ASTR Exam 2 Study

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ASTR Exam 2 Study
2015-03-30 15:45:44

ASTR Exam 2 Study
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  1. Planetesimals
    Small dust particles that collect and form larger clumps
  2. Protoplanets
    • When planetesimals collide with each other and form larger bodies called Protoplanets. Protoplanets are at least partially molten
    • -Dense material falls to core and less dense material goes to surface
  3. Terrestrial Planets
    • -External crust (low density (hard rock)
    • -Mantle(medium density, plastic flow)
    • -Core (High density, hard metal)
    • -Rigid Lithosphere: Crust and small upper part of mantle
  4. Terrestrial Planets: Sources of Heat
    • -Accrecion: When kinetic energy from incoming materials turns into thermal energy and mass is added to the object being struck by the foreign body
    • -Differentiation: When sinking dense material and rising less dense material move, it creates heat
    • -Radioactive decay of elements within a planet cause heat
  5. Terrestrial Planets: Cooling Processes
    • -Convection: Hot material rises and cools
    • -Thermal Conduction: The transfer of heat energy from one end of the lithosphere to the other
    • -Radiated Heat: heat coming off the planet and radiating into space
    • -Volcanic Eruptions: Nuff' said
  6. S and P Waves
    • -P Waves: Primary waves. Like pushing a person
    • -S Waves: Secondary waves, like creating waves with a jump rope. These do not travel through the Earth's core
  7. Surface Waves
    Like Water waves, roll on the surface
  8. Tidal heating
    Tidal forces created by the gravitational pull from a nearby object can heat a planet. Example: Moon
  9. Ways to learn about inner earth
    • Most accurate: Earthquakes.
    • Other methods include the magnetic field and observing rotation of the earth
  10. Terrestrial Planets
    • Magnetic Fields
    • -Mercury: Has a global magnetic field
    • -Venus: Spins too slow for a magnetic field
    • -Earth: Global magnetic field
    • -Mars: No global magnetic field but had one in the past
    • Volcanos
    • -Mercury: No volcanos and probably no internal activity
    • -Venus: Possibly active volcanos but most extinct, active interior
    • -Earth: Active volcanos, active interior
    • -Mars: Extinct volcanos extinct interior
  11. Magnetic Fields
    A planet must have a liquid core/mantle and be spinning quickly enough to have a magnetic field
  12. Isostay
  13. Terrestrial Shaping Processes
    • -Fluvial: Liquid flow, such as river canals
    • -Aeolian: Formed by air such as dunes
    • -Glacial: Formed by solid glaciers
    • -Impact Craters
    • Terrestrial Shaping Processes by Type
    • -Internal (volcanos/plate tectonics)
    • -Erosion
    • -Impact craters (Dominant geological process on most bodies)
  14. Impact Craters
    • -Galileo first to see them but did not speculate about their source
    • -Robert Hooke made first detailed drawings of craters and considered impacts as the source but ultimately went with the theory that volcanoes caused them
    • -Ernst Chladni proposed that meteorites were real and it was later accepted
  15. Evidence of Meteorites
    • -Shatter cone features in rocks
    • -High pressure polymorphs and shock features in quartz followed quickly
  16. Crater Size Progression
    • -Simple, bowl-shaped craters. Less than 15 km diameter on the moon
    • -Complex craters with central peaks and terraced rims. From 30 to 200 km diameter on the moon
    • -Peak-ring craters. About 300 km diameter on the moon 
    • -Multi-ring basins. Largest sizes, more than 500 km diameter on the moon
  17. Asteroid Impact Probability
    • -30-meter sized asteroids come close to Earth about every 2 years and strike Earth every 6,000 years
    • -10km sized asteroids hit Earth every 100 million years
  18. Planetary Atmospheres
    • -A layer of gas that surrounds a planet/moon
    • -Only a “true” atmosphere if gas molecules collide with each other more often than the surface.
