselliptical(slightlystretchedoutfromcircular),itsdistancefromJupitervaries,andthemoon’snearsidefeelsJupiter’sgravitymorestronglythanitsfarside.ThemagnitudeofthisdifferencechangesasEuropaorbits,creatingtidesthatstretchandrelaxthemoon’ssurface. Flexingfromthetideslikelycreatesthemoon’ssurfacefractures.IfEuropa'soceanexists,thetidalheatingcouldalsoleadtovolcanicorhydrothermalactivityontheseafloor,supplyingnutrientsthatcouldmaketheoceansuitableforlivingthings. Formation Formation Jupiter’slargeGalileansatellites(Io,Europa,Ganymede,andCallisto)likelyformedoutofleftovermaterialafterJupitercondensedfromtheinitialcloudofgasanddustsurroundingthesun,earlyinthehistoryofthesolarsystem.Thosefourmoonsarelikelyaboutthesameageastherestofthesolarsystem–about4.5billionyearsold. Infact,theGalileansatellitesaresometimescalleda“minisolarsystem”sincetheyformedfromtheleftoversofJupitersimilartohowEarthandotherplanetsformedfromgasanddustleftoverfromtheformationofourSun.Thesimilaritiesdon’tendthere.Eachplanetintheinnersolarsystemislessdensethantheirinnerneighbor–MarsislessdensethanEarth,whichislessdensethanVenus,whichislessdensethanMercury.TheGalileanmoonsfollowthesameprinciple,beinglessdensethefarthertheyarefromJupiter.Thereduceddensityatgreaterdistancesislikelyduetotemperature:denser,rocky,andmetalmaterialcondensesoutfirst,closetoJupiterortheSun,whilelighter-weighticymaterialonlycondensesoutatlargerdistanceswhereitiscolder. DistancefromJupiteralsodetermineshowmuchtidalheatingtheGalileansatellitesexperience—Io,closesttoJupiter,isheatedsomuchthatitisthemostvolcanicallyactivebodyinthesolarsystem,anditlikelylongagodroveoffanywaterithadwhenitformed.Europahasalayeroficeandwaterontopofarockyandmetalinterior,whileGanymedeandCallistoactuallyhavehigherproportionsofwatericeandsolowerdensities. Structure Structure Likeourplanet,Europaisthoughttohaveanironcore,arockymantle,andanoceanofsaltywater.UnlikeEarth,however,Europa’soceanliesbelowashelloficeprobably10to15miles(15to25kilometers)thick,andhasanestimateddepthof40to100miles(60to150kilometers).Whileevidenceforaninternaloceanisstrong,itspresenceawaitsconfirmationbyafuturemission. Surface Surface Europa’swater-icesurfaceiscrisscrossedbylong,linearfractures.Basedonthesmallnumberofobservablecraters,thesurfaceofthismoonappearstobenomorethan40to90millionyearsold,whichisyouthfulingeologicterms(thesurfaceofCallisto,anotherofJupiter’smoons,isestimatedtobeafewbillionyearsold).AllalongEuropa'smanyfractures,andinsplotchypatternsacrossitssurface,isareddish-brownmaterialwhosecompositionisnotknownforcertain,butlikelycontainssaltsandsulfurcompoundsthathavebeenmixedwiththewatericeandmodifiedbyradiation.Thissurfacecompositionmayholdcluestothemoon'spotentialasahabitableworld. NASA'sGalileospacecraftexploredtheJupitersystemfrom1995to2003andmadenumerousflybysofEuropa.GalileorevealedstrangepitsanddomesthatsuggestEuropa’sicelayercouldbeslowlychurning,orconvecting(cooler,densericesinks,whilewarmerless-denseicerises)duetoheatfrombelow.Long,linearfracturesareoftenonly1-2kilometerswidebutcanextendforthousandsofkilometersacrossEuropa’ssurface.Someofthesefractureshavebuiltupintoridgeshundredsofmeterstall,whileothersappeartohavepulledapartintowidebandsofmultipleparallelfractures.Galileoalsofoundregionscalled"chaosterrain,"wherebroken,blockylandscapeswerecoveredinmysteriousreddishmaterial.In2011,scientistsstudyingGalileodataproposedthatchaosterrainscouldbeplaceswherethesurfacecollapsedabovelens-shapedlakesembeddedwithintheice. Atmosphere Atmosphere Europahasonlyatenuousatmosphereofoxygen,butin2013,NASAannouncedthatresearchersusingtheHubbleSpaceTelescopefoundevidencethatEuropamightbeactivelyventingwaterintospace.Thiswouldmeanthemoonisgeologicallyactiveinthepresentday.Ifconfirmedbyfollow-upobservations,theplumesofwatercouldbestudiedbyfuturespacecraftsimilartohowtheCassinisampledtheplumeofSaturn’smoonEnceladus. Magnetosphere Magnetosphere