1. Chapter 27: Planets of the solar system

2. Section 27.1 – Formation of the Solar System
What exactly is a solar system anyway?
Consists of the Sun, all the planets, and any other body that revolves around the Sun
And what exactly is a planet?
Any primary bodies that orbit the Sun (Earth, Venus, etc.)
Where did it all come from?

3. Nebular Hypothesis
1976, French mathematician Pierre-Simon, marquis de Laplace came up with explanation for creation of the solar system
Sun and other planets came together and condensed at the same time out of a rotating cloud of gas and dust

4. Solar Nebula
Solar Nebula – the rotating cloud of gas and dust from which the sun and planets formed
Also any nebula from which stars and planets (outside our solar system) may form
99% of the material in
the Sun is matter that
was originally in the
solar nebula

5. Steps in the process
1.) Start with a solar nebula (rotating cloud of gas and dust)
2.) Contraction of gas and dust into rotating disk
3.) Cooling causing condensing into tiny (dust sized) solid particles
4.) Collisions between these form larger bodies
5.) The larger bodies accrete (or build up) to form planets

6. Let’s break it down into steps…
#1 Solar Nebula
What “fuels” the nebula?
Energy from collisions and pressure from gravity makes the center of the nebula HOT and DENSE
99% of all the material in the nebula is in the sun
Think back to our solar nebula activity! Where is most of the material located?

7. Next Step…
#2 The nebula flattens as it rotates and gets warmer near the center
Starts to look like a disk
Temperature begins to rise more at the center
Think ice skater doing a spin!!

8. Third Step… #3 Things begin to form
Planetsimals begin to form within the swirling disk
As they grow, gravitational pull increases and they continue to grow more
Planetesimals - “mini planets” or small bodies from which a planet originated in the early stages at the beginning of the solar system)

9. Fourth Step…
#4 Small planetesimals collide with larger ones and the planets begin to grow
As the planetesimals get bigger, their gravity grows and they become protoplanets
Protoplanets are
planetesimals that have
collided due to gravity
to form larger bodies

10. Fifth Step…
#5 The extra dust and gas is gradually removed from the solar nebula by the collisions
The removal of the other material leaves mainly just planets around the sun and creates a new solar system

11. Creation of Planets
KEY THOUGHT: THE FEATURES OF A NEWLY FORMED PLANET DEPEND ON THE DISTANCE BETWEEN THE PROTOPLANET AND THE DEVELOPING SUN
IT ALL RELATES TO GRAVITY
What has the most gravity in a solar system?
THE SUN!

12. Inner vs. Outer Planets
Inner protoplanets (which are?) contained lots of heavy elements
Venus, Earth and Mercury contain lots of nickel and iron
These elements stuck around because they couldn’t be blown away or evaporated by the Sun’s heat and wind

13. More about inner planets
As the inner planets formed, dense material sank towards the middle of the planets and lighter material stayed on top, forming layers
Inner planets have solid surfaces (like Earth)
Inner planets are smaller, rockier, and denser than outer planets

14. Inner vs. Outer Planets
Outer protoplanets (which are?) contained lighter elements
Jupiter, Saturn, Uranus, and Neptune contain hydrogen, helium, and methane
These planets are cold, have low densities, and are HUGE

15. More on outer planets Outer planets known as “Gas Giants” because:
Mostly made of gases and are low density
Jupiter’s density is only 24% of Earth’s but Jupiter’s diameter is 11 times Earth’s
Have liquid cores and gas outer layers

16. Pluto! Not considered an inner or outer planet
Characteristics of Pluto
Very small (smaller than Earth’s Moon!)
Very COLD – it’s an ice ball made of frozen rock and gas

17. More on Pluto
Recently, scientists found many, many objects in the universe that are similar to Pluto beyond Neptune
Because Pluto is more like these other common objects rather than other planets, it is no longer considered a PLANET.

18. Formation of Solid Earth
3 sources of energy contributed to the original HOT temperatures on Earth:
Energy produced during collisions with other planetesimals
Increased pressure on inner layers of Earth from weight of outer layers
Radioactive materials were abundant in Earth during its formation

19. Early Solid Earth
Differentiation – the process that occurred as Earth developed where denser molten materials sank to the center and less dense materials were forced to the outer layers

20. 3 Layers of Earth
Core – the center of Earth that is made of dense rocks
Nickel and Iron most common
Mantle – Earth’s thick middle layer
Iron and Magnesium-rich rock
Crust – Outermost layer of Earth
Least dense material, including silica-rich rocks

21. Present Solid Earth
As time went on, Earth’s surface cooled enough for solid rock to form
While Earth already had distinct layers, the surface continued to change from:
Heat inside the Earth
Impacts and interactions with the forming atmosphere

22. Formation of Earth’s Atmosphere
Like the Earth’s interior, the atmosphere formed due to differentiation
Hydrogen and helium (lightest gases) rose to surface of the Earth
SO, the early atmosphere was mostly made of H and He

23. The Early Atmosphere
Hydrogen and helium gas are so light, Earth’s gravity couldn’t hold them in for long
The Sun’s heat heated them up and they blew away into space
Also, Earth’s magnetosphere (protects our current atmosphere) was possibly not developed fully

24. OUTGASSING (no that’s not what you think it is)
The Earth’s surface continued to evolve with creation of volcanoes and other land forms
Volcanoes released additional gases into atmosphere:
Water vapor, carbon dioxide, nitrogen, methane, sulfur dioxide, and ammonia
What’s missing from this list?????

25. More on outgassing
Gases released from volcanoes then interacted with sun light and heat
Breakdown of ammonia and water vapor into OZONE (or three oxygen)
Ozone is a shield against UV rays of the Sun

26. The PRESENT Atmosphere
Later, some plant life evolved that used carbon dioxide from the atmosphere to produce food (photosynthesis!)
OXYGEN is the main product of photosynthesis
About 2 billion years ago, the amount of oxygen in the atmosphere increased a lot
Composition of “air” is now stable

27. Oceans – Where did they come from?
Possibly from space!
Some icy bodies (ex. comets) collided with Earth and added water vapor to atmosphere
As Earth cooled, water vapor condensed to liquid rain
First ocean was probably FRESH water

28. Why are oceans salty?
Although first oceans were likely fresh, as water flowed over land and rocks, it dissolved minerals and salts carried them to the oceans
After the water cycle was in place, the concentration of salt in oceans increased

29. How did Oceans Affect Atmosphere?
Scientists believe the early atmosphere was changed as oceans began to dissolve carbon dioxide
Current atmosphere likely has more carbon dioxide than original atmosphere
Earth’s early climate likely cooler than today
Does CO2 in the atmosphere affect climate today????

30. ASSIGNMENTS
Outline Section 27.1 and Key Terms 27.1
Due: