Example CRs on Pluto. The features indicated by red arrows, called CRs, change in appearance among these three images of part of Pluto’s Sputnik Planitia. The CRs are dark relative to their surrounding terrain at low solar phase angle (left panel, 25°), barely/not apparent at intermediate solar phase angle (middle panel, 47°), and brighter than their surrounding terrain at high solar phase angle (right panel, 151°). All three images were acquired within a period of ≈2 hr. The CRs’ changes of appearance are more likely due to the changes of solar phase angle than temporal change on Pluto. Other changes of appearance are also attributed to the changes of imaging geometry. S, NW, and NE indicate the southernmost, northwesternmost, and northeasternmost example CRs, respectively.