NASA's New Horizons finds evidence of recent liquid nitrogen flows on Pluto

When NASA's New Horizons spacecraft flew past Pluto in 2015 and 2016, it sent back images of a vast glacier called Sputnik Planitia—a frozen expanse larger than Texas and Oklahoma combined, made almost entirely of nitrogen ice. What caught scientists' attention were the dark markings scattered across its northern region: thin lines and broader patches that seemed to tell a story about movement, about something wet having touched the surface. For years, researchers had theorized that liquid once flowed on Pluto in the distant past. Now, a new analysis of those images suggests something more startling: that liquid may still be moving across Pluto's surface today, or at least has done so within the last million years.

The dark features on Sputnik Planitia bear an uncanny resemblance to patterns that appear on Earth's glaciers—specifically on Greenland's ice sheet—where liquid water sits on top of frozen ground and creates distinctive dark markings. When researchers at the Southwest Research Institute compared New Horizons images directly with NASA Landsat 9 photographs of Greenland, the parallel was striking enough to suggest a mechanism: subsurface liquid nitrogen, rising from beneath the glacier through cracks and fissures, wetting the frozen surface above. Liquid nitrogen cannot fall as rain on Pluto; the dwarf planet's temperature and atmospheric conditions make that impossible. But the evidence points to something happening from below.

Computer models developed by researchers at the SETI Institute offer a plausible explanation for how this could work. Nitrogen ice at the base of Sputnik Planitia, several kilometers down, can melt under pressure and heat. That liquid nitrogen could then rise through narrow channels—much like water moving through geyser tubes or lava tubes—pushed upward by buoyancy or pressure from deeper layers. Once it reaches the surface, the liquid could flow downhill across the glacier long enough to wet the surrounding ice and create the dark patterns that New Horizons observed. The surface of Sputnik Planitia itself is young, probably less than a million years old based on models of how the glacier overturns and refreshes itself, which means any features visible today must have formed relatively recently.

Dr. Alan Stern, the principal investigator for New Horizons and lead author of the research published in the Planetary Science Journal, described the finding as characteristic of Pluto's capacity to surprise. The discovery suggests not only that liquids have recently expressed themselves on Pluto's surface, but that the dwarf planet may harbor time-variable features—geological phenomena that change over periods we can actually measure and observe. Dr. Kelsi Singer, a co-author on the study, emphasized that Pluto's unique conditions offer a laboratory for understanding how materials behave in environments that are nearly impossible to recreate on Earth, where the physics of solid nitrogen under extreme stress and strain remains poorly understood.

The implications extend beyond Pluto itself. More than half of the dwarf planet has never been mapped at high resolution, leaving open the possibility that similar processes could be occurring in other regions. The same mechanism—melting and upward movement of subsurface liquid—may help explain activity observed elsewhere in the solar system. Neptune's largest moon, Triton, displayed geysers erupting from its surface when Voyager 2 flew past it decades ago. Scientists say additional high-resolution observations of Pluto and other bodies in the Kuiper Belt will be necessary to determine whether these processes are widespread in the distant solar system, or whether Sputnik Planitia represents something more singular: a window into geological activity happening right now, on a world we once thought was frozen solid.