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| The Nine-eyed MISR |
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Why do clouds and plumes of smoke look white? After all, clouds are made of water droplets, and water isn't white. Smoke is made mostly of carbon particles, and carbon certainly isn't white!
Clouds and plumes of smoke look white because they scatter sunlight. Notice the shadows under the clouds and the smoke plume in these pictures. The shadows are there because the water and smoke particles in the air have reflected some of the sunlight back into space. This sunlight never reaches the ground.
But when stuff burns, it isn't just particles that get pumped into the sky. When people burn gasoline in cars and trucks, or jet fuel in planes, or coal or oil in power generating plants, gases are also formed. These gases (carbon dioxide mostly) can trap some heat energy near Earth's surface and not let it escape into space at night. Thus, these gases may be causing Earth to get a little warmer each year. That is why these gases are called "greenhouse gases." They act like the glass roof of a greenhouse, letting in the warming rays of the sun and then trapping the heat inside. And this effect on Earth is what scientists mean when they talk about "global warming."
If people are the cause, this is not a good thing!
Photos by Barbara Gaitley, JPL |
| There are no easy answers up there in the sky! We need to learn a lot more in order to understand how our human activities may be causing unwanted changes on our home planet. |
| This is a picture of a spacecraft named after the planet it was made to study. The spacecraft is called Terra, which is another name for Earth. Terra was launched in December 1999. Terra carries five special instruments for observing Earth in different ways. |
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 One of the instruments is the Multi-angle Imaging SpectroRadiometer, or MISR ("Miser") for short. MISR is nine cameras in one, each pointing in a different direction. As MISR passes over an area, each camera gets a shot from its own angle. Seeing the same piece of Earth's surface or atmosphere from nine different angles tells scientists a lot more than seeing it from just one angle. |
| Here are some examples. Click on the small pictures to see bigger ones and to find out what they are. Some are 3-D images that you can see if you have a pair of red/blue 3-D glasses..
You can buy these at comic book stores or from sellers on the web.
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Four angles on the Appalachian Mountains in Eastern United States. |
| Delaware Bay, Chesapeake Bay, and the Appalachian Mountains. |
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Big Island of Hawaii, including a 3-D picture. |
| Hurricane Carlotta, including a 3-D picture. |
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San Cristobal Volcano, in Nicaragua, including a 3-D picture. |
Did you try the MISR Crossword Puzzle yet?
Make your own greenhouse gases from gumdrops.
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