The earth is made up of three parts: land, sea, and air. The air around the earth is called the atmosphere. The air has some oxygen in it.

When earth was very young, it had no atmosphere. Plants appeared and helped make oxygen in the air. We need oxygen to breathe.

Explore Space ... Not Drugs!
Hear what astronauts have to say about staying drug-free.
Last modified: Thu Oct 9 13:49:20 PDT 1997