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A1 11 Moons


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Miller's Astronomy 1 lecture notes on Gas Giant Moons

Miller's Astronomy 1 lecture notes on Gas Giant Moons

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  • 1. Moons of the Gas Giants LACC §11.1,2,3 • Understand the conditions and processes that shaped the outer planets’ moons • Know the following moons in some detail: Io, Europa, Ganymede, Callisto, Titan, Triton • Understand a moon’s history by its surface An attempt to answer the “big questions”: what is out there? Are we alone? Wednesday, March 24, 2010
  • 2. sse_flipflop2.shtml Wednesday, March 24, 2010
  • 3. Jupiter: Galilean Moons SunFamily.htm#Moons Wednesday, March 24, 2010
  • 4. Galilean Moons: Gravitational Resonances (CALLISTO 1:9.43) Wednesday, March 24, 2010
  • 5. Galilean Moons: Interiors Data recently obtained from the Galileo spacecraft has revealed the surprising result that Callisto might have a salty ocean lying beneath its icy crust.... Beneath the suggests that the interior is composed of compressed rock and ice with the percentage of rock increasing as depth increases. The interiors of Io, Europa, Callisto, and Ganymede, clockwise from http:// upper left. All except Callisto have metallic (iron/nickel) cores, shown in gray, surrounded by rock in brown. The rock shells in Europa and /cap/jup/calint.htm Ganymede are surrounded by liquid water (blue) and ice (white). Wednesday, March 24, 2010
  • 6. Jupiter’s Io: Active Volcanoes The reddish materials may be associated with very recent fragmental volcanic deposits (pyroclastics) erupted in the form of volcanic plumes. Dark materials appear in flows and on caldera floors. Bright white materials correspond to sulfur dioxide frost, and bright yellow materials appear to be in new flows such as those surrounding Ra Patera. The red material may be unstable since the color appears to fade over time. This fading appears to occur most rapidly in the equatorial region and more slowly over the polar regions; surface temperature may control the rate of transformation. Comparisons of these images to those taken by the Voyager spacecraft 17 years ago have revealed that many changes have occurred on Io. Since that time, about a dozen areas at least as large as the state of Connecticut have been resurfaced. Wednesday, March 24, 2010
  • 7. Io: Volcanic Eruption Explanation: Io's surface is active. Geyser-like eruptions from volcanoes on this Jovian moon were seen by both Voyager spacecraft in 1979 and were also spotted this year in late June by Galileo's camera from a distance of about 600,000 miles. The blue plume seen at the moon's edge (magnified in the inset) arises from Ra Patera, a large shield volcano, and extends about 60 miles above the surface. The blue color is attributed to condensing and freezing sulfur dioxide gas. Galileo images have also revealed that the plume glows in the dark - perhaps due to fluorescence of excited sulfur and oxygen ions. Io's surface is cold, its temperature averages about -230°F, so why is it so active? The most likely cause is the gravitational tug of war over Io between Jupiter and the other Galilean moons which perturbs Io's orbit. The orbital changes would result in tidal force variations heating Io's interior and and generating the sulfurous volcanic activity. Wednesday, March 24, 2010
  • 8. Io: Volcanic Eruption ...taken February 22 [2000] came from Galileo's closest pass ever of Io. From Galileo's vantage point, a scant 124 miles (200 kilometers) above the surface, the probe could discern features as small as a house. Galileo also took new pictures of a strange volcanic region called Tvashtar Catena, which was seen to be erupting last fall. The images show that Tvashtar's mile- high volcanic plume -- gasses and lava -- has shifted directions and its temperature has reached almost 1,900° F (1,038° C). That's hotter than any eruption on Earth. Io is the most volcanically active body in the solar system. Until Galileo, scientists were aware of only about 20 volcanic regions, fleetingly photographed during the two Voyager-probe flybys two decades ago. With the new data, scientists now have confirmed the existence of 80 active volcanoes and suspect Io is riddled with at least 200 more. Wednesday, March 24, 2010
