Earth: Planet 3

		Diameter		7,926 miles (12,756 km)
		Average Distance from Sun		93,000,000 miles (149,600,000 km)
		Planet Composition		rock surrounding a nickel-iron core
		Atmosphere		nitrogen, oxygen
		Average Temperature		+59°F (15°C)
		Number of Moons		1
		Orbital Period		365.2 days (1 year)
		Period of Rotation		23 hours 56 minutes

Earth is probably the only planet in our solar system with liquid water on its surface. Water covers over 70% of the Earth's surface, and white clouds of water vapor often hide large parts of Earth.

Earth is quite colorful from space. The oceans, land and clouds easily show up as blue, brown, and white.

The abundant water and oxygen-rich atmosphere support a a wide variety of complex life forms. Life has not been found anywhere else in the solar system.

The 23.5° tilt of the Earth's axis cause the changes in the seasons as the planet orbits the Sun.

Although the atmosphere shields the planet from hazardous radiation and the huge temperature extremes of space, it is only a few miles thick. The moderate temperature on Earth is not only caused by its distance from the Sun, but also the composition of the atmosphere. Even a slight change in the amount of different gasses or dust in the air could turn Earth into either a frigid ice planet or a scorching hot world.

Earth's one moon, Luna, has no protective atmosphere. If you faced the Sun, your front would be boiling hot while your back would be 270 below zero!

The moon is only about 1/4 Earth's diameter.

The dark spots on the moon were caused long ago when meteorites collided with the moon. The impacts melted huge amounts of rock that flowed like lava, and later hardened.

The moon is covered with mountains, valleys, and craters. It has more craters than the Earth because there is no wind or water to wear them away. Features on the moon, including the footprints left by the Apollo astronauts, last for millions of years.

For more information about our planet, its moon, and its motions through space, see the Morehead Planetarium show Earth, Moon, and Sun and the many accompanying activities and links.