NASA’s New Horizons spacecraft has revealed possible evidence of recently flowing liquid nitrogen on Pluto, suggesting that nitrogen may be rising from beneath the dwarf planet’s vast Sputnik Planitia glacier.
This Pluto mosaic was created from images captured by NASA’s New Horizons spacecraft on July 14, 2015, from a distance of 49,700 miles (80,000 km). The view looks northeast across the dark, cratered Cthulhu Regio toward Sputnik Planitia, the bright, smooth nitrogen-ice plain that forms the western lobe of Pluto’s heart-shaped Tombaugh Regio. Image credit: S.A. Stern et al.
Sputnik Planitia is a nitrogen-ice-filled basin measuring approximately 1,200 by 2,000 km (746 by 1,243 miles). The enormous glacier occupies the western lobe of Tombaugh Regio, Pluto’s iconic heart-shaped region.
New Horizons images from the spacecraft’s 2015 flyby show dark, narrow streaks and broader dark patches along the boundaries of Sputnik Planitia’s polygonal convection cells. According to the researchers, these features may record the movement of liquid nitrogen across the glacier’s surface.
The patterns resemble features seen on Earth’s ice sheets, where meltwater can darken the ice by enlarging ice grains or depositing dark impurities. On Pluto, however, solar heating and other conventional processes appear too weak or diffuse to create such sharply defined features.
“The surface of Sputnik Planitia is quite young, probably less than one million years based on modeling of the surface overturn, and thus these features that we are looking at must have formed since then,” said Southwest Research Institute principal scientist Dr. Kelsi Singer.
“Pluto has many unique terrains seen nowhere else in the Solar System, and this area of Sputnik Planitia is one of them.”
“Its surface provides a different set of conditions compared to what we are used to on Earth, and exploring that allows us to better understand how materials behave in environments that are difficult to produce on Earth.”
Pluto’s northern Sputnik Planitia glacier is shown in a color mosaic created from NASA’s New Horizons imagery. The red box indicates the region containing dark features that may have formed when liquid nitrogen from basal melting reached the glacier’s surface. Image credit: NASA / Johns Hopkins APL / SwRI.
The researchers propose that heat from Pluto’s interior melts nitrogen ice beneath Sputnik Planitia. The liquid nitrogen could accumulate in underground reservoirs before rising through narrow fractures in a process similar to volcanic dike systems on Earth.
Liquid nitrogen is less dense than the surrounding solid nitrogen ice, allowing it to rise buoyantly toward the surface. Once it reaches the glacier, the liquid may emerge near the centers of convection cells, flow toward their edges and eventually refreeze, leaving behind the darkened surface patterns observed by New Horizons.
Modeling suggests that these events would need to occur in brief, powerful pulses. Each episode could release approximately 100,000 to 1 million m3 of liquid nitrogen over several hours to a few days. A slow, continuous supply of underground meltwater would not be sufficient to produce the observed surface flows.
“Pluto never stops surprising us,” said New Horizons principal investigator Dr. Alan Stern of the Southwest Research Institute.
“In addition to suggesting that liquids have recently expressed themselves on Pluto’s surface, this result also suggests a new kind of time-variable feature on Pluto.”
If confirmed, the proposed nitrogen flows could help scientists understand how liquids move through the icy crusts of other outer Solar System bodies. Similar processes may occur on Neptune’s moon Triton, where geysers have puzzled researchers since Voyager 2 observed them during its 1989 flyby. The distant dwarf planet Eris may also be a candidate because it appears to contain thick deposits of nitrogen ice.
“We point out that Eris could be a good candidate to also display evidence for basal melt and/or liquid flows to its surface,” the researchers said.
“Presently, no other Kuiper Belt dwarf planet has shown evidence for nitrogen ice on its surface, but if such discoveries are later made, the mechanism we have described here might also be operating.”
“Of course, for both Eris and dwarf planets where deep nitrogen reservoirs may be discovered in the future, evidence for this phenomenology would have to await high-resolution mapping akin to what has been accomplished on Pluto.”
A paper describing the findings was published July 31 in the Planetary Science Journal.
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S.A. Stern et al. 2026. Evidence for Possible N2 Basal Flow beneath Pluto’s Northern Sputnik Planitia. Planet. Sci. J 7, 185; doi: 10.3847/PSJ/ae7e85
Source: www.sci.news