On the Moon there is no air to breathe. However, there is a very thin layer of gases on the surface that can almost be called an atmosphere. In fact, it could technically be considered an exosphere. In an exosphere, gases are so dispersed that they rarely collide with each other. Furthermore, in the Moon’s atmosphere there are only 100 molecules per cubic centimeter, while the Earth’s atmosphere has approximately 100 billion million molecules per cubic centimeter.
On the other hand, the total mass of these lunar gases is about 25,000 kilograms, about the same weight as a full dump truck. Every night, the low temperatures cause the atmosphere to lower to the ground, rising during the day by the solar wind. This shows that the lunar atmosphere is not a permanent atmosphere, but a concentration of particles dependent on the ex-lunar environment.
Composition of the atmosphere
Although the full composition of the lunar atmosphere is still unknown, helium and argon atoms have been detected, as well as traces of oxygen, methane, nitrogen, carbon monoxide and carbon dioxide. Also, ground spectrometers have detected sodium and potassium, while the Lunar Prospector (a space probe designed to study the Moon) found radioactive isotopes of radon and polonium.
Scientists have also found water molecules less than a millimeter thick that could survive on the lunar surface. Additionally, the impact of sunlight, solar wind, and surface-hitting micrometeorites can also release gases that were buried in the lunar soil, in a process called sputtering.
These gases fly into space or bounce off the lunar surface. Sputtering also explains how ice accumulates in lunar craters, as comets colliding with the Moon could leave some water molecules on the surface. For this reason, the polar craters on the Moon could host ice, especially those that are permanently in the shadow of the Sun.
