Chapter 14 Jupiter And Saturn

11/6/2015The Outer PlanetsChapter 14Jupiter and SaturnThe Jovian planets – Jupiter, Saturn, Uranus and Neptune.http://abyss.uoregon.edu/ js/images/jovian worlds.gifThe Outer Planets (2)Jupiter and Saturn have liquid metallic hydrogen in theirinteriors, have rings, emit more energy than they absorbfrom the sun and have belt and zone circulation.The Outer Planets (3)Uranus and Neptune have interiors with gaseous hydrogenand a rock and metal core, but no metallic lanets/giantplanets interiors.phpThe Outer Planets /giantplanets interiors.phpJupiterLargest and most massiveplanet in the solar system:Contains almost ¾ of allplanetary matter in the solarsystem.Most striking features visiblefrom Earth: Multi-colored cloudbeltsExplored in detail by severalspace probes: Pioneer 10,Pioneer 11, Voyager 1,Voyager 2, GalileoVisual imageAll of the outer planets have extensive satellite systems, withmany moons of many different sizes.Infrared false-color imagehttp://abyss.uoregon.edu/ js/images/jovian worlds.gif1

11/6/2015Jupiter’s InteriorFrom radius and mass Average density of Jupiter 1.34 g/cm3 Jupiter can not be made mostly of rock, like Earthlike planets.The Chemical Composition ofJupiter and Saturn Jupiter consists mostly of hydrogen and helium.T 30,000 KDue to the high pressure,hydrogen is compressed into aliquid, and even metallic state.Jupiter’s RotationJupiter’s Magnetic FieldJupiter is the mostrapidly rotating planetin the solar system:Discovered through observations of decimeter (radio) radiationMagnetic field at least 10times stronger thanEarth’s magnetic field.Rotation periodslightly less than 10hr., and the centerrotates faster than thehigher latitudes.Magnetosphere over 100times larger than Earth’s.Extremely intenseradiation belts:Very high energyparticles can be trapped;radiation dosescorresponding to 100times lethal doses forhumans!Centrifugal forcesstretch Jupiter into amarkedly oblateshape.Aurorae on JupiterJupiter’s AtmosphereJust like onEarth, Jupiter’smagnetosphereproduces auroraeconcentrated inrings around themagnetic poles. 1000 timesmore powerfulthan auroraeon Earth.Jupiter’s liquid hydrogenocean has no surface:Gradual transition fromgaseous to liquid phases astemperature and pressurecombine to exceed the criticalpoint.Jupiter shows limb darkening hydrogen atmosphereabove cloud layers.Only very thin atmosphereabove cloud layers;transition to liquid hydrogenzone 1000 km below clouds.2

11/6/2015Jupiter’s Atmosphere (2): CloudsThreelayers ofclouds:The Cloud Belts on JupiterDark belts and bright zones.Zones higher and cooler than belts;high-pressure regions of rising gas.1. Ammonia(NH3)crystals2. Ammoniahydrosulfide3. WatercrystalsThe Cloud Belts on Jupiter (2)The Great Red SpotSeveral bright and darkspots mixed in with cloudstructure.Just like on Earth, high-and low-pressure zones arebounded by high-pressure winds.Largest and mostprominent: The Great RedSpot.Has been visible for over330 years.Jupiter’s cloud belt structure has remained unchanged sincehumans began mapping them.Comet Impacts on JupiterVisual:Impacts seenfor many daysas dark spotsImpacts released energies equivalent to afew megatons of TNT (Hiroshima bomb: 0.15 megaton)! 2x the diameter of EarthComet Impacts on Jupiter (2)Impactsoccurred justbehind thehorizon asseen fromEarth, butcame intoview about15 min. later.Impact of 21fragmentsof cometSL-9 in1994Formed by rising gascarrying heat from belowthe clouds, creating a vast,rotating storm.Impact sitesappeared verybright in theinfrared.Impact of fragment Acreated a fireball abovethe planet as imaged bythe HST.Spectroscopic studiesrevealed absorptionlines in the Jovianspectrum due todiatomic sulfur (S2),carbon disulfide (CS2),ammonia (NH3) andhydrogen sulfide (H2S),along with Fe, Mg, eases/1994/30/image/a/format/web/3

