We combine laboratory and Apollo observations to describe the sputtering of the lunar surface and the composition of the ejecta with special reference to O. The atmospheric inventory appears to be dominated by micrometeorite vaporization of lunar grains. Sputtering effects are observable in the local plasma due to ion ejection, in the extended atmospheric through energetic neutral ejection, and grain surfaces through the chemical fractionation of the redeposited sputter-ejecta. Ionization of the micrometeorite-vapor also contributes to the local plasma. ¿American Geophysical Union 1991