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Origin of the Solar System
The Solar Nebula Hypothesis
Differentiation
Atmospheres
Oceans
Life
What observations were used to
formulate a hypothesis?
Formation of the solar system…
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1. All of the planets orbit the sun in the same direction, in the same plane, and in nearly circular orbits
Pluto is the exception – and it’s not a planet!!
2. Most* of the planets spin on their axes in the same direction
*except Venus and Uranus
3. Planets can be put into two groups:
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4. We have an asteroid belt, a Kuiper Belt, and comets
These observations lead
us to assume a common
origin for the planets in
the solar system
The prevailing hypothesis
is called the Solar Nebula
Hypothesis
Implication
The Eagle Nebula ~ a site of active
star formation
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Question The diagram below shows the solar system during the
time that planets were forming. Where does the solar nebula hypothesis predict that large, Jovian planets would form?
temperatures
too hot for
water to be
solid
temperatures
cold enough for
water to be
solid
outer regions
of disk – not
much material
here
Practice
• In groups, complete the “Solar System Formation” worksheet (handed out).
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Question
Which statement best describes the solar nebula hypothesis?
1. The solar system formed from the remnants of a collision between two stars.
2. The solar system formed from the collapse of a large spinning cloud.
3. The solar system formed from a giant explosion.
4. The solar system formed from material that was thrown off when the Sun started to spin too fast.
Question
Would you expect a Jupiter-like planet to form in the region of Venus?
1. Yes, because gas was distributed evenly throughout the solar system during planet formation.
2. No, because the solar wind blew gases away from that region during planet formation.
3. No, because there was no ice available in that region during planet formation.
4. No, because protoplanets in that region were spinning too fast to gather gases during planet formation.
Question
This plot shows the temperature gradient during the formation of another solar system (red line; our solar system is the black line). What type of planet would you expect to find at 1 AU?
1. A terrestrial planet.
2. A jovian planet.
3. It is impossible to say.
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Does the nebular hypothesis explain the observations?
1. Most of the planets orbit the sun in the
same direction, in the same plane, and in
nearly circular orbits
2. Most of the planets spin on their axis in
the same direction
3. The planets can be put into two groups
4. We have an asteroid belt, a Kuiper Belt, and
comets
Early planets were HOT!
Differentiation
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Comparison of Interiors
3.8 to 4.28 billion years old
Earth’s oldest rock has its own
facebook page!!
Primary atmosphere: collected during planet formation
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Secondary atmosphere: from outgassing during differentiation and comet impacts
Tertiary atmosphere: when a secondary atmosphere undergoes significant modification
Earth’s evolving
atmosphere
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right temp
= oceans
?
Development of plants & animals
“Age of
Invertebrates”
“Age of Fishes”
“Age of
Reptiles”
“Age of
Mammals”
Humans develop Extinction of
dinosaurs and
many other
species 1st flowering plants
Extinction of
trilobites and
many other
marine animals First reptiles
First fishes
Trilobites dominant
1st shelled organisms
First insect fossils
First land plants
Dinosaurs dominant
1st birds
1st multicelled organisms
“Age of
Amphibians”
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Questions you should be able to answer.
• What observations led to the Solar Nebula Hypothesis?
• Describe the Solar Nebula Hypothesis.
• Why did some planets develop into terrestrial planets and some into Jovian planets?
• Why were early planets hot?
• How old is the oldest rock on Earth?
• What is differentiation?
• What is the difference between a primary, secondary, and tertiary atmosphere? Where in the solar system can I find examples of each?