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