Atmospheric Layers

Earth has five major atmospheric layers. You can think of each layer as a concentric 'shell' or sphere around the Earth. The molecules within each layer are bound to Earth by gravity, gradually grading into one another.

Earth has five atmospheric layers. From outermost to innermost, they are the Exosphere, Thermosphere, Mesosphere, Stratosphere, and Troposphere.

Exosphere

Earth's exosphere is the outermost layer, where the atmosphere meets outer space. It is extremely 'thin' in terms of the number of air molecules - this layer is so far from Earth's surface that Earth's gravitational pull is too weak to hold many molecules.

Thermosphere

The thermosphere is the hottest part of the atmosphere. It can reach up to 2200 degrees Fahrenheit (or 1204 degrees Celsius) because it is bombarded with the most intense amount of solar radiation. The thermosphere extends 600 km (372 miles) from Earth's surface. It is also where the Northern and Southern lights (auroroa borealis and aurora australis) occur.

Mesosphere

The mesosphere is the coldest part of the atmosphere, reaching -130 degrees Fahrenheit (-90 degrees Celsius) and reaching 85 km (53 miles) from the ground. Although much 'thinner' in terms of the number of air molecules than the troposphere or stratosphere, there is enough air density to cause debris to burn when it enters this layer. This where 'shooting stars' occur in the atmosphere - they are space rocks and debris burning up as they enter the mesosphere.

Stratosphere

The stratosphere is about 15-50 km (or about 9-30 miles) above Earth's surface. The stratosphere is also known as Earth's ozone layer due to a high concentration of ozone gas. The ozone layer plays an important function by absorbing most of the Sun's ultraviolet radiation. Most airplanes fly in the lower levels of the stratosphere - it is less dense (meaning, fewer air molecules), allowing planes to fly faster and expend less fuel.

Troposphere

The troposphere is the layer closest to Earth, roughly 8-15 km (or about 5-9 miles) from the ground. It is the layer that supports the biosphere. It's also the layer where almost all weather takes place - most clouds, water particles, and dust are within the troposphere. The troposphere is the final layer encountered by incoming solar radiation.