Layer 5: Exosphere
The fifth layer of the atmosphere, or outmost layer, is called the exosphere. This layer is between approximately 600 km to 10,000 km above the surface.
![](http://www.ei.lehigh.edu/learners/cc/atmosphere/exosphere.jpg)
This layer contains the fewest molecules within the Earth’s atmosphere. From the exosphere, molecules can escape into outer space. NASA’s Mercury MESSENGER spacecraft took this photo on a mission to observe the Earth’s exosphere.