There is no atmosphere on the moon because
The escape velocity of gas molecules is greater than their root mean square velocity.
Explanation for the correct option:
We know that the mass of the moon () = kg, the radius of the moon () = m, and
So the escape velocity of the moon is given as,
⇒
⇒ = km/s
There is no atmosphere on the moon because the escape velocity is less than the average square velocity of the gas molecules on the moon. Therefore, all gas molecules escape.
Hence, option (C) is correct.