  • 9. Jupiter’s Europa: Oceans? Speculation is rampant that oceans exist under these tortured ice-plains that could support life. Europa, the smallest of Jupiter's Galilean moons, was photographed last month in natural color by the robot spacecraft Galileo, now in orbit around Jupiter. The brown patches are what one might think: dirt -- tainting an otherwise white ice-crust. Europa, nearly the same size as Earth's Moon, similarly keeps one face toward its home planet. The hemisphere of Europa shown above is the one that always trails. Why is Europa's surface the smoothest in the Solar System? Where are Europa's craters? Wednesday, March 24, 2010
  • 10. Jupiter’s Ganymede: Largest Explanation: If Ganymede orbited the Sun, it would be considered a planet. The reason is that Jupiter's moon Ganymede is not only the largest moon in the Solar System, it is larger than planet Mercury. The robot spacecraft Galileo currently orbiting Jupiter has been able to zoom by Ganymede several times and snap many close-up pictures. Ganymede, shown above in its natural colors, sports a large oval dark region known as Galileo Regio. In general, the dark regions on Ganymede are heavily cratered, implying they are very old, while the light regions are younger and dominated by unusual grooves. The origin of the grooves is still under investigation. Wednesday, March 24, 2010
  • 11. Jupiter’s Callisto: Oldest Callisto is the most heavily cratered object in the solar system. It is thought to be a long dead world, with a nearly complete absence of any geologic activity on its surface. In fact, Callisto is the only body greater than 1000 km in diameter in the solar system that has shown no signs of undergoing any extensive resurfacing since impacts have molded its surface. With a surface age of about 4 billion years, Callisto has the oldest landscape in the solar system. Wednesday, March 24, 2010
  • 12. Other Large Moons Wednesday, March 24, 2010
  • 13. Titan’s: Internal Structure ...graphic illustration of Titan's internal structure.... Methane is locked in the methane-rich water ice that forms a crust above an ocean of liquid water mixed with ammonia. Wednesday, March 24, 2010
  • 14. Saturn’s Titan: Atmosphere Although Titan is classified as a moon, it is larger than the planet Mercury. It has a planet-like atmosphere which is more dense than those of Mercury, Earth, and Mars. The atmospheric pressure near the surface is about 1.6 bars, 60 percent greater than Earth's. Titan's air is predominantly made up of [92% N2, 6% Ar, 2% CH4] and trace hydrocarbon elements which give Titan its orange hue. These hydrocarbon rich elements are the building blocks for amino acids necessary for the formation of life. Scientists believe that Titan's environment may be similar to that of the Earth's before life began putting oxygen into the atmosphere. Wednesday, March 24, 2010
  • 15. Saturn’s Titan: Atmosphere -170°F -170°F -245°F -330°F -290°F Wednesday, March 24, 2010
  • 16. Saturn’s Titan: Huygens Pic Methane rain, evaporating lakes, flowing rivers, and water ice- volcanoes all likely exist on Saturn's moon Titan, according to preliminary analyses of recent images taken by the successful Huygens lander. A snaking and branching riverbed is identified with the dark channel near the top of the above image, while a dark lakebed is identified across the image bottom. Both the riverbed and lakebed were thought to be dry at the time the image was taken but contained a flowing liquid - likely methane - in the recent past. Titan's surface ... is so cold that methane flows and water freezes into rock-hard ice. Wednesday, March 24, 2010
  • 17. Saturn’s Titan: Surface! This color view from Titan gazes across a suddenly familiar but distant landscape on Saturn's largest moon. The scene was recorded by ESA's Huygens probe after a 2 1/2 hour descent through a thick atmosphere of nitrogen laced with methane. Bathed in an eerie orange light at ground level, rocks strewn about the scene could well be composed of water and hydrocarbons frozen solid at an inhospitable temperature of [-290°F]. The light-toned rock below and left of center is only about 15 centimeters across and lies 85 centimeters away. Touching down ... the saucer-shaped probe ... into a surface with the consistency of wet sand or clay. Huygen's ... transmitted data for more than 90 minutes after landing. Wednesday, March 24, 2010
  • 18. Huygens Probe lands on Titan docid=-287238877012213463&ei=c0BGSobjPIHaqAPG3PDABg&q=Titan&hl=en&client= safari Wednesday, March 24, 2010
