1. Earth: Why is it so nice?
(… so “Habitable” for Life?)
 Our Atmosphere takes care of it!

2. Benefits of an Atmosphere: Heat Circulation
(W  E, & Poles  Equator)

3. Benefits of an Atmosphere: Burns up Meteors! (Large and Small)

4. Benefits of an Atmosphere: Oxygen!
(For Breathing – a Source of Energy – and a Sign of Life!)

5. Benefits of an Atmosphere: UV Protection from its
“Ozone Layer”!

6. Problem: The Ozone “Hole”

7. All Hot Objects Emit Light…
…Warm Objects Emit
Infrared (IR) Light!

8. Benefits of an Atmosphere: “Greenhouse Effect” Warming

9. Problem: Excessive “Global Warming”!
Too much of the Infrared (IR) Light emitted by Earth
absorbed by increasing amounts of Greenhouse Gases…

16. Venus: “Runaway Greenhouse Effect”

17. The Atmosphere of Venus today:

18. Mars: “Runaway Freeze-Out”

19. The Atmosphere of Mars today:

20. What Mars “Used to Be” (we believe…)
(…before its Core Solidified, so its Magnetic Fields died away,
and its Atmosphere was stripped by the Solar Wind,
and the remaining Water Vapor & Carbon Dioxide froze over…)