If the matter of the body wasn't disassembled during scanning and an identical copy could be created that would clearly be a second and separate instance of a person from the original. So this shows the newly created person is a separate instance. If the scanning is destructive it doesn't change anything, the first person is destroyed and a new, identical instance created, as above. Indistinguishable from the perspective of others but not the same continuous consciousness of the original. However the copy would insist it was of course.

Actually oxygen is rather abundant on the moon - 45% by weight of crustal rock apparently (http://www.lunarpedia.org/index.php?title=Oxygen)