Understanding Pluto: Studying the Dwarf Planet's Dark Side Reveals a Lot About its Atmosphere and Planetary Cycles

Almost all of the photographs of Pluto's unusually complex surface taken by NASA's New Horizons mission in 2015 were of the side illuminated by the sun. The dwarf planet's other hemisphere was cloaked in darkness. Some of it had not seen the sun in decades, such as the region near the south pole.