There's a misunderstanding in your question. While Pluto does indeed have moons, including Nix, Nix itself does not have an atmosphere.

Here's why:

* Size and Gravity: Nix is relatively small (about 42 km in diameter) and has weak gravity. This makes it difficult for it to retain an atmosphere.

* Temperature: The surface of Nix is extremely cold (around -230°C), further hindering the ability of any gases to stay on the surface.

Therefore, while Pluto has a thin atmosphere, its moons like Nix do not.