Top: adopted Pluto units for modeling (white = N₂, gray = CH₄, black = H₂O/tholin). Bottom: map of Pluto created from images taken from June 27 to July 3 by the Long Range Reconnaissance Imager (LORRI) on New Horizons, combined with lower resolution color data from the spacecraft’s Ralph instrument⁷. Cthulhu Regio is the dark region covering ~30°E-160°E longitudes. Sputnik Planum is the southern part of the bright region immediately to the east (informal names are taken from Stern et al. 2015).