Study Vision and Goals
• Whyisthisimportant?• High-leveloverviewofstudy
objectives• Suggestedmainareasoffocusfor
workshop• Thiscanchange
• Plansforfinalreport
Why is this important? • Tidalheatingisafundamentalplanetaryprocess,importanttoEarth/Moon,outerplanetsatellites,exoplanetsandexomoons• Heatflowaffectsinternalstructureandgeologicactivity• Coupledorbital-thermalevolution
• Tidalheatingimportanttooceanworlds• Potentiallyhabitable• Tidalheatingmaintainsoceansovergeologictimeandsustainschemicaldisequilibrianeededforlife
• WhyanemphasisonJupitersystemandespeciallyIo?• LaplaceresonanceIo-Europa-Ganymede• Ioissointenselyheatedthatwecanseewidespreadvolcanicactivityandmeasuretheheatflow
• Whynow:• Junoinorbit;EuropaClipperandJUICE(approvedmissions)willprovideimportantdata
• ExploringIoisthemajorgaptounderstandthefullsystem• Otherpotential/proposedmissionstorelevantworlds:Dragonfly,EuropaLander;missionconceptstoIo,Enceladus,Triton,etc.
• Synthesizingnewresultsfromlaboratoriesandorbitalstudiesmayalreadyenableustoadvancetheparadigm.
• Keygoalofthisworkshop:Determinethenextstepsneededtounderstandtidalheating.
Relevance to NASA’s Decadal Survey for planetary science Tidalheatingisrelevantto5/10ofthekeyquestionsfromVision&Voyages:• BuildingNewWorlds
• Howdidthegiantplanetsandtheirsatellitesystemsaccrete,andisthereevidencethattheymigratedtoneworbitalpositions?
• Whatgovernedtheaccretion,supplyofwater,chemistry,andinternaldifferentiationoftheinnerplanetsandtheevolutionoftheiratmospheres,andwhatrolesdidbombardmentbylargeprojectilesplay?
• PlanetaryHabitats• BeyondEarth,aretherecontemporaryhabitatselsewhereinthesolarsystemwithnecessaryconditions,organicmatter,water,energy,andnutrientstosustainlife,anddoorganismslivetherenow?
• Workingsofsolarsystems• HowdothegiantplanetsserveaslaboratoriestounderstandEarth,thesolarsystem,andextrasolarplanetarysystems?
• Howhavethemyriadchemicalandphysicalprocessesthatshapedthesolarsystemoperated,interacted,andevolvedovertime?
Barretal.,2018:Planetsbandcexperienceenoughheatingfromplanetarytidestomaintainmagmaoceansintheirrockmantles;planetcmayhavesurfaceeruptionsofsilicatemagma,potentiallydetectablewithnext-generationinstrumentation.Tidalheatfluxesonplanetsd,e,andfaretwentytimeshigherthanEarth’smeanheatflow.
TidalheatinginTrappist-1system
What have we learned about tidal heating from past spacecraft missions? • GalileanSatelliteswerediscoveredbyGalileoGalileiin1610;in1771Laplacedescribedthe4:2:1resonance
• Significancerealized200yearslater• TransientIRbrighteningofIoobservedbyWittebornetal(1979)• Pealeetal.(1979)MeltingofIobyTidalDissipation
• LaplaceresonancecreatessignificantforcedeccentricityinorbitsofIoandEuropa,sotheyareperiodicallydeformedbymassiveJupiter,generatinginternalheating
• PredictedrunawaymeltingoftheinteriorofIo,thinningthelithospheresothatitcouldconductawaytheheat.• PredictedthatVoyagerspacecraftmightobservewidespreadandrecurrentvolcanism
• PredictionconfirmedafewmonthslaterbyVoyager1• Manysignsofactivevolcanism• ButIohadlargemountainsupto17kmhigh!Howisthatpossiblewithathinlithosphereoveramolteninterior?
• Galileomission:• Magneticinductionsignaturefromconductinglayers
• SaltywaterinCallisto,Ganymede,Europa;magmainIo[Kivelson,Khuranaetal.)
• Veryhigh(ultramafic)lavatemperaturesonIo?[McEwenetal.]
