Our home planet, the third from the Sun in the solar system. The Earth orbits the Sun at an average distance of 93 million miles (149 million km/1 astronomical unit) and has a mass of 6x10^24 kg. It is made of solid, rocky materials such as iron, nickel, and silicon, and it has an atmosphere composed mainly of nitrogen and oxygen with traces of argon, carbon dioxide, and other compounds. Liquid water covers 71 percent of the planet's surface. Earth has one moon.