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Prometheus

Moons of Saturn. 1 large moon Titan 6 medium moons Enceladus Iapetus 56 known small moons 150+ suspected “moonlets”. 100 km. Helene. Atlas. Methone. Prometheus. Polydeuces. Calypso. Telesto. Pan. Pandora. Small Moons of Saturn > 100 km. Hyperion. Epimetheus. Phoebe. 200 km.

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Prometheus

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  1. Moons of Saturn 1 large moon • Titan 6 medium moons • Enceladus • Iapetus 56 known small moons • 150+ suspected “moonlets” 100 km Helene Atlas Methone Prometheus Polydeuces Calypso Telesto Pan Pandora

  2. Small Moons of Saturn > 100 km Hyperion Epimetheus Phoebe 200 km Janus

  3. Medium Moons of Saturn 1000 km Enceladus Tethys Iapetus Mimas Dione Rhea

  4. Mimas – the Death Star

  5. Tethys

  6. Dione

  7. Rhea

  8. Rhea and Rings • Indirect evidence indicates Rhea has rings around it • First rings around a moon • Ring material seems to fall onto equator, discoloring it

  9. Iapetus – the Yin/Yang Moon • Extreme contrast light vs. dark • Probably caused by debris collected on leading side as it orbits • Large mountain ridge along equator

  10. Enceladus • 500 km in diameter • Ice surface • Interior – probably rock and metal Ice Rock/Metal

  11. Enceladus - Surface • Southern “Tiger stripes” • Most of surface typical cratered

  12. Close Up of a Tiger Stripe • Tiger stripes are hot cracks on the crust In 3D

  13. Ice Volcanoes on Enceladus • At these temperatures, ice behaves like rock • “Ice volcanoes” spew water

  14. Explanation of Volcanoes • Tidal heating heats rock and melts ice • Pressurized water escapes through cracks

  15. Titan: Saturn’s Large Moon • Second largest moon in Solar System • Larger than Mercury • Close to Ganymede • Significant atmosphere • Pressure = 1.6  Earth’s • Atmosphere very hazy • Atmosphere composition: • Mostly nitrogen (like Earth) • Some methane • Complex hydrocarbons “smog” • Surface temperature – about 94 K Mercury Q. 50: Titan’s Atmosphere

  16. Titan’s Hazy Atmosphere • Complex hydrocarbons • Similar to pollution on Earth

  17. Titan: Composition • Rock/metal core • Probably mixed with ice • Icy outside • Mostly water • Liquid intermediate layer • Atmosphere outside

  18. Titan: Global View • Peer through the haze with infrared • Emphasize atmosphere in ultraviolet

  19. Titan: Infrared

  20. Titan: Radar

  21. Titan: Visible and Infrared • Huygens probe parachuted to surface • Saw smooth “rocks” • They are ice • Look smoothed

  22. Titan: Rivers • Rivers on the surface • Too cold for water • Liquid methane

  23. Titan: Lakes • Radar indicates perfectly smooth parts of Titan • Lakes of liquid methane

  24. Titan: Climate and Weather • Winds blow on surface of Titan • Winds produce sand dunes • “Sand” is ice crystals • Clouds observed • Too cold for water clouds • Mostly methane clouds • “Rain” of methane probably falls on surface Titan Earth Q. 51: Smooth “rocks”

  25. Titan: Life? • Titan has liquid on surface • Maybe not as good as water, but worth considering • Chemistry would have to use unusual energy sources • Possibly acetylene (C2H2), an energetic compound • Combined with hydrogen (H2) • Acetylene is getting destroyed somewhere on Titan • No known mechanism • Hydrogen is flowing downwards to the surface • Possibly evidence for life?

  26. The Moons of Uranus Umbriel 1000 km • Mostly named for Shakespeare characters • 5 medium moons • Miranda • 22 known small moons Ariel Miranda Puck Belinda Oberon Titania

  27. Titania

  28. Oberon

  29. Ariel

  30. Umbriel

  31. Miranda • Incomplete differentiation • Rotated layering?

  32. Miranda – The Chevron

  33. Miranda – Detail • A scarp

  34. The Moons of Neptune • 1 large moon • Triton • 1 medium moon • 12 known small moons Galatea Larissa 300 km Nereid Proteus

  35. Triton • A little smaller than our Moon Composition: • Large rocky core • Ices on top • Thin nitrogen atmosphere! Moon Orbit: • Goes backwards around Neptune! • Probably captured Kuiper belt object

  36. Triton - Appearance • Thin atmosphere • Active geysers • Probably nitrogen • Very few craters • Flat regions • Variety of terrains

  37. Triton - Appearance

  38. Triton - Appearance

  39. Triton - Appearance

  40. Triton - Geysers https://www.youtube.com/watch?v=pKn7TuNa9Dc

  41. Triton - Atmosphere

  42. Triton – Cantaloupe Terrain

  43. Triton – Flat Plains

  44. Triton – Retrograde Orbit • Triton orbits Neptune retrograde (backwards) compared to rotation • Tidal force is drawing Triton slowly closer to Neptune Q. 52: The Fate of Triton

  45. Rings Star How We Know What We Know • Voyager 1 and 2 flyby • Galileo Orbiter – Jupiter • Cassini Mission – Saturn • Juno Mission – Jupiter • Occultations! Q. 53: Detecting Rings • Tiny objects scatter light mostly forward • Ice is shiny, dust is dark

  46. Saturn’s Rings • Chunks of ice, size ranges from micrometers to meters • A few objects 1 km and more • Small moonlets • Main rings about100 m thick • Relatively speaking, thinner than a sheet of paper

  47. Ring Particles - Origin • Ring particles get slowly blasted by micrometeorites • All but largest chunks would be ground to nothing by now • Pieces that get too close to Saturn will be absorbed • Conclusion: Ring particles must be renewed somehow • Small, icy moons get chunks knocked loose • These go into their own orbit around Saturn • Collisions make them fall into very thin plane • Gravitational interactions – complicated – make patterns • They adjust their orbits • Sometimes they stick together to make new moons • Sometimes, small moons can collide and shatter

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