Pluto’s atmosphere is visible when the planet is backlit, as in this 2015 image from New Horizons, taken as it sped away from the dwarf planet into deeper space. Image via NASA/ Johns Hopkins/ SwRI.
Pluto’s atmosphere is disappearing
Distant Pluto has a highly elliptical orbit around the sun. The shape of its orbit brings Pluto closer to the sun than Neptune for about 20 years in every Plutonian “year” (248 Earth-years). Pluto was last closer than Neptune from 1979 to 1999. And, while it was still relatively close to Earth, scientists rushed to send a spacecraft to Pluto. In 2015, when the New Horizons spacecraft made its dramatic sweep past Pluto, data it returned to Earth suggested Pluto’s atmosphere was doubling in density every decade. But more recently, during a 2018 occultation of a star by Pluto – an event that backlit Pluto’s atmosphere – data suggested Pluto’s atmosphere was starting to decrease and would eventually vanish.
The scientists presented these results on October 4, 2021, at the 53rd annual DPS meeting. They said their new work confirms the idea that, as Pluto gets farther from the sun again in its highly elliptical orbit, its atmosphere is freezing ...