(a) there is no atmosphere on moon
(b) there is a fall in temperature with altitude
(a) There is no atmosphere on the moon because the gravitational force is small and the Vrms is the greater on the moon such that the escape velocity of the molecule is
greater than that of the air. Also, the distance between the moon and the sun is the same as the distance between the moon and the earth. Therefore, the rms speed of
the molecule increases such that it can be more than the escape velocity. Therefore, there is no atmosphere on the moon.
(b) There is a fall in temperature with altitude because at the higher altitude the gas molecules expand and there is a decrease in temperature as the expansion of gas
resulting in cooling of the surrounding. This results in an increase in the kinetic energy of the molecules. When the kinetic energy increases, temperature decreases.