Does a aerial gas contribute to a planets gravity

It depends on where you are interested in knowing the "planet's gravity"

Remember, gravitational field is a LOCAL function.


Here on the surface, the atmosphere doesn't contribute to the gravity of Earth.

BUT...the atmosphere DOES contribute to the gravity of Earth that the moon experiences.


IT is a standard exercise in vector integral calculus to prove that ONLY mass contained within your Gaussian sphere contributes to the gravitational field, and to prove that it can be treated as a point mass.

Gravity due to an external spherical shell is ZERO for everywhere within it.

yes if you are outside the atmosphere.

not if you are on the surface.

yes the gravity of a planet depends on the entire mass of all its parts.