What is the composition of a gas giant's atmosphere?

[vanesch]

I have a silly question:

what do people understand by "the atmosphere of a gas giant" ?

Isn't most of the planet "all atmosphere", or how should one picture this ?

 

[russ_watters]

My first thought at seeing the title was exactly your interpretation: a gas giant is an atmosphere (for all intents and purposes). And if someone pressed beyond that, I'd go into more specifics about the solid(?) metal core and the high pressure (above the critical point) transition between liquid and gas.

 

[Nabeshin]

I think the reference "the atmosphere of a gas giant" refers specifically to those gasses present in the outer layers of the planet. Therefore, it is distinguished between the "surface" of a gas giant which may or may not be solid, but contains the heavier metals and other compounds not observed in the outer layers.