RoadmapstoOceanWorldsOPAG

September2017LaJolla

AmandaHendrix(PSI),TerryHurford(GSFC)

co-chairs

CongressionalDirecMon

•  FromtheCommerce,JusMce,Science,andRelatedAgenciesAppropriaMonsBill,2016–  “…TheCommi+eedirectsNASAtocreateanOceanWorldExplora<onProgramwhoseprimarygoalistodiscoverextantlifeonanotherworldusingamixofDiscovery,NewFron<ersandflagshipclassmissionsconsistentwiththerecommenda<onsofcurrentandfuturePlanetaryDecadalsurveys.”

•  ConnectedtotheviewofOceanWorldsasperhapshabitableandpotenMallyinhabitedworlds

OPAGChargetoROW•  OPAGcharteredROW;wearecoordina4ngwithSBAGsincesome

“SBAG-owned”bodiescouldbeoceanworlds•  IdenMfyandprioriMzescienceobjecMvesforOceanWorlds

–  MedtotheDecadalSurvey•  Designroadmaptoexploretheseworldstoaddressscience

objecMves–  Missionsequences,sustainedexploraMoneffort

•  AssesswhereeachOceanWorldfitsintotheoverallroadmap•  Summarizebroadmissionconcepts

–  Consideringmissiondependences&internaMonalcooperaMon•  Recommendtechnologydevelopmentanddetailedmissionstudies

insupportofthenextdecadalsurvey•  PlaceexploraMonofOceanWorldsintothelargercontextofSolar

SystemexploraMon

TeammembersAmend,JanAye,MichaelBannister,MicheleBarge,LaurieBeauchamp,PatriciaBeddingfeld,ChloeBland,MichaelBowman,JeffBraun,BobbyBrinckerhoff,WilliamBura\,BonnieByrne,PaulCable,MorganCabrol,NathalieCartwright,RichardCasMllo-Rogez,JulieCollins,GeoffreyCooper,JohnCrary,FrankDhingra,RajaniDiniega,SerinaElder,Catherine

Neish,CatherineNeveu,MarcNordheim,TomOlkin,CathyPappalardo,RobertPa_erson,WesPa_hoff,AlexPhillips,CynthiaPontefract,AlexandraPortyankina,GannaPoston,MichaelQuick,LynnaeRhoden,AlyssaRicco,AntonioSchaible,MicahSchaible,GeorgeSchenk,PaulSchmidt,BritneyScully,JenniferSherwood,BrentShock,Evere_Singer,Kelsi

Emerson,DaveEubanks,MarshallFurfaro,RobertoGerman,ChrisGlein,ChrisGoodman,JasonHand,KevinHayes,AlexHibbard,KennethHibbi_s,KarlHoehler,ToriHoller,BryanHosseini,SonaHowe_,CarlyKargel,JeffreyLindensmith,ChrisLopes,RosalyMacKenzie,ShannonMalaska,MichaelMarMn,EmilyMcKay,ChrisMoore,Jeff,

Soderblom,JasonSoMn,ChristopheSuch,PamelaTurtle,ElizabethVance,SteveVerbiscer,AnneWalker,CatherineWestlake,JosephWray,James

OceanWorldDefiniMon

Wedefinedan“oceanworld”asabodywithacurrent liquidocean(notnecessarilyglobal).Allbodies in our solar system that plausibly canhave or are known to have an ocean will beconsidered.TheEarthisawell-studiedoceanworldthatweuseasareference(“groundtruth”)andpointofcomparison.

OverarchingGoal

•  TheROWteamhasfocusedonadradforthemaingoalforOceanWorldsinordertostartformulaMngdrivingsciencequesMons:

Iden<fyoceanworlds,characterizetheir

oceans,evaluatetheirhabitability,searchforlife,andul<matelyunderstandanylifewefind.

