Question

at moon there is no atmosphere because

Answer 1

The moon has insufficient gravity to return as atmosphere

Answer 2

Moon has no atmosphere because the value of acceleration due to gravity ‘g’ on the surface of moon is small. Therefore, the value of escape velocity on the surface of moon is small. The value of r.m.s. velocity of the molecules of different gases is much above the value of escape velocity on moon. That is why all the molecules of gases escaped and there is no atmosphere on moon.