Pluto's thin atmosphere probably is comprised of nitrogen, carbon monoxide and methane. The pressure is very small, being only a few microbars and is frozen during most of its orbit. However, when it is closest to the Sun, the atmosphere is in its gaseous state and may even be interacting with Charon. In the future, the Pluto Express mission will visit the planet at its perihelion, when the atmosphere is gas.
Atmosphere 
