is there such thing as a exosphere
in the case of bodies with substantial atmospheres such as earth s atmosphere the exosphere is the uppermost layer where the atmosphere thins out and merges with interplanetary space it is located directly above the thermosphere several moons such as the moon and the galilean satellites of jupiter have exospheres without a denser atmosphere underneath referred to as a surface boundary exosphere here molecules are ejected on elliptic trajectories until they collide with the surface