11/6/2015Jupiter’s RingGalileo spacecraftimage of Jupiter’sring, illuminatedfrom behindJupiter’s RingNot only Saturn, but all fourgas giants have rings.Jupiter’s ring: dark andreddish; only discovered byVoyager 1 spacecraft.Composed of microscopicparticles of rocky materialLocation: Inside Roche limit, wherelarger bodies (moons) would bedestroyed by tidal forces.Jupiter’s Family of MoonsRings must beconstantly resupplied with newdust.Ring material can’t be oldbecause radiation pressureand Jupiter’s magnetic fieldforce dust particles to spiraldown into the planet.Callisto: The Ancient FaceOver two dozen moons known now; new onesare still being discovered.Tidally locked to Jupiter, like all of Jupiter’s moons.Av. density: 1.79 g/cm3Four largest moons already discovered by Galileo: TheGalilean moons composition: mixture ofice and rocksDark surface, heavilypocked with craters.No metallic core: Callistonever differentiated toform core and mantle. No magnetic field.IoEuropaGanymedeCallistoLayer of liquid water, 10 km thick, 100 km below surface,probably heated by radioactive decay.Ganymede: A Hidden PastLargest of the 4 Galilean moons. Av. density 1.9 g/cm3 Rocky core Ice-rich mantle Crust of ice1/3 of surface old, dark, cratered;rest: bright, young, grooved terrainBright terrain probably formedthrough flooding when surfacebrokeEuropa: A Hidden OceanAv. density: 3 g/cm3 composition: mostly rockand metal; icy surface.Close to Jupiter should be hit bymany meteoroid impacts; but fewcraters visible. Active surface; impactcraters rapidly erased.4

11/6/2015The Surface of EuropaThe Interior of EuropaEuropa is too small to retain its internal heat Heating mostlyfrom tidal interaction with Jupiter.Core not molten No magnetic field.Cracked surface and high albedo (reflectivity)provide further evidence for geological activity.Europa has a liquid water ocean 15 km below the icy surface.Io: Bursting EnergyThe History of JupiterMost active of all Galilean moons; no impact craters visible at all.Over 100 activevolcanoes! Formed from cold gas in theouter solar nebula, where iceswere able to condense. Rapid growthActivity poweredby tidalinteractions withJupiter. Soon able to trapgas directly throughgravityAv. density 3.55 g/cm3 Interior ismostly rock. Heavy materialssink to the centerThe History of JupiterSaturn In the interior,hydrogen becomesmetallic (very goodelectrical conductor)Mass: 1/3 of mass of JupiterRadius: 16 % smaller than Jupiter Rapid rotation strong magnetic field Rapid rotationand large size belt-zone cloudpattern Dust from meteorite impacts ontoinner moons trapped to form ringAv. density: 0.69g/cm3 Wouldfloat in water!Rotates about as fast as Jupiter, but is twice asoblate No large core of heavy elements.5

11/6/2015SaturnSaturn-CassiniMostly hydrogen and helium; liquid hydrogen core.Saturn radiates 1.8times the energyreceived from the sun.Backlit image of Saturn and its rings.Probably heated by liquid helium droplets falling towards e/Saturn – Cassini (2)Saturn’s AtmosphereCloud-belt structure, formed through thesame processes as on Jupiter,An amazing viewshowing the shadowof Saturn’s complexring system.but not as distinct as on Jupiter; colder thanon me/Saturn’s Atmosphere (2)The Yet Yawning GulfThree-layeredcloudstructure, justlike on JupiterMaindifference toJupiter:Fewer windzones, butmuchstrongerwinds thanon Jupiter:Winds up to 500 m/s near the equator!The “Yet Yawning Gulf”, a giant hurricane-like storm on thesouth pole of e/6

