This is a drawing showing the composition of the interior of Pluto.
Image from: NASA

What Pluto & Charon are made of

Pluto's atmosphere is roughly 90% Nitrogen, and 10% other complex molecules such as methane. The composition of Pluto's atmosphere is very similar to the Earth's which is also 80% Nitrogen.

The complex molecules probably come from radiation, which forces new molecules to be created from the surface of Pluto.

Pluto's interior is primarily composed of water ice of different phases. The drawing shows a possible layout of the different phases of ice in Titan's interior. Titan is a moon of Saturn. In this respect, Pluto is very much like other icy moons.

Deep inside Pluto are to be found the more heavier, rocky elements such as silicates. These form the core of Pluto.

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