A New Kind of 'Wet' World
Scientists have found the first evidence that liquid may have recently flowed on Pluto's surface. But this isn't water. Instead, a new study published in the Planetary Science Journal suggests that liquid nitrogen could be welling up from beneath the dwarf
planet's massive heart-shaped glacier, known as Sputnik Planitia. Researchers from the Southwest Research Institute (SwRI) analyzed images captured during the New Horizons flyby in 2015, focusing on dark, linear features that cut across the glacier's northern regions. These mysterious patterns bear a striking resemblance to wetted areas on Earth's own glaciers, leading to the startling new hypothesis.
Signs from a Distant World
Pluto's frigid atmosphere makes nitrogen rain impossible, so any liquid must be coming from below. The dark streaks and patches appear at the boundaries of large, city-sized convection cells on the nitrogen ice sheet. These cells are constantly, albeit slowly, overturning as part of a giant geologic conveyor belt. The new theory proposes that this process is being influenced by liquid nitrogen. Researchers compared the New Horizons images with satellite photos of Greenland's ice sheet, where meltwater creates similarly dark paths across the snow and ice. The visual parallels strengthened the case that a liquid process is at work on Pluto.
The Engine Room Below
So where would this liquid nitrogen come from? Computer models suggest that beneath Sputnik Planitia's kilometers-deep ice, the pressure could be immense enough to melt the nitrogen at its base. This liquid nitrogen, being less dense than the solid ice above it, would then be forced upward through cracks and fissures. Alan Stern, the principal investigator for the New Horizons mission and lead author of the study, described the finding as another one of Pluto's many surprises. This process suggests that Pluto isn't a static, frozen world, but one that remains geologically dynamic, capable of reshaping its own surface.
A More Complex Dwarf Planet
This isn't the first time scientists have suspected Pluto of having a dynamic interior. For years, researchers have debated the possibility of a vast subsurface ocean of liquid water, kept from freezing by heat from the planet's core. While this new study focuses on nitrogen, it adds to the growing body of evidence that Pluto is far more active than its size and distance from the Sun would suggest. The idea of subsurface liquids bursting forth onto the surface is a form of cryovolcanism, or ice volcanoes. This activity could be responsible for replenishing the nitrogen on Pluto’s surface and in its thin atmosphere, which is constantly escaping into space. The findings suggest Pluto may host previously unknown, time-variable features, meaning its face could be changing even now.
