Earth is a watery planet –70 per cent of its surface appears blue –and the only one that can support life. From space, astronauts have observed cities, forest fires, roads, airports, dams and other large structures, such as the Great Pyramid and the Great Wall of china. Diameter: 12,756.3km Mass: 59,720,000,000,000 tonnes Average distance from Sun: 149,600,000 km Rotation: 0.99727 days Orbit: 365.256 days Average temperature: +15 ◦ C Moons: 1