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Studying for Exam II

Studying for Exam II. Same type of exam as first one Chapters covered: parts of Ch.1, Ch. 4-8. Very little from Chapters 7&8. Mars. Northern Hemisphere basically huge volcanic plains Similar to lunar maria Valles Marineris – Martian “Grand Canyon”

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Studying for Exam II

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  1. Studying for Exam II • Same type of exam as first one • Chapters covered: parts of Ch.1, Ch. 4-8. • Very little from Chapters 7&8

  2. Mars • Northern Hemisphere basically huge volcanic plains • Similar to lunar maria • Valles Marineris – Martian “Grand Canyon” • 4000 km long, up to 120 km across and 7 km deep • So large that it can be seen from Earth

  3. Martian Volcanoes • Olympus Mons • Largest known volcano in the solar system • 700 km across at base • Peak ~25 km high (almost 3 times as tall as Mt. Everest!)

  4. Martian Surface Iron gives the characteristic Mars color: rusty red! View of Viking 1 1 m rock Sojourner

  5. Outflow Channels Runoff channels Water on Mars? Mars Louisiana

  6. Life on Mars? • Giovanni Schiaparelli (1877) – observed “canali” (channels) on Martian surface • Interpreted by Percival Lowell (and others) as irrigation canals – a sign of intelligent life • Lowell built a large observatory near Flagstaff, AZ (Incidentally, this enabled C. Tombaugh to find Pluto in 1930) • Speculation became more and more fanciful • A desert world with a planet-wide irrigation system to carry water from the polar ice caps? • Lots of sci-fi, including H.G. Wells, Bradbury, … • All an illusion! There are no canals…

  7. Viking Lander Experiments (1976) • Search for bacteria-like forms of life • Results inconclusive at best

  8. Atmospheric Histories • Primary atmosphere: hydrogen, helium, methane, ammonia • Too light to “stick” to a planet unless it’s very big  Jovian Planets • Secondary atmosphere: water, CO2, SO2, … • Outgassed from planet interiors, a result of volcanic activity

  9. Atmospheric Histories - Venus • Venus is closer to Sun than Earth hotter surface • Not a lot of liquid water on surface initially • CO2 could not be absorbed by water, rocks because of higher temperatures •  run-away Greenhouse effect: it’s hot, the greenhouse gases can’t be be stored away, it gets hotter …

  10. Earth’s Atmospheric History • Volcanic activity spews out water steam • Temperature range allowed water to liquify • CO2 dissolves in oceans, damping greenhouse effect • More water condenses, more CO2 is absorbed • If too cold, ice forms  less cloud cover  more energy • No oxygen at this point, since it would have been used up producing “rust” • Tertiary atmosphere: early life contributes oxygen • 1% 800 Myrs ago, 10% 400 Myrs ago

  11. Mars – Freezing over • Mars once had a denser atmosphere with liquid water on the surface • As on Earth, CO2 dissolves in liquid water • But: Mars is further away from the Sun  temperature drops below freezing point  inverse greenhouse effect • permafrost forms with CO2 locked away • Mars probably lost its atmosphere because its magnetic field collapsed, because Mars’ molten core cooled down

  12. Greenhouse Effect • Earth absorbs energy from the Sun and heats up • Earth re-radiates the absorbed energy in the form of infrared radiation • The infrared radiation is absorbed by carbon dioxide and water vapor in the atmosphere

  13. Global Warming • Excessively “politicized” topic • Very complex problem scientifically • Slow changes over long periods of time • Sources of heating, sources of cooling themselves are temperature dependent

  14. Man-made CO2 in the Atmosphere goes up

  15. Correlation: Temperatures rise when Carbon Dioxide levels rise • This is true since prehistoric times

  16. Saturn Jupiter Neptune Uranus The Jovian Planets

  17. Terrestrial close to the Sun closely spaced orbits small radii small masses predominantly rocky high density solid surface few moons no rings Jovian far from the Sun widely spaced orbits large radii large masses predominantly gaseous low density no solid surface many moons many rings Comparison

  18. History • Jupiter and Saturn known to the ancients • Galileo observed 4 moons of Jupiter and Saturn’s rings • Uranus • Discovered telescopically by William Herschel in 1781 (actually barely visible to naked eye) • Neptune • Predicted from observed perturbations of Uranus’ orbit: Adams (1845) and Leverrier (1846) • Observed by Galle (1846) • Discovery great triumph for computational astronomy/physics

  19. Grand Tour of Voyager 1 & 2 • Used gravitational slingshot to get from planet to planet

  20. Rotation • About 10 hours for Jupiter and Saturn; about 17 hours for Uranus and Neptune • Differential rotation: rotation speed varies from point to point on the “surfaces” • Gaseous bodies with no solid surfaces! • On Jupiter, the equatorial regions rotate 6 minutes slower than polar regions • On Saturn the equatorial region is about 26 minutes slower • Tilt of rotation axes: • Jupiter: almost none – no seasons! • Saturn, Neptune: about like Earth • Uranus: weird

  21. Uranus’ Strange Seasons

  22. Jupiter’s Atmosphere • Cloud bands parallel to equator • Great Red Spot • First observed in 1664 by Robert Hooke

  23. Jupiter’s Atmosphere • 86% Hydrogen, 14% Helium; some methane, water, ammonia • Several layers of clouds: ammonia, ammonium hydrosulfide, water • Colors mostly due to compounds of sulfur and phosphorus

  24. Jupiters’ Bands: Zones and Belts • Belts: cool, dark, sinking • Zones: warm, bright, rising • Jovian weather mostly circles the planet due to high rotation rate • Bands exhibit east–west flow Great Red Spot lies between regions of opposite wind flow

  25. Great Red Spot • About twice the diameter of the Earth • A hurricane that is hundreds of years old!

  26. Saturn’s Atmosphere • 92% Hydrogen 7% Helium; some methane, water, ammonia • Belt structure similar to Jupiter’s, but fainter • Storms are rarer • White spot seen, 1990 (Voyager)

  27. Uranus’ and Neptune’s Atmospheres Neptune’s Dark Spot • Ammonia frozen out; more methane • Methane absorbs red light, leads to bluish color • Almost no band structure on Uranus

  28. Magnetospheres • Very strong – Jupiter's extends past the orbit of Saturn! • Indicate the presence of conducting cores

  29. Rings Saturn Uranus Neptune Jupiter

  30. Saturn • Rings composed of small, icy fragments, orbiting in concentric circles • Orbits obey Kepler’s laws (of course!) • Inner rings move faster than outer ones

  31. Visibility of Saturn’s Rings 2009

  32. How Do They Form? • Miscellaneous debris • Moons or other small bodies torn apart by tidal forces • Roche limit – distance inside of which an object held together by gravity will be pulled apart

  33. Ring Formation • Rings may be short lived (on the time scale of solar system) • Means that they must form fairly frequently • A moon may pass too close to a planet (within the Roche limit) and be destroyed by tidal forces • This will probably happen to Triton (a moon of Neptune) within 100 million years!

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