Activity 1: Why is Water So Central to Life?
Activity 2: Is There Water on Mars and Europa?
Activity 3: How Does an Atmosphere Influence a Planet’s Habitability?
Activity 4: What Is Density?
Activity 5: How Do Planetary Cycles Influence Habitability?
Activity 6: What Are the Habitable Zones in Our Solar System?

Science on the Internet

Water on Mars and Europa
Astrobiology Magazine - New Signs of Recent Water (Mars)
NASA Mars Rover Scientists Wring Water Story From Rocks
CNN Pictures Support Theory of Water on Europa
SolarViews Europa

Greenhouse Gases
What Are Greenhouse Gases?
Wikipedia Greenhouse Gases

Water Cycle
USGS Water Cycle
Dr. Art's Guide to Planet Earth - The Water Cycle