MASON ASTR 111 - Jupiter and Saturn’s Satellites of Fire and Ice

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Jupiter and Saturn’s Satellites of Fire and IceGuiding QuestionsJupiter’s Galilean satellites are easily seen with Earth-based telescopesSlide 4Data from spacecraft reveal the unique properties of the Galilean satellitesThe Galilean satellites formed like a solar system in miniatureThe Galilean satellites probably formed in a similar fashion to our solar system but on a smaller scaleIo is covered with colorful sulfur compounds ejected from active volcanoesSlide 9Slide 10Tidal HeatingSlide 12Slide 13Jupiter’s magnetic field makes electric currents flow through IoSlide 15Slide 16Europa is covered with a smooth layer of ice that may cover a worldwide oceanOther indications are a worldwide network of long cracks and ice rafts that indicate a subsurface layer of liquid water or soft iceSlide 19Slide 20Slide 21Liquid water may also lie beneath the cratered surfaces of Ganymede and CallistoGanymedeSlide 24Slide 25Titan has a thick, opaque atmosphere rich in methane, nitrogen, and hydrocarbonsSlide 27Jupiter has dozens of small satellites that have different originsThe icy surfaces of Saturn’s six moderate-sized moons provide clues to their historiesSlide 30Key WordsJupiter and Saturn’s Satellitesof Fire and IceChapter FifteenGuiding Questions1. What is special about the orbits of Jupiter’s Galilean satellites?2. Are all the Galilean satellites made of rocky material, like the Earth’s moon?3. What could account for differences between the inner and outer Galilean satellites?4. Why does Io have active volcanoes? How does Io’s volcanic activity differ from that on Earth?5. How does Io act like an electric generator?6. What is the evidence that Europa has an ocean beneath its surface?7. What is unusual about the magnetic fields of Ganymede and Callisto?8. How is it possible for Saturn’s moon Titan to have an atmosphere?9. Why do some of Jupiter’s moons orbit in the “wrong” direction?10.What kinds of geologic activity are seen on Saturn’s medium-sized satellites?Jupiter’s Galilean satellites are easily seenwith Earth-based telescopes•The four Galilean satellites orbit Jupiter in the plane of its equator•All are in synchronous rotation•The orbital periods of the three innermost Galilean satellites, Io, Europa, and Ganymede, are in the ratio 1:2:4Data from spacecraft reveal the unique propertiesof the Galilean satellites•The two innermost Galilean satellites, Io and Europa, have roughly the same size and density as our Moon•They are composed principally of rocky material•The two outermost Galilean satellites, Ganymede and Callisto, are roughly the size of Mercury•Lower in density than either the Moon or Mercury, they are made of roughly equal parts ice and rockThe Galilean satellites formed like a solar systemin miniatureThe Galilean satellites probably formed in a similar fashion to our solar system but on a smaller scaleIo is covered with colorful sulfur compounds ejected from active volcanoesTidal Heating•The energy to heat Io’s interior and produce the satellite’s volcanic activity comes from tidal forces that flex the satellite•This tidal flexing is aided by the 1:2:4 ratio of orbital periods among the inner three Galilean satellitesJupiter’s magnetic field makes electric currentsflow through Io•The Io torus is a ring of electrically charged particles circling Jupiter at the distance of Io’s orbit•Interactions between this ring and Jupiter’s magnetic field produce strong radio emissions•Io may also have a magnetic field of its ownEuropa is covered with a smooth layer of icethat may cover a worldwide ocean•While composed primarily of rock, Europa is covered with a smooth layer of water ice•The surface has hardly any craters, indicating a geologically active history •As for Io, tidal heating is responsible for Europa’s internal heat•Minerals dissolved in this ocean may explain Europa’s induced magnetic fieldOther indications are a worldwide network of long cracks and ice rafts that indicate a subsurface layer of liquid water or soft iceLiquid water may also lie beneath the crateredsurfaces of Ganymede and CallistoGanymede•Ganymede is highly differentiated, and probably has a metallic core•It has a surprisingly strong magnetic field and a magnetosphere of its own•While there is at present little tidal heating of Ganymede, it may have been heated in this fashion in the past•An induced magnetic field suggests that it, too, has a layer of liquid water beneath the surface•Two types of terrain are found on the icy surface of Ganymede:–areas of dark, ancient, heavily cratered surface–regions of heavily grooved, lighter-colored, younger terrain•Callisto has a heavily cratered crust of water ice•The surface shows little sign of geologic activity, because there was never any significant tidal heating of Callisto•However, some unknown processes have erased the smallest craters and blanketed the surface with a dark, dusty substance•Magnetic field data seem to suggest that Callisto has a shallow subsurface oceanTitan has a thick, opaque atmosphere richin methane, nitrogen, and hydrocarbons•The largest Saturnian satellite, Titan, is a terrestrial world with a dense nitrogen atmosphere•A variety of hydrocarbons are produced there by the interaction of sunlight with methane•These compounds form an aerosol layer in Titan’s atmosphere and possibly cover some of its surface with lakes of ethaneJupiter has dozens of small satellites that havedifferent origins•As of early 2004, Jupiter has a total of 63 known satellites•In addition to the Galilean satellites, Jupiter has four small inner satellites that lie inside Io’s orbit•Like the Galilean satellites, these orbit in the plane of Jupiter’s equator•The remaining satellites are small and move in much larger orbits that are noticeably inclined to the plane of Jupiter’s equator•Many of these orbit in the direction opposite to Jupiter’s rotationThe icy surfaces of Saturn’s six moderate-sizedmoons provide clues to their histories•As of early 2004, Saturn has a total of 31 known satellites•In addition to Titan, six moderate-sized moons circle Saturn in regular orbits: Mimas, Enceladus, Tethys, Dione, Rhea, and Iapetus•They are probably composed largely of ice, but their surface features and histories vary significantly•The other, smaller moons include shepherd satellites that control the shapes of Saturn’s rings and captured


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MASON ASTR 111 - Jupiter and Saturn’s Satellites of Fire and Ice

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