A new study of images from NASA's 2015 New Horizons flyby has identified unusual dark marks on Sputnik Planitia, Pluto's vast nitrogen glacier. Some marks form narrow lines, while others spread across wider areas between large blocks of ice. Researchers say their appearance resembles patterns left when water wets glaciers on Earth. The comparison offers evidence that liquid may have reached Pluto's surface relatively recently.
Pluto's temperature and atmosphere make rain made of liquid nitrogen physically impossible. The team therefore proposes that nitrogen sometimes rises through cracks from beneath the glacier and briefly wets the surface. This interpretation remains cautious because it is based on landscape patterns rather than a direct measurement of flowing liquid. Even so, the finding suggests that Pluto may still experience short-lived surface changes, adding a dynamic process to scientists' picture of the distant world.