Liquid nitrogen may have recently flowed across Pluto's heart-shaped glacier

Pluto’s hazy atmosphere may be beginning to collapse as it drifts further from the sun, according to a study led by planetary scientist Amanda Sickafoose. The research, published in the Planetary Science Journal, suggests that the dwarf planet has already started losing atmospheric pressure, marking a possible shift toward a more tenuous existence in the cold reaches of the outer solar system. This change comes as Pluto continues its elliptical orbit, moving away from the sun and into increasingly distant regions of space. It will not return to its closest approach until 2114, making this a unique phase in its history. The findings stem from observations of Pluto’s atmosphere conducted over several years, using a method known as stellar occultation. During these events, Pluto passes in front of a distant star, casting a shadow on Earth. By tracking how starlight dims and brightens as it passes through Pluto’s atmosphere, scientists can infer details about the composition and density of the atmosphere. Between 2017 and 2023, Sickafoose and her team recorded 10 such occultations, analyzing the subtle shifts in light to understand how Pluto’s atmosphere might be evolving. From 2015 to early 2021, the team noted that Pluto’s atmospheric pressure remained relatively stable. However, starting around mid-2021, a noticeable decline began. By July 2023, the overall atmospheric pressure had dropped by approximately 16%, indicating a gradual thinning of the atmosphere. The researchers modeled their findings based on data collected during the 2015 New Horizons flyby, which revealed a hazy atmosphere composed of complex organic molecules. The current decrease in pressure aligns with predictions that Pluto’s atmosphere would become less dense as it moves farther from the sun. Observing these occultations requires careful planning, as the shadow paths can span vast distances, sometimes crossing oceans or remote landscapes. To maximize the chances of accurate measurements, the team mapped potential shadow routes and coordinated with observatories located along these paths. Four of the 10 occultations were successfully observed from multiple sites, allowing for cross-checking of data and improved accuracy. Observers stationed closer to the path could verify results from distant locations, providing a more complete picture of Pluto’s atmospheric structure. The process involves measuring the intensity of starlight before, during, and after the occultation. As Pluto’s atmosphere bends and scatters the starlight, the brightness of the star decreases gradually, creating a characteristic dimming effect. When the star is fully obscured by Pluto, the light drops almost entirely, revealing the presence of the dwarf planet itself. These light curves help scientists determine the thickness and composition of Pluto’s atmosphere, offering insights into how it might change over time. As Pluto continues its journey beyond Neptune, its atmosphere will likely undergo further transformations. With no active spacecraft currently monitoring the dwarf planet, researchers rely on these indirect methods to track its evolution. The upcoming years will be critical in understanding whether the atmospheric loss is a temporary fluctuation or the start of a long-term trend. Future observations will need to continue mapping these occultations and refining models to predict how Pluto’s environment might evolve in the decades ahead. For now, the data suggests that Pluto is on the brink of a significant atmospheric transition.