11/6/2015Saturn – Cassini, RingsSaturn’s RingsA RingRing consists of 3 mainsegments: A, B, and CRingseparated by emptyregions: divisionsAn exceptional view of Saturn taken by the Cassini spacecraft.The Cassini-Huygens mission has been one of the mostsuccessful (2004-present).B RingC RingRings can’t have beenformed together withSaturn because materialwould have been blownaway by particle streamfrom hot Saturn at timeof formation.CassiniDivisionRings must be replenished by fragments ofpassing comets & ffame/Composition of Saturn’s RingsShepherd MoonsRings arecomposed ofice particlesmoving at largevelocities aroundSaturn, but smallrelative velocities(all moving in thesame direction).Divisions and ResonancesSome moons onorbits close to therings focus the ringmaterial, keepingthe rings confined.Titan About the size of Jupiter’smoon Ganymede. Rocky core, but also largeamount of ice. Thick atmosphere, hiding thesurface from direct view.Moons do not only serve as “Shepherds”.Where the orbital period of a moon is a small-number fractionalmultiple (e.g., 2:3) of the orbital period of material in the disk(“resonance”), the material is cleared out Divisions7

11/6/2015TitanTitan’s AtmosphereBecause of the thick, hazyatmosphere, surface featureswere only visible in infraredimages.In 2004, the Cassinispacecraft arrived atSaturn with the probeHuygens.This is a view of themethane-richatmosphere of Titanfrom an early flyby ofCassini.Many of the organiccompounds in Titan’satmosphere may have beenprecursors of life on Earth.Surface pressure: 50% greaterthan air pressure on EarthSurface temperature: 94 K (-290 tan’s AtmosphereTitanA high-resolutionimage of Titan,showing the cloudsand some surfacefeatures. methane and ethane are liquid!Methane is gradually converted toethane in the atmosphere Methane must be constantlyreplenished, probably throughbreakdown of ammonia /TitanTitanRadar map of Titan, done by Cassini between 2004 and2011. Xanadu is the large elevated region in the A16844/The dark lines in this image are linear dunes, similar to sand dunes onEarth in Egypt and Namibia. The dune fields on Titan encircle the moonbetween the latitudes of 30 degrees north to 30 degrees south, withthe notable exception of the continent-sized Xanadu (bright hazy area toleft). At upper right is the crater Ksa. Dunes, craters and large upliftedregions are major features of 14500/8

11/6/2015TitanTitanComposite image of the terrain surrounding Huygensduring its descent onto the surface of Titan.“Lake Country” on Titan. Methane lakes and rivers cross thesurface of Titan. Ligeia Mare, about 50,000 square miles(125,000 square kilometers) in area, is the large lake near thebottom of both offame/TitanRiver channels onTitan’s surfacecaptured duringHuygen’s descentin January, Saturn’s Smaller MoonsStunning full-colorimage of Titan takenafter Huygen’shistoric landing onTitan on January 14,2005. “Rocks” areprobably frozenwater /photos/halloffame/Saturn’s Smaller Moons (2)Hyperion: Too small to pull itselfinto spherical shape.Saturn’s smaller moons formed of rockand ice; heavily cratered and appeargeologically dead.All other known moons are large enough toattain a spherical shape.Tethys:Iapetus:Leading (upperHeavily cratered;right) side darkermarked by 3 kmthan rest ofdeep, 1500 km longsurface because ofcrack.dark deposits.Enceladus:Possibly active; regionswith fewer craters,containing parallelgrooves, possibly filledwith frozen water.9

11/6/2015TethysIapetusHuge crater on Tethyscaptured by Cassini in2012. Lit terrain is onthe leading hemisphereof Tethys (660 miles, or1,062 kilometersacross). A similarfeature on Mimas gaveit the name “DeathStar”.Iapetus showing itsdark leading edge.Dark deposits areprobably ame/EnceladusA false-color imageof Enceladusshowing an eruptionof heated water nearits south pole. Heatfrom tidal forcescreates the uniquegeysers.Image of Enceladus’ south pole geysers taken duringclose flyby on October 28, mas wasnicknamed “TheDeath Star” becauseof this large crater.Mimas is 396kilometers (246miles) across, andthe crater is 130 km(86 miles) across.Sponge-like Hyperion(168 miles, or 270kilometers across)has an irregularshape, and it tumblesthrough its /http://saturn.jpl.nasa.gov/photos/halloffame/10