In this lesson, you’ll learn about the layers of the atmosphere and what’s special about each layer. You’ll also learn how the conditions change as you move up from the ground into outer space.

## The Atmosphere

The atmosphere is the layer of gas that surrounds the Earth, including the air that you breathe. The atmosphere might be invisible, but there’s a lot going on up there! It even has different layers, starting on the ground and stretching all the way up into space. Let’s explore each layer on a journey to space.

## The Lower Atmosphere

Imagine you’re an astronaut taking off in a space shuttle. When you’re on the ground walking to your ship, you’re breathing in air from the lowest layer of the atmosphere. This layer is called the troposphere. Now hop in the space shuttle and get ready for your trip to space.

3… 2… 1… Takeoff! Your ship leaves the ground and starts rising through the troposphere. The troposphere is where weather happens. As you rise up through the troposphere, you might see clouds, rain, and other weather patterns. Most clouds stay inside the troposphere. If a cloud stretches up to the top of the troposphere, it gets squished and starts spreading outwards instead of reaching up any higher.

The troposphere stretches up 4 to 12 miles from the Earth’s surface. In the troposphere, the higher up you get, the colder the temperature gets.

## The Middle Atmosphere

After the troposphere, you keep going up in your space shuttle into the middle atmosphere. The middle atmosphere has two layers: the stratosphere and the mesosphere.

The stratosphere is right above the troposphere. It’s 19-27 miles thick. From here on up, it’s lucky you’re in a space shuttle, because the air would be too thin to breathe otherwise. The stratosphere has different gases than the troposphere. Because of the different gases, the air in the stratosphere gets warmer as you go higher up. As you fly through the stratosphere in your space shuttle, you might see some balloons. These are weather balloons. They take pictures of clouds and other weather from above.

The next layer up is the mesosphere. The mesosphere is around 22 miles thick. Watch out for meteors as your space shuttle flies through this layer! Whenever a meteor shower hits the Earth, the mesosphere is where the meteors burn up and turn into shooting stars. In the mesosphere, the temperature switches around again and starts getting colder as you get higher up.

The top of the mesosphere is around 53 miles above the ground. If you drove in a car on a highway, it would take you almost an hour to drive 53 miles.

## The Upper Atmosphere

As your space shuttle keeps heading up into the upper atmosphere, there are two more layers left: the thermosphere and the exosphere.

The thermosphere is about 322 miles thick. That would take around five and a half hours to drive on a highway. In the thermosphere, the temperature gets higher as you go higher up.

Finally, the exosphere is the top layer of the atmosphere. Up here, the air is very thin. The upper edge of the exosphere stretches up into space. Once you’ve flown up through the exosphere, you’re in space!

## Lesson Summary

The atmosphere is the circle of gas that surrounds planet Earth, and it has five layers. From the ground up, they are the troposphere, mesosphere, stratosphere, thermosphere, and exosphere. You can remember them by their initials: Tr, M, S, Th, E (that also stands for Trolls are More Smelly Than Elves).