Move to another planet? Sounds interesting! In our imaginary spaceship, let's check out the planets in our solar system. Mercury is closest, but it has no air, and it's either sizzling hot or bitterly cold. The atmosphere on Venus is poisonous; plus, human beings would cook there. Mars might work, but you'd always have to be in a protective shelter. And if you got to the outer planets, you couldn't even land as they are mostly made of gas! Our home planet is looking good. Why is Earth so comfortable for plants, animals, and people? As Robert E. Wells explains, it's because of our just-right position form the sun, marvelous atmosphere, and abundant water. Our planet is very special and perfect for us, and that's why we must do all we can to keep Earth healthy.