| A | B |
|---|
| atmosphere | the gases around a planet |
| condense | to make or become more closely packed together |
| gigantic | very big |
| hemisphere | one half of a globe |
| permafrost | a permanently frozen layer under the earth's surface |
| polar | related to the North or South Poles |
| solar system | the sun and everything that revolves around it |
| air pressure | the force of the air |
| axis | the line around which something, such as the earth turns |
| carbon dioxide | a colorless gas |
| dunes | a hill of sand formed by the wind |
| equator | an imaginary circle around the earth's middle |
| orbit | the path followed by one heavenly body traveling around another |
| tilt | to tip |
