1. Life on Earth
and nowhere else…

2. Describe the perfect place to grow a plant.
What makes it grow well?

3. Now, compare this to Earth.
What makes Earth the perfect place to live?

4. The Goldilocks Zone
Earth’s life-sustaining conditions are possible because of its position in the solar system
It is not too hot and not too cold – if the Earth was any closer or further away from the Sun, the planet could not support life

5. Other Life Sustaining Conditions
Earth’s rotation on its axis and orbit around the Sun helps distribute heat evenly around the planet
Earth’s magnetic field protects the planet from deadly radiation and particles
Earth’s gravitational field holds the atmosphere in place preventing oxygen, nitrogen, and carbon dioxide from escaping into space

6. Four Conditions for Life
Stable Temperature Range
The Importance of Water
The Importance of Gases
The Role of the Atmosphere

7. Stable Temperature Range
A stable temperature range (-50 to about +50 degrees Celsius) allows life to thrive – the average temperature has been between degrees Celsius for 3.5 billion years
The greenhouse effect allows for heat in the atmosphere (carbon and water vapor) to be re- radiated back to Earth
Without proper water and carbon, the earth would be -73 degrees C.

8. The Importance of Water
First water likely came from volcanic activity – water collected on the cooling surface and as vapour in the atmosphere creating the water cycle
Biologists believe earth first began in the oceans – blue-green algae
Oceans cover 2/3 of the Earth – absorbs heat and distributes it around the world and controls our weather patterns and climates
Helps distributes nutrients to plants and other organisms
No living thing consists of less than 50% water
Water is the metabolizing agent that allows plants and animals to dissolve minerals and nutrients to create energy

9. The Importance of Gases
78% nitrogen, 21% oxygen, carbon dioxide 0.03% - quite different than other planets in the solar system
The plants have removed most of the carbon dioxide that originally existed and produced lots of oxygen
Without life on earth, carbon dioxide would increase
The production of carbohydrates, fats, and proteins require oxygen, carbon, and nitrogen atoms from the atmosphere, and hydrogen from water

10. The Role of the Atmosphere
Layer of gases about kms thick – very thin compared to size of Earth
Helps maintain a consistent temperature
Shields earth from collisions with cosmic particles (meteors)
Oxygen levels at 21 allow for life, if they drop, animal life would not be possible, if it exceeds 25% most plants would be consumed by fire
Oxygen is produced by plants and consumed by animals and the burning of plants and fossil fuels

11. So, why can we not live on other planets?
Let’s find out!

12. Time for Teamwork!
Each group will be responsible for collecting information about an assigned planet.
You will use the information provided to complete the “Planet Exploration” sheet with your group.
You will have 15 minutes to complete this task.
Every member of your group must have all of the important information recorded.

13. Finding Earth’s Mate (aka match.com)
Now that you have become an expert on a particular planet, it’s time to find out about all of the others.
Our mission today is to find the planet that is most similar to Earth. Would it be possible to live on any of these other planets?
You will have 15 minutes to move around the room seeking out potential candidates to be Earth’s mate.
You will use the “Finding Earth’s Math” handout to record the information that you collect.
Find someone representing a planet other than yours. Exchange information with that person, and then seek out another planet.
Repeat this process until your entire sheet is filled.
Once your sheet is filled, return to your seat, and analyze your data.
Which planet could be Earth’s mate?