OneofthemostimportantmeasurementsmadebytheGalileomissionshowedhowJupiter'smagneticfieldwasdisruptedinthespacearoundEuropa.Themeasurementstronglyimpliedthataspecialtypeofmagneticfieldisbeingcreated(induced)withinEuropabyadeeplayerofsomeelectricallyconductivefluidbeneaththesurface.BasedonEuropa'sicycomposition,scientiststhinkthemostlikelymaterialtocreatethismagneticsignatureisaglobaloceanofsaltywater,andthismagneticfieldresultisstillthebestevidencewehavefortheexistenceofanoceanonEuropa. A3DmodelofEuropaClipper,afuturemissiontoJupiter'soceanmoon.Credit:NASAVisualizationTechnologyApplicationsandDevelopment(VTAD) ›DownloadOptions Thispageshowcasesourresourcesforthoseinterestedinlearningmoreaboutoceanworlds. OceanWorldsResources Tomostofus,dustisanannoyance.Butthesetinyparticlesthatfloataboutandsettleonsurfacesplayanimportantroleacrossthesolarsystem. 10Things:DustintheWind(onMarsandWellBeyond) FromdeepbelowthesoilatEarth’spolarregionstoPluto’sfrozenheart,iceexistsalloverthesolarsystem...andbeyond. Frozen:IceonEarthandWellBeyond ThispageshowcasesourresourcesforthoseinterestedinlearningmoreaboutJupiter. JupiterResources Theagency’smissiontoexploreJupiter’sicymoontakesabigstepforwardasengineersdeliveramajorcomponentofthespacecraft. NASA'sEuropaClipperMissionCompletesMainBodyoftheSpacecraft OnApril9,2022,theJunoCaminstrumentcapturedwhatitwouldlookliketoridealongwiththeJunospacecraft. JunoSkimstheCloudTopsofJupiter Scienceinstrumentsandotherhardwareforthespacecraftwillcometogetherinthemission’sfinalphasebeforealaunchtoEuropain2024. NASABeginsAssemblyofEuropaClipperSpacecraft MissionslikeNASA’sEuropaClipperareacomplexbalancingactofmeetingscientificandtechnicalrequirements. MissionDispatch:SystemsEngineeringforEuropaClipper Anewstudyfinallyrevealshigher-frequencyX-raysandexplainswhytheyeludedanothermission30yearsago. NASATelescopeSpotsHighest-EnergyLightEverDetectedFromJupiter EuropaClipperwillneedtoknowitsorientationwhiletravelingfromEarthtoJupiterandinorbitaroundJupiter.Toaccomplishthis,itwillusethestars. EuropaMissionDispatch:TrackingtheStars TheNextFullMoonistheWolfMoon,IceMoon,theMoonafterYule,andtheOldMoon. FullMoonGuide:January-February2022 Our2021round-upofNASAplanetaryscienceispackedwiththeyear’smostspectacularimages,ground-breakingdiscoveries,andincrediblemissionevents. NASAPlanetaryScienceHighlights:2021 NASA'sJunospacecraftcapturedsoundsofJupiter'smoonGanymededuringaJune7,2021,closeflyby. NASA'sJunoSpacecraft‘Hears'Jupiter'sMoon FindingplumesatEuropaisanexcitingprospect,butscientistswarnit’llbetricky,evenfromupclose. AreWaterPlumesSprayingfromEuropa?NASA'sEuropaClipperisontheCase NASA’sHubbleSpaceTelescopehascompletedthisyear'sgrandtouroftheoutersolarsystem. Hubble'sGrandTouroftheOuterSolarSystem Duringits36thlowpassoverJupiter,NASA’sJunospacecraftcapturedthisviewofstrikingJupiter'scloudbandsandswirls. MochaSwirlsinJupiter'sTurbulentAtmosphere NASAscientistsarecallingforaframeworkthatprovidescontextforfindingsrelatedtothesearchforlife. AreWeAloneintheUniverse?NASACallsforNewFramework NewJunofindingsprovideafullerpictureofJupiter’scolorfulatmosphericfeatures,andoffercluesaboutwhat'sbelowtheclouds. NASA'sJuno:ScienceResultsOfferFirst3DViewofJupiterAtmosphere JPL'sluckypeanutsareanunofficialtraditionatbigmissionevents. WhatAreJPL'sLuckyPeanuts? HubbleobservationsofEuropahaverevealedthepresenceofpersistentwatervapor–but,mysteriously,onlyinonehemisphere. HubbleFindsEvidenceofPersistentWaterVaporinOneHemisphereofEuropa Windsintheoutermost"lane"ofJupiter'sGreatRedSpotareaccelerating–adiscoverymadepossiblebyHubble. HubbleShowsWindsinJupiter'sGreatRedSpotAreSpeedingUp TheNextFullMoonistheHarvestMoon,theFruitMoon,theBarleyMoon,andtheCornMoon. FullMoonGuide:September-October2021 JunouseditsinfraredinstrumentduringrecentflybysofGanymedetocreatethismapadecadeafterJuno’slaunch. NASA'sJunoCelebrates10YearsWithNewInfraredViewofMoonGanymede Thisweekin2011,theJunomissiontoJupiterlaunchedfromNASA’sKennedySpaceCenteraboardanAtlasV-551rocket. ThisWeekinNASAHistory:JunoMissiontoJupiterLaunches Forthefirsttime,astronomershaveuncoveredevidenceofwatervaporintheatmosphereofJupiter'smoonGanymede. HubbleFindsFirstEvidenceofWaterVaporatJupiter'sMoonGanymede