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

The Solar System

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

Mass in the Solar System

The Planets and Their Characteristics

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 Stages in Solar System Formation

The Inner Planets –Small and Rocky

Jupiter – Gas Giant Planet

The Science of Life

• Gravity and bones

The Formation of Earth

• Planetesimals– Combined to form earth

• Great bombardment– Meteors– Growth of planet

• 20 metric tons per day

Artists Impression of the Earth’s Great Bombardment

Disk around a Young Star

Differentiation

• Differentiation– Heat from collisions– Dense material sank to center– Lighter material rose to surface

• Structure– Core– Mantle– Crust

The Principal Layers of the Earth

Technology

• Producing world-record high pressures

The Formation of the Moon

• Big splash– Large object impacted earth– Parts of mantle blown into orbit– Moon formed from this material

Formation of the Earth’s Moon

Planetary Idiosyncrasies

• Cratering– Mercury, Mars, Moon– None on earth

• Weathering

• Rotation– Venus – Earth’s axis– Uranus

The Science of Life

• When could life begin?• Effect of collisions

The Evolution of Planetary Atmospheres

• Earth’s atmosphere– Early– Outgassing

• Atmosphere was N2, CO2, H2, and 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

Surface of Mars

The Phoenix Lander on Mars

Science of Life

• Why look for life on Mars?

• Source of science fiction

• Current views

The Outer Solar System

• Jupiter, Saturn, Uranus, Neptune– Layered structure– No solid surface

• Jupiter– Comet Shoemaker-Levy– Galileo spacecraft

• Saturn– Cassini spacecraft

Theoretical View of the Interior of Jupiter

Comet Shoemaker-Levy Impacted Jupiter in 1994

Saturn with Its Rings and Moons

Moons and Rings of the Outer Planets

• Moons– Io– Europa– Titan

• Rings– Ice and rock

Artist’s Conception of the Oceans of Europa

Pluto and the Kuiper Belt

• Pluto– .3% of Earth’s mass– Orbit tilted out of plane of other planets– Three moons– Formation

• Captured comet or asteroid• Still open to question

– Plutoid designation in 2008

Pluto and Its Moon, Charon

Science in the Making

• The discovery of Pluto• Xena

– Orbits sun every 560 years– One moon– Larger than Pluto

Science in the Making

• The Voyager Satellites• Discoveries

Asteroids

• Asteroids– Small rocky bodies– Orbit sun– Most in belt between Mars and Jupiter

Comets

• Comets– Dirty snowballs

• Orbit outside Pluto• Oort cloud• Kuiper belt

– Halley’s Comet– Stardust and Deep Impact missions

Comet’s Tail

Meteors

• Meteoroids, meteors, and meteorites– Meteor showers– Original solar system material

Major Meteor Showers

Science in the Making

• Discovering new planetary systems• Use the Doppler effect• Search for transits

Changes in Redshift or Blueshift of Light

Planet in Front of a Star

Kepler Satellite