There is no atmosphere in its traditional sense on the Moon. So, there is no air, however there is an extremely light coat of gases, basically someone might call it an atmosphere. From the scientific point of view, it is rather exosphere.
The gas masses in the exosphere are so rarified that they almost don’t interact with each other. They simply follow the trajectory of the lunar surface, turning into different directions time after time. In order to provide understanding of how rare the atmosphere of the Moon is, let’s compare it to the Earth’s: at sea level our planet atmosphere has approximately 100 billion billion molecules per cm2, while the Moon’s – 100 molecules per cm3.
The total weight of lunar’s atmosphere doesn’t exceed 55,00 pounds. Every night there is a cold temperature on the Moon, which makes the gases heavier, and then in the morning when it gets warmer they are lifted by the solar wind. So, it is not the atmosphere we are used to, as it is too unexpected.
The lunar atmosphere has different components within. Apollo missions provided the information that there is Ar, He, O2, CH4(methane), N, CO, and CO2. The measurements got from our planet have indicated the sodium and potassium and the Lunar Prospector orbiter classified some radioactive isotopes of radon and polonium there. The fresh studies report that micro molecules of water could survive on the Moon as well.
The interesting thing is helium on the Moon, especially its origin. It might be of internal origin, forming after radioactive decay in rocks. Also, it might be present because of external reason like solar wind.
Moon’s atmosphere is majorly created by the interaction of internal gasses and following outgassing. Outgassing often leads to lunar quakes. As soon as gasses are released they are dissolved in the outer space, so continuous outgassing fills the lunar atmosphere with gas.
The influence from light, wind and space objects also greatly impact Moon’s soil, releasing gasses from the deeper parts of lunar surface. The gasses released either dissolve in the outer space or circulate over the orbit of lunar atmosphere. Water on the Moon could have been brought there by extraterrestrial objects like comets, and sputtering helped water molecules to be preserved. Especially, when such molecules gather in dark and cold craters, leading to ice formation. Ice on the Moon is also very controversial and disputable topic in the scientific community, which only sets goals for further explorations. In order to understand and go through lunar surface, people need to develop new equipment that is moon dust-proof.