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Planetary Geology. Planets Rock!. Goals. What determines why planets look the way they do. What are the 4 main process that affect a planet’s surface. How does planetary interior affect planetary atmospheres?. Why are planets different?. Different planets look different. - PowerPoint PPT Presentation
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Planetary Geology
Planets Rock!
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Goals
• What determines why planets look the way they do.
• What are the 4 main process that affect a planet’s surface.
• How does planetary interior affect planetary atmospheres?
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Why are planets different?
• Different planets look different.
• What determines this?• To understand the outside,
you must understand the insides.
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Concept Test
• The cores of the terrestrial worlds are made mostly of metal because ______. a. the terrestrial worlds as a whole are made
mostly of metal.b. the core contained lots of radioactive
elements that decayed into metals.c. over billions of years, convection gradually
brought dense metals downward to the core.
d. metals sunk to the centers a long time ago when the interiors were molten throughout.
e. None of the above.
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Internal Heat• Why is heat the
driver of geological processes?
• What is heat?• Think of temperature
on an atomic scale.• Where do you expect
change?
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Accretion• Planets form out of
primordial cloud of gas and dust.
• Atoms to dust to grains to rocks to asteroids to planetesimals to planets.
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Differentiation
• Accreted material is all mixed.• Friction generates heat.
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Lithosphere – Radius at which rock is too cool to flow by convection.
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Concept Test
• Given this description of planetary interiors, we expect:a. Smaller planets should cool off faster than
bigger ones.b. Larger planets should have thinner
lithospheres than smaller planets.c. There should be fewer signs of geological
activity on the surfaces of smaller planets compared to larger ones.
d. All of the above.e. None of the above.
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How do we know?• How do we know what is really going
on inside planets?1. Look for signs of surface activity. Has
anything changed recently?2. Look for magnetic fields around planet.
1. Fluid core2. Convection of fluid3. Rapid rotation
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Comparative Planetology• 4 main surface altering processes
– Cratering (exogenic)– Volcanism (endogenic)– Tectonics (endogenic)– Erosion (endogenic)
• In order for endogenic processes to occur, energy must be available.
• Small planets (and moons, and asteroids) generally have little internal heat, and, therefore, little endogenic activity.
• Exogenic processes affect everything.
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Volcanoes
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Volcanoes
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Tectonics
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6Figure 9.13B
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Plate Tectonics
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Erosion
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Alluvial Fan
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New Surface vs. Old• Impacts happen over time.• Can date a surface by the number of
craters on its surface. Date since last geologic activity.
• Pot holes on road:– Many holes = old road.– Few holes = new road
• Resurfacing = energy– One or more endogenic
processes.• Another clue to insides.
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Why is Earth so Different?• Why do we have oceans of water?• Why doe we have an atmosphere
with:– so little carbon dioxide?– so much O2 and N2?
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Atmosphere Origins• Outgassing• Volcanoes.• CO2 and H2O
main gases.• Mt. St. Helens
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Concept Test
• For which terrestrial planets is the main atmospheric gas one of the two main gases produced by outgassing?a. Only Moon & Mercuryb. All five planetsc. Only Venus, Earth and Marsd. Only Earthe. Only Venus and Mars
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The Terrestrial PlanetsWorld Atmos.
Compsn.Surface Pressure
Ave Surface Temp.
Winds, Weather
Clouds, Hazes
Mercury He, Na, O 10-14 bar Day: 800FNight: -280F
none none
Venus 96% CO23.5% N2
90 bars 880F Slow winds, acid rain
Sulfuric acid clouds
Earth 77% N221% O2H2O
1 bar 60F Winds, hurricanes, rain, snow
H2O clouds, pollution
Moon He, Na, Ar 10-14 bar Day:260FNight: -280F
none none
Mars 95% CO22.7% N2
0.007bar -60F Winds, dust storm
H2O and CO2 clouds, dust
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Goldilocks Planet• Delicate balance:
Earth is just right.– No oceans without
greenhouse gasses.– Without oceans too
many greenhouse gasses.
– Without oceans no life.
– Without life, no ozone.
– No ozone, no life.• How does Earth
maintain this balance?
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Carbon Cycle
Tectonics are crucial!
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Nature’s Thermostat
• Carbon Cycle has negative feedback.• Increasing temperatures lead to
feedback that decreases temperatures, etc.
• Positive and negative feedbacks have nothing to do with desirability of outcome.
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Too CoolLess RainLess CO2 dissolves in oceans.More CO2 builds up in atmosphereIncreased greenhouseHeats Up.
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Too WarmMore RainMore CO2 dissolves in oceans.Less CO2 builds up in atmosphereDecreased greenhouseCool Down.
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Cycles
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Human Input
• Affecting CO2 cycle.
• Moving C from ground to air at increased rate.
• No increase in rate of C from air to ground.
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Mars Today
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Positive Feedback• Fossil Fuels – Increase CO2 to
atmosphere.• Deforestation – decrease CO2 from
atmosphere• Increase CO2 – Increase greenhouse
effect• Increase temp – Melting glaciers, ice
sheets, polar caps• Less ice – lower planetary albedo• Lower albedo – Earth absorbs more
light• More absorption – Increasing surface
temperatures.
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Homework #6• Due Monday January 30:• Read Bennett Chapter 6.• Do: Chapter 6 Quiz
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