Scientists may have detected the first signs that Pluto’s thin atmosphere is beginning to collapse as the dwarf planet slowly travels farther from the sun. When this happens, the star’s light passes through Pluto’s atmosphere before disappearing behind the dwarf planet. By carefully measuring how the starlight fades and then reappears, scientists can determine the structure and pressure of Pluto’s atmosphere. Pluto’s atmosphere contains tiny haze particles formed when sunlight triggers chemical reactions involving methane and other carbon-containing gases. If Pluto’s atmosphere continues losing pressure, scientists expect these hazes to become thinner and gradually settle closer to the surface as the gases freeze out.