The Greenhouse Effect on a Planetary Scale
Why is Venus so hot?  Why is Mars so cold?  And why is Earth "just right"?

This astronomical version of Goldilocks is a question that scientists have studied for more than sixty years, and we've learned enormously about how our own planet's climate works by studying our neighbors in space.  That effort has already helped us to understand the effects of greenhouse gas emissions from industrialization and natural causes, and our continued study will help us find solutions, too.