Atmosphere is the air. Most planets and even some moons have atmospheres. It’s the gases and particles in the air surrounding the rock. The air in different places is very different. This chart shows the types and amounts of gases in Earth’s atmosphere.

We can’t really see atmosphere, but if you look at light pouring through a window maybe you’ll see little particles floating in the air. And of course, when you feel wind, you are feeling the atmosphere moving around you.

When we are breathing in, we are breathing in the atmosphere, which is mostly nitrogen, not oxygen. There is water vapor in our atmosphere as well. All this atmosphere reaches out from Earth about 100 kilometers.

Atmosphere is made up of matter, since it’s made of “stuff.” It has an actual mass. Outside of our atmosphere, out in space, there is no air. We call space a vacuum, or an absence of atmosphere.

Our air can be polluted with other gases, such as smoke. Gases and particles that get picked up in the atmosphere (think of a dust storm) get carried in the wind and travel to other areas.

The “other” gases in our atmosphere are very important. Carbon dioxide, which humans breathe out, absorbs radiation, which may sound bad, but it is one of the things that enables life to exist on earth. It absorbs infrared radiation, which may sound like a bad thing, but it means it keeps the Sun’s heat on earth so that when the sun goes down at night, we don’t freeze.

Some scientists are concerned that if too much carbon dioxide gets trapped in the atmosphere then the atmosphere will trap too much heat and Earth will get too hot.

Another gas in the atmosphere is ozone. There is a layer of the atmosphere called the ozone layer. Ozone is a molecule made up of three atoms. It absorbs another type of radiation, ultraviolet. It’s like Earth’s sunscreen. It protects Earth. People worry about losing ozone, which would also result in Earth getting too hot.

Images of Atmosphere

Blue light is scattered more than other wavelengths by the gases in the atmosphere, giving Earth a blue halo when seen from space.
Average amount of water vapor in the air
Space Shuttle Endeavour orbiting in the thermosphere. Because of the angle of the photo, it appears to straddle the stratosphere and mesosphere that actually lie more than 250 km below. The orange layer is the troposphere, which gives way to the whitish stratosphere and then the blue mesosphere.
The geomagnetic storms cause beautiful displays of aurora across the atmosphere.
Limb (edge) view of Earth’s atmosphere. Colors roughly denote the layers of the atmosphere.
This image shows the Moon at the center, with the limb of Earth near the bottom transitioning into the orange-colored troposphere. The troposphere ends abruptly at the tropopause, which appears in the image as the sharp boundary between the orange- and blue-colored atmosphere. The silvery-blue noctilucent clouds extend far above Earth’s troposphere.
Earth’s atmosphere backlit by the Sun in an eclipse observed from deep space on board Apollo 12 in 1969.