Exosphere

The exosphere is the outermost layer of our atmosphere.

The exosphere is the highest layer of the atmosphere. It extends from the top of the thermosphere up to 10,000 kilometers.

Air atoms and molecules are constantly escaping to space from the exosphere.

The thermosphere is located above the mesosphere and below the exosphere.

"Scientists weren't even sure Dione would be big enough to hang on to an exosphere" ('Cassini Detects Hint of Fresh Air at Dione', , JPL, Mar. 02, 2012)