Due to its extremely distant nature from the Sun, Pluto has an icy surface comprised of 98% nitrogen (N2) with small amounts of methane (CH4) and carbon monoxide (CO). Its surface temperature can drop to -223 degrees Celsius (-370 degrees Fahrenheit), freezing its thin atmosphere, having an atmospheric pressure, 1/100,000 of that on Earth.
Sometimes the atmosphere is in its gaseous form due to Pluto's highly eccentric orbit, making it even closer to the Sun than Neptune at times (its perihelion is 30 AU while its aphelion is 50 AU).
Although exact details of the planet's surface are still unknown, the Pluto planned to be launched in 2001, express will uncover much about the atmosphere and the surfaces of Pluto and its satellite.
Surface Composition of Pluto 
