Charon
Charon is the largest moon of the dwarf planet Pluto. It is technically the largest known moon relative to its parent planet in our solar system. But because Pluto is a dwarf planet, our own moon is still cited as the largest natural satellite. This mysterious and distant world was discovered in 1978. One of its defining geological features is Mordor Macula, a large reddish area near the moon's north pole named after the black land called Mordor in J.R.R. Tolkien's 'The Lord of the Rings.' Image: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Alex Parker.