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Earth and The Terrestrial Worlds

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Title: Earth and The Terrestrial Worlds


1
Chapter 7
  • Earth and The Terrestrial Worlds

2
Principles of Comparative Planetology
  • Comparative Planetology is the study of the solar
    system through examining and understanding the
    similarities and differences among the planets.
  • Planetary Geology
  • The study of surface features and the processes
    that create them is called geology.
  • Today, we speak of planetary geology, the
    extension of geology to include all the solid
    bodies in the solar system.

3
Viewing the Terrestrial Worlds
  • Spacecraft have visited and photographed all of
    the terrestrial worlds. Some have even been
    landed on!
  • Because surface geology depends largely on a
    planets interior, we must first look inside the
    terrestrial worlds.

4
Global views and surface close-ups
Venus surface- atmosphere is not shown. Surface
mapped from Megellan spacecraft radar data
5
  • Surface Views of some of the terrestrial worlds.
  • Venus, the Moon and Mars have all been landed on
    successfully by spacecraft from Earth.

Venus Venera Missions (1961-1983)
Apollo Lunar Missions (1969-1972)
Links Mars Exploration Rover Mission The
Mission Mars Pathfinder
Mars Pathfinder Mission (1996-1997)
6
Inside the Terrestrial Worlds
  • When subjected to sustained stress over millions
    to billions of years, rocky material slowly
    deforms and flows.
  • Rock acts more like Silly PuddyTM , which
    stretches when you pull it slowly but breaks if
    you pull it sharply.
  • The rocky terrestrial worlds became spherical
    because of rocks ability to flow.
  • When objects exceed about 500 km in diameter,
    gravity can overcome the strength of solid rock
    and make a world spherical

7
  • Gravity also gives the terrestrial worlds similar
    internal structures.
  • Distinct layers are formed by differentiation.
  • Differentiation is the process by which gravity
    separates materials according to their density.
  • This resulted in three layers of differing
    composition within each terrestrial planet.
  • Core
  • Mantle
  • Crust

8
  • Lithosphere Outer layer of relatively rigid rock
    that encompasses the crust and the uppermost
    mantle.

9
  • Heat flows from the hot interior to the cool
    exterior by conduction and convection.
  • Condution Heat transfer as a result of direct
    contact.
  • Convection Heat transfer by means of hot
    material expanding and rising and cool material
    contracting and sinking.
  • A small region of rising and falling material is
    called a convection cell.

10
Shaping Planetary Surfaces
There are four main geological processes
  • Impact Cratering the excavation of bowl-shaped
    depressions (impact craters) by asteroids or
    comets striking a planets surface.
  • Volcanism the eruption of molten rock, or lava,
    from a planets interior onto its surface.
  • Tectonics the disruption of a planets surface
    by internal stresses.
  • Erosion the wearing down or building up of
    geological features by wind, water, ice, and
    other phenomena of planetary weather.

11
Impact Process
Ejecta
Impact
Ejecta Blanket
12
Cratering
13
Volcanism
14
(Mount St. Helens)
  • c) Sticky lava makes steep-sloped
    stratovolcanoes.

Picture by US Geological Survey scientist, Austin
Post, on May 18, 1980.
15
Tectonic Forces at work.
Convection Cells
16
Comparing Planetary Atmospheres
17
Atmospheric Structure
18
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19
Visible Light Warming the Surface and Coloring
the Sky
Atmospheric gases scatter blue light more than
they scatter red light. Longer wavelength red
light is more penetrating
20
Infrared Light the Greenhouse Effect, and the
Tropsosphere
  • The Troposphere becomes warmer than it would if
    it had no greenhouse gases.
  • Greenhouse gases include
  • CO2
  • Water Vapor

21
The Greenhouse Effect
22
Temperatures of the Terrestrial Worlds
23
  • Ultraviolet light is absorbed in the
    Stratosphere.
  • X-Rays are absorbed in the Thermosphere and
    Exosphere.

24
The Magnetosphere
  • The Magnetosphere blocks the Solar Wind
  • This produces two regions where the charged
    particles get trapped Van Allen Belts.

25
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26
  • The interaction of the charged particles from the
    solar wind near the poles, produces the
  • Aurora Borealis (Northern Lights)
  • Aurora Australis (Southern Lights)

27
Aurora Borealis Norhern Lights
28
Atmospheric Origins and Evolution
  • Outgassing from Volcanic activity was most
    responsible for producing the earths early
    atmosphere. (Volcanoes give off H2O, CO2, N2, and
    sulfur compounds.
  • As life developed, it too influenced the
    atmosphere of the Earth, allowing it to become
    what it is today. (e.g. plants give off O2 and
    consume CO2)

29
Many gases can escape from the planet if their
thermal speed is greater than the escape speed of
the planet.
Five Major Processes By Which Atmospheres Lose
Gas.
30
A Tour of the Terrestrial Worlds
31
The Moon 1,738-km radius, 1.0AU from the Sun
Astronaut explores a small crater
An ancient lava river
32
Mercury (2,440-km radius, 0.39AU from the Sun)
33
Dust Storm over northern ice cap, Mars
Global Surveyor
Polar Ice Cap (Mars) Viking Orbiter
Edge of polar ice cap showing layers of ice and
dust.
Mars (3,397-km radius, 1.52 AU from the Sun)
34
Cratering, Volcanism and Tectonics
Valles Marineris
Heavy cratering in Southern Hemisphere (Mars)
Olympus Mons largest shield volcano in the
solar system
35
Martian outflow channels and flood planes
Ancient River beds
Outflow channels indicate catastrophic flooding
Water eroded crater
Gullies on a crater wall formed by water flows?
36
Venus (6,051-km radius, 0.72 AU from Sun)
Shield Volcanoes are common
Impact craters on Venus are rare
Fractured and twisted crust
37
Earth (6, 378 km radius, 1.0 AU from the Sun)
38
Time-Line of Geologic Activity
39
End of Section
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