1. Our Habitable Earth: What conditions allow Earth to support and maintain life?
List the basic requirements for human survival:

2. What conditions allow Earth to support and maintain life?
Proximity to the sun
Atmosphere
Gravity
Magnetic Field
Liquid Water

3. Proximity to the Sun
How does proximity to the Sun contribute to a planet’s temperature and ability to support life?

4. Proximity to the Sun
The “Habitable Zone” is the region around a star where it is possible for a planet with the correct atmospheric pressure to maintain liquid water on its surface
The Earth resides in the “Habitable Zone” of our nearest star…the sun!
Too far and the planet would be too cold for liquid water; too close and the planet would be too hot for liquid water.
Living organisms require liquid water to survive. There are a few types of bacteria that can survive in frozen water.

5. Atmosphere
What is air?
"Air" refers to an atmosphere, a collection of gases, which can only exist around a semi-massive object in space.
Is there “air” between earth and the moon?
No because there is no atmosphere between the Earth and moon.

6. Atmosphere
How does the presence and composition of an atmosphere help to determine a planet’s surface temperature?

7. Atmosphere
The atmosphere is like a blanket around the Earth -- and is made up of 78% nitrogen, 21% oxygen, 0.9% argon, 0.03% carbon dioxide and trace amounts of other gasses.
The atmosphere does two main things –
It absorbs energy from the Sun (traps heat).
Recycles water and other chemicals (water cycle).

8. Layers of the atmosphere
The atmosphere is thicker the closer it is to the Earth.

9. Atmosphere

10. Gravity The Atmosphere is held in place due to gravity.
The gravitational pull of an object is due to the mass of the object.
Too little mass and you would not have much of an atmosphere (like the Moon or Mars)
Too much mass and the air pressure would squash a human flat (like Jupiter or Saturn)

11. Magnetic Field
A complex, invisible region that surrounds Earth. You could think of it like a force field.
The magnetic field protects us from Solar Winds and Storms.
Solar Winds and Storms are highly energized particles ejected from the sun.

12. The magnetic field is formed by the motion of the molten iron in the core of the Earth.
The magnetic field allows us to use compasses and forms the magnetic North and South Poles.
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13. Magnetic Field
Mars
What do you think the solar winds are doing to the planet Mars?

14. Magnetic Field
Earth
What do you think the solar winds are doing to the planet Earth?

15. Water
Water is necessary for life as we know it. What evidence is there that water may exist now or may have existed at one time on other celestial bodies?
All of the water on or near the earth is called the hydrosphere.
This includes the oceans, rivers, lakes, and even the moisture in the air.
97 % of the earth's water is in the oceans.
The remaining 3 % is fresh water; ¾ of the fresh water is solid and exists in ice sheets/glaciers.

16. Water

17. Water on other Worlds Evidence for water on Mars:
Mars has defined polar regions that contain water ice
Mars rover Curiosity has identified a streambed

18. Water on other Worlds
Evidence for water on Europa (Jupiter’s 6th moon):
Galileo Spacecraft inferred through observation the presence of a global salt water ocean containing more water than is present on Earth covered in a thick, ice shell
Tidal forces on Europa (gravity interaction between Jupiter, Europa and the other moons) would be enough to keep the interior of Europa liquid

19. HOLD ON!
Gliese 581g?
Astronomers say they have for the first time spotted a planet beyond our own in what is sometimes called the Goldilocks zone for life: Not too hot, not too cold. Juuuust right.
Not too far from its star, not too close. So it could contain liquid water. The planet itself is neither too big nor too small for the proper surface, gravity and atmosphere. It's just right. Just like Earth?
We’ll see what future study of this finding brings us…

20. Exo-Planets