Mercury is about one-third of the Earth's distnace from the sun. Mercury's diameter is about one-third of the Earth's diameter. Mercury has phases, like the moon. Mercury looks like a crescent moon when it passes between Earth and the sun. Mercury has no moons.
Earth is the fifth largest planet and the third from the sun.
Earth's atmosphere is made of 77 percent nitrogen and 21 percent oxygen, with traces of argon, carbon dioxide, and water. Liquid water covers 71 percent of the Earth's surface. The other 29 percent is made of rock and soil. Earth is the only planet that has liquid water on its surface. While clouds of water vapor hide much of the Earth's suface.