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 surface of Venus is shrouded in clouds, but the Magellan spacecraft produced radar images of the surface. In this computer-generated view of a Venusian volcano, the vertical relief has been greatly exaggerated.

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

Researchers attain high pressures, equivalent to those deep inside the Earth and other planets, using the diamond anvil cell. Looking through such diamond cells you can observe pressurized samples such as this high-pressure ice crystal that was formed at room temperature by squeezing water.

• The temperature of the atmosphere is a complicated function of altitude.

Earth’s AtmosphereEarth’s Atmosphere

Our Atmosphere

50% below 3.5 miles

90% below 10 miles

99% below 20 miles

ozone hole

global warming

The concentration of which gas is increasing in our atmosphere leading to

global warming?

a) water

b) acetone

c) carbon dioxide

d) carbon monoxide

e) tri-carbon

A Clicker Question.

• Ozone absorbs photons with a wavelength between 240 and 310 nm.

• Most of the ozone is present in the stratosphere

• Between 30 and 90 km photodissociation of oxygen is possible:

O2(g) + h 2O(g)

Ozone and the Upper Ozone and the Upper AtmosphereAtmosphere

• The oxygen atoms can collide with oxygen molecules to form ozone:

O(g) + O2(g) O3(g)

Ozone and the Upper Ozone and the Upper AtmosphereAtmosphere

Depletion of the Ozone Layer

• In 1974 Rowland and Molina showed that chlorine from chlorofluorocarbons (CFCs) deplete the ozone layer by catalyzing the formation of ClO and O2.

Ozone and the Upper Ozone and the Upper AtmosphereAtmosphere

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