ExploreOceanWorlds

FourScienMfically-richSteps/Themes:–  IdenMfyoceanworlds– CharacterizeOceans– AssessHabitability– SearchforLife

K.P.Hand/M.Theissen/NaMonalGeographic

IdenMfyOceanWorldsExampleofIndirectEvidence:Tectonics

KnownOceanWorlds PossibleOceanWorlds

IdenMfyOceanWorldsConfirmaMonofOceansWorlds

GravityScienceExample(Iessetal.)

MagnetometerExample(Khuranaetal.,1998)

Theme1:Iden<fyoceanworldsinthesolarsystem•  Isthereasufficientenergysourcetosupportapersistentocean?

–  IsthereremnantradiogenicheaMng?–  IstheregravitaMonalenergyfromaparentplanetorsatellite?–  CantheplanetorsatelliteconvertavailableMdalenergyintoheat?–  Aretheplanet’sorsatellite’sorbitalorrotaMonalproperMesfavorabletoMdaldissipaMon?

•  AresignaturesofongoinggeologicacMvity(orliquids)detected?–  DosignaturesofgeologicacMvityindicatethepossiblepresenceofasubsurfaceocean?(surfacehotspots,

plumes,crater-freeareas,volcanoes,tectonics)–  DoesthebodyexhibitMdaland/orrotaMonalevidenceindicaMngthepresenceofasub-surfaceocean?–  Doesthegravityandtopographyofthebodyindicatethepresenceofasub-surfaceocean?–  Aretemporalchangesobservedatthebodythatwouldindicatethepresenceofasub-surfaceocean?–  Isthereanatmosphereorexospherethatcouldbelinkedwiththepresenceofasub-surfaceocean?–  DoestheelectromagneMcresponseofthebodyindicatethepresenceofasub-surfaceocean?–  CanthesurfacecomposiMonbelinkedwiththepresenceofasub-surfaceocean?–  Isthesignatureofasurfaceliquidobserved(e.g.specularreflecMon)?

•  HowdomaterialsbehaveundercondiMonsrelevanttoanyparMculartargetbody?(*R&A*)–  WhatarethephaserelaMonsofmaterialcomposingoceanworldsatrelevantpressuresandtemperatures?–  WhatisthecomposiMonandchemicalbehaviorofmaterialscomposingoceanworlds?–  WhataretherheologicmechanismsbywhichmaterialdeformsundercondiMonsrelevanttooceanworlds?–  Howdoesenergya_enuaMon/dissipaMonoccurundercondiMonsrelevanttooceanworlds?–  WhatarethethermophysicalproperMesofmaterialundercondiMonsrelevanttooceanworlds?

Characterize Oceans &

Assess Habitability

Waiteetal.,2009

Theme2:Characterizetheoceanofeachoceanworld

•  Characterizetheocean’sphysicalproperMes–  Whatisthethickness,composiMon,andporosityoftheiceshell(crust)andhowdotheseproperMesvary

spaMallyand/ortemporally?–  Whatisthethickness,salinity,densityandcomposiMonoftheocean?HowdotheseproperMesvaryspaMally

and/ortemporally?–  Whatarethedriversfor,andpa_ernof,fluidmoMonwithintheocean?

•  Characterizetheoceaninterfaces–  Characterizetheseafloor,includingthehigh-pressureocean–silicateinteracMon–  Characterizetheice-oceaninterface

Theme3:Characterizethehabitabilityofeachoceanworld

•  Whatistheavailability(typeandmagnitude/flux)ofenergysourcessuitableforlife,howdoesitvarythroughouttheoceanandMme,andwhatprocessescontrolthatdistribuMon?

–  Whatenvironmentspossessredoxdisequilibria,inwhatforms,inwhatmagnitude,howrapidlydissipatedbyabioMcreacMons,andhowrapidlyreplenishedbylocalprocesses?

–  (Where)iselectromagneMc(orotherenergeMc)radiaMonavailable?Inwhatwavelengths(orenergy)andintensity?

