Is the element oxygen rare

Oxygen is actually considered to be the most common element in Earth's crust (by mass), and is believed to be one of the top 3 most common elements in the galaxy.

While we think of Oxygen being in the air we breathe. However, it binds to many other elements, and thus is very common.

Oxygen combines with Hydrogen to form Water.
Oxygen combines with Silicon to form Silicon Dioxide, very common in stones, as well as all the glass we have.
Aluminum, Iron, etc, are all found in oxides.


While there is very little atmospheric Oxygen on the Moon, it is also a key element in all of the moon rocks. So, if the moon is ever colonized, it is likely that the required oxygen could be recovered from moon rocks.