Your class looks at a picture projected onto a screen in your classroom. The teacher asks everyone to guess what is shown in the picture.

Many questions are heard. Is it a real picture? Does it show something we have seen before? What is the object in the picture used for?

The teacher answers, "Yes, it is a picture of a real object taken by a camera. Yes, you have seen this object many times before. People use the object to become intelligent."

You look closely at the picture. You can see bright colors --reds and blues. The picture has many dark areas. A large, dark object has a rectangular shape. It looks like someone took this picture from an airplane. You share this information with your teacher.

The teacher smiles at you. She tells the class that this picture was taken by a satellite in space above the Earth. Your school is in the picture.

A Landsat satellite took the pictures. The satellite was over 700 miles (1,126 kilometers) above the school when the picture was taken. The red areas in the picture show plants. Red is a color that is easier to see in pictures than natural green. Blue areas show water. Man-made objects like schools are usually gray or black.

Satellites used by NASA study Earth with special cameras that measure waves our eyes cannot see. They can see gases and particles in the atmosphere that are invisible to our eyes.

One satellite is called Terra - Latin for "land." The Terra satellite carries six instruments, one of which can tell that temperatures in one land area are warmer than temperatures in another area. These temperature differences appear as different colors in a picture. This camera also helps geologists study volcanoes. If magma is getting close to the surface of a volcano, the ground in one area looks warmer to Terra and lets geologists know magma is below the volcano when they cannot actually see the magma.

Aqua - Latin for "water" - is another ESE satellite. Aqua carries instruments that help scientists study the atmosphere. One of the elements in the atmosphere that Aqua studies, is aerosols. The Earth can become cooler if there are too many aerosols in the atmosphere. This condition would help block sunlight from reaching Earth's surface. We can't see the tiny aerosol particles but Aqua can!

Terra and Aqua are 2 of about 20 satellites used by NASA to study Earth's land, water, and air. NASA understands how important it is to forecast changes on Earth. These changes can affect animals, plants, and people. It is good to know that NASA uses satellites to help us understand how to keep Earth healthy. After all, Earth really is the only planet on which we can easily live.