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Jupiter and Its Moons History and Interior of Jupiter • Accreted as gas giant (H2, He) • Gaseous atmosphere, underlain by liquid, Trace compounds Fluid molecular with small core Hydrogen • Interior heat Transition zone generated by Fluid metallic hydrogen gravitational Possible core collapse? Cloud tops — aerosols Ammonia crystals Ammonium hydroxide clouds Ice crystal clouds Water droplets 20Mm 40Mm 60Mm G302 Development of the Global Environment Jupiter’s Atmosphere Various Prominent Banded Features • Pronounced zonal winds, eddies • White ovals, brown blebs, streaks, bands • Great Red Spot • cyclonic feature Great Red Spot white ovals Brown blebs Great Red Spot eddies G302 Development of the Global Environment 1 Jupiter’s Gravity Comet Shoemaker-Levy 9 • Broken into fragments by Jupiter’s gravity in 1992 • Each fragment impacted Jupiter’s surface in 1994 Impact of Fragment G • Chains of Jul 18 1994 impacts also observed on moons Jupiter and Comet Shoemaker -Levy 9 G302 Development of the Global Environment Jupiter’s Moons 17 Moons and a Ring System • Range of Distances, Sizes, and Orbital Periods: • 128 - 24,200 x 103 km (Moon = 384) • 20km - 5,276km (Moon = 3476km) • 0.3 - 774 days (proportional to distance) • Galilean satellites: Callisto Name Size (km) Distance (103 km) Callisto Europa Ganymede Io 4,880 3,126 5,276 3,629 1,883 671 1,070 422 Ganymede Europa Io G302 Development of the Global Environment 2 Jupiter’s Moons: Io History and Features of Io • Heated by tidal forcing sulfur, rock mantle • caused loss of icy mantle? • Volcanically active • Density: ~3.5g/cm3 • Atmosphere: Fe, rock core • 90% sulfur • Composition: • silicates • sulfur • iron volcano and lava plain G302 Development of the Global Environment Jupiter’s Moons: Europa Features of Europa cracked surface • Ice crust with cracks • • • • • stressed and heated by tidal forcing • evidence of ice volcanism • ice movement in plates? Rocky interior and core Density: ~3.0g/cm3 No atmosphere Liquid water below ice surface? • viable environment for life? • focus for astrobiological studies refrozen ice flows G302 Development of the Global Environment 3 Jupiter’s Moons: Ganymede History of Ganymede ice crust • Surface features metallic core • older cratered dark regions (40%) • younger light grooved terrain from faulting and water release (60%) • Metallic core (400-1500km) grooved terrain • Density: ~1.9g/cm3 water/ice mantle cratered dark region tectonic features old terrain G302 Development of the Global Environment Jupiter’s Moons: Callisto History of Callisto • Geologically inactive • crust frozen at formation • highly cratered (maximal density) • no signs of tectonism • Interior • partially differentiated? • or homogeneous, never molten • low abundance of radioactive isotopes • little tidal forcing • Density: ~1.9g/cm3 • mixture of rock and ice Valhalla crater G302 Development of the Global Environment 4 Galilean Moons: Comparisons Io Europa Ganymede Callisto G302 Development of the Global Environment Saturn, Its Moons and Rings History and Interior of Saturn • Accreted as gas giant (H2, He) • Gaseous atmosphere, with interior largely liquid, plus small core and mantle • Interior radiates heat from internal heat source (gravitational collapse?) G302 Development of the Global Environment 5 Interior of Saturn Characteristics of Core Possible composition of interior • Formed by accretion and gravitational collapse? • Iron core surrounded by liquid H2 and ice? Sequential formation of core by aggregation and separation G302 Development of the Global Environment Features of Saturn General Characteristics and Surface • Low density (0.7 g/cm3) • Fast rotation (10-11 hours) • Bands, anticyclones, storms around great white spot • High velocity winds (up to 1800 km/hr?) • Aurora in upper atmosphere anticyclone (size of Earth) aurora white spot G302 Development of the Global Environment 6 Saturn’s Atmosphere auroras 250 tropopause 200 Layered Structure haze layers 0.5 visible cloud tops altitude (km) 150 NH3 ice? 1 100 pressure (bar) • Aurora in upper atmosphere • Ammonia (NH3) • Ammonium hydrosulfide (NH4HS) • Water (H20) • Liquid layers below (H2, He, CH4, NH3, H20) 0.1 NH4HS ice? 50 Troposphere H2, He, CH4, NH3, H2O 10 H2O ice? 0 H2O fog? 0 G302 Development of the Global Environment 200 400 600 800 temperature (K) Saturn’s Rings Five Major Components • G, F, A, B and C rings, with innumerable ringlets • Cassini division between A, B • Composed of particles, mainly ice crystals spokes major ring and ringlets G302 Development of the Global Environment 7 Saturn’s Moons General Characteristics • 19 moons named, most are icy (densities 1-1.5 g/cm3), but may have rocky constituents, cratered • Many are locked by tidal forces. G302 Development of the Global Environment Saturn’s Moon Titan Characteristics • Opaque atmosphere with several layers of haze • Primary liquid N2, with 1% CH4 • Thick smog composed of hydrocarbons? • Oceans of CH4, ethane (C2H6) • Surface temperature -180°C Titan Variations in Titan’s surface G302 Development of the Global Environment 8 Saturn’s Moons Major Moons Tethys • Icy surfaces, with impact craters • Mimas impact ~25% of diameter • Some ‘shepherd moons’ stabilize rings Rhea Mimas Iapetus G302 Development of the Global Environment Uranus Major Characteristics • Discovered in 1781 by Herschel • Gas giant: hydrogen and helium (1.2g/cm3), also heavier elements • Rotational axis 8°off orbital plane • Rings (> 5, rock not ice?) and many moons (5 major, 10 smaller), some may be ‘shepherd moons’ • Methane (gives blue color), ethane, acetylene, diacetylene in atmosphere. Surface is -210°C G302 Development of the Global Environment 9 Uranus’s Icy Moons Shakespherian Names • Miranda, Ariel, Umbriel, Oberon, Titania, Ophelia, Bianca, Cressida, Desdemona, Juliet, Portia, Rosalind, Belinda, Puck, Caliban, Sycorax, Prospero, Setebos, Stephano Oberon Miranda is geologically active: tidal forcing? Miranda Ariel Umbriel Titania Oberon G302 Development of the Global Environment Neptune Major Characteristics • Discovered in 1845 • Gas giant: H2, He (1.6g/cm3), also heavier elements • Internal heat source • Methane (gives blue color) in atmosphere. Surface is -216°C • ‘Great dark spot’ long-lived storm system; winds 1000 km/hr. • Faint rings (dust grains?) and two large moons; weak magnetic field Great dark spot G302 Development of the Global Environment 10 Neptune’s Moons Triton and Nepeid • Triton: comparable in size to Earth’s Moon • Retrograde motion around Neptune (captured?) • Thin atmosphere (mostly N2) and polar ice cap of solid N2 Triton • Giant faults on surface • Volcanoes of N2 ice vent through surface of CH4 ice? • Nepeid: highly eccentric orbit (captured asteroid?) G302 Development of the Global Environment Pluto Major Characteristics • Discovered in 1930 by Tombaugh • Smaller than the Moon, about 20% the size of the Earth • Irregular orbit, tilted at 17°, rotation rate about 6.5 days • One moon - Charon (discovered 1978 by Christy) • Surface is -240°C • Planet or Kuiper belt object (One of 200,000,000 comets) G302 Development of the Global Environment 11