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The Outer Planets Cosmic Abundance of Elements Hydrogen H 1 1,000,000 Helium He 2 80,000 Carbon C 6 363 Nitrogen N 7 112 Oxygen O 8 851 Neon Ne 10 117 Sodium Na 11 2 Magnesium Mg 12 32 Aluminum Al 13 3 Silicon Si 14 45 Sulfur S 16 16 Argon Ar 18 1 Calcium Ca 20 2 Iron Fe 26 36 Nickel Ni 28 2 Major Constituents Gas Formula Jupiter Saturn Hydrogen H2 86% 92% Helium He 14% 7% Methane CH4 0.2% 0.2% Ammonia NH3 0.02% 0.02% Water H2O ~0.2% (?) ~0.4% (?) Interiors: Big H2 Atmospheres Jupiter vs Saturn Jupiter’s Ammonia Clouds: Belts: Dark bands Zones: Bright bands Great Red Spot White Ovals The GRS has lived at least 300 yrs. Ovals have been seen to survive tens of years Jupiter’s clouds result from convection. 1) Hot air expands. 2) Lighter than the rest of the air, it rises. 3) As it rises, it cools and condenses forming clouds. 4) When it is cooler than the ambient air, it sinks. Great Red Spot Saturn’s Clouds Uranus Absorption of sunlight at red wavelengths by methane renders the planet blue. Neptune Neptune emits more energy from its interior than does Uranus. This energy drives weather. The colder temperatures cause methane to condense in the upper atmosphere – these are the clouds that we see. Jupiter’s Rings Silicate dust, 10,000 times more transparent than window glass. Moons Their densities tell us that they are 1/2 rock & 1/2 ice. A typical, heavily cratered, terrain. Saturn’s moon, Tethys Jupiter’s Moons Europa Few craters A terrain containing elements that were recently dislodged can be seen to neatly fit together if rotated and translated in position. IoIo • Images\iovol_vgr.gif What fuels Io? Each time Ganymede orbits once, Europa orbits twice, and Io orbits 4 times. Plumes fountain 500 km above the Surface Io’s surface is almost devoid of craters, for it is being repaved at a rapid rate. The glow of warm lava. A pool of lava (black) covered with sulfur deposits (orange). This is called Tupan Patera after the Brazilian thunder god. Images taken from the Galileo spacecraft. Io is hot Lava flows on Io exceed 1500 K in temperature. Lavas this hot are not sulfur (which would evaporate immediately). This is hotter than present lavas on Earth (1300-1450 K). Instead these lavas are likely ultramafic (rich in Mg and Fe), similar to the lavas that occurred on early Earth. Present hypothesis, a ~100 km thick crust floats on top of a worldwide ocean of magma 800 km deep. Neptune’s Largest Moon: Triton Triton On Triton the main component of the atmosphere, nitrogen, exits in vapor pressure equilibrium. That is, it exists as an ice on the surface and as vapor in the atmosphere, in the same way that water exists as liquid and ice on Earth’s surface and as a gas in the atmosphere. The amount of gas depends on the temperature. Less exists at cooler temperatures. Atmosphere: This is seen on Earth with the condensation of water at dew point. 1.6x10-7 bar 38K Nitrogen Summary • Giant planets are large gas planets with nearly solar elemental abundances. • They have small ice-rock cores. • Their moons are ½ rock and ½ ice. • Most moons display heavily cratered terrains. Io, Europa, Triton and Titan are exceptions. • All jovian planets sport rings of differing thicknesses, compositions & character. • Titan supports an atmosphere second only to Venus’ (considering bodies with proper surfaces). It is rich with organics, and its origin is unknown. • The Cassini mission to the saturnian system is in route and functioning well. Titan: a moon with an atmosphere Saturn’s largest moon