JupiterandSaturnRevisitedDaveStevenson

Caltech

InsightCruises,January28,2018

Exploration of the Giant Planets:Pioneer, Voyager, Galileo, Cassini & Juno

Io Europa

Ganymede Callisto

Juno JupiterMass 318 MEarth

Radius 11 REarth

TheFacts

• Moremassivethanalltheotherplanetsputtogether• Mostlyhydrogen&helium;bottomlessatmosphere• Mostofthishydrogenismetallic,probablythemostabundantmetalintheuniverse

• Emits2.5timestheenergyreceivedfromtheSun• Internalheatsourceismostlycooling,partlyheliumrain

• Strongestradiosourceinthenightsky• Largemagneticfield,generatedbyadynamo

Jupitersendsstuffourway

TheQuestions

• Doesithaveacore?• Acentralconcentrationofheavyelements,maybe~10Earthmasses

• Howmuchwater?• Onlymeasurementthusfargaveverylittlewater

• Whatdrivesthewinds?• Andhowdeepdotheygo

• DidJupiterdictatethearchitectureofthesolarsystem?• IncludingplanetEarth

Gravityfield

MagneticField

WaterAbundance

NatureandextentofheavyelementenrichmentinJupiter’score

Whathappenedwhenourplanetsformed?

+poleposition

Gas giant planets formed beyond the frost line where hydrogen gas

captured onto ice & rock core

WhymightaPlanethaveaCore?

BottomUp

Accreteouterlayer

TopDown

Differentiate

WhymightaPlanethaveaCore?

BottomUp

Accretegas

TopDown

Differentiate

PopularGiantPlanetPicture

WellestablishedTerrestrialPlanetPicture

Water H2O

NH4SH

km

AmmoniaNH3

Temperature (Kelvin)

Ammonia cloudscolored by ??phosphine??sulfur compounds, ??

WindsonJupiter

HowtoGetaBillionDollarMissionYourtaxpayer’smoneyatwork

• Collectabunchofcleverscientists• Includinginternationalpartners(ItalyforJuno).

• Talktoabunchofcleverengineers• Writeaproposal• Winthecompetition• Startspendingthemoney• Lotsofmeetings• ConvinceNASAHQthatyouknowwhatyou’redoing.• Makeitwork…..

Spacecraft & Payload

WavesRadio & plasma

MWRMicrowaves

SPACECRAFT DIAMETER: 20 m POWER: ~500 W SPIN PERIOD: 30 s

JEDIHigh-energy particles

JADELow-energy particles

Magnetometer

JIRAMIR spectrometer

Gravity Science

JunoCamcamera

UVSUV spectrometer

Earth Flyby

DeepSpace

Maneuvers

Jupiter Orbit Insertion

Juno Launch 5 Aug 2011

TheOrbit: Keyto theWholeMission

Duck under radiation belts… Skim above clouds…

~32polarorbits

2 Hours pole-to-pole!

Juno Science Instruments OffJupiter

Orbit Insertion

4th July 2016

Juno Science Instruments On!Perijoves 1-10

Aug. 2016– Jan. 2018

Map Gravity & Magnetic Field32 orbits ~evenly spaced in longitude

4 orbits->90°8 orbits->45°16 orbits->23°32 orbits->11°

Measuring Jupiter’s Magnetic Field

Juno

Juno Science Presentation 47Juno Site Visit – Use or disclosure of any of the information of this package is subject to the

• Ioejects 1 ton per secondvolcanic gases

• Europa

• Ganymede• Callisto

Jupiter’s magnetic field extends beyond orbits of the 4 big moons

Hubble Space Telescope

Molecular state

Plasma state

•At Plasma Phase Transition Hydrogen is conducting• Jupiter spins every 10 hours• Internal heat drives convection➢ strong magnetic dynamo

~2.5 Mbar phase transition

R ~ 0.8- 0.95 RJ

Jupiter

Heimpel& Aurnou

Juno Modeling Jupiter's Interior to Match Juno Gravity Data

• No distinct core

• Heavy elements partially mixed

• Helium raining out of outer layer

• All boundaries fuzzy?!

Incomingplanetesimalsencounterenoughgastobreakupwhenthecoreisonly~1ME

AtmosphericbasalTis~4000Kwhencoreis1ME,sufficienttodissolvealltheincomingmaterial

We would like to know the structure at early time (end of accretion)

The structure we see now is not necessarily the same

Smaller core

Enriched envelope

Partialdissolutionofthecore

“Ohthatthistootoosolidfleshwouldmelt,Thawandresolveitselfintoadew!”

-Shakespeare,Hamlet

Wilson&Militzer,2011,2012

Juno Microwave Radiometry

Infrared Image

Mic

row

ave Infra

red

Juno'sobservationsofmicrowavescomingfrom the interiorshow absorption by ammoniain a deep circulation pattern

First hints of deepcirculation.....

JIRAM’s5MicronImager

JIRAM’s IR Poles at 5 μ

North Pole

South Pole

Public voteswhich images JunoCAM takes– and submits their own images

http://missionjuno.swri.educlick on “Junocam”

JunoCAM – The People’s Camera

Composite ofmultiple images

•62

NASA Cassini Maksim Kakitsev

Saturn's polar vortex& hexagon

MassSaturn

~1/3 MassJupiter

Clouds deeper

PJ8

PJ6 –May19th

Juno passed over the Great Red Spot

July 10th!

