Transcript Earth, one of the planets that orbit the Sun, formed 4.5 billion years

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 highpressure ice crystal that was formed at room temperature
by squeezing water.
Earth’s Atmosphere
• The temperature of
the atmosphere is a
complicated
function of
altitude.
Our Atmosphere
50% below 3.5 miles
90% below 10 miles
99% below 20 miles
ozone hole
global warming
A Clicker Question.
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
Ozone and the Upper
Atmosphere
• 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
Atmosphere
• The oxygen atoms can collide with oxygen molecules to
form ozone:
O(g) + O2(g)  O3(g)
Ozone and the Upper
Atmosphere
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.
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