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Jupiter=Zeus=Indra • King of the Gods. God of sky &thunder • Orbital period = 11.9 years (one year in each zodiacal constellation) @5.2 AU Saturn = Cronus • • • • God of Harvest, Agriculture. Saturnday Father of Jupiter, Neptune, Pluto. Son of Uranus and Gaia. Faintest + Farthest planet easily visible to naked eye Jupiter and Saturn Physical properties • • • • Radius 10 Earths and 9 Earths: Volume ~ 1000 Earths But Mass only 318 Earths and 59 Earths so Density 1.3gm/cm3 and 0.7 gm/cm3 Not like Earth, all rock & iron =5gm/cm3 Differential Rotation • Jupiter: Cloud period = 9h50min @ Equator & 9h55min @ pole =Differential Rotation • Radio/magnetic field = 9h55min • Saturn: Rotation 10h14m to 10h46m =Differential Rotation Oblate • So fast that Equatorial Bulge & Flat Poles = Oblate • The mountain most distant from the center of Earth is Chimoborazo Jupiter’s Atmosphere • 86% Hydrogen and 14% Helium like the sun & stars • Small amounts of methane CH4, ammoniaNH3 and water vapor H2O • • • • Structure of Atmosphere Galileo probe measured temperature, pressure etc. Clouds in three layers – NH3, ammonia hydrosulfide &H2O Colors from phosphorus & sulfur? No carbon chains Saturn’s Atmosphere • Composed of Hydrogen 92% & Helium 7.4% - missing Helium! • Temperature of 100 Kelvin • Thick methane haze covers/mutes clouds: ammonia, ammonium hydrosulfide, water clouds Atmospheric Bands • Convection = High/Low pressure regions smeared by rapid rotation into dark Belts & white Zones Jupiter’s Zonal Flow • Winds 550 km/hr similar to Earth’s jet streams Spots/Storms on Saturn • IR image: Dragon Storm“ produced lightning & radio static • Super storm wrapped around Saturn by a zonal flow faster than Jupiter’s Great Red Spot • First observed by Hooke 1680 • Twice the size of the Earth • Rising Gas produces 30km high thunderhead-lightning White Ovals • 3 white ovals merged to form Red Spot Junior Polar Vortex • Spring in North allows Cassini probe to see North pole surrounded by hexagon • Centered on Pole is hurricane (Vortex) with low clouds in red & high clouds in green (infrared) Jupiter’s Internal Structure • Radiates 1.7X more energy than it receives from the sun • Core temp~40,000K, not rocks • No solid surface • Liquid metallic hydrogen Internal Energy Source • Radiates 2 times energy it receives from sun • Infrared picture shows hot spot at south pole • Helium precipitation: Helium & Neon “Rain” falling on core releases heat Jovian Planets Have Magnetic Fields • • • • No solid surface – critical point of hydrogen Forms liquid metallic hydrogen @depth of 20,000km Conducting, convecting core & rotation produces magnetic fields Some reversed, tilted, offset?? – large magnetospheres Jupiter’s Magnetosphere • Larger than sun • 20,000 times Earth’s field • Jupiter’s rotation moves field past Io-radio emission • Sweeping up ions, forming Plasma torus • Radiation Belts & Aurora Aurora on Saturn • Magnetic field aligned with rotational axis • Smaller mass means smaller amount of liquid metallic hydrogen so a smaller magnetic field • Saturn’s radio noise in AM band – reflected by ionosphere Jupiter is oblate because: a) It has differential rotation b) It has belts and zones c) It contains liquid metallic hydrogen d) It is emitting more heat/energy than it receives from the sun e) It rotates so quickly Jupiter’s Moons • Jupiter has 68 moons (2014) Many irregular satellites are captured asteroids – orbits: retrograde, eccentric, inclined • Saturn 62; Uranus 27 , Neptune 14, Pluto 5; Eris 1; Asteroid Balam 2 • ~20 discovered by DAO astronomer JJ Kavelaars; teaches Astr255 Inner Moons & Rings • Metis, Adrastea, Amalthea, Thebe • Amalthea is ~ 250km diameter • Inner 4 prograde moons supply material for Jupiter’s rings Galilean Moons • • • • Companions/lovers of Zeus/Jupiter Io, Europa, Ganymede, Callisto Sizes~Moon-Mercury: Density~2gm/cc So made of rock and ice not much iron Tidal Heating • Orbital Resonance 4:2:1 Makes orbits eccentric • Constant rotation: “nearly” synchronously • Tidal bulge of ~100meters changes height • Bulge moves across moon flexing/heating it Callisto • • • • • Radius =Mercury but Mass of Moon Density 1.8 gm/cm3 so rock and ice Orbital period= synchronous rotation= 16.7days Heavily cratered icy surface = Old terrain Undifferentiated but possibly water/slushy mantle • • • • • Ganymede Largest moon in solar system Radius>Mercury Density ~Callisto so rock & ice Crater counts indicate - Old dark terrain Young bright impact craters & grooved terrain Interaction of Ganymede’s with Jupiter’s magnetic field indicates liquid water 170km down and 5 km thick • Period 4 times Io’s and 2 times Europa’s = orbital resonance Europa • White smooth surface with very few craters = very young ~million years • Theory: A km of ice &100km salt water ocean • Salt water ocean affects Jupiter’s magnetic field Surface Features on Europa • Observe: Cracks & compression ridges & crust broken & moved • Newly reported & unconfirmed observations of Hydrogen & Oxygen at south pole only at apojove • Geyser/Volcano - 7tons ~200km high at ~1km/sec Life on Europa?? • As much liquid water as Earth • Europa seems to have a tidally heated ocean • Maybe Black Smoker type life forms???? • JUICE ESA launch 2022, orbit 2030, ice penetrating RADAR Io • Io-Jupiter distance same as Moon-Earth, but period=1.8days • Size &density ~Moon; no impact craters! =youngest surface • Io plasma torus: doughnut of volcanic ejecta swept up by Jupiter’s magnetic field surrounds Jupiter in Io’s orbit; lethal to people &probes 100 Volcanoes on Io • Hot interior from tidal heating • Sulfur in volcanic ejecta color surface white, black & yellow • Prometheus has been erupting for 18 years (since Voyager I) Lava on Io • Temperature of some of Io’s lava is hotter than Earth’s • Lava is enriched in magnesium and iron • Infrared photo of Jupiter & Io shows red spot in white & lava below volcanic plume Juno = Jupiter’s Wife • • • • • • • Launched 2011-Arrival 2016 Oxygen isotopes= formation Polar orbit studies Aurora Size of rocky core: Core-accretion or Gravitational Instability Jupiter’s moon Io is very hot because: a) It has so many volcanoes b) It has not had time to cool since its formation c) Of impacts from the dust in the plasma torus d) Electric currents generated by its motion through Jupiter’s magnetic field e) Orbital resonances with Europa and Ganymede cause tidal heating Geological Map of Ganymede