https://www.newscientist.com/article/2170151-pluto-is-not-a-planet-its-a-billion-comets-squished-together/

Pluto is chock full of nitrogen. Currently, it is found in gas form in Pluto’s tenuous atmosphere, and in solid form in giant glacier made of nitrogen-rich ice, called Sputnik Planitia, which is found in the left lobe of Pluto’s heart-shaped plain.

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