As Pluto moves closer to the Sun, ices on its surface warm slightly and sublime ("evaporate" from solid to gas) to form a thin, mostly nitrogen atmosphere. As it moves away from the Sun, the gases cool and refreeze. The atmosphere may vanish as Pluto moves farther from the Sun.
Many Hubble Space Telescope images were combined to create these views of Pluto's surface. Distinct geologic features can't be seen, but the colors may indicate different surface compositions. When compared with earlier observations, these images suggest Pluto's face may change through time, perhaps due to seasonal changes in surface ices.