Voyager image

CassiniatSaturn

CassiniatSaturn

Cassini’slastlook

HowisSaturnsimilartoJupiter?

• Similarradii• Bothmostlyhydrogen• Mostofthathydrogenismetallic• Roughlytenhourspinperiods• StrongEast-Westwinds• CoreofaroundtenorsoEarthmasses• Magneticfields• Extensivesatellitesystems• Rings

HowisSaturndifferentfromJupiter?

• Saturnhasamuchsmallermassandsolowerinternalpressures• WindsonSaturnarefourtimesstronger(upto400m/s)andextendthreeorfourtimesdeeper(to12000km)

• CoreonSaturniswelldefinedwhereasonJupiteritisfuzzy?• SaturnmagneticfieldismuchsmallerandmuchsimplerthanJupiter’sfield

• Saturn’sringsaremuchmoremajestic… butthey’reprobablyyoung!

What’sNext?

• Certain• Europaclipper(mid20’s)• EuropeanmissionJUICEtotheJovianmoons,especiallyGanymede.(2030)

• 50%Likely• Missiontothelakes&seasofTitan

• Possible• Probes?EspeciallyforSaturn.• Seismology… theonlyrealwaytounderstandtheinterior• Enceladus… thelittlemoonthatcould

Questions?

WhyistheCoreanInterestingIssue?

• Presenceofcorecouldtellusabouttheformationprocess• ThiswasamajorpartofthejustificationforJuno• Jupitermaydefinesolarsystemarchitecture

• PersistenceofacoremaytellusthermodynamicsofmixtureswithinJupiter&theconvectivestate

• Relevanttotheheatflow• Possiblyrelevanttothedynamo

SomeDefinitions

• By“core”ImeanacentralconcentrationofelementsheavierthatHandHe

• Thiscoredoesnothavetobesolid(itprobablyisnot)• Thiscoredoesnothavetoberock&iron(itcouldalsocontainice)• Thiscoreneednothaveasharpboundary(itprobablydoesnot)- inthisrespectitisfundamentally differentfromearth’score

• ThiscorecouldcontainsomeHandHemixedintoit(andIwillarguethatitdoes)

"JusttheplaceforaSnark!Ihavesaidittwice:Thataloneshouldencouragethecrew.JusttheplaceforaSnark!Ihavesaiditthrice:WhatItellyouthreetimesistrue.

-LewisCarroll

JunoarrivedatJupiteronJuly4,2016&isspendingoverayearinorbitcollectingdata

Conclusions

• WewillbeabletotellwhetherJupiterhasacoreandevenestablishthemassofthatcoreprovidedwedefinethecoretobetheexcessofheavyelements

• Assumesgoodunderstandingofhydrogenequationofstate

• Wemayhavedifficultyestablishingthenatureofthatcorewithanyconfidence(i.e.,theextenttowhichitisdispersedratherthanconcentrated)by“conventional”techniques(gravitymoments)

• Precession(ifaccurateenough)• Unconventionalincludestidalresponse,normalmodesandperhapsmagneticfield

GreatRedSpot

NASA /JPL/MSSS /Gerald Eichstadt/Sean Doran

NASA /JPL/SwRI/MSSS /Gerald Eichstadt/Sean Doran

Perijove 9 – October

NASA /JPL/SwRI/MSSS /Peitho-54

Not bad for a "public outreach" camera, eh?

Jupiter's aurora is structured & dynamic•75

Juno UVS

NASA /JPL/MSSS /Gerald Eichstadt/Sean Doran

2017-10-24 17:24

South Temperate Zone

NASA /JPL/MSSS /Gerald Eichstadt/Sean DoranAltitude: 15306 km Spatialscale: 10.3 km/pixelSubs/clatitude: -32.4 2017-10-24 17:59

SouthTemperateZone:String of Pearls whiteoval

NASA /JPL/MSSS /Gerald Eichstädt/Sean Doran2017-10-24 17:59

NASA /JPL/MSSS /Gerald Eichstadt /Sean Doran

2017-10-24 18:03

Altitude: 20742 kmSpatial scale: 14 km/pixelSubs/c latitude: -40

WhiteOval inString of Pearls

Southern hemisphere Oval- zoom

NASA /JPL/MSSS /Gerald Eichstadt /Sean Doran2017-10-24 18:03

SouthernHemisphere

Altitude: 33115 km Spatialscale: 22.3 km/pixelSubs/c latitude: -53

2017-10-24 18:11

NASA /JPL/MSSS /Gerald Eichstadt/Sean Doran

Southern Hemisphere Coverage

2017-10-24 18:11 NASA /JPL/MSSS /Gerald Eichstädt/Sean Doran

StackingflybysPJ6

PJ8

PJ9

NorthernStorms

NASA /JPL/MSSS /Gerald Eichstadt /Sean Doran

True Color

NASA /JPL/MSSS /Bjorn Jonsson

2017-09-01 22:03Altitude: 12143 km

Juno

Where’s the water?

What drives the winds?

Jupiter’sAtmosphere