Earth

EARTH in space is compared to a blue marble covered with white swirls. The blue is ocean, of course. It covers 7l% of Earth’s surface, and it is made even bluer by the sky. The white swirls that blanket almost half the earth are clouds. Around the poles there is more white-the polar ice cap that covers everything, land and sea. All of these, the ice, clouds, and ocean, are made out of water.

Below the clouds, between the oceans, a space traveler can see solid land. These are the continents and they look unchanging but scientist have shown that they are all in motion. The continents and the oceans are both carried on the backs of giant, slowly moving pieces of crust called plates. They are still moving. How fast do they move? About as fast as your fingernails grow.

The careful space traveler would notice that the continents are not all the same color. There are brownish-yellow patches of desert, but there are also large areas of light and dark green. These are the regions covered by plant life: grasses, shrubs, and forests. There is also animal and human life here, too, but the traveler could not see it from out in space. No other planet in the Solar System is anything remotely like Earth.

The Earth’s blue atmosphere contains a gas that is rare elsewhere in the Solar System: oxygen! The carbon from the carbon dioxide has become part of every living thing on Earth. It’s the basic chemical building block of all life. And the oxygen is all around us. It makes up nearly 20% of the air we breathe. (The other 80% is mostly a gas called nitrogen). The oxygen was created by living things, plants and bacteria. These living things take in carbon dioxide from the air and use the sun’s energy to split it into carbon and oxygen.

moon_3x4.jpg (24974 bytes) Moon

The Earth has one moon which orbits the Earth. Next to the sun, the moon is the brightest object in the sky. Ancient people worshipped it as a god or a goddess.

Astronauts have walked on the moon. There is no air there, and that’s why they wear space suits. Most of the moon is covered with craters and mountains. There are also some patches called maria from the Latin word "seas" (even though the moon has no water).

The maria are really lava plains, huge flat regions covered with dark lava rock. The largest of the maria is called the Ocean of Storms.

Not much has happened to the moon since the maria were formed. A few more craters have been added. Then about 800 thousand years ago, a meteoroid smashed into the Ocean of Storms and raised the most easily seen crater on the moon. It is surrounded by rays of light rock that were splashed out of the crust by the impact. You can easily see it with binoculars. It is named Copernicus, in honor of the astronomer who first proposed that the earth and the planets went around the sun.