  • 19. Saturn’s Enceladus Remarkably high temperatures, at least 180 Kelvin (minus 135°F) were registered along the brightest fracture. For comparison, surface temperatures elsewhere in the south polar region of Enceladus are below 72 Kelvin (minus 330°F). ...a mass spectrum that shows the chemical constituents sampled in Enceladus' plume by Cassini's Ion and Neutral Mass Spectrometer during its fly- through of the plume on Mar. 12, 2008. Wednesday, March 24, 2010
  • 20. Enceladus: H2O Ice Geysers Cassini scientists infer that the temperature of the ice in the south polar region must be close to its melting point (shown in red). A layer of liquid water (dark blue) might exist between the ice and the silicate core (brown), allowing the ice to deform independent of the rock, providing even more mechanical energy and more flexing of the icy shell for extreme tidal heating. Tidal heating could also cause friction in faults near the surface, leading to pockets of partially melted ice. Wednesday, March 24, 2010
  • 21. Neptune’s Triton: Volcanoes [Triton] shares many similarities with Pluto, the best known world of the Kuiper Belt. Triton's thin atmosphere is composed mainly of nitrogen with small amounts of methane. This atmosphere most likely originates from Triton's volcanic activity which is driven by seasonal heating by the Sun. Triton is one of the coolest objects in our solar system.... (38 K, about -391° Fahrenheit); it is so cold that most of Triton's nitrogen is condensed as frost.... The dark streaks ... are believed to be an icy and perhaps carbonaceous dust deposited from huge geyser-like plumes... is the only large moon in our solar system that orbits in the opposite direction of its planet's rotation - a retrograde orbit. Object=Triton Wednesday, March 24, 2010
  • 22. Moons on Parade Wednesday, March 24, 2010
  • 23. Large Moons: Composition and Evolution The three moons to the left illustrate three possible stages in the history of an icy satellite. The satellite can be cold and so have no internal activity. In that case, the surface is unchanged, old, and heavily cratered. This case may be illustrated by Callisto, the top moon in the picture. The craters are left over from the formation of the moon itself, 4 billion years ago. Nothing has happened to this moon to ever change its surface appearance. If there was some internal heating, then the surface may show some changes and will not be as heavily cratered. This case may be illustrated by Ganymede, the moon in the middle of the picture. Ganymede has many craters but also trenches and grooves which indicate that the surface flowed at some point in time. If the heating took place over a long time, then the surface may show many changes, and in fact may still be evolving. This case may be illustrated by Europa, the third moon in the picture. The surface of Europa is lightly cratered with evidence of cracks and fractures. Many moons in the solar system exhibit features of evolution somewhere between those of Ganymede and those of Europa. Examples of these moons include Dione, Rhea, Enceladus, Tethys, Ariel, Umbriel, Miranda, Titania, Oberon, and Triton. Wednesday, March 24, 2010
  • 24. Small Moons Composition and Evolution ...not much is known about the [small moon’s] surface features or composition. With no knowledge of the composition, and no clues from the surface, little can be determined about the course of their evolution. Nevertheless, from the location of some of the moons, as well as their shape, it can be determined that some moons are fragments of a larger moon, or are captured asteroids. Examples of moons such as these are Epimetheus, Janus, and Hyperion. [Based on their densities,] It is thought that most small moons are icy. Wednesday, March 24, 2010
  • 25. Moons of the Gas Giants LACC §11.1,2,3 • Understand the conditions and processes that shaped the outer planets’ moons: formed outside the frost line w/ ices (CH4, NH3, H2O) • Know the following moons in some detail: Io (volcanoes), Europa (ocean under ice), Ganymede (largest), Callisto (oldest), Titan (atmosphere), Triton (retrograde, geysers) • Understand a moon’s history by its surface: Light = icy and young, Dark = dusty and old; fresh cracks = geological activity, more craters = older An attempt to answer the “big questions”: what is out there? Are we alone? Wednesday, March 24, 2010
  • 26. HW Ch 11: Franknoi, Morrison, and Wolff, Voyages Through the Universe, 3rd ed. • Ch 11, pp. 263-264: 1. • Ch 12: Image Analysis Quiz accessible from: fid=M20b&product_isbn_issn=9780495017899&discipline_number=19 Must Know: 1, 3 Important: 4, 5 Due at the beginning of next class period. Be working your Solar System project. Wednesday, March 24, 2010