•  Whatistheavailability(chemicalformandabundance)ofthebiogenicelements,howdoesitvarythroughouttheoceanandMme,andwhatprocessescontrolthatdistribuMon?

–  Whatistheinventoryoforganiccompounds,whataretheirsourcesandsinks,andwhatistheirstabilitywithrespecttothelocalenvironment?

–  Whatistheabundanceandchemicalformofnitrogen,oxygen,phosphorus,sulfur,andinorganiccarbon,whataretheirsourcesandsinks,andarethereprocessesofirreversiblelossorsequestraMonrelaMvetotheliquidenvironment?

Search for Life

?

Wedon’thaveanyexamplesofthisyet!Butwe’reworkingonit!

Theme4:Understandhowlifemightexistateachoceanworldandsearchforlife

•  WhatarethepotenMalbiomarkersineachhabitableniche?(determinewhat

we’relookingfor)–  WhatcanwelearnaboutlifeonoceanworldsfromstudyingEarth?–  Whatnichesforlifearepossibleonoceanworlds?–  Whatcanwelearnaboutlifebyunderstandingthehistoryofoceanworldsfrom

theirformaMontothepresent?–  Whatshouldbeourtargetindicators?(LifeDetecMonLadder)–  HowdowedisMnguishextantfromexMnctlifeinenvironmentsinwhichlifemight

develop,andwhichMmescales(e.g.,formetabolism,reproducMon,dormancy)ma_er?

•  Howtosearchforandanalyzedataindifferentenvironments?–  Howcanwelookforextantlifeonanoceanworldremotely(fromorbitorduringaflyby)?–  Howcanwelookforextantlifeonanoceanworldinsitu(landed,underwater,plume)

invesMgaMons?–  Howcanwelookforextantlifeonanoceanworldwithsamplereturnscience?–  WhichscienceoperaMonalstrategiesshouldbeusedtodetectlifeonoceanworlds?

Targetteams•  Weformedtargetteamsforthefollowing(groupsof)

targets–  Enceladus–  Europa–  Pluto,Charon&KBOs–  Ceres&smallbodies–  GanymedeandCallisto–  Triton–  Titan–  Othersatellites(“upandcoming”)

•  Targetteamsassessedthestatusofeachtarget:howwellareeachoftheThemesciencequesMonsknown,whatdoweknowaboutthem,whatistheirleveloftheir“ocean-worldness”

Goals,ObjecMves,InvesMgaMons(GOI)Document(h_p://www.lpi.usra.edu/opag/ROW/)

EnergySources

OceanSignatures

Solvents Rock/OceanInterface

EnergyforLife

Physico-chemicalCondi<onsforLife

Biomarkers

OceanW

orlds

Enceladus

Europa

Titan

Ganymede

Callisto

PossibleOceanW

orlds

Ceres/SmallBodies

Pluto/Charon/KBOs

Triton

SolidFoundaMon

OtherSaturnianIcySatellites*

KeyInformaMon

OtherUranianIcySatellites**

*Mimas,Tethys,Dione,Rhea,Iapetus**Miranda,Ariel,Umbriel,Titania,Oberon

SearchforLife

Iden<fyOceanWorlds

CharacterizeOceans

AssessHabitability

“StatusofKnowledge”chart

Nextstep:TheRoadmap•  Philosophy

–  Abalancedprogramisimportant•  Addressknownoceanworldsto

–  Lookforlife(ifconsideredhabitable)–  Characterizeocean(asneeded)–  Characterizehabitability–  Searchforlife

•  Useavarietyofmissionarchitectures(flagships->smallsats,aspossible)–  wewanttoadvanceourknowledge(extendthebars)onALLofthese

bodies(eventually)–  consideringthatinthiscommunitywedothingsviadecadalsurveys(DS)–  AprimarytaskofROWistomakesomewell-definedrecommendaMonsfor

thenextDS:•  whattheyshouldconsidertobehighpriority,andalso•  whatmissionconceptsshouldbestudiedinadvanceofthatDS.

