1. “Life in the Goldilocks Zone”
Habitable Zone Notes
“Life in the Goldilocks Zone”

2. Necessary Components for Life:
1. Gravity
The sun’s large mass causes a gravitational pull on all planets. The smaller the mass of the planet, the stronger the gravitational pull and thus the closer the planet is to the sun.
Earth’s mass enables it to be the perfect distance from the sun. Earth is the only planet in the habitable zone: area the space that has ideal conditions to enable life to exist.
In our solar system, the habitable zone extends from after Venus to just before Mars, so Earth is the only planet within it.

3. The 3rd planet from the sun
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The habitable zone is the only spot in space where life can exist because it meets all 8 necessary components for life.
Earth
The 3rd planet from the sun
= Too hot
= Too cold
= Just right

4. Necessary Components for Life:
2. Energy Source: The Sun
The sun is the vital energy source for life on our planet. Producers get their energy from the sun through photosynthesis, fueling the food web on Earth.
Producers are the start of the food web

5. Necessary Components for Life:
3. Temperature
The sun radiates thermal energy that is absorbed by Earth.
Other factors that increase the heat of Earth to a temperature that can sustain life include:
Geothermal Energy from Earth’s Molten Iron Core
The Greenhouse Effect
Plate Tectonics: Divergent, Convergent, and Transform plate boundaries
Convection Currents provide geothermal energy

6. Necessary Components for Life:
4. Green House Heating
Large amounts of green house gases, such as Carbon Dioxide, reflect that heat back to the surface of a planet and warm it.
The ability of a planet to retain it’s gases, depends on the composition of the atmosphere and the strength of the planet’s gravity.
READ ONLY: Greenhouse gases are a positive until we over-increase the amount of them. Burning fossil fuels release pollutants into the air and increases the amount of carbon dioxide. The more carbon dioxide in the air, the warmer the planet will get. Since plants convert CO2 into O2 through photosynthesis, removing plant life will also increase the amount of CO2 in the atmosphere.

7. Greenhouse Effect aka Global Warming
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Greenhouse Effect aka Global Warming
The greenhouse effect is a process by which thermal radiation from the sun is absorbed by atmospheric greenhouse gases (Carbon Dioxide, Water Vapor, and Methane), and is re-radiated in all directions. Since part of this re-radiation is back towards the surface and the lower atmosphere, it results in an elevation of the average surface temperature above what it would be in the absence of the gases
The primary source of Greenhouse gases are from the burning of fossil fuels (coal, oil, and natural gas). Volcanic eruptions and decomposition in landfills also increase greenhouse gases.

8. READ ONLY

9. Advantages of Greenhouse Gases
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Advantages of Greenhouse Gases
The gases slow down the rate that heat leaves the Earth System
Without greenhouse gases, the Earth would have freezing temperatures
Disadvantages of Greenhouse Gases
Global warming
Melting of Polar Ice Caps
Rising Sea Levels
Flooding of Costal Areas
Increase of storms and hurricanes
Increase in tropical diseases (malaria)

10. Necessary Components for Life:
5. Plate Tectonics
Plate Tectonics create volcanoes release the greenhouse gas, Carbon dioxide, into the air which causes a planet’s temperature to rise.
Early Earth had many Volcanoes, putting large amounts of Carbon dioxide into the atmosphere.
Plate tectonics
regulate the surface temperature of the planet
create a magnetic field -- Van Allen Radiation Shield-- to block the planet from the deadly solar winds
create dry land on a water-covered world

11. Van Allen Radiation Shield
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Earth’s magnetic field
Van Allen Radiation Shield

12. 6. Composition of the Atmosphere
Necessary Components for Life:
6. Composition of the Atmosphere
Earth’s gravity is strong enough to retain it’s atmosphere. Earth’s atmosphere has changed over time.
Today, Earth’s atmosphere consists of
78% Nitrogen
21% Oxygen
0-.4% Water Vapor
.93% Argon
.03% Carbon dioxide
Trace amounts of Neon, Helium, Methane, and Hydrogen

13. Necessary Components for Life:
7. Mass
Planets must have the ideal mass to promote the existence of life.
More mass= stronger pull of gravity
A planet smaller than Mars could not hold on to it’s atmosphere, over time the gases would diffuse into space.
A planet with a very large mass will hold onto any gases surrounding it, and become a densely clouded like the outer planets of our solar system and are not suitable for life.

14. Necessary Components for Life:
8. Presence of Water
Liquid water is directly linked to the existence of life.
In order for LIQUID water to exist, warm temperatures are essential.
Temperatures needed for water to be a liquid:
32-212⁰F or 0-100⁰C

15. To make each of the 8 necessary components stand out in your notes, pick one of the following:
BOX IN
HIGHLIGHT
BOLD
The sun’s large mass causes a gravitational pull on all planets. The smaller the mass of the planet, the stronger the gravitational pull and thus the closer the planet is to the sun.
Earth’s mass enables it to be the perfect distance from the sun. Earth is the only planet in the habitable zone: area the space that has ideal conditions to enable life to exist.
In our solar system, the habitable zone extends from after Venus to just before Mars, so Earth is the only planet within it.
1. Gravity
Necessary Components for Life:
2. Energy Source: The Sun
The sun is the vital energy source for life on our planet. Producers get their energy from the sun through photosynthesis, fueling the food web on Earth.
EXAMPLE
Habitable Zone Notes

16. Assignment:
Sketch the picture of the Habitable Zone shown below. Explain what this term means (in your own words) and why this is also referred to as the “Goldilocks Zone”
USE the 8 Necessary Components for Life to support your answer.