Prepared by Mark R. Noll

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• Prepared by Mark R. Noll
• SUNY College at Brockport

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The Solar System

• Our solar system consists of the Sun, 9 planets,
  61 known moons, asteroids, comets, etc.
• All objects move in regular orbits around the sun
• May be divided into three major groups

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Fig. 25.1. Three types of planets
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The Solar System

• Inner Planets
• Terrestrial Planets
• Mercury, Venus, Earth, Mars, Io
• Small rocky planets composed of silicates and
  iron
• Likely layered structure
• Some have atmospheres of volatile gases

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The Solar System

• Outer Planets
• Jupiter, Saturn, Uranus, Neptune
• Large planets with low densities
• We see the tops of thick atmospheres
• Likely have a rocky core similar to the
  terrestrial planets

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The Solar System

• Icy Planetary Bodies
• Pluto, comets most moons of outer planets
• Consist of ices of water, methane, ammonia
  nitrogen
• May have silicate materials mixed with ice for a
  core

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The Moon

• Rocky body, less dense than Earth
• Lacks significant iron core
• Lacks atmosphere hydrosphere
• Erosion due only to impact craters
• Evidence of early history preserved

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The Moon

• Impact processes are fundamental in planetary
  development
• Impact craters have huge size range
• Meteorite strikes - kinetic energy causes
  compression and relaxation
• Material is ejected out forming ejecta blanket
  and rays

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The Moon

• Lunar Surface
• Landforms indicate 2 major periods of formation
• Older highlands are densely cratered
• Mare are flood basalts that smoothed the surface
• No evidence of tectonic activity since

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Fig. 25.3. The Moon
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Lunar History

• Lunar geologic time scale
• Formation by accretion excess heat promotes
  layer differentiation
• Large asteroid bombardment produced huge
  multi-ring basins
• Flood basalts fill lowlands
• Period of light bombardment

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Fig. 25.4. Lunar time scale
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Mercury

• Small, high density planet with no atmosphere
• 1.5x diameter of Moon
• Density similar to Earth
• Evidence for Fe core
• Old cratered surface, possible flood basalts
• No evidence for tectonic activity

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Mars

• Many similar surface features to Earth
• Half the diameter of Earth
• Generated more internal heat than Mercury or the
  Moon
• More geologic activity
• Shield volcanoes deformation features
• Evidence for liq. water atmosphere

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Figs. 25.6-9. Mars
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Mars

• Life on Mars
• Meteorites from Martian surface contain evidence
  of microorganisms
• Age of meteorite
• Existence of life dependent on liquid water
• Life on Mars today is still a question

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Venus

• Most like Earth in size and density
• Similar tectonic processes likely
• Thick CO2 atmosphere with sulfuric acid clouds
  obscure view of surface
• Radar images of surface show terrain similar to
  Earth
• Not heavily cratered - still tectonic activity

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Venus

• Surface lacks significant depositional features
• Dominated by volcanic activity
• Tectonic features minimally modified by erosion

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Fig. 25.12. Topographic map of Venus
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Jupiter

• Jupiter its moons form a planetary system of
  their own
• Jupiter has no known solid surface
• Density of 1.3 g/cm3
• Composed primarily of H and He
• Jupiters moons are solid planetary bodies

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Fig. 25.14. Jupiter its moons
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Io

• Innermost moon of Jupiter
• Lacks icy outer surface
• Composed of silicates, slightly larger than the
  Moon
• Volcanically active, no cratered surface
• Tidal forces may be source of energy

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Europa

• Composed mainly of silicate
• Density of 3 g/cm3
• Covered by frozen ice ocean
• No cratered surface
• Water lava erupts on surface
• Liquid water ocean may be beneath

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Ganymede

• Jupiters largest satellite
• Slightly larger than mercury
• Density of only 1.9 g/cm3
• Water ice surrounding a rocky core
• Two types of terrain evident
• Degree of impact cratering suggests older
  younger ages

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Saturn

• Saturn is similar to Jupiter
• Gaseous giant
• Numerous satellites
• Rings are distinct feature composed of icy
  particles
• Most of Saturns moons are tiny icy bodies

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Saturns Moons

• Titan
• Larger than Mercury
• Only moon in solar system with an atmosphere
• N2 dominated with traces of CH4
• Enceladus
• Evidence for slushy lavas ice tectonics

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Fig. 25.18 Saturn its moons
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Uranus

• Similar in structure to Jupiter Saturn
• Smaller, only about 4x Earths diameter
• Atmosphere contains methane
• Thin ring system
• Axis of rotation lies near plane of orbit
• Unique among planets
• Five major moons rotate around equator

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Fig. 25.20. Uranus its moons
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Neptune

• Similar to Uranus, slightly smaller
• Both thought to have water ice rock cores
• Methane in atmosphere
• Evidence for storm systems
• Rings system of icy particles
• Thin atmosphere of N2 CH4

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Pluto

• Furthest, smallest, coldest, darkest
• 250 yr orbit
• Lacks thick H-He atmosphere of other outer
  planets
• Similar to moons of Neptune
• Surface is frozen nitrogen
• Has one moon, Charon

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Asteroids

• Small rocky bodies, most form belt between Mars
  Jupiter
• Highly cratered surfaces suggest very old origin
• None are large enough to have internal heat
  driven geologic systems
• Meteorites are fragments of asteroids

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Fig.25.24a-b. Asteroids Ida Eros
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Comets

• Small bodies composed of ice and dust
• Ices composed of H2O, CO2, CO, CH4 and NH3
• Tail formed by vaporization of ices
• Some have huge orbits
• Tens of thousands of years for 1 rotation
• Orbital paths are complex

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Origin of the Solar System

• Gravitational collapse of huge gas dust cloud
• Rotation around a central mass
• Disk shaped cloud
• Temperature variations segregated matter
• Small particles accreted into larger
  planetesimals, finally planets

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Origin of the Solar System

• Planets continued to grow by sweeping up
  remaining debris
• Cratered surfaces
• Heating from accretion caused some melting
• Differentiation created layered structure

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Impact Processes

• Impact processes are important in formation
  development of planets
• Formation on moon may be from impact or glancing
  collision
• Impacts form large basins on many planets moons
• Impact of Shoemaker-Levy 9 shows importance of
  similar events

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End of Chapter 25