Title: Earth and The Terrestrial Worlds
1Chapter 7
- Earth and The Terrestrial Worlds
2Principles 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.
3Viewing 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.
4Global 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)
6Inside 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.
10Shaping 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.
11Impact Process
Ejecta
Impact
Ejecta Blanket
12Cratering
13Volcanism
14(Mount St. Helens)
- c) Sticky lava makes steep-sloped
stratovolcanoes. -
Picture by US Geological Survey scientist, Austin
Post, on May 18, 1980.
15Tectonic Forces at work.
Convection Cells
16Comparing Planetary Atmospheres
17Atmospheric Structure
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19Visible 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
20Infrared 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
21The Greenhouse Effect
22Temperatures of the Terrestrial Worlds
23- Ultraviolet light is absorbed in the
Stratosphere. - X-Rays are absorbed in the Thermosphere and
Exosphere.
24The Magnetosphere
- The Magnetosphere blocks the Solar Wind
- This produces two regions where the charged
particles get trapped Van Allen Belts.
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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)
27Aurora Borealis Norhern Lights
28Atmospheric 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)
29Many 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.
30A Tour of the Terrestrial Worlds
31The Moon 1,738-km radius, 1.0AU from the Sun
Astronaut explores a small crater
An ancient lava river
32Mercury (2,440-km radius, 0.39AU from the Sun)
33Dust 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)
34Cratering, Volcanism and Tectonics
Valles Marineris
Heavy cratering in Southern Hemisphere (Mars)
Olympus Mons largest shield volcano in the
solar system
35Martian 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?
36Venus (6,051-km radius, 0.72 AU from Sun)
Shield Volcanoes are common
Impact craters on Venus are rare
Fractured and twisted crust
37Earth (6, 378 km radius, 1.0 AU from the Sun)
38Time-Line of Geologic Activity
39End of Section