Scientists have uncovered evidence suggesting that liquid nitrogen might have flowed across Pluto’s surface in the recent past, according to a study led by the Southwest Research Institute (SwRI). Using data from NASA's New Horizons spacecraft, researchers found that dark features on Sputnik Planitia — Pluto’s massive heart-shaped glacier — may be caused by liquid nitrogen rising from beneath the ice. This research, published in the peer-reviewed Planetary Science Journal, adds to our understanding of Pluto's dynamic and icy landscape. Sputnik Planitia is a vast region of frozen nitrogen, larger than the combined area of Texas and Oklahoma. Images from New Horizons reveal that the glacier’s northern part contains large, city-sized convection cells separated by thin dark lines and broader, darker patches. A new analysis suggests these features may have been temporarily wet in the past, with liquid nitrogen rising from beneath the surface as the most likely source. To explore this idea, the SwRI-led team compared New Horizons images of Sputnik Planitia with images of Earth’s glaciers from NASA’s Landsat 9 satellite. On Earth, narrow dark markings appear where liquid water is present on top of ice and snow. Similar patterns on Pluto led researchers to propose that subsurface nitrogen could be melting and rising to the surface, creating the dark features seen in the images. Computer models suggest that nitrogen ice at the bottom of Sputnik Planitia — several kilometers deep — can melt and flow upward through narrow channels, much like lava or water moving through underground tubes. The study suggests that liquid nitrogen may still exist beneath Sputnik Planitia today or may have been present very recently. The surface of Sputnik Planitia is estimated to be less than one million years old, based on models of surface renewal. Dr. Kelsi Singer of SwRI noted that Pluto’s unique landscapes, such as those in Sputnik Planitia, offer a chance to study materials and processes that are difficult to replicate on Earth. While no clear evidence of similar liquid flows has been found elsewhere on Pluto, more than half of the dwarf planet remains unmapped at high resolution, leaving open the possibility of similar processes in other regions. These findings may also help explain geological activity elsewhere in the solar system, such as the geysers observed on Triton, Neptune's largest moon.