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Transcript
Chapter 12: Jupiter and Saturn Jupiter Visuals jupiter.jpg jupiterearthspot_comparison.jpg Saturn Visuals saturn-rings1.jpg planets_size.avi vital statistics Jupiter Saturn Orbital distance 5.2 AU 9.5 AU Orbital period 11.9 years 29.5 years Rotation period 9.9 hrs, differential 10.7 hrs, differential Axial tilt 3º 27º Known Satellites 16 18 Mass 318 x MEarth 95 x MEarth Radius 11.2 x REarth 9.5 x REarth Density 1.33 0.69 Surface Gravity 2.54 g 1.08 g Global Temp 125 K 95 K Escape Velocity 60 km/s 36 km/s (earth’s 11.2 km/s) 1 largest and most massive planets [Figure 12-5] Jupiter takes up 70% of planetary matter low density => mostly hydrogen and helium differential rotation [12_6.mov] equator and poles rotate at different rates! → fluid bodies rapid rotation + fluid body → flattened shape Voyager 2 Missions [Fig 12.2, 1] 2 Saturn and Jupiter: “surface” features zonal winds and belt features [Figure 12-6,8(jupiter), 7,9(saturn) ] similar to Earth’s jet streams Great Red Spot of Jupiter [Figure 12-6,11] present since at least 1665 (Cassini) a high pressure system (direction of rotation) other storms: smaller white spots last decades [Fig 12-6,12] dark spots last years [fig 12.13]. Some smaller high pressure systems also appear on Saturn[fig 12.14] 3 Atmospheres of Jupiter and Saturn mostly (99.9%) Hydrogen and Helium Jupiter has 3x as much Hydrogen as Helium, by mass Approximately Solar mix Saturn has Helium deficit (7 to 1 ratio) Convection Cells [figure 12-17] produce belts on Jupiter Temperature banding: Jupiter (IR [figure 12-15] ) and Saturn (radio [figure 12-16]) Temperature decreases with altitude (increases towards interior) [Figure 12-18] Clouds: ammonia, ammonium hydrosulfide ice and water coloration [Figure 12-19, 20 (artist conception based on galileo data)] 4 Interiors: [Figure 12-21] Gradual change from gas to liquid High pressures (Jupiter ~ 50 Mb, Saturn ~10Mb) and Temperatures (~20,000 K) → “exotic” states of matter → metallic Hydrogen (fluid conductor) Density indicates some heavier materials rock, metals and ice at core Interiors hot, planets radiate more than they absorb self luminous (in infrared) Internal energy source! Jupiter: leftover from initial contraction initially had ~1% of sun’s brightness (but 1/4 Sun's temp) Saturn: initial contraction energy essentially used up current source: helium settling in core explains Helium deficit 5 Magnetospheres [figure 12-22] strong magnetic fields dynamo: rapid rotation + convection in liquid conductor (metallic hydrogen) field rotates with planet, dragging trapped ions along rotation magnetodisk: plasma (lifted by rotation) around equator Aurora [figure 12-23] 6 Rings (both Jupiter and Saturn have ring systems) [figure 12-24, 25, 27, jupiter: figure 29,30] individual particles in independent orbits (not solid [figure 12-26]) Structure [figure 12-31,32,34,35] resonances: partial explanation of structure orbital period of particles an integer fraction of the orbit of one of the moons [figure 12-33 12_31.mov] collisions “flatten” rings [figure 12-28] most of rings appear within Roche Distance [figure 12-36] Roche Distance: closest distance an object can orbit a planet without being torn apart by tidal forces (~2.5 planet radius) →possible ring origin rings should dissipate, must be (relatively) young particles either work inward and hit atmosphere or work outward and escape into space. Saturn's moon Enceladus is 'feeding' Saturn's largest ring tidal force heating induced volcanism [PIA08386_enceladus_r.jpg] 7 Comet Shoemaker-Levy (remnant) impact (JULY 1994) [ http://www2.jpl.nasa.gov/sl9/ ] from: http://nssdc.gsfc.nasa.gov/planetary/planets/ Missions to Jupiter Past Missions * Cassini - NASA/ESA Mission to Saturn via Jupiter * Galileo Orbiter - NASA Mission to Jupiter * Galileo Probe - NASA Mission to Jupiter * Voyager 1 - NASA Mission to Jupiter and Saturn * Voyager 2 - NASA Mission to Jupiter, Saturn, Uranus, Neptune, and beyond * Ulysses - NASA/ESA Mission to study the solar wind via Jupiter * Pioneer 10 - NASA Jupiter flyby (1973) * Pioneer 11 - NASA Jupiter flyby (1974) Future Missions * Jupiter Icy Moons Orbiter (JIMO) - NASA Proposed Europa, Ganymede, and Callisto Orbiter (2015) * Juno - NASA New Frontiers Jupiter Polar Orbiter under study Missions to Saturn Current and Past Missions * Cassini - NASA/ESA Mission to Saturn * Huygens - NASA/ESA Mission to Saturn's satellite Titan * Voyager 1 - NASA Mission to Jupiter and Saturn * Voyager 2 - NASA Mission to Jupiter, Saturn, Uranus, Neptune, and beyond * Pioneer 11 - NASA Saturn flyby (1979) 8