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