I thought I would check my figures and "our" bit of the atmosphere is only 10 miles thick and as you know - you can barely breath on Everest.
http://www.learner.org/exhibits/weather/atmosphere.html
The structure of the atmosphere
The atmosphere is made up of several layers: the troposphere, stratosphere, mesosphere, ionosphere, and exosphere. Closest to Earth is the troposphere. Most of the clouds you see in the sky are found in the troposphere, and this is the layer of the atmosphere we associate with weather. Extending up to 10 miles above Earth's surface, the troposphere contains a variety of gases: water vapor, carbon dioxide, methane, nitrous oxide, and others. These gases help retain heat, a portion of which is then radiated back to warm the surface of Earth.
Above the troposphere is the stratosphere, which includes the ozone layer. The stratosphere extends from about 10 to 30 miles above the surface of Earth. Ozone molecules, which are concentrated in this layer, absorb ultraviolet radiation from the Sun and protect us from its harmful effects.
Thirty to 50 miles above the surface is the mesosphere, the coldest part of the atmosphere. Above the mesosphere, in a layer called the ionosphere (also called the thermosphere), things start to heat up. Temperatures in the ionosphere, which extends about 50 to 180 miles from the surface of Earth, can reach up to several thousand degrees Fahrenheit. Beyond the ionosphere is the exosphere, which extends to roughly 500 miles above the surface of Earth. This is the outermost layer of the atmosphere, the transition zone into space.