• Cassinimission:• Enceladus:Activejetscontainssaltsandorganics,emanatingfromwarmfissures• EvidenceforsubsurfaceoceansinTitanandEnceladus
• Astrometryofsatelliteorbitmigrationrates[Laineyetal.]
• Telescopicdiscoveriesofexoplanetsystems
• Observationalresultshavespurredtheoreticaladvances
Propertiesoforbitandprimary
Composition,structure,andstateofsatellite
interior
Stressesonsatellites
Deformationandheatingofmaterials
Globaldeformationandheatingofsatellite
Geologicalactivityandoutgassedatmosphere
FundamentalProperties
ProcessesandFeedbacks
Outcome
1. Identifythespecificpartsofthisprocessthatarenotunderstood.2. Whatexperiments,measurements,ortheoreticalworkarestillneeded?3. Whatnewtechnologies(spacecraftmissions/instruments,telescopeinstruments,labset-ups,algorithms)willberequired?
TidalHeating
Propertiesoforbitandprimary
Composition,structure,andstateofsatellite
interiorStressesonsatellites
Deformationandheatingofmaterials
Globaldeformationandheatingofsatellite
Geologicalactivityandoutgassedatmosphere
FundamentalProperties
ProcessesandFeedbacks
Outcome
HeatFlowandGeologicalActivity
TidalDeformationandResponseTidal,
Rotational,andOrbitalEvolution
TidalHeating
Heat Flow and Geological Activity: Key Questions • Water/magmaoceans:Howdotidescreateandmaintainsubsurfacewaterorsilicatemelt?Overwhattimescalesaretheseliquidsstable?Whatfeedbacksdothesematerialshaveonwhereandhowmuchtidalheatdissipationoccurs?• Geologicalactivity:Howdotides(asdistinctfromotherheatsources)drivethespecificnatureofgeologicalactivity,includingmountainformation,tectonics,plumes,and(cryo-)volcanism
Heat Flow and Geological Activity: Key Questions • Heatdeposition:Whatisthe4Ddistributionofheating(x,t)inasatellite’sinterior,andhowdoesthistranslatetoamagnitudeanddistributionofsurfaceheatflowovertime?• Heattransport:Howisheattransportedthroughsatelliteinteriors,andtothesurface,e.g.magmatransportthroughacrustundercompression?
Heat Flow and Geological Activity How do we make progress? Addressingthesequestionsrequiresstudyingwhat’sgoingoninsatelliteinteriors.Howdowedothis?• Howcanwemeasurethestate,temperature,andcompositionofasatellite’smantle,eitherfromEarth,fromorbit,orfromthesatellite’ssurface?• Whatarethesurfaceobservablesthatgiveindirectinformationontheinterior?Whatnewlaboratoryormodelingeffortsareneededtoformamorerobustlinkbetweenobservablesandinteriorproperties?Whatarethecapabilitiesofthecurrentlyavailableinstruments?
Tidal, Rotational, and Orbital Evolution • Therotationalandorbitaldynamicsofasatellitewithanon-zeroorbiteccentricityandnon-sphericalmassdistributionisinfluencedbythetidalforceraisedbytheprimarybody.
• Overlongtimescales,tidescanalterthestructureofamoon,changingitstidalresponseanddrivingfeedbacksbetweentherotational,orbital,andthermalevolutionofthesatellite.
Whatdoweneedtoknow?1. Whatarelong-term(andshort-term)tidaleffectsontherotationalandorbital
evolution?Howaretheyparameterized?2. Whataretherequiredobservations?3. Whatobservationsarecurrentlyavailable(bothastrometricandsurface-based)
andwhatdoweknowfromtheseobservations?4. Whattechnologiesareneededtoimprovefutureobservations?
Tidal Deformation and Response • Tidaldeformationcanbemeasureddirectly,bydetectingperiodicchangesintheshapeandgravityfieldofamoon,andindirectly,bymeasuringthetidalheatproducedororbitalmotionssuchaslibration.
• Moonswithaweakregioninthesubsurface,suchasliquidwaterormagma,areexpectedtoshowlargertidalresponse.
• Theresponseofmaterialstoperiodicdeformationhasbeenstudiedinthelaboratory,showingthattemperatureandforcingfrequencybothhaveastrongeffectondeformation.
