Why is there no moon to the Earth atmosphere ?

Why is there no moon to the Earth atmosphere ?Arab scientific journal .. VII .. space questions......................The Earth's moon a thin layer of gases surrounding it, but they do not live up to be the envelope air Kalmtaref it , due to the gravitational field of the weak and very high temperature , which makes the gas molecules surrounding the moon dispersed in outer space away from him , in order to be a planet or moon that atmosphere , must be the average speed of the movement of gas molecules consisting of the cover less than one-sixth of the actual speed necessary to escape from the field of attractiveness , such as the planet Earth , which has a strong gravitational field and the estimated speed of escape from the attractiveness of 25,000 miles per hour . But Moon , who eluting quarter the size of the land it has gravity field is very weak and the speed of escape does not exceed 5,300 miles per hour , with an average temperature of 250 degrees Fahrenheit ( 121 degrees Celsius ) , which raises the speed of the gas molecules surrounding it in order to easily reach 883 mph at any one-sixth the speed of escape from the appeal , so the gas molecules surrounding a satellite earth which are mostly of hydrogen and helium dispersed in space away from him , in contrast, satellites such as Titan 's Saturn has an atmosphere a thickness of ten times as much as the thickness of the Earth's atmosphere , this is due to the sheer size of the moon and low temperature -290 degrees Fahrenheit ( -179 degrees Celsius ) .