Question

There is no atmosphere on the moon because

• A. it is closer to the earth
• B. it revolves around the earth
• C. it gets light from the sun
• D. the escape velocity of gas molecules is less than their root mean square velocity here

Answer 1

The correct option is D the escape velocity of gas molecules is less than their root mean square velocity here

On moon, due to the lower $g$, the escape velocity of gas molecule is less than their root mean square velocity. Thus moon has no atmosphere.