Lec24-Apr15 - 4/15/11 Quiz QuesGon #1 Saturn’s...

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Unformatted text preview: 4/15/11 Quiz QuesGon #1 Saturn’s rings are composed mainly of Astro 109 Lecture 24: Jovian Moons and Rings April 15 A.  B.  C.  D.  E.  hydrogen and helium. ice or ice ­covered parGcles. rock parGcles. iron and nickel. liquid methane. Apr. 15 Quiz QuesGon #2 The lakes and rivers on Titan contain liquid A.  B.  C.  D.  E.  water. ammonia. methane and ethane. nitrogen. helium. Key Concepts •  dynamic Titan and Enceladus •  ring structure and dynamics •  Gdal disrupGon, Roche limit / zone •  interacGons with moons Apr. 15 Apr. 15 Apr. 15 Apr. 15 1 4/15/11 Discussion QuesGon Titan and Mercury are about the same size. Why does Titan have a thick atmosphere while Mercury does not? A.  Titan formed more recently than Mercury, and thus sGll retains its atmosphere. B.  The temperature of Titan is low enough that gas molecules do not reach escape speed. C.  Titan receives a lot of gas from frequent impacts by icy objects common in the outer solar system. D.  Titan’s atmosphere is produced by organic life. Apr. 15 Apr. 15 hXp://apod.nasa.gov/apod/ap060215.html Huygens lander hXp://solarsystem.nasa.gov/mulGmedia/display.cfm?IM_ID=7383 arGst’s impression hXp://www.esa.int/SPECIALS/Cassini ­Huygens/SEM5KSLJ74G_1.html Apr. 15 Apr. 15 hXp://photojournal.jpl.nasa.gov/catalog/PIA12817 false color! Surface liquid Apr. 15 hXp://solarsystem.nasa.gov/mulGmedia/display.cfm?IM_ID=10147 hXp://photojournal.jpl.nasa.gov/catalog/PIA12818 hXp://solarsystem.nasa.gov/mulGmedia/display.cfm?IM_ID=4763 Apr. 15 2 4/15/11 Earth Discussion QuesGon We say that methane plays a role on Saturn’s moon Titan analogous to that of water on Earth because A.  methane and water have similar melGng and boiling temperatures. B.  methane can exist as a solid, liquid, and vapor on Titan. C.  methane is the most abundant gas in Titan’s atmosphere. D.  methane escapes easily from the upper atmosphere. E.  residents of Titan use it to wash their clothes. Apr. Titan 15 Apr. 15 Enceladus “Volcanic” plumes (false color) Wikipedia Apr. 15 Apr. 15 Mimas hXp://photojournal.jpl.nasa.gov/catalog/PIA13891 Apr. 15 Apr. 15 3 4/15/11 Neptune’s moon Triton Uranus’s moon Miranda Apr. 15 Apr. 15 hXp://solarsystem.nasa.gov/mulGmedia/display.cfm?IM_ID=9103 Saturn Apr. 15 Apr. 15 Discussion QuesGon Saturn’s rings are A.  B.  C.  D.  Apr. 15 hXp://mydarksky.org/2008/12/30/ringless ­saturn/ solid enough to stand on. a collecGon of solid parGcles. a collecGon of liquid drops. thin streams of gas. Apr. 15 4 4/15/11 RotaGon Inside the rings •  1895: James Keeler used the Doppler effect to study how the rings rotate •  discovered they are a swarm of individual parGcles ArGst’s concept, based on inferred distribuGon of parGcle sizes Apr. 15 Apr. 15 hXp://www.sunflower ­astronomy.com/KCKCC_Docs/Saturns_Rings.pdf 7 cf. Lec 23 Tidal disrupGon Discussion QuesGon Why don’t the parGcles in Saturn’s rings collect together to make a moon? A.  The Gdal field of the planet pulls apart any that gather together. B.  Comets colliding with the rings break them down into smaller parGcles. C.  The parGcles are not sGcky enough. D.  The parGcles never collide. 8 Gdal forces are stronger closer to the planet too close, and the moon can be ripped apart! Apr. 15 Apr. 15 hXp://www.astro.washington.edu/users/smith/Astro150/Tutorials/TidalHeat/ Roche limit, or Roche zone A B C Cassini division Wikipedia Apr. 15 Apr. 15 5 4/15/11 Discussion QuesGon What causes the Cassini division? The Cassini division is caused by A.  B.  C.  D.  E.  a = 117580 km •  Inner radius of Cassini division: collisions between ring parGcles. bending waves in the ring plane. spiral density waves in the ring plane. resonance with Saturn’s moon Mimas. shepherd moons. P2 •  Orbital period: Moon Orbital period (d) Mimas 0.942 Enceladus 1.37 Tethys 1.89 Dione 2.74 Rhea 15.95 Iapetus Gravity from Mimas tends to “kick” parGcles out of this region. 4.52 Titan Apr. 15 ⇒P a3 M = 0.476 d ∝ 79.33 Apr. 15 Natural color Wikipedia Apr. 15 Apr. 15 hXp://apod.nasa.gov/apod/ap040723.html False color to illustrate variaGons Apr. 15 hXp://solarsystem.nasa.gov/mulGmedia/display.cfm?IM_ID=2048 Apr. 15 hXp://apod.nasa.gov/apod/ap110308.html 6 4/15/11 Daphnis and Keeler Gap Shepherd moons Pandora Apr. 15 Prometheus hXp://photojournal.jpl.nasa.gov/animaGon/PIA07712 Apr. 15 hXp://photojournal.jpl.nasa.gov/catalog/PIA11653 Enceladus and E ring Earth! hXp://apod.nasa.gov/apod/ap040723.html Apr. 15 Apr. 15 Jupiter’s ring Apr. 15 hXp://photojournal.jpl.nasa.gov/catalog/PIA01529 Apr. 15 7 4/15/11 Near infrared Uranus’s rings: occultaGon Apr. 15 Apr. 15 hXp://pds ­rings.seG.org/uranus/earthbased/PIA01278.html Neptune’s rings hXp://photojournal.jpl.nasa.gov/catalog/PIA02202 Apr. 15 hXp://pds ­rings.seG.org/uranus/voyager/PIA00142.html Apr. 15 8 ...
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