In 2015, NASA's New Horizons flew past Pluto and captured detailed images of its frozen surface. More than a decade later, scientists revisited the images and found evidence that liquid nitrogen may have once flowed across the dwarf planet

When NASA’s New Horizons spacecraft passed Pluto in 2015, it gave scientists their first close look at a distant world that had previously been little more than a blur. More than a decade later, those same images are still revealing new clues. A new peer-reviewed analysis suggests that liquid nitrogen may have risen from beneath Pluto’s frozen surface and briefly flowed across Sputnik Planitia, leaving dark marks behind.

The finding does not mean scientists watched a liquid stream moving across Pluto. Instead, researchers combined unusual surface features, comparisons with Greenland and computer models to build a possible explanation for what happened. The study, titled “ Evidence for possible N2 basal flow beneath Pluto’s northern Sputnik Planitia ,” was published in The Planetary Science Journal.