In 1985 it was discovered that Pluto has an atmosphere, albeit a very tenuous one. Pluto's atmosphere arises only when it approaches closer to the Sun during its highly eccentric, 248 earth years long orbit. The atmosphere likely consists of nitrogen, methane, and carbon monoxide, which sublimate directly from Pluto's frozen surface. As Pluto's orbit moves it away from the Sun, these gases are believed to slowly precipitate back to Pluto's surface.