–  focusontheimportantnextmissionstodifferentclassesofbodies•  Knownoceanworlds•  Possibleoceanworlds

•  Theconceptsonthefollowingslideshavenotbeenfullyve_edbyallofROWyet,buthasbeendistributedforcommentandfeedbackhasbeenposiMve[resultsarenotfinal]

OceanWorldsRoadmap,MissionsScenarios,&Technologies

•  TargetTeamshaveprovided–  inputonkeymeasurementsneededtomoveourunderstandingofeachtargetforward

–  inputonfuturemissiontypesneeded

•  Technologysub-group(P.Beauchamp)hasprovided–  Inputonneededtechnologies

Roadmap

•  Thehighestprioritytargetsaretheknownoceanworlds(nopriorityimplied):

Roadmap

•  Thehighestprioritytargetsaretheknownoceanworlds(nopriorityimplied)– Europa

Roadmap

•  Thehighestprioritytargetsaretheknownoceanworlds(nopriorityimplied)– Europa– Enceladus

Roadmap

•  Thehighestprioritytargetsaretheknownoceanworlds(nopriorityimplied)– Europa– Enceladus– Titan

Roadmap•  Thehighestprioritytargetsaretheknownoceanworlds(nopriorityimplied)– Europa– Enceladus– Titan

•  TheOWprogramalsoneedstogoaderapossibleoceanworldinthenextdecade(forbalance)

Roadmap•  Thehighestprioritytargetsaretheknownoceanworlds(nopriorityimplied)– Europa– Enceladus– Titan

•  TheOWprogramalsoneedstogoaderapossibleoceanworldinthenextdecade– Triton

[resultsarenotfinal]

Europa•  Europa:EuropaClipperisaflagshipmissioninPhaseBof

development;theoverarchinggoalofClipperistoestablishthehabitabilityofEuropa.ArmedwithrecentobservaMonsofpossibleacMvityatEuropaandinanMcipaMonofClipperresults,afollow-onsearch-for-lifemissioncouldbesenttoEuropa.Anastrobiology-focusedEuropaLandermissionhasrecentlybeenstudied(Handetal.,2016).

•  EuropaRecommenda<onsforDecadalSurveyandSurveyPreparaMon:TheROWteamrecommendsthattheEuropaClippermissionconMnueasplannedforitsimportanceincharacterizingthehabitabilityofEuropa.TheROWteamsupportsaEuropasearch-for-lifemission,especiallyifasciencepayloadcanbeincludedthatcanyieldimportantinformaMoneveniflifesignatureresultsareambiguous.SuchamissionwilladvancethetechnologiesneededtodetectlifesignaturesatOWtargets,especiallyfrominsitumeasurements.

[wordingnotfinal]

Enceladus•  Enceladus:ThehabitabilityofEnceladus’oceanhasbeen

establishedusingCassinimeasurements,andthustoaddressOWgoals,asearch-for-lifemissioncouldbesentasanextstep.GiventheongoingNewFronMers4(NF4)compeMMon,theROWteamdoesnotprioriMzeanyofthese.

•  EnceladusRecommenda<onsforDecadalSurveyand

SurveyPreparaMon:TheROWteamrecommendsthatasearch-for-lifemissionatEnceladusbeofhighpriority.IfanEnceladusmissionisselectedforNF4,addiMonalEnceladusmissionarchitecturesthataddressthesearch-for-lifecouldbestudied,potenMallyasafollow-ontotheNF4.IfanEnceladusmissionisnotselectedforNF4,asearch-for-lifemissionatEnceladusshouldbestudiedinadvanceofthenextDecadalSurvey. [wordingnotfinal]

Titan•  Titan:ThehabitabilityofTitan’ssubsurfaceoceanandany

interfacesbetweentheoceanandsurface,alongwiththesurfacelakesandseasofmethane/ethane,hasyettobeestablished.Thus,ahabitability/oceancharacterizaMonmissiontoTitanisanaturalnextsteptoadvanceOWgoalsatthisbody.NumeroustypesofmissionatTitanarepossible,andgiventheongoingNF4compeMMon,ROWdoesnotprioriMzeanyofthese.

