Inside Dwarf Planet Pluto
Credit: Karl Tate, SPACE.com
Discovered in 1930 and once considered a major planet, Pluto was reclassified as a dwarf planet in 2006.  Pluto is sometimes
considered a double planet system because its largest  moon, Charon, is about half Pluto’s size. It takes Pluto 248 years to orbit the Sun.
 
A temporary nitrogen-methane atmosphere forms when Pluto's surface ice thaws, when Pluto is closest to the sun.
 
Pluto’s rocky core is probably surrounded by a mantle of ice, with methane and nitrogen frost coating its surface. 
 

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