Question

Moon has no atmosphere because

• A. it is a satellite of earth
• B. it does not have population
• C. it is colder then earth
• D. r.m.s velocity of all the gases is more than the escape velocity from its surface

Answer 1

The correct option is D r.m.s velocity of all the gases is more than the escape velocity from its surface

The size of moon compared to earth is extremely small and thus its gravitational acceleration is very small ($1.62m{s}^{-2}$). This pull results in very small escape velocity from its surface, which is even smaller than the r.m.s velocity from its surface, which is even smaller than the r.m.s velocity of all the gases. Thus moon has no atmosphere.