TUCSON, USA, July 31, 2026 - Pluto's atmosphere may be beginning to freeze out as the dwarf planet travels away from the Sun, according to a team led by Amanda Sickafoose of the Planetary Science Institute.^[1][2] The team found that Pluto's atmospheric pressure stayed constant from 2015 to mid-2021, then dropped 16% between mid-2021 and July 2023.^[3][4] The drop was measured in the lower atmosphere.^[5] The findings were published in the Planetary Science Journal.^[6] To track the atmosphere, the scientists used stellar occultations, the moments when Pluto passes in front of a distant star.^[7] They observed 10 occultations starting in 2017,^[8] though only four of them were seen from more than one location on Earth.^[9] The research suggests Pluto's atmosphere may be starting to collapse.^[10] Astronomers first detected that atmosphere in 1988,^[11] and NASA's New Horizons spacecraft flew past Pluto in 2015.^[12] Pluto's air is mostly nitrogen, with methane and carbon monoxide.^[13] The dwarf planet is still moving away from the Sun^[14] and will not stop doing so until 2114.^[15] It takes 248 years to complete one orbit.^[16] The next good opportunity to observe a Pluto occultation comes in 2027.^[17] Space Nugget. On small, icy worlds far from the Sun, an atmosphere can be fed by surface ice turning into gas. As such a world drifts farther out and its surface cools, more of that gas freezes back onto the ground as frost, and the atmosphere thins. A stellar occultation lets astronomers weigh a distant atmosphere from Earth: as a world slides in front of a star, the way the starlight fades and returns reveals how dense the gas is at different heights.