•  TitanRecommenda<onsforDecadalSurveyandSurveyPreparaMon:ROWrecommendsthatmissionstocharacterizeTitan’soceanorassessitshabitabilitybeofhighpriority.IfaTitanmissionisselectedforNF4,addiMonalTitanmissionsthatadvancetheunderstandingofTitanasanOWshouldbestudiedpriortotheDecadalSurveyandconsideredbytheDSpanel. [wordingnotfinal]

Lower-priorityknownoceanworlds•  Ganymede:TheESAJUICEmissionissettoexploreGanymede.JUICEwill

characterizethesubsurfaceoceantobe_erunderstandtheformaMonandevoluMonofthisOW.

•  GanymedeRecommenda<onsforDecadalSurveyandSurveyPreparaMon:The

ROWteamsupportstheESAJUICEmission.

•  Callisto:ThisknownOWremainstobefullycharacterized.ItsdeepsubsurfaceoceananditslocaMonontheedgeoftheGalileansatellitesystemlimitsnotonlycommunicaMonbetweentheoceanandthesurface,butalsovitalenergyinputtotheocean.ItmayserveasanendmemberontheOWspectrumandhelp,alongwithCeres,tocharacterizethelimitoftheabilityofbodiestomaintainoceanswithsparseMdalinput.InaddiMon,becauseGanymede’soceansitsbetweenlayersofhighpressureices,communicaMonbetweenthesubsurfaceoceanandthesurface,andenergyinputintotheoceanlayerarealsolimitedthere.FutureCallistostudiescouldthereforealsoinformstudiesofGanymede’socean,astheycouldplaceboundsonthehabitabilityofoceansthatareseparatedfromtheirrockymantles.

•  CallistoRecommenda<onsforDecadalSurveyandSurveyPreparaMon:TheROWteamsupportsmissionstudiestocharacterizeCallisto’soceananditssustainability.AmissiontoCallistoshouldbestudiedtotestifsmallmissionclassescanhelpadvanceOWobjecMves.

Triton•  Triton:Ofthepossibleoceanworlds,Tritonisdeemedthehighestpriority

targettoaddressaspartofanOceanWorldsprogram.ThispriorityisgivenbasedontheextraordinaryhintsofacMvityshownbytheVoyagerspacecrad(e.g.geyser-likeacMvity;smooth,walledplainsunits;thecantaloupeterrainsuggesMveofconvecMoninaliquidlayer)andthepotenMalforocean-drivenacMvitygivenCassiniresultsatEnceladus.Furthermore,manyTritonmissionarchitectureswouldsimultaneouslyaddressIceGiantgoalsonwhichhighprioritywasplacedintheVisions&VoyagesDecadalSurvey.Finally,asTritonlikelyrepresentsacapturedKuiperBeltobject(KBO),comparaMveplanetologywithKBOscouldalsobeaddressedinaTritonmission.

•  Tritonrecommenda<onsforDecadalSurveyandSurveyPreparaMon:

PriortothenextDecadalSurvey,amissionstudyshouldbeperformedthatwouldaddressTritonasapotenMalOceanWorld;suchasstudycouldbepartofalargerNeptuneorbitermission.TheDecadalSurveyshouldplacehighpriorityonTritonasatargetintheOceanWorldsprogram.

