Titan which is smaller than mars has an atmosphere but mars is not able to maintain atmosphere. Even Luna doesn't have an atmosphere.
Apparent magnitude is a rather complex way to determine the brightness of a star. Quoting the introduction text from the linked to Wikipedia page: The apparent magnitude (m) of a celestial body is ...
Since the moon has gravity, it's almost impossible that there aren't some gasses trapped on the surface by the moon's gravity. Has any free-floating oxygen been found on the Moon? If so, in what ...