Dark markings along the northern edge of Sputnik Planitia, the vast nitrogen-ice glacier that dominates one face of Pluto, are best explained by liquid nitrogen that recently reached the surface, according to a new analysis of data from NASA’s New Horizons spacecraft. The team, led by planetary scientist Alan Stern, says the finding suggests Pluto has stayed geologically active far longer than researchers assumed when the spacecraft flew past in 2015.
Sputnik Planitia is a glacier larger than Texas and Oklahoma combined, filling a heart-shaped basin on a world only about three-quarters as wide as the continental United States. Even at that scale, the features driving the new claim are subtle: faint dark streaks and diffuse patches clustered where New Horizons’ cameras had their sharpest view of the glacier’s edge during the flyby.
A basal melt reaching the surface
The mechanism the researchers describe starts well below the surface. Nitrogen ice at the base of the glacier, under pressure and heat rising from Pluto’s interior, melts into pockets of liquid that then push upward through narrow channels toward the surface, a process the team compares to lava tubes or geyser conduits on Earth before the liquid evaporates into Pluto’s thin atmosphere, according to the researchers’ account of the mechanism.
Kelsi Singer, a principal scientist at the Southwest Research Institute and a co-author of the study, said this stretch of Sputnik Planitia is geologically young — probably less than one million years old, based on models of how quickly the glacier’s ice overturns. “Pluto has many unique terrains seen nowhere else in the solar system,” Singer said, adding that its surface offers a set of conditions with no real parallel on Earth.
No spacecraft has returned to Pluto since. Every image behind the new claim was already sitting in New Horizons’ archived data, waiting for someone to look at that one stretch of the glacier closely enough.
Data from a decade-old flyby, still yielding new results
New Horizons has operated since its launch on January 19, 2006, according to the mission’s own page at the Johns Hopkins University Applied Physics Laboratory, which built and operates the spacecraft for NASA. It gathered the high-resolution imagery behind the new claim, captured with its Ralph and LORRI cameras, during its single close pass by Pluto in July 2015, and scientists have kept mining that same dataset for fresh discoveries a decade on.
NASA’s own summary of the discovery describes the dark features as resembling patterns on Earth’s glaciers where liquid seeping up from below has wetted the surface, according to the agency’s account of the study. Nitrogen rain is effectively ruled out at Pluto’s temperatures and atmospheric pressure, which is part of why the team argues the liquid must be rising from beneath the ice rather than falling onto it.
That distinction matters for how planetary scientists think about small, distant worlds generally. A body this cold and this far from the sun was long assumed to be geologically frozen in place, its surface shaped mostly by ancient impacts rather than ongoing internal activity. Sputnik Planitia already complicated that picture once, when New Horizons’ first close images showed a surface of city-sized polygon cells that pointed to slow convection inside the nitrogen ice, rather than a static ice sheet billions of years old. A liquid-nitrogen seep, if the new interpretation holds up, would add a second and much more dynamic process to that same patch of ground, and raise the question of whether comparable activity is hiding on other icy Kuiper Belt bodies that no spacecraft has ever visited closely enough to check.
Modeling a substance no lab can easily reproduce
Orkan Umurhan, a senior research scientist at the SETI Institute who led the computer modeling behind the proposed mechanism, said the results make a strong case for a much closer look at how solid nitrogen behaves under stress at extremely low temperatures, conditions that are difficult to reproduce in any laboratory on Earth. The team published its full analysis in the Planetary Science Journal on July 31, 2026, several weeks before NASA and the Southwest Research Institute publicized the result.
Stern, the mission’s principal investigator, described the discovery as a new kind of time-variable feature on Pluto, a phrase that captures how much the dwarf planet has kept upending the picture scientists drew of it right after the 2015 flyby. Sputnik Planitia’s surface was already known for its slow-churning convection cells; a liquid-nitrogen seep would add an entirely different kind of activity to that list.
Whether liquid nitrogen is still moving beneath Sputnik Planitia today, or did so only in a narrow window sometime within the glacier’s last million years, is a question the current dataset cannot settle. Stern’s team says answering it will likely require either a future spacecraft mission or far more sensitive telescope observations than are currently possible from Earth or lunar orbit.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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