Life on Earth and nowhere else…

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

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

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

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

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

Stable Temperature Range A stable temperature range (-50 to about +50 degrees Celsius) allows life to thrive – the average temperature has been between 10-20 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.

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

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

The Role of the Atmosphere Layer of gases about 80-100 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

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

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.

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?