Pluto’s Atmosphere May Be Collapsing

Pluto orbits the Sun every 248 years, yet humans have known about it for less than half of that time. One peculiar aspect of Pluto is its atmosphere, a rare feature among objects beyond Neptune’s orbit. This atmosphere is primarily composed of nitrogen, along with traces of methane, carbon monoxide, and hydrocarbons. Pluto’s atmospheric pressure and composition undergo dramatic fluctuations as it experiences significant changes in sunlight due to its elliptical orbit around the Sun.

The first direct observation of Pluto’s atmosphere occurred in 1988, using a technique called stellar occultation. This method involves monitoring the starlight traveling through Pluto’s atmosphere, allowing scientists to measure its height, pressure, and other properties. In 2015, NASA’s New Horizons spacecraft visited Pluto, providing detailed images of its atmosphere and uncovering its complex structure. Since then, researchers have continued to track Pluto’s atmospheric changes through stellar occultations.

Amanda Sickafoose, a planetary scientist at the Planetary Science Institute, led a recent study that synthesized 30 years of Pluto occultation data, including 10 new observations from 2017 to 2023. The team reanalyzed the data to minimize discrepancies between different telescopes and methods, resulting in a more consistent dataset.

Their analysis revealed that Pluto’s upper atmosphere remained stable from 2015 to 2021, with pressure levels remaining relatively constant. However, the researchers observed a significant drop of 16% in the lower atmosphere’s pressure over the same period.

This decrease in pressure suggests that Pluto’s atmosphere may be beginning to collapse as it enters winter. As the colder temperatures cause nitrogen particles to condense, haze particles in the lower atmosphere precipitate as nitrogen snow. This phenomenon aligns with existing theories about the freezing and collapse of Pluto’s atmosphere during its prolonged winter season.

While a 16% pressure reduction may seem minor, it represents a rapid change occurring over just a few years, indicating that ice condensation is taking place on Pluto.