Pluto was discovered on February. 18, 1930

76 years later we sent our first mission to Pluto called the New Horizons

Thanks to New Horizons we know that Pluto is 2/3 Rock and 1/3 ice

When Pluto revolves around the sun the ices vaporize causing a temporary atmosphere

http://www.nasa.gov/audience/forstudents/k-4/stories/nasa-knows/what-is-pluto-k4.html

http://coolcosmos.ipac.caltech.edu/ask/164-Does-Pluto-have-an-atmosphere-

http://www.history.com/this-day-in-history/pluto-discovered