Does the Moon have an atmosphere?
The moon may once have had an atmosphere. But due the low mass and consequently low gravity of the Moon, the atmosphere has slowly leaked out into space. At present, for all practical purposes, the Moon has no atmosphere.
Why is there no atmosphere on the Moon?
Every star, planet or moon exerts a gravitational force on objects on its surface. An object has to achieve a critical velocity to permanently leave the star, planet or moon. If the velocity of the star, planet or moon. If the velocity of the object is less than the escape velocity it will fall back to the surface. The escape velocity is 60 kmps on Jupiter hence the gas molecules in its atmosphere hardly escape from it. On earth, the escape velocity is 12 kmps, so which is insufficient to hold on to the gas molecules in its leaked into space. Generally an escape velocity of at least 3.5 kmps is necessary to retain the atmosphere. Mars with an escape velocity of 5 kmps also has an appreciable atmosphere and even changing seasons.
Why is the north-south direction on the Moon inverted as compared to that on Earth?
Generally astronomical maps are produced from images obtained through an astronomical telescope. Since these images are formed inverted, they can be used directly if the north-south direction is also inverted for convenience.
How do we denote north and south on Moon maps?
On a Moon map, the north is usually at the bottom and the south at the top. This is the opposite of the north-south representation on an Earth map.