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GEOL 3045: Planetary Geology. Lysa Chizmadia Saturn’s Satellites. Introduction. At least 60 moons Classification of Moons: A-ring Moonlets Ring Shepherds Co-orbitals Inner Large Moons Alkyonides Trojans Outer Large Moons Irregular Moons Inuit Group Norse Group Gallic Group.
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GEOL 3045: Planetary Geology Lysa Chizmadia Saturn’s Satellites
Introduction • At least 60 moons • Classification of Moons: • A-ring Moonlets • Ring Shepherds • Co-orbitals • Inner Large Moons • Alkyonides • Trojans • Outer Large Moons • Irregular Moons • Inuit Group • Norse Group • Gallic Group Image from: http://solarsystem.nasa.gov/planets/ profile.cfm?Object=Saturn&Display=Moons Image from: http://en.wikipedia.org/wiki/Saturn
A-ring Moonlets • 4 discovered in 2006 by Cassini • 8 more discovered in 2007 • Tiny moons inside the A-ring • Diameters: 0.06 to 0.14 km • Probably formed due to shattering of inner satellite during impact • Discovered by propeller-shaped disturbances in ring Photo Credit: NASA Image from: http://www.theregister.co.uk/2007/10/25/moonlets_a_ring/
Ring Shepherds Pan in Encke Division • Orbit within or just outside rings • Sculpt the rings • Giving them sharp edges & gaps • 5 named & 3 unconfirmed • Pan • Daphnis • Atlas • Prometheus • Pandora • S/2004 S3, S/2004 S4, S/2004 S6 Image from:http://en.wikipedia.org/wiki/Pan_%28moon%29 Prometheus (left) & Pandora (right) in Saturn’s F-ring Ripples caused by Daphnis Image from: http://en.wikipedia.org/ wiki/Daphnis_%28moon%29 Image from: http://en.wikipedia.org/wiki/Shepherd_satellite
Co-orbitals • Epimetheus & Janus • Orbit differs by only 50 km • Inner orbits are faster so must approach each other • When inner moon catches outer moon, gravitational attraction boosts inner’s momentum, increasing orbit • Opposite happens to outer moon • Thus, they trade places when they pass each other Images from: http://en.wikipedia.org/wiki/ Epimetheus_%28moon%29 Epimetheus Janus Image from: http://en.wikipedia.org/wiki/ Janus_%28moon%29
Inner Large Moons Mimas • Mimas (Herschel crater) • Methone • Anthe • Pallene • Enceladus * • Tethys • Telesto (L4) • Calypso (L5) • Dione (ice cliffs) • Helene (L4) • Polydeuces (L5) http://en.wikipedia.org/wiki/Mimas_%28moon%29 Dione http://en.wikipedia.org/wiki/Dione_%28moon%29
Enceladus • Ice ridges & Cryovolcanism Images from: http://en.wikipedia.org/wiki/Enceladus_%28moon%29
Outer Large Moons Rhea Hyperion • Rhea • Homogeneous interior • 2 adjacent large craters • Possible ring system • Titan * • Hyperion • Chaotic rotation • Sponge-like texture • Iapetus • 2 tone coloration • High inclination • Equitorial ridge Image from: http://en.wikipedia.org/wiki/Rhea_%28moon%29 Image from: http://en.wikipedia.org/wiki/Hyperion_%28moon%29 Iapetus Iapetus Images from: http://en.wikipedia.org/wiki/Iapetus_%28moon%29
Titan • Only moon w/ dense atm • Pressure: 1.6 bars • 98.4% N2, 1.6% CH3 & H-Cs • CH3 must be produced • Not from comets b/c CO • Not from nebula b/c He, Ne • Only body with liquid on surface • Other than Earth • Liquid CH3 lakes • Diameter: 5150 km • Mercury: 4879 km • Moon: 3474 km Images from: http://en.wikipedia.org/wiki/Titan_%28moon%29
Irregular Moons • 3 main groups • Inuit Group • Norse Group • Gallic Group Pheobe Images from: http://en.wikipedia.org/wiki/Phoebe_%28moon%29
Inuit Group • Prograde irregular satellites • Semi-major axes: 11-18 x 106 km • Inclinations: 40-50 degrees • Eccentricities: 0.15-0.48 • Spectral homogeneity • Similar to Gallic Group • Break up of single object • 5 members: • Kiviuq • Ijiiraq • Paaliaq • Siarnap • Tarqeq Image from: http://en.wikipedia.org/wiki/Ijiraq_%28moon%29
Norse Group • Retrograde irregular satellites • Semi-major axes: 12-42 x 106 km • Inclinations: 136-175 degrees • Eccentricities: 0.13-0.77 • Composed of > 4 subgroups • two i=174 subgroups • Skathi subgroup • Narvi subgroup Image from: http://en.wikipedia.org/wiki/Saturn%27s_Inuit_group_of_satellites
Gallic Group • Prograde irregular satellites • Semi-major axes: 16-19 x 106 km • Inclinations: 35-40 degrees • Eccentricities: ~0.53 • Spectral homogeneity • Similar to Inuit Group • Break up of single object • 4 members: • Albiorix • Bebhionn • Erriapus • Tarvos Image from: http://en.wikipedia.org/wiki/Ijiraq_%28moon%29
At least 60 moons At least 6 groups A-ring moonlets Shepherd moons Co-orbitals Inner large moons Includes Enceladus Outer large moons Includes Titan Irregular Moons Inuit group Norse group Gallic group Mimas Herschel Crater Dione Whispy ice ridges Enceladus Ice ridges ~ Europa Cryovolcanism Rhea Homogeneous interior Possible ring system Titan H-C rich atmosphere Liquid HC on surface Hyperion Sponge-like surface texture Iapetus Two-tone surface colors Equatorial ridge Summary