    • -Usually very thin compared to the radius
    • -To have an atmosphere, a planet must be big enough (have enough of a gravitational pull) and be cool enough for gasses to not evaporate away into space
  19. Detecting a Planet's Atmosphere
    • -Spectroscopy to identify gases
    • -Stellar Occultations: Observing how a star's light dims as it passes behind a planet can give clue to an atmosphere
  20. What Does an Atmosphere Do?
    • -Warms Planet with greenhouse gas effect
    • -Reduces differences between day and night temperatures
    • -Absorbs high energy radiation
    • -Scatters light, which brightens and colors daytime sky
    • -Allows for wind, weather, and erosion
    • -Creates pressure in an atmosphere, allowing for water
  21. Atmosphere Properties
    • -Hydrostatic Equilibrium: Atmosphere pressure rises the closer one is to the surface of the earth
    • -Scale Height: Atmospheric thickness. It goes down as one raises in elevation
    • -The atmospheric pressure decreases by a factor of 2.7 (e1) for every scale height above the surface.
  22. Greenhouse Gases
    • -Water vapor most prevalent/prominent
    • -Carbon Dioxide
    • -Methane
    • -Nitrous Oxide
    • -Greenhouse gas maintains Earth's temperature at a livable state, but human tampering is increasing this effect
  23. Earth:
    • -Solar system's most dense planet
    • -Largest terrestrial planet
    • Only planet to currently have:
    • -Plate tectonics
    • -Liquid water on surface
    • -Life
    • -Oxygen-rich atmosphere
  24. Continental Drift
    • -Continents drift 3cm a year
    • -Continents all together 250 MYA
    • -Plate tectonics responsible for mountains, volcanos, and shapes of oceans and continents
  25. Types of Rocks
    • -Igneous: Cooled from molten
    • -Sedimentary: Chipped away by wind, water, or ice
    • -Metamorphic: Shaped by intense heat and pressure
  26. Evolution of Earth's Atmosphere
    • -1st Atmosphere had H2 and some HE. Was lost b/c Earth didn't have enough gravity or magnetic field, so solar wind stripped it.
    • -2nd Atmosphere: Caused by volcanic outguessing. No O2 yet. Oceans form from condensing volcanic steam
    • -3rd Atmosphere: Oxygen
    • -Small amount created by breakup of H2O by UV
    • -Once life takes hold, O2 sky rockets
    • Carbon dioxide
    • -Mostly rained out and stored in limestone
  27. Atmospheric Circulation
    • -If Earth didn't spin, cold dry air would flow everywhere
    • -Because it spins, we see the Hadley Cell effect
  28. Coriolis Effect
    • -Atmospheric patterns are influenced by this
    • -The spin of the earth has an effect on moving objects and alters their path
    • -Because of the Earth’s rapid rotation, the
    • circulation in its atmosphere is complex, with three circulation cells in each hemisphere
  29. Earth's Magnetosphere
    • -Shields the planet from solar wind
    • -Carves a cavern in the solar wind
    • -The Van Allen radiation belts are part of Earth’s
    • magnetosphere – huge intensities of charged
    • particles are trapped there
  30. Exploring the Moon
    • -1960's: Many unmanned orbiters from USA and USSR
    • -69'-73': 6 Manned US Apollo missions
    • -70'-76': 3 unmanned USSR Luna missions
    • -Orbiters still revolve moon
  31. Lunar Features
    • -Impact Craters
    • Formed by impacts from asteroids and comets
    • -Maria
    • Younger and Darker, Fewer craters
    • -Highlands
    • Older and Brighter, Lots of craters
    • -Regolith
    • Fine powdery dust-like material. Footprints left behind by 12 astronauts
    • -No evidence for plate tectonics or
    • volcanoes
    • -All rock is igneous
    • -Density suggests a small core
  32. Water on the Moon
    • -All in ice form, it forms in deep impact craters at the poles, which never see light.
