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The Atmosphere

Earth's atmosphere as seen from space.

Earth's atmosphere as seen from space.

     The Earth is surrounded by gases called “the atmosphere”. Earth’s atmosphere is mostly made up of nitrogen and oxygen. There are also some other gases in the atmosphere such as methane, helium, neon, krypton, and the carbon dioxide we exhale or breathe out. Nitrogen and oxygen make up about 99% of the air in the atmosphere. All of the other gases combined make up about 1% of the air in the atmosphere.

Our atmosphere is made up of Nitrogen and Oxygen. We breathe oxygen.

Our atmosphere is made up of Nitrogen and Oxygen. We breathe oxygen.

     The atmosphere allows people to live on Earth because it does several important jobs. The atmosphere blocks some of the Sun’s heat, so the Earth doesn’t get too hot. It also traps some heat, so the Earth doesn’t get too cold. On the moon, which doesn’t have an atmosphere, it is boiling hot when the moon faces the Sun and freezing when the moon faces away from the Sun. Our atmosphere protects the Earth from these extreme temperatures.

People wear sunscreen to protect their skin from the dangerous radiation from the Sun.

People wear sunscreen to protect their skin from the dangerous radiation from the Sun.

     The atmosphere also blocks radiation from the Sun. This protects the Earth from some of the dangerous rays that could harm people. For example, ultraviolet rays can cause cancer. The atmosphere blocks a lot of the ultraviolet rays, but people should still wear sunscreen to protect themselves.

     The atmosphere is not the same everywhere. There are layers in the atmosphere. Each of these layers has a different name and unique properties.

All weather happens in the troposphere.

All weather happens in the troposphere.

The moon doesn't have an atmosphere.

The moon doesn't have an atmosphere.

     The lowest layer in the atmosphere is called the troposphere. The troposphere is all around us. Weather only occurs in the troposphere. This is because 99% of the water vapor in the entire atmosphere is located in the troposphere. Also, the air mixes a lot in the troposphere which causes different kinds of weather. The air mixes because warm air rises and cool air falls. The air around us is always rising or falling.

     The second layer in the atmosphere is called the stratosphere. The ozone layer is located in the stratosphere. The ozone layer absorbs a lot of the radiation from the Sun, so it doesn’t reach the surface of the Earth. In the troposphere the air temperature gets cooler as you move up. It is colder on top of a mountain than it is in a valley. In the stratosphere, the opposite is true. The higher you move in the stratosphere, the warmer the air temperature gets. This is because the air molecules absorb so much energy from the Sun. This energy is turned into heat. The higher molecules absorb more energy, and they are hotter. As a result, the air doesn’t mix as much in the stratosphere as it does in the troposphere.

Airplanes often fly at the top of the troposphere.

Airplanes often fly at the top of the troposphere.

     The next layer is called the mesosphere. We don’t know very much about the mesosphere because it is too high for airplanes or weather balloons to reach, but it is too low for a satellite. Scientists can send rockets through the mesosphere, but these trips are short.

Scientists can send weather balloons into the sky to study the atmosphere, but weather balloons can't reach the mesosphere.

Scientists can send weather balloons into the sky to study the atmosphere, but weather balloons can't reach the mesosphere.

     We do know that meteorites burn up in the mesosphere. The meteorites leave behind iron and other metals. These particles are abundant in the mesosphere.

The International Space Station travels through the thermosphere.

The International Space Station travels through the thermosphere.

     The next layer of the atmosphere is the thermosphere. The thermosphere is the hottest layer of the atmosphere. Temperatures can reach 2000° C because the particles in the thermosphere absorb so much of the Sun’s radiation. However, the thermosphere feels very cold because only particles can hold head. Empty space is very cold. There aren’t very many air particles in the thermosphere, so being outside in the thermosphere feels like being in outer space. Many satellites and the International Space Station orbit the Earth within the thermosphere.

     The final layer of the atmosphere is the exosphere. The exosphere begins at the edge of the thermosphere and then fades into outer space. There are almost no air particles in the exosphere. Some scientists even argue that the exosphere should be considered part of outer space instead of part of the Earth’s atmosphere.

While other planets have atmospheres, we don't know of any other planet in our solar system that supports life.

While other planets have atmospheres, we don't know of any other planet in our solar system that supports life.

     Earth is not the only planet in our solar system with an atmosphere, but ours is the only atmosphere we know of that can sustain life. The gas giants of our solar system, Jupiter, Saturn, Uranus, and Neptune, all have thick atmospheres filled with gases such as hydrogen, helium, methane, and ammonia. Mars and Venus both have atmospheres made up primarily of carbon dioxide. However, Venus’ atmosphere is incredibly thick, and Mars’ atmosphere is thin.

     A thick atmosphere of carbon dioxide makes the temperature on Venus very high, about 800 degrees Fahrenheit. Mars’ thin atmosphere makes the planet very cold, around -67 degrees Fahrenheit. You can see why Earth’s atmosphere is so important to sustaining life!

     Earth’s atmosphere provides people with air to breathe, the right temperature to live, and protection from dangerous radiation from the Sun. Without the atmosphere, we could not live on Earth. Scientists are studying our atmosphere and the atmospheres of other planets to learn more about what makes a planet habitable. This information may someday help humans live on another planet.