Whatdoweneedtoknow?1. Howpartiallymoltenmaterialsrespondtoperiodicforcing.2. Observationalconstraintsontidalsurfacedeformationandtheassociatedphase
lag(onlymeasuredfortheMoon).3. Modelsthatdonotassumesphericallysymmetry.4. Betterunderstandingoflong-periodforcing.
Draft topics for breakout sessions • Typically3-4groupspersession• Firstbreakoutcanaddresskeyquestionsis3groupsfromourproposalorganization:• Tidal,rotational,andorbitalevolution• Tidaldeformationandresponse• Heatflowandgeologicalactivity
• Subsequent4-5breakouts;topicstobedecidedatworkshop,butherearesomeideas:• Makesurewemixandmatchpeopleindifferentwayssowearenotalwaystalkingtothesamepeople
• Techniques:• Magneticinductionandelectricalconductivityofrealisticplanetaryinteriors• Seismology• Gravityscience,tides• MeasuringlavatemperaturesandheatflowonIo• Astrometry• Remote-sensingtechniques• Laboratoryexperiments• Modeling
• Keysciencequestions• Seeotherslides
• Keyplaces(Jupitersystem,Saturnsystem,Io,Enceladus,exoplanets,Earth/Moon,etc.)
Draft topics for 10-minute lightning talks
• 10minutetalk+5minutesforquestions• Keyissuesthegroupshouldbetterunderstand
• Usepostersforyourownlatestresearch• Fullgroupwilldecidewhattalkstosolicit
The Final Report • DevelopoutlineandwritingassignmentsonFriday
• Decideonreportaudience/wheretosubmitit&deadlineforcompletion;identifyauthorsforsections.
• Note-takingmattersforthefinalreport!• Everyoneencouragedtotakenotes• Haveoneofficialnote-takerforbreakoutsessionsandplenarydiscussions
• Slidesprovideinformationonmoreformalpresentationsandplenarysummariesofbreakouts
Determinethemostcriticalquestionsthatweneedanswertoadvanceourparadigmofhowtidalheatisgenerated,transported,andexpressedthroughtime;andidentifythemeasurements,experiments,andtheoreticalapproachesthatarerequiredtoanswerthesequestionsinthenext20years.
Back-up slides after this point
Heat Flow and Geological Activity Summary for easy reference
• Water/magmaoceans:Howdotidescreateandmaintainsubsurfaceoceans,waterorsilicate?Overwhattimescalesaretheseoceansstable?Whatfeedbacksdotheseoceanshaveonwhereandhowmuchtidalheatdissipationoccurs?
• Heatdeposition:Whatisthe4Ddistributionofheating(x,t)inasatellite’sinterior,andhowdoesthistranslatetoamagnitudeanddistributionofsurfaceheatflowovertime?
• Heattransport:Howisheattransportedthroughsatelliteinteriors,andtothesurface,e.g.magmatransportthroughacrustundercompression?
• Geologicalactivity:Howdotides(asdistinctfromotherheatsources)drivethespecificnatureofgeologicalactivity,includingmountainformation,tectonics,plumes,and(cryo-)volcanism.
Addressingthesequestionsrequiresstudyingwhat’sgoingoninsatelliteinteriors.Howdowedothis?• Howcanwemeasurethestate,temperature,andcompositionofasatellite’smantle,eitherfromEarth,fromorbit,orfromthesatellite’ssurface?• Whatarethesurfaceobservablesthatgiveindirectinformationontheinterior?Whatnewlaboratoryormodelingeffortsareneededtoformamorerobustlinkbetweenobservablesandinteriorproperties?
KeyQuestions Howdowegetthere?
Draft topics for 10-minute lightning talks • Keyissuesthegroupshouldbetterunderstand
• Usepostersforyourownlatestresearch• Fullgroupwilldecidewhattalkstosolicit
• Exampleideas:• Howdoesdeformationcontrolmeltextraction• Electricalconductivityofplanetarymaterials• Telescopiccapabilitiesrelevanttotidalheating• Howinternalstructureaffectslibration• Howtomeasurelibration• Spatialpatternsoftidalheating• Mantleconvection• ARGUSIomissionconcept• Stylesofvolcaniceruptions• PlasmaprocessesnearIoandEuropa• Radarsoundingofplanetarycrusts• Seismicstudies• Tectonicstyles