CHAPTER 27: PLANETS OF THE SOLAR SYSTEM

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?

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

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

1.) Start with a solar nebula (rotating cloud of gas and dust)2.) Contraction of gas and dust into rotating disk3.) Cooling causing condensing into tiny (dust sized) solid particles 4.) Collisions between these form larger bodies5.) The larger bodies accrete (or build up) to form planets

Steps in the process

#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?

Let’s break it down into steps…

#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!!

Next Step…

#3 Things begin to forma. Planetsimals begin to form within the swirling diskb. 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)

Third 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

Fourth 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

Fifth Step…

• 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!

Creation of Planets

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

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

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

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

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

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.

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

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

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

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

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

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

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?????

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

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

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

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

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????

ASSIGNMENTS

Outline Section 27.1 and Key Terms 27.1

Due: