JOAN CARTAN-HANSEN: The moon is the earth's only natural satellite. A satellite is an object that travels around another object. It takes the moon about 27 days and 8 hours to go around the earth.

The moon is about 238,000 miles away. That sounds like a lot but in terms of space that's pretty close.

Our next nearest neighbor is the planet Venus and that's 25 million miles away.

The moon is made of rock. From earth we can only see one side of the moon and it's always the same side. Its surface has thousands of craters. Craters are ring-shaped flatlands with wall around them.

A crater forms when a meteorite hits the surface of the moon. A meteorite is basically a piece of rock flying through space. There are also wider flat places on the surface of the moon and that's where humans first went.

Twelve men have walked on the moon as part of the Apollo space missions. This is what it looked and sounded like when Apollo 15 landed on the moon.

ASTRONAUT #1: You could land over here. There's the stuff, val. You're on your own.

ASTRONAUT #2: Starting down, starting down.

ASTRONAUT #1: Okay. Very good. Looking great. 60 seconds. 40 feet. 3 feet per second. Looking great. 20 feet. 3 feet per second. Contact! We are on the surface. Okay. We made a good landing.

ASTRONAUT #2: Roger.

JOAN: Here, two astronauts - Alan Shepherd and Edgar Mitchell - explored the moon's surface and collected moon rocks. Gravity or the force that holds you down on earth is much less on the moon - about one sixth as strong. You could still fall down but it's easier to bounce back up. There's no water or weather on the moon and there's no air and because there's no air the moon is totally silent.

The moon has a long day and a long night, each lasting about two weeks. it can get pretty hot and pretty cold on the moon. In the daytime the temperature rises to about 250 degrees fahrenheit. That's hotter than boiling water, and at night the moon gets icy cold - about 290 degrees below zero. Astronauts need special suits to protect them and to keep them the right temperature. They also carry tanks of air on their backs so they can breathe. With no air or water around the moon's surface has changed very little so scientists can learn lots about how it was formed.

These astronauts found something interesting when they explored part of the moon called fra mauro.

ASTRONAUT# 1: Visible from oh, about the armpits up right now. ASTRONAUT #2: Nothing like being up to your armpits in lunar dust.

JOAN: Not all of the moon's surface is that deep in moon dust. The apollo 15 astronauts also collected 173 pounds of moon rocks and brought them back to the scientists on earth to study. Scientists learn a lot about the moon by looking at its rocks. They discovered the moon is about the same age as the earth but the moon's soil and rocks are different than our planet's. For one thing, moon rocks contain no water unlike rocks here on earth. Apollo 17 was the last space ship to carry people to the moon in December of 1972. When the astronauts departed they left behind a falcon feather and a 4-leaf clover just to remind everybody of all the living things here on earth. Scientists want to go back to the moon to learn more, for the imprints of the solar system's history can be found on the moon.

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