compared to Jupiter’s largest moons Titan Size:5150 km Mass: 1.3x1023 Callisto Size: 5268 Mass: 1.1x1023 Ganymede Size: 4800 Mass: 1.5x1023 Observações da alta atmosfera Composition of Titan’s stratosphere Molecule N2 CH4 H2 CO CH3D C2H6 C2H2 C3H8 C2H4 HCN HC3N CH3C2H C4H2 C2N2 CO2 Abundance 65-98% 2-10% 0.2-0.6% 6-150 ppm 5-180 ppm 13-20 ppm 2-5 ppm 0.5-4 ppm 0.09-3 ppm 0.2-2 ppm 80-250 ppb 4-60 ppb 1-40 ppb 5-16 ppb 1.5-14 ppb Derived from radiative transfer analyses of Voyager, ISO and ground-based data. Oceans? hν H2 CH4 + CH4 -> other hydrocarbons Methane in atmosphere is depleted in107 years. Either methane is supplied or we are witnessing Titan at a particular moment in its history. haze Oceans containing methane explain the near saturated tropospheric conditions, provide a source for methane, and don’t require a penchant for being lucky. C2H2 C2H6 Ocean (CH4, C2H6, N2) Flasar et al. Science 221, 55 Lunine et al. Science 222, 1229 Production Rate Species Flux Depth* Phase C2H6 5.8x109 cm-2 s-1 600 m liquid C2H2 1.2x109 cm-2 s-1 100 m solid C3H8 1.4x108 cm-2 s-1 20 m liquid HCN Haze 2.0x108 cm-2 s-1 1.5x10-14 g cm-2 s-1 20 m 60 m solid solid * Depth assuming global coverage & 4.5 Gyr of production Taken from Lunine et al. 1989. Based on Yung et al. 1984, Raulin (1984) Expected Surface Scenario Sagan & Dermott 1982 QuickTime™ and a decompressor are needed to see this picture. QuickTime™ and a decompressor are needed to see this picture. Titan’s Surface HST images Peter Smith et al. U. of Arizona QuickTime™ and a decompressor are needed to see this picture. QuickTime™ and a decompressor are needed to see this picture. Testing Cassini (Jet Propulsion Laboratory, California) We can see the main antenna. All the instruments (e.g. the cameras) are covered. Huygens Probe, European Space Agency We can see the shield that protects the instruments against the heat of entry into the atmosphere. In 2005, the desent of Huygen’s into Titan’s atmosphere. At 170 km altitude, Huygens releases the shield and begins measurements. 15 October 1997 Cassini-Huygens spacecraft, on a Titan IV rocket, waiting for takeoff. A perfect takeoff that saved fuel. ISS Images Huygens DIRS Descent Movie Ice Mountains View of Landing Site Landing Site Huygen’s DISR Images PI: Marty Tomasko University of Arizona Foreground stones are 6 inches More DISR Images. DISR Washes flow downhill Tomasko et al. Nature 438, 765 Huygens aterrizou ~30km ao sul das dunas Imagem do Cassini Radar (no modulo orbital) Sitio de aterrissagem Larry Soderblom Tropical Dunes Washes in Xanadu Cassini RADAR Lakes Seas Titan ~ 1 m of surface CH4 ~ 4 m of atmospheric CH4 Cassini Radar 60o N latitude line 2.7 km of water on the surface 2.5 cm of atmospheric water Earth Cryovolcanism Sotin et al. Nature 435, 786 (2005) A Mystery about Titan Where is the ethane (C2H6)? C2H6 N2, CH4 Atmosphere A Mystery about Titan Where is the ethane (C2H6)? C2H6 N2, CH4 Atmosphere Titan’s Two Kinds of Clouds Ethane (C2H6) 40 20 Methane (CH4) QuickTime™ and a decompressor are needed to see this picture. Summary Titan, Saturn’s largest moon, has an atmosphere10 times thicker than Earth’s. This atmosphere is mainly of N2 and contains a lot of organic material. Titan sports a methane cycle, with clouds, rain & seas. Methane is the source of organic material in Titan’s atmosphere and on its surface. It’s not entirely clear how and when Titan outgassed its methane, but the dearth of ethane suggests that it happened within 1 billion years. The complexity of the organic chemistry is unclear. Um Balão para Titã