Earth is the only planet we know of that humans can live on. About 71 percent of Earth is covered with water although only 1 percent of it is drinkable. Earth is the fifth largest planet and the third planet from the sun.

Mars is the seventh largest planet, although it is much smaller than Earth. The largest volcano we know of isn't on Earth - it's on Mars. Olympus Mons is the tallest volcano in our solar system and is three times taller than Mt. Everest. There's also a huge canyon called Vallis Marineris.