[wordingnotfinal]

Ceres•  Ceres:Ceresisauniquecase,ahydrousdwarfplanetinthe

asteroidbelt.Ceresharborsliquids(Ceresis~50%H2Oinvolumeandhasa40kmthickshelldominatedbyvolaMles,withadensityof1.25g/cm3)butwhetherthisconsMtutesacurrentoceanisunlikely.CeresisincludedintheOWroadmapnotbecauseitisconsideredapresent-dayoceanworld,butbecauseitmaybeanancientoceanworld;itisasmallandheat-limitedbody,likelyintheprocessoffreezing,soitmayprovideanend-memberscenarioformedium-sizedicysatelliteswithoutMdalheaMng.R&Afundingforbe_ermodelingandexperimentalresearchinlightofCeresresultsfromtheDawnmissionarerelevanttounderstandingoceanworldsasawhole.

•  CeresRecommenda<onsforDecadalSurveyandSurvey

PreparaMon:ACeresmissionwithaprimaryobjecMvetodetectandcharacterizeanyliquidswithinCeresshouldbestudiedtotestifsmallmissionclassescanhelpadvanceOWobjecMves.

[wordingnotfinal]

Pluto•  Pluto:PlutoisthefirstlargeobjectvisitedintheKuiperbeltandit

showsyoung,potenMallycryovolcanicterrainsindicaMngacMvitymayhaveconMnuedthroughmuchofitshistory.LikethecaseofTriton,thesourceofrelaMvelyrecentinternalheatonPlutoisnotenMrelyconstrained,butmodelssuggestanoceanmaypersistintothepresent.StudyinglargeKBOsopensupanewregimeforexploringoceanworldsinthesolarsystem,andbycomparaMveplanetologyhelpsusunderstandwhatispossibleforicymoonsthatarenotcurrentlyMdallyheated.

•  Plutorecommenda<onsforDecadalSurveyandSurvey

PreparaMon:MissionstudiesshouldbeperformedtoaddresstechnologyadvancesallowingexploraMonoftheKuiperbeltorareturntoPlutowithanorbiter(necessarytostudyapotenMalocean).StudiestoexploreapotenMalKBOrendezvousasanextendedpartofanothermissiontotheoutersolarsystem(e.g.,toagasgiant)arealsoencouraged.

[wordingnotfinal]

Roadmap•NextupforeachbodytomaintainOWprogrammaMcbalance:•  EuropaHabitabilitymission–Clipperinprogress•  TitanHabitability/Oceanmission–possibilityofNF4missionselec4on

•  Enceladussearch-for-lifemission-possibilityofNF4missionselec4on

•  Tritonoceanmission–TritonorbiterorNeptuneorbiterwithmanyTritonflybys(withmagnetometer,gravity)

[resultsnotfinal]

DecisionRules•  IfaTitanmissionisnotselectedinNF4,thenthenextDecadal

SurveyshouldrankhighlyaTitanmission(whatevertheclass)–orbiter,plainslander,aerialexplorer,lakelanderand/orsubmarine;sucharchitecturescouldincludeinsituatmosphericstudyatarangeofalMtudes.

•  IfanEnceladusmissionisnotselectedinNF4,thenthenextDecadalSurveyshouldrankhighlyanEnceladusmission(whatevertheclass).

•  IfneitherEnceladusnorTitanareselectedintheNF4call,thenextDecadalSurveyshouldplaceanespeciallyhighpriorityonamissiontostudylife/habitabilityatoneorbothofthesebodies.AmissionthataddressesbothEnceladusandTitanshouldbeconsidered.

[wordingnotfinal]

ROW-RecommendedMissionStudies

•  TritonoceancharacterizaMon•  EnceladusandTitanmissionsorjointmission(regardlessofNF4outcome)

•  Ceresand/orCallistomissionstodetect/characterizesubsurfaceoceans/reservoirs(perhapsDiscovery-class?)

•  PlutooceancharacterizaMon

[notfinal]

Finally

•  Wealsosaywordsinthereportaboutotherimportantbutlower-prioritybodies(e.g.Ariel,Miranda,Dione)–  Justnotdiscussedhere–  Importantforunderstandingthespectrumofoceanworlds,thoughwedobynecessityneedtolimitourrecommendaMonstothenextDecadalSurvey

[notfinal]

Let’s go out and study some ocean worlds!