    • -Accumulated from comets
  33. Giant Impact Theory
    The theory that the moon was formed when a giant Mars sized body crashed into Earth. This released a lot of debris, added to the Earth's mass, and the leftover debris came together to form the moon
  34. Mercury
    • -Smallest planet (1/3 size of Earth)
    • -Closest planet to Sun
    • -Orbital period: 88 days
    • -3:2 spin-orbit resonance (spins 3 times for every 2 orbits around the Sun)
    • -Rotational period: 58.6 days
    • -Largest eccentricity(0.206)
    • -Daytime: +662 °F, nighttime: -274 °F
    • -Has magnetic field (but weaker than Earth’s)!
  35. Mercury Exploration
    • -Mariner 10: 74'-75'
    • -MESSENGER: 2004-Present
    • -Less craters than moon, had active tectonic activity at one point
    • -Mercury has a every large core, volcanic vents, semi-active surface.
    • -Mercury was likely formed somewhere else before getting to its current orbit
    • -Water-ice on Mercury inside polar impact craters
  36. Venus
    • -85% the size of Earth (our “sister” planet)
    • -Rotational period: 243 days (slow!)
    • -Retrograde b/c tidal forces?
    • -Very thick atmosphere of CO2
    • -Runaway greenhouse effect
    • -Total CO2 similar to Earth, but not stored in
    • limestone
    • -Extreme pressures
    • -Surface temperature: 750 K (890 °F)
  37. Venus' Atmosphere
    • -Clouds rotate in the same direction as the planet but much more quickly, about once every 4 days
    • -The temperature on Venus us almost identical at the equator as the poles
  38. Runaway Greenhouse Effect
    • Venus used to have water, but then un grew hotter, evaporating it into the atmosphere. This added to the greenhouse effect, and less water meant less dissolved CO2 and SO2, so this also stayed in atmosphere, increasing greenhouse gas effect.
    • -On Venus, greenhouse gases are not recycled and stay in the atmosphere, on Earth they are recycled.
  39. Venus' Surface
    • -Venus has two major continents and no plate tectonics. This can be attributed to the surface being too hot to be a solid plate and lack of water
    • -it is very flat with gently rolling hills
    • -Some volcanos and highlands
  40. Mars
    • -Orbital period: 686.98 days (1.9 Earth years)
    • -Rotational period: 24.62 hours
    • -About 10% the size of Earth
    • -Tilt: 25.19° (similar to Earth’s 23.5°)
    • -Surface temperature
    •  max: 70 °F
    •  min: -220 °F
    •  mean: -63 °F
  41. Mars at Opposition (from Earth)
    • -Occurs every 780 days
    • -Best time to view Mars and to launch Mars missions
  42. Early Mars Observations/Exploration
    • -Schiaparelli described surface features as canals
    • -Many thought these were canals dug by alien races
    • -Mariner 4 69': Mars as dead, thin atmosphere
    • -Mariner 9 71': Found volcanos and riverbeds
    • -Viking 1,2 75-80': Mapped surface, found no life
    • -Many more recent missions
  43. Mars' Surface
    • -Southern highlands older, more heavily cratered, and higher in elevation than north.
    • -Not well understood: One giant basin? Multiple basins? Plate tectonics?
    • -Red surface because it is oxidized
    • -Used to have a magnetic field
    • -Mars has tenuous CO2 atmosphere (0.75% of Earth’s pressure) with only weak greenhouse effect (5 °C)
    • -Small amounts of methane suggest Mars might still be outgassing, because methane is quickly decomposed by sunlight (about 100 years)
  44. Valles Marineris
    • -A rift valley separating north and south regions
    • -3,000 miles long
    • -Up to 6 miles deep in some places
    • -Formed by upwelling magma plumes in mantle
  45. Volcanos and Craters on Mars
    • -Olympus Mons: 16 miles high and as large as France
    • -Basaltic rocks
    • -Most lava flows heavily cratered
    • -Crater patterns similar to the Moon