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Earth and Other Planets
Chapter 16
Great Idea:Earth, one of the planets that orbit the Sun, formed 4.5 billion years ago from a great cloud of dust.
Chapter Outline
• The Formation of the Solar System
• Exploring the Solar System
The Formation of the Solar System
Clues to the Origin of the Solar System
• Solar system
–Objects gravitationally bound to Sun
• Deduction of origin
–Observations
• Earth
• Space
Clue #1: Planetary Orbits
• Features of solar system
–All planets orbit in same direction
–Orbits in same plane
–Most rotate in direction of orbit
Clue #2: Distribution of Mass
• Most material within Sun
• Two types of planets– Terrestrial planets
– Jovian planets
• Other objects– Moons, asteroids, comets
The Nebular Hypothesis
• Nebular Hypothesis– Cloud of dust and gas
– 99% H and He
• Collapse of nebula– Planetary orbits– Clumping of matter
– Planetesimals – Temperature
The Formation of Earth
• Planetesimals
–Combined to form
earth
• Great bombardment
–Meteors
–Growth of planet
• 20 metric tons per day
Differentiation
• Differentiation
– Heat from collisions
– Dense material sank to center
– Lighter material rose to surface
• Structure
– Core
– Mantle
– Crust
The Formation of the Moon
• Big Splash
– Large object impacted earth
– Parts of mantle blown into orbit
–Moon formed from this material
Planetary Idiosyncracies
• Cratering
–Mercury, Mars, Moon
–None on earth
• weathering
• Rotation
–Venus
– Earth’s axis
–Uranus
The Evolution of Planetary Atmospheres
• Earth’s atmosphere
–Early
–Outgassing
• Atmosphere was N2, CO2, H2, & H2O
–Gravitational escape
– Living organisms
Exploring the Solar System
The Inner Solar System
• Mercury, Venus, Mars
–Mercury and Venus too hot for life
• Mars Exploration
–Multiple missions
– Found evidence of water
The Outer Solar System
• Jupiter, Saturn, Uranus, Neptune
– Layered structure
– No solid surface
• Jupiter
– Comet Shoemaker-Levy
– Galileo spacecraft
• Saturn
– Cassini spacecraft
Moons and Rings of the Outer Planets
• Moons
– Io
– Europa
– Titan
• Rings
– Ice and rock
Pluto
• Pluto
–Outermost planet
– .3% of earth’s mass
– Three moons
– Formation
• Captured comet or asteroid
• Still open to question
A Tenth Planet?
• Xena
–Orbits sun every 560 years
–One moon
– Larger than Pluto
Asteroids, Comets, and Meteors
• Asteroids– Small rocky bodies– Orbit sun– Most in belt between Mars and Jupiter
• Comets– Dirty snowballs
• Orbit outside Pluto• Oort cloud
• Kuiper belt
– Halley’s Comet– Stardust and Deep Impact missions
• Meteoroids, Meteors, and Meteorites– Meteor showers– Original solar system material