Why Doesn't the Moon Have a Thick Atmosphere?

[sandhiya]

Homework Statement

why moon has no atmosphere?

Homework Equations

The Attempt at a Solution

 

[fluidistic]

I guess it has a small one.
Meanly because gases that form atmosphere are composed of molecules. And generally at ambiant temperature or so, they move with speed close to the escape speed of the Moon. Hence any (light or maybe even somewhat heavy) gas on Moon would tend to leave the Moon out.

 

[aerospaceut10]

Well, technically the moon does have an atmosphere, but just a very thin one. The moon doesn't have enough mass to retain an atmosphere as "thick" as ours as its a much smaller planet. Much like Mars...it's much bigger than the moon, but still smaller than the Earth, resulting in an atmosphere that is still thinner.