Planetary researchers examining images from NASA’s New Horizons spacecraft have uncovered potential evidence indicating that liquid nitrogen may continue to seep from below Pluto’s majestic glacier, Sputnik Planitia. This marks the first instance of suggested recent liquid flow on Pluto’s surface.
This mosaic of Pluto was created from New Horizons LORRI images captured on July 14, 2015, from a distance of approximately 49,700 miles (80,000 km). The image looks northeast over Cthulhu Regio toward the expansive, icy plains known as Sputnik Planum. Image credit: S.A. Stern et al.
Sputnik Planitia, a vast nitrogen-ice-filled basin measuring 1,200 x 2,000 km (746 x 1,243 miles), resides in the western lobe of Tombaugh Regio, the iconic heart-shaped feature of Pluto.
The imagery from New Horizons’ 2015 flyby reveals a complex network of dark streaks and softer dark patches outlining the glacier’s polygonal convection cells.
This pattern closely mimics the processes observed on Earth’s ice sheets, where meltwater causes the surface to darken either by enlarging ice grains or depositing dark impurities.
Given that conventional explanations like solar heating are insufficient to create such distinct features on Pluto, liquid nitrogen emerges as the most plausible explanation.
“The surface of Sputnik Planitia is relatively young, probably less than one million years old based on surface modeling, suggesting that these features formed recently,” stated Dr. Kelsi Singer, a principal scientist at the Southwest Research Institute.
“Pluto’s diverse terrains are unlike anything else in the Solar System, and Sputnik Planitia is a prime example,” she added.
“Studying this region allows us to explore conditions that we cannot replicate on Earth, enhancing our understanding of material behavior in unique environments.”
This color mosaic showcases Pluto’s northern Sputnik Planitia glacier, highlighting the regions with dark features attributed to liquid nitrogen wetting the glacier from below. Image credit: NASA / Johns Hopkins APL / SwRI.
The researchers propose that heat from Pluto’s interior causes nitrogen ice at the base of the glacier to melt, forming reservoirs that erupt through narrow fractures, akin to volcanic dike systems on Earth.
As liquid nitrogen is less dense than the surrounding solid ice, it would rise, reaching the surface at the centers of the convection cells before spreading and refreezing, leading to surface darkening.
The team calculates that such eruptions must occur in short, intense pulses, releasing approximately 100,000 to 1 million m³ of liquid over hours to days, since the underground melt is too gradual to explain the observed flows alone.
“Pluto never ceases to amaze,” remarked Dr. Alan Stern, principal investigator for New Horizons and associate at the Southwest Research Institute.
“This discovery not only suggests that liquid dynamics are occurring on Pluto’s surface but also introduces a new type of time-variable feature for the planet.”
Similar processes might also be happening elsewhere in the outer Solar System, including on Neptune’s moon Triton, which has baffled scientists with its geysers since the Voyager 2 flyby in 1989, and potentially on the distant dwarf planet Eris, where thick deposits of nitrogen ice have also been identified.
“Eris could serve as a compelling candidate for basal melt and liquid flow evidence,” the researchers noted.
“Currently, no other Kuiper Belt dwarf planet has shown nitrogen ice on its surface; however, future discoveries could reveal similar mechanisms at play.”
“To confirm these phenomena for Eris and other dwarf planets with potential deep nitrogen reservoirs, high-resolution mapping akin to Pluto’s would be necessary.”